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Ecology

Ecology

I. Human EcologyAmos H. Hawley

BIBLIOGRAPHY

II. Cultural EcologyJulian H. Steward

BIBLIOGRAPHY

I HUMAN ECOLOGY

The term “ecology,” which has its root in the Greek word oikos (household or living place), came into use in the latter part of the nineteenth century in the works of zoologists and botanists to describe the study of the ways in which organisms live in their environments. Soon two branches of ecology were distinguished: autecology, the study of the individual organism’s interaction with environment, and synecology, the study of the correlations between the organisms engaged with a given unit of environment. The latter study has prevailed, however, and has become the principal connotation of ecology, since it became evident in numerous field studies that organisms, whether plant or animal, establish viable relationships with environment, not independently but collectively, through the mechanism of a system of relationships. Bioecologists were thus led to employ a set of concepts and techniques of investigation that imparted a markedly sociological coloration to their work.

Origins and history

The ecological approach was introduced as human ecology into the field of sociology at a critical period in the development of the latter discipline. In the 1920s the reformistic phase of sociology was drawing to a close, and the subject was gaining acceptance as a respected discipline in the curricula of American universities. That the transition would have been effected so quickly without the aid of a theoretical framework lending itself to empirical research seems doubtful. Ecology opportunely provided the necessary theory. A period of vigorous research followed that was to prove instrumental in launching sociology on its career as a social science.

Sociologists made free use of analogy as they borrowed heavily from the concepts of plant and animal ecology. The Darwinian notion of animate nature as a web of life became at once a general orienting concept and a basic postulate; it directed attention to the necessary interdependence among men as well as among lower forms of life. A second concept, the balance of nature, denoting a tendency toward stabilization of the relative numbers of diverse organisms within the web of life and of their several claims on the environment, provided human ecology with its characteristic equilibrium position. The more or less balanced web of relationships, when viewed in a specific local area, presented the aspect of community, a concept with obvious appeal for students of human social life.

According to plant and animal ecologists, the community, or ecosystem, is a population comprising a set of species whose reactions to the habitat and coactions between each other constitute an integrated system having some degree of unit character. Coactions involve members behaving both with reference to their similarities in an mtraspecific relationship known as commensalism and with reference to their differences in what is called symbiosis, an interspecific relationship. The community develops from simple to more complex forms through a sequence of stages described as succession. Each stage in the sequence is marked by an invasion of a new species or association of species, the series culminating in a climax stage in which a dominant species appears. The dominant species is related to the environment in such a way that it is able to control and maintain the community indefinitely. The community, then, tends to approximate a self-maintaining, or “closed,” system.

Community and environment

The application of the concepts from plant and animal ecology to the human community carried with it the implication that the community was essentially a natural phenomenon, which meant that it had developed independently of plan or deliberation. From this it was a short, though uncritical, step to the interpretation of human ecology as a study of the biotic or subsocial aspect of human social organization (Park 1936), a view that was elaborated at some length by Quinn (1950). Not only did the subsocial characterization convey an excessively narrow concept of social organization, but it posed an operational problem for which there was no workable solution.

A somewhat different definition of human ecology, which ignored any reference to the cognitive level of events, was enunciated by McKenzie ([1924] 1925, pp. 63–64), whose formulation of the subject as a study of the spatial and temporal relations of human beings, affected by the selective, distributive, and accommodative forces of the environment, was widely accepted as authoritative. Although McKenzie’s definition inspired a large amount of fruitful research effort, it had the unfortunate effect of concentrating attention almost exclusively on spatial distributions and correlations. In consequence, many promising implications of ecological assumptions were neglected.

Hawley, in attempting to restore a conceptual continuity with plant and animal ecologies, advanced the view of human ecology as the study of the form and development of the human community (1950, p. 68). Community, in this connection, is construed as a territorially localized system of relationships among functionally differentiated parts; human ecology, then, is concerned with the general problem of organization conceived as an attribute of a population—a point of view that has been shown to be consistent with a long-standing sociological tradition (Schnore 1958). Although the emphasis is centered on the functional system that develops in a population, it is not intended to exclude concern with spatial and temporal aspects; rather, these aspects are regarded as useful dimensions for the measurement of organization.

A further step in making the orientation of human ecology explicit within the larger context of general ecological theory was made by Duncan (1959, pp. 683–684), who described four principal variables of human ecology—population, organization, environment, and technology—that constitute an ecosystem. In other words, while any one of the four may be treated as a dependent variable for certain purposes, it is also reciprocally connected with each of the other variables. The virtue of this perspective lies in the range of problems it opens to the student of human ecology. Yet it seems unlikely tin various eco-logical studies, although hat that advantage can be fully enjoyed without a clear notion of how organization is constituted.

Other applications

While sociologists were at work defining human ecology for their purposes and pursuing many of its research leads, the concept spread into various other fields of inquiry. Human geographers wondered if the term “human ecology” was not a more apt characterization of their discipline; but their historic preoccupation with the landscape and their general addiction to a macroscopic treatment of occupance led them to discard this notion. Archeologists, in their efforts to reconstruct population distributions, have made use of ecological concepts and techniques, but without attempting to give formal statement to the approach.

Studies of human evolution by anthropologists involved questions of the man-environment relationship, which, in turn, led them to describe their work as human ecology; indeed, social or cultural anthropologists have long engaged in various ecological studies, although not until recently have they so defined their activity. One definition by an anthropologist is that of Steward (1955), for whom human ecology is the study of the adaptation of specific items of culture to particular environments. This conception, which reduces ecology to something akin to a research technique, is shared by a number of Steward’s contemporaries.

The language of human ecology has also made its appearance in economics, psychology, epidemiology, and other fields. In some instances, the term is used merely as a label for an environmental emphasis; in others, it is put forward in an effort to broaden the purview of a discipline.

But in spite of the widespread diffusion of ecological concepts, responsibility for systematic development of human ecology has been left to sociologists, who have drawn heavily on related fields for both theoretical and technical aid. The writings on real estate, finance, public administration, demography, planning, history, and other areas of inquiry, in addition to the literature of the fields previously mentioned, have at one time or another been exploited in the interest of human ecology. The reason for that catholicity of taste is not hard to find; human ecology is concerned with sociological problems in their fullest breadth. It overlaps, therefore, all the spheres of learning that concern the social life of man.

Distinctive features of human ecology

As human ecology has moved toward a major concern with the general problem of social organization and thus closer to the central concern of sociology, it has retained certain distinctive features. Foremost among these is the importance attributed to environment.

The broad, positional hypothesis is that organization arises from the interaction of population and environment. Environment, however, defined as whatever is external to and potentially or actually influential on a phenomenon under investigation, has no fixed content and must be defined anew for each different object of investigation. Environment is seen both as presenting the problem of life and as providing the means for its resolution; to adopt this position is to place the problem in a time-space context.

A second distinguishing characteristic is the emphasis on population as the point of reference; organization, it is contended, is exclusively the property of a population taken as a whole and not of an assemblage of individuals. Obvious as this position may be, it has profound methodological and theoretical implications for the manner in which the ecological problem is put, the variables employed, and the data to be observed. The concreteness of population, however, in contrast with the seemingly ephemeral nature of organization, tends to beguile the student to a view of population as the independent variable in all things pertaining to organization. It is obviously more convenient to proceed from the more accessible to the less accessible by asking how a population makes a unitary response to its environment; yet that is merely a common-sense way of approaching the problem, and investigation soon makes it apparent that population is for many purposes better regarded as the dependent variable, delimited and regulated by organization.

A third characteristic is the treatment of organization as a more or less complete and self-sustaining whole. The interaction of population and environment is seen as culminating in a system of relationships between differentiated parts which gives the population unit character and enables it to maintain its identity. As the property of a population, organization lends itself most readily to a morphological, or structural, analysis. The parts are the units—individuals or clusters of individuals—that perform functions and the relationships by which these units are linked. Differing configurations of unit functions and relationships are expected to occur with differences in relationship to environment and at different stages in development.

A morphological concern does not exclude the problem of development. Presumably, any given form of organization had an earlier form and is capable of having a later form. Every organization has a history, perhaps a natural history, the knowledge of which may shed light on the nature of organizations by indicating, for example, at what points they are vulnerable to change and how change spreads through them.

Related to the conception of organization is a fourth distinctive, although by no means unique, attribute of human ecology: the central position given to an equilibrium assumption. Morphological change is assumed to be a movement toward an equilibrium state, whether through a succession-like sequence of stages or through a process of continuous modification. Unlike the equilibrium notion in some of its other applications, such as in functionalist theory, the ecological usage of the term harbors no teleological overtones; on the contrary, this usage merely implies that as an organization attains completeness, it acquires the capacity for controlling change and for retaining its form through time, although the interval need not be specified. To put it differently, to the extent that an organization possesses unit character, an approximation to equilibrium obtains.

There is a further implication that a stable relationship with environment is contingent on relative stability in the relationships between the parts of an organization. A population always remains open to environment, but the formation of organizations canalizes environmental influences and makes for increasing selectivity of response.

The term “community” has commonly been used to denote the unit of organization for ecological purposes. Operationally defined as that population which carries on its daily life through a given system of relationships, the community is regarded as the smallest microcosm in which all the parameters of society are to be found. For reasons that were largely fortuitous, human ecologists at first focused their attention on the city and its tributary area as the prototype of community; later, in an effort to encompass the antecedents of cities, they broadened their consideration to include all forms of nucleated settlement. The term “community,” however, has the disadvantage of referring to the organization of a more or less localized settlement unit that does not always approximate a self-maintaining whole. For example, in an extensively urbanized society, local settlement units are usually components of more inclusive systems; in that event, the entire system must be treated as the object of study. But the difference between a simple, compact organization and a large, diffuse one is primarily a difference in scale; accordingly, the principles of organization should be the same in each. Since the designation of both simple and complex systems as communities threatens confusion, a more neutral term, such as “social system,” is to be preferred.

Principles of ecological organization

Inasmuch as principles of organization hinge on what is meant by population, it is imperative that the concept be developed more fully.

A human population is an aggregate of individuals who possess the following characteristics. As a living organism, every individual must have access to environment, for that is the only possible source of sustenance. Moreover, the interdependence of individuals is necessary; this condition, which obtains for all forms of life, holds true to an exceptional degree in the case of man, because of the naked state in which he comes into the world and his long period of postnatal maturation. Interdependence is the irreducible connotation of sociality.

The human being also possesses an inherent tendency to preserve and expand his life to the maximum permitted by prevailing circumstances; this is a general motive of which all other motives are special cases. In its most elementary sense, expansion of life refers to the multiplication of man-years through either the leaving of progeny or the extension of longevity; but it also includes all that is involved in the realization of that objective. Another important characteristic is the indeterminacy of the human being’s capacity to adapt; there is no known restriction on the kind or extent of refinement of activity in which he can engage. Finally, the human individual, again like other organisms, is time-bound; the recurring needs for food and rest fix the fundamental rhythm of life and regulate the allocation of time to all other activities. Accordingly, the time available for movement is limited and, in consequence, the space over which activities can be distributed is correspondingly limited.

These several attributes of individuals not only define the kind of population with which human ecology deals, but they also constitute a cardinal set of assumptions from which principles of ecological organization may be deduced. The following are some of the more salient of these principles of organization.

Principle of interdependence

Interdependence develops between units on each of two axes: the symbiotic (on the basis of their complementary differences) and the commensal (on the basis of their supplementary similarities). That is, units that combine in a symbiotic union may also enter into other combinations of a commensal character; the effect of each type of union is to raise the power of action above what it would be were the units to remain apart.

The effect, however, is not the same in each case. The symbiotic union enhances the efficiency of production or creative effort; the commensal union, since its parts are homogeneous, can only react and is suited, therefore, only to protective or conservative actions. Although commensalism is an elemental form of union, it is applicable to a wide array of situations. The point of importance at present is that a population tends to be knit together through an interwoven set of symbiotic and commensal relationships.

It should be evident that interdependence has temporal and spatial implications for the units involved. Relations of functional complementation and supplementation require mutual accessibility among units; since this is contingent on the time available for movement, the distance separating related units is always subject to some limitation. In general, for every set of related units, there should be, other things being equal, an appropriate pattern of distribution in the temporal and spatial dimensions.

Principle of the key function

A second principle may be described as the principle of the key function. That is, in every system of relationships among diverse functions, the connection of the system to its environment is mediated primarily by one or a relatively small number of functions, the latter being known as the key function or functions. To the extent that the principle of the key function does not obtain, the system will be tenuous and incoherent; in the extreme case, in which no system exists, every function has the same relationship to environment. Given a functional system, then, there are always some functions or functional units directly involved with environment and others that secure access to the environment indirectly, through the agency of the key function.

The notion of key function invokes the question of how to define the notion of environment, which can refer to many different kinds of things. For present purposes, these things may be classified in two broad categories: the natural and the social. Although every organized aggregate must contend with both, the relative importance of each may vary over a wide range. In some instances, because of the inaccessibility of the settlement, activities of necessity center on the exploitation of the local natural environment, while influences from the social field are relatively infrequent or of no great consequence. In this event, the key function is the activity that extracts the principal sustenance supply from local resources. But where the product from local resources, or a substantial part of it, is exchanged for other sustenance materials, whether through trade or other distributive mechanisms, the key function is determined by the comparative importance of production and of trade as sources of sustenance.

In many such instances, no distinction is necessary because the producer is also the trader—two functions combined in one functionary. But even before the two functions appear as separate specialties, the requisites of trade or distribution begin to regulate the uses of local resources. As the reliance on exchange advances, the social environment actually displaces the natural environment as the critical set of influences. A population is never emancipated from its dependence on physical and animate matters, but the importance of locale declines with increasing involvement in a network of intersystem relations; the natural environment is extended and diffused, and contacts with it are mediated through a variety of social mechanisms. Hence, the functions that link the local system to the social environment come to occupy the key position.

Principle of differentiation

The extent of functional differentiation varies with the productivity of the key function or functions; this is the principle of differentiation. A corollary is that the size of population supportable by the system varies with the productivity of the key function. For given the simplifying assumption that each unit is fully occupied, the number of people is determined by the number of functions to be performed.

In a hunting and gathering community, for instance, productivity is usually low, even though the physical environment is richly endowed; hence, there is little time or opportunity available for the cultivation of more than a few specialized functions. Nor is it possible to support enough people to staff even a moderate extent of specialization. By contrast, where the key function is devoted to stable agriculture, the range of possibilities is much greater, while in an industrial system productivity is so great that there are no known upper limits on either the number of specializations or the size of the population that can be supported.

The productivity of the key function, then, constitutes the principal limiting condition on the extent to which a system can be elaborated, on the size of population that can be sustained in the system, and on the area or space the system can occupy.

A question of some importance has to do with the relative number of units engaged in each of several interrelated functions. That question remains unanswered at present. It may be suggested, however, that the number of units engaged in any given function is inversely proportional to the productivity of the function and directly proportional to the number of units that utilize the product of the function.

It follows, of course, that functional differentiation involves a differentiation of environmental requirements. As the materials and conditions used by diversely specialized units differ, so also will their needs for location in space and time. In general, units performing key functions have the highest priority of claim on location. Other units tend to distribute themselves about the key function units, their distances away corresponding to the number of degrees of removal separating their functions from direct relation with the key functions. The temporal spacing may be expected to reveal a similar pattern. Special location requirements, however, as for type of soil or other resource, may obscure the tendency to a symmetrical arrangement of functions by degree of indirectness of relationship with key functions.

An important implication of the principles of the key function and of differentiation is that of transitivity in the relation among functional units. Relations with environment are necessarily transitive for some units. By the same token, relations among many units are transitive. The advance of specialization increases transitive relations more than proportionally and lengthens the transitive sequences. Thus, it is possible for functional units widely removed from one another so far as direct encounters are concerned to be inextricably linked through their respective linkages with one or more units performing intervening functions. All functions, regardless of kind, are subject to the environmental nexus. They differ only in the immediacy with which influences reach them. Those which operate at or near the ends of chains of relationships may appear to have large degrees of independence of environment. The appearance is illusory, however. It is due, rather, to the time required for effects to reach them and, in complex systems, to their having positions in two or more relational sequences which expose them to countervailing influences.

Principle of dominance

Given the principles stated above, it is a simple inferential step to a principle of dominance. According to this principle, functional units having direct relations with environment, and thus performing the key function, determine or regulate the conditions essential to the functions of units having indirect relations with environment. Dominance, in other words, is an attribute of function.

But while the power inherent in a system is unevenly distributed, it is not confined to the key function unit. Power is held in varying degrees by all other units, in measures that vary inversely with the number of steps of removal from direct relation with the unit performing the key function. A single power gradient running through all the units involved in a system assumes a very simple situation, of course, one in which a single unit occupies a key function position. Before introducing complications into this overly simplified conception, it is opportune to note some further implications of the dominance principle.

Where the progress of differentiation has distinguished a relatively large number of units, they tend to form clusters or complex units. A corollary to the dominance principle sheds light on how that comes about: the greater the extent to which variously specialized units are subject to the environmental conditions mediated by some one unit, the greater their tendency to coalesce in a corporate body. The interdependence among such units is manifestly close, and their requirements for mutual accessibility are correspondingly acute. A hierarchic pattern emerges in which the number of strata corresponds to the number of degrees that the parts are removed from direct relations with the key function; thus, symbiotic subsystems appear as components of a parent system. The nuclear family, although its origins are obscure, fits this principle. But instances with more proximate origins are found in the combinations of specialists to form producing enterprises, welfare agencies, governing bodies, etc., and again in the combinations of producing enterprises, retail establishments, or governments to constitute larger, more complex units. There is no restriction of scale or complexity in the formation of symbiotic or corporate units.

On the other hand, units that are of a given functional type and therefore occupy equivalent positions in the power hierarchy may raise their power potential by the formation of categoric unions. Any threat to a function or to the conditions of its performance can provoke such a response; groups of elders, the medieval guilds, labor unions, professional associations, councils of churches, retail associations, and associations of manufacturers are examples of categoric units. A social class is at most a loose form of categoric unit.

As with the corporate union, the categoric union may be composed of units of any size or kind. It may appear as a federation of categoric units or as an association of corporate units. So long as it retains its pure categoric form, however, such a unit can do little more than react to circumstances affecting it. Nor can it have more than a transitory existence, since in order to engage in positive action of any kind and to attain some measure of permanence, it must develop at least a core of specialists. Although the categoric unit tends to assume the characteristics of the corporate unit, it remains distinctive as long as its criterion for membership is possession of a given, common characteristic. In any event, the categoric unit is a source of rigidity in a social system, and once formed, its effect is to preserve the position of a functional category in the system.

The concept of dominance has been widely employed for the purpose of delimiting the boundaries of systems. It is argued that centers of settlement, such as cities, exercise dominance over their surrounding areas, in diminishing degrees as the distance from the center increases; the margin of influence marks the boundary of the system. Empirical support for this proposition is provided by the evidence of nonrandom distribution of related functions and by the gradient pattern that appears in the frequencies with which outlying functions are involved with central functions.

Two qualifications of this conclusion are needed; first, dominance is exercised from and not by centers, since it resides in functional units rather than in the places where they are located. Further, the apparent decline of dominance results less from an effect of distance in reducing control over related functions than from the increased difficulty of establishing dominance uniformly over an exponentially widening area.

Isomorphism. A principle of isomorphism has been implied in much that has been said and needs now to be stated. Units subject to the same environmental conditions, or to environmental conditions as mediated through a given key unit, acquire a similar form of organization. They must submit to standard terms of communication and to standard procedures in consequence of which they develop similar internal arrangements within limits imposed by their respective sizes. Each unit, then, tends to become a replica of every other unit and of the parent system in which it is a subsystem.

Since small units cannot acquire the elaborate organizations of which large units are capable, they jointly support specialized functions that complement their meager organizations. For example, whereas a large unit may include among its functionaries accountants, lawyers, engineers, public relations experts, and other specialists, the small unit must purchase comparable services from units specializing in each of the relevant functions. The principle of isomorphism also applies to the size of units, at least as a tendency; that is, all units tend toward a size that enables them to maintain contact with all relevant sectors of the parent system.

Closure and social change

Operation of the several principles mentioned thus far moves a system toward a state of closure. This term must be employed here with circumspection, for it cannot have its usual connotation of independence of environment. Closure can only mean that development has terminated in a more or less complete system that is capable of sustaining a given relationship to environment indefinitely. For closure to be realized, it is required not only that the differentiation of function supportable by the productivity of the key function has attained its maximum but also that the various functions have been gathered into corporate and categoric subsystems; moreover, the performance of the key function should have been reduced to one unit or to a number of units united in a categoric federation. Then a system is highly selective of its membership and capable of exercising some control over factors that threaten change in the system.

Under these circumstances, certain conditions of equilibrium are held to obtain: the functions involved are mutually complementary and collectively provide the conditions essential to the continuation of each; the number of individuals engaged in each function is just sufficient to maintain the relations of the functions to each other and to all other functions; and the various units are arranged in time and space so that the accessibility of one to others bears a direct relation to the frequency of exchanges between them. Needless to say, equilibrium as thus defined is a logical construct; the conditions express an expected outcome if the principles of organization are allowed to operate without any external disturbances.

Origins and effects of change

Every social system is continuously subject to change, for since the environment is always in some state of flux, the equilibrium that can be attained is seldom more than partial. A system founded on nonreplaceable resources is faced with “immanent change”; sooner or later it will either pass into decline or shift perforce to a different resource base. Such, for instance, has been the experience of innumerable mining communities; in a similar manner agricultural communities often alter the soil composition of their lands by the uses they practice, with the ultimate result that the lands will no longer support the systems as they are constituted. Instances of maladaptation, such as the reliance of the Irish on the potato as a food staple in the nineteenth century, can lead to catastrophic consequences.

In general, however, change has an external origin, a proposition that follows by definition from an equilibrium position. Some influences emanate from the physical or biotic environment, such as variations in the growing season or invasion by parasites. To the extent that episodic occurrences of that order fail to modify one or more functions comprised in the system, their effects are transitory; the system returns to its original form. But where a function, particularly a key function, is substantially modified, the system must be reconstituted. The disappearance of a game supply, the silting of an estuary, or the eruption of a volcano may render a key function inoperative in its usual location. The population must relocate and work out a new system of activities. Unless there is an increase of productivity, new ways of acting will merely displace old ways, and the change will not be cumulative.

Cumulative change

Cumulative change, or growth of the system, presupposes an increase in the productivity of a key function. Only in this way is it possible to multiply specialization, to employ a greater variety of techniques, and to support a larger population. The probability of the occurrence of disturbances having that effect rises with the number of points of contact with a social environment; location, therefore, is an important factor. A site on a traveled route is more exposed to external influences than one situated at a distance from an avenue of movement; a site at a conflux of routes is much more vulnerable to disturbances from without. Any location that fosters frequent meetings of people from diverse backgrounds is a gateway for the infusion of alien experiences and techniques into the social system centered there. Whether change is released through a deposit of numerous small additions to the culture or through a simple, dramatic innovation is immaterial.

The process of cumulative change may be generalized as a principle of expansion. Expansion is a twofold process involving, on the one hand, the growth of a center of activity from which dominance is exercised and, on the other hand, an enlargement of the scope of the center’s influence. The process entails the absorption and redistribution of the functions formerly carried on in outlying areas, a centralization of mediating and control functions, an increase in the number and variety of territorially extended relationships, a growth of population to man a more elaborate set of activities, and an accumulation of culture together with a leveling of cultural differences over the expanding domain. After the revival of trade in Europe, from the tenth century onward, the favorably situated village with its narrow vicinage grew into a market town that served as a center of an enlarged territorial organization. That gave way, in turn, to the emergent city capable of exercising an integrating influence over an area of regional scope. Most recently, the metropolis has superseded the city and has brought under its dominion a vast interregional territory. Although the process is as old as recorded history, it has not advanced in a simple linear progression. It has moved and then stalled in one place, only to surge ahead in another; it has faltered and even on occasion has seemed to turn back upon itself, but it has always resumed its course with renewed vigor.

The limits to expansion are sometimes fixed by the facility of movement between center and periphery—by the maximum distance over which the exercise of dominance is feasible. More often than not, however, the limits are drawn at the points of juncture with the expanding domains of social systems in neighboring regions. As a system encounters its limits, however they are fixed, it loses capacity to absorb further change, and equilibrium tendencies begin to assert themselves once more.

In many instances, however, the first symptoms of change are experienced at the periphery of a system. Since the effects of dominance grow more uneven with increased distance from a center, boundaries are apt to be permeable at many points. Yet, in the degree to which a system is integrated, events at the boundary are transmitted directly to the key unit, from which they are communicated to ancillary units; it is always at the boundary that one system begins its absorption of another. Expansion may be resumed at any moment and in any of the systems that hem in one another. An innovation, even though it might present itself to all systems about the same time, gains admission to one or another by virtue of a more favorable location for its use, a more appropriate organization for its acceptance, or some other local advantage. The renewed expansion encroaches upon the territories of adjoining systems, sometimes reducing them to mere components of a single, greatly enlarged system.

Under conditions of closure, environmental effects, and particularly cultural innovations, would be expected to enter a system through the key function, for the obvious reason that it has the most direct connection with environment. And, presumably, change would spread through the system by affecting units successively in the order in which they are removed from direct relation with a key function. But in a system centered on a convergence of routes, many units may have direct, although not equal, access to the outside world. Change may therefore enter the system at many points, at least until its structure is fully developed with the parts systematically arrayed relative to a key unit. An expanding system, in other words, is an open system, and it remains so until the limits to expansion are reached.

Burgess’ hypothesis of city growth

A hypothesis of city growth, stated by E. W. Burgess ([1925] 1961, pp. 37–44), pertains to a special case of the more general principle. According to that proposal, city growth takes the form of expansion from a zone centered on a highly accessible location. Growth involves increasing density of occupance of the central zone and, at the same time, a redistribution of activities or land uses scattered around the center to conform to a gradient pattern of variation of intensity of land use according to distances from the center. Redistribution results from increasing pressure at the center and a consequent encroachment by high-intensity uses into the spaces occupied by lower-intensity uses in a succession-like manner. Alternating periods of redistribution and stabilization of distribution, and those of growth and partial equilibrium, create a wavelike effect more or less visible in a set of concentric zones. By venturing to describe, in rather specific terms, the content of the zones and by thus reifying a set of statistical constructs, Burgess diverted attention from a growth process and caused it to be fixed on a specious distribution pattern. His argument, therefore, seemed to acquire a historical limitation that it need not have had.

The miscarriage of the import of the Burgess hypothesis is evident in criticisms that have opposed the preindustrial city to the industrial city as a qualitatively different phenomenon. Whereas Burgess suggested that the social-economic status of residents is higher in each successive concentric zone, critics have shown that in the preindustrial city the social-economic gradient runs in the opposite direction. Useful as that finding may be, it misses the essential point. That is, the significant gradient is one of dominance; units tend to distribute themselves over space in a way that reflects their relationships to the dominant unit. In this respect, both industrial and preindustrial cities are similar. The qualitative difference lies in the kinds of units that exercise dominance. In the preindus-trial city, all functions are carried in familial or household units, and power is unevenly distributed among them. But in the industrial society, the household unit has been relegated to a minor position; specialized functions are performed by extra-familial units, and the separation of functions from the household has involved a spatial separation as well.

Furthermore, the notion of a monocentered system is applicable only to the simplest instances. All others include a constellation of settlement nuclei, that is to say, subsidiary service centers within cities, and villages, towns, or cities within hinterlands. Each serves as a locus of influence over a localized area, varying in scope with the types of functions centered in the nucleus. Thus, as Christaller observed, the constellation of nuclei forms a hierarchy by size and number of places and by order of functions performed (1933). Small places provide low-order, or ubiquitous, functions, whereas each larger place performs, in addition to low-order functions, higher-order functions for broader domains. At the apogee of the hierarchy is the metropolis, in which the integrating and coordinating functions for the entire system are domiciled. Thus, dominance is exercised downward and outward through nested sets of subsidiary centers [seeCentral Place].

The least satisfactory aspect of the theory of change concerns its temporal incidence. The idea of succession, borrowed initially from bioecology, lingers in the dictionary of human ecology. Change as cyclical in form, consisting in movements between equilibrium stages, is clearly the most intelligible conception. Nevertheless, apart from the difficulty in empirically identifying an equilibrium stage, there are unsolved conceptual problems of the spacing of stages, and of the factors governing the intervals between stages. Thus far, succession has been applied only in retrospect. Its utility will remain uncertain until it can be projected into prediction. Quite possibly, that may have to wait for more extensive work on social system taxonomy.

The limits of human ecology

Human ecology has progressed since its inception from an effort to apply the concepts of plant and animal ecology to human collective life, through an extended period of preoccupation with spatial configurations, to an increasing concern with the form and development of territorially based social systems. In the last phase, human ecologists have sought to clarify the assumptions of ecology and to draw out their implications for organization. Although the results of that work are far from complete, it seems clear that they indicate the direction in which human ecology will continue to develop.

As with most approaches in social science, human ecology has limited objectives. It seeks knowl-ledge about the structure of a social system and the manner in which the structure develops. Hence, it is not prepared to provide explanations for all of the manifold interactions, frictions, and collisions that occur within the bounds of a social system. The findings of human ecology, however, define the context in which all such phenomena take place, and which is therefore pertinent to their full understanding.

Human ecology is not qualified to deal with the normative order in a social system. Yet consistent with its position is the expectation that a normative order corresponds to and reflects the functional order. The two are different abstractions from the same reality.

Amos H. Hawley

[See alsoCity, article onComparative Urban Structure; Environment; Environmentalism; Geography; and the biographies ofBurgess; Darwin; Park.]

BIBLIOGRAPHY

Burgess, Ernest W. (1925) 1961 The Growth of the City: An Introduction to a Research Project. Pages 37–44 in George A. Theodorson (editor), Studies in Human Ecology. Evanston, Ill.: Row, Peterson.

Christaller, Walter 1933 Die zentralen Orte in Siiddeutschland: Eine okonomisch-geographische Untersuchung iiber die Gesetzmdssigkeit der Verbreitung und Entwicklung der Siedlungen mit stddtischen Funktionen. Jena (Germany): Fischer.

Duncan, Otis Dudley 1959 Human Ecology and Population Studies. Pages 678–716 in Philip M. Hauser and Otis Dudley Duncan (editors), The Study of Population: An Inventory and Appraisal. Univ. of Chicago Press.

Hawley, Amos H. 1950 Human Ecology: A Theory of Community Structure. New York: Ronald.

McKenzie, Roderick D. (1924) 1925 The Ecological Approach to the Study of the Human Community. Pages 63–79 in Robert E. Park, Ernest W. Burgess, and Roderick D. McKenzie, The City. Univ. of Chicago Press. -* First published in Volume 30 of the American Journal of Sociology.

Park, Robert E. (1936) 1952 Human Ecology. Pages 145–158 in Robert E. Park, Human Communities: The City and Human Ecology. Collected Papers, Vol. 2. Glencoe, Ill.: Free Press. → First published in Volume 42 of the American Journal of Sociology.

Quinn, James A. 1950 Human Ecology. Englewood Cliffs, N.J.: Prentice-Hall.

Schnore, Leo F. 1958 Social Morphology and Human Ecology. American Journal of Sociology 63:620–634.

Steward, Julian H. 1955 Theory of Culture Change: The Methodology of Multilinear Evolution. Urbana: Univ. of Illinois Press.

II CULTURAL ECOLOGY

Cultural ecology is the study of the processes by which a society adapts to its environment. Its principal problem is to determine whether these adaptations initiate internal social transformations or evolutionary change. It analyzes these adaptations, however, in conjunction with other processes of change. Its method requires examination of the interaction of societies and social institutions with one another and with the natural environment.

Cultural ecology is distinguishable from but does not necessarily exclude other approaches to the ecological study of social phenomena. These approaches have viewed their special problems—for example, settlement patterns, the development of agriculture, and land use—in the broad context of the complexly interacting phenomena within a defined geographical area. Explanatory formulations have even included the incidence of disease, which is related to social phenomena and in turn affects societies in their adaptations. This modern concept of ecology has largely superseded other concepts, such as “urban,” “social,” and “human” ecology, which employed the biological analogy of viewing social institutions in terms of competition, climax areas, and zones.

Cultural ecology is broadly similar to biological ecology in its method of examining the interactions of all social and natural phenomena within an area, but it does not equate social features with biological species or assume that competition is the major process. It distinguishes different kinds of sociocultural systems and institutions, it recognizes both cooperation and competition as processes of interaction, and it postulates that environmental adaptations depend on the technology, needs, and structure of the society and on the nature of the environment. It includes analysis of adaptations to the social environment, because an independent tribe is influenced in its environmental adaptations by such interactions with its neighbors as peaceful trading, intermarriage, cooperation, and warfare and other kinds of competition, in the same way a specialized, dependent segment of a larger sociocultural system may be strongly influenced by external institutions in the way it utilizes its environment.

The cultural ecological method of analyzing culture change or evolution differs from that based on the superorganic or culturological concept. The latter assumes that only phenomena of a cultural level are relevant and admissible, and it repudiates ”reductionism,” that is, consideration of processes induced by factors of a psychological, biological, or environmental level. The evolutionary hypotheses based upon this method deal with culture in a generic or global sense rather than with individual cultures in a substantive sense, and they postulate universal processes. Cultural ecology, on the other hand, recognizes the substantive dissimilarities of cultures that are caused by the particular adaptive processes by which any society interacts with its environment.

Cultural ecology does not assume that each case is unique. Its method, however, requires an empirical analysis of each society before broader generalizations of cross-cultural similarities in processes and substantive effects may be made. Cultural ecologists study highly diversified cultures and environments and can prescribe neither specific analytic formulas nor theoretical or ideal models of culture change; there can be no a priori conclusions or generalizations concerning evolution. The heuristic value of the ecological view-point is to conceptualize noncultural phenomena that are relevant to processes of cultural evolution.

Empirical studies disclose that among the simpler and earlier societies of mankind, to whom physical survival was the major concern, different social systems were fairly direct responses to the exploitation of particular environments by special techniques. As technological innovations improved man’s ability to control and adjust to environments, and as historically derived patterns of behavior were introduced, the significance of both the environment and the culture was altered and the adaptive processes not only became more complex but also acquired new qualities.

The ecological concept of interacting phenomena draws attention to certain general categories of relevant data. The resources, flora, fauna, climate, local diseases and their vectors of occurrence and many other features of the environment constitute potential factors in one part of the interacting system. The nature of the culture, especially its exploitative and adaptive technology but also features of the internal and external social environment, constitutes the other part. The interaction involves the social arrangements that are required in land exploitation; population density, distribution, and nucleation; permanence and composition of population aggregates; territoriality of societies; intersocietal relationships; and cultural values. In each case the empirical problem is whether the adaptation is so inflexible as to permit only a certain pattern or whether there is latitude for variation which may allow different patterns to be developed or borrowed.

Explanations in terms of cultural ecology require certain conceptual distinctions about the nature of culture. First, the various components of a culture, such as technology, language, society, and stylistic features, respond very differently to adaptive processes. Second, sociocultural systems of different levels of integration profoundly affect the interaction of biological, cultural, and environmental factors. Societies having supracommunity (state or national) institutions and the technological ability to expand the effective environment beyond that of the local or primary group can utilize resources within and outside the area controlled by the larger society. The adaptive responses of complex societies are thus very unlike those of a tribal society, which adapts predominantly to its own environment.

Culture history and ecological adaptations

The historical processes by which a society acquires many of its basic traits are complementary to studies of adaptive processes. The historical processes include the extensive borrowing of many cultural traits and trait complexes from diverse sources; the migrations of people; the transmission of cultural heritages to successive generations; and local innovations or inventions. Recognition of these historical processes, however, does not relegate environment to the circumscribed role of merely permitting or prohibiting certain cultural practices so that all origins must be explained by such history. It is obvious that fishing will have minor importance in desert areas and that agriculture is impossible in arctic regions. It is equally clear that abundant fishing resources cannot be exploited without appropriate techniques and that agricultural potentials cannot be utilized without domesticated plants. The presence of gold, oil, and uranium is unimportant until the society has demands for them and means of extracting them.

The Indians of the Southwest had at one time been predominantly food collectors, but the introduction of food crops, largely from Mesoamerica, provided the basis for the development of the more complex Pueblo village culture. Many details of this culture, such as ritual elements, were borrowed from the south, but the development of Pueblo sociocultural patterns are comprehensible only in terms of the processes of population growth, extension of biological families into lineages, eventual consolidation of lineages into larger settlements, and the appearance of many village institutions that cut across kinship groups.

Dissimilar ecological adaptations may also occur among societies that have been subjected to similar historical influences. The Indians of California and of the semiarid steppes and deserts of the Great Basin shared substantially the same devices for collecting wild foods and for hunting, but the vastly greater abundance of flora and fauna in California supported a population thirty times that of the Great Basin. The California Indians lived in fairly permanent villages which had developed some social elaborations, whereas the Great Basin Indians were divided into independent family units which foraged over large territories during most of the year and assembled only seasonally in encampments that did not always consist of the same families.

The investigation of cultural ecological processes must consider the possibility that basic sociocultural patterns may have diffused or been carried by migrations from one kind of environment to another, but it also must examine whether these patterns have been modified. Assessment of modifications requires a distinction between the outer embellishments of the culture, such as ritual elements, art styles, and kinds of architecture, and those social patterns which are human arrangements for self-perpetuation.

Biological factors

Man’s adaptations to his natural environment cannot be comprehended in purely culturological terms because man not only shares basic biological needs with all animals but also has distinctively human characteristics. All activities are culturally conditioned, but ecological factors cannot be wholly distinguished from inherent biological and psychological factors which are the basis of behavior. Analyses that ascribe importance to inherent human qualities bear directly upon the validity of common hypotheses and raise new problems.

It has generally been assumed that the nuclear family consisting of parents and children has always been the irreducible social structure because the sexes serve complementary functions in meeting procreational and subsistence needs and in caring for and training the young during their long period of dependency. This assumption is generally valid for all ethnographically known societies, especially for primitive societies, among whom there is a clear sexual division of labor in subsistence, maintenance of the household, and child rearing. In contemporary industrial societies, however, the biological family has surrendered many of its functions, and cultural differences between sex roles have been diminished. Conceivably, the nuclear family might be reduced to little more than a procreational unit if its cultural functions are lost.

In primitive societies, larger suprafamilial bands or other groups that developed in response to cooperative needs, especially in subsistence activities, had a biological basis, especially through lineages. The patrilineages of hunting bands, for example, had the advantage that particular skills, knowledge of the environment, and obedience to authority were transmitted from father to son in a male-dominated group. Biological relationships have so long been fundamentally important in culture history that they may be ascribed excessive importance, as when the position of head of a family or even kingship is transmitted through primogeniture. The biological basis survived because of the lack of patterned alternatives.

Another basic biological factor in cultural ecological adaptations is the prolonged period of human growth. The factors of age and environment interact in many ways to affect behavior patterns. The Shoshoni child may help in rabbit drives but not in big game hunting; the east African boy may herd cattle but not go to war; modern American youths attend school for a required number of years; in areas of precarious subsistence the aged may be abandoned to die, while in other areas they may be accorded special consideration; and everywhere the marriage age group is determined by biological development, culture, and adaptations to the environment.

There are, however, many problems concerning the interaction of biological and cultural ecological factors. One of these arises from the assumption that the nuclear or biological family is a basic part of every human society. This assumption might rest on the obvious biological nature of the family or upon the universal cultural functions the family is believed to serve. The higher primates usually live in fairly small bands that consist of females and their dependent offspring, a single powerful male, and subordinate adult males. In certain depressed segments of modern society, however, the matrifocal family or kin group, which consists of women and dependent children and somewhat subordinate males who are loosely attached to the family, appears to be the irreducible social unit. This family represents an adaptive response to restricted territoriality, low income, and lack of opportunity for improvement.

Although the transition from a precultural primate society to the nuclear family has not been explained, the contemporary existence of the matrifocal kin group raises the question of origin. How did the nuclear family develop from an early kind of society which may have lacked the cultural ecological processes that created and have subsequently supported it?

Speculation about the origin of the family must be based on what is known archeologically about the origins of technology and on ethnographic evidence. In all ethnographic cases of pref arming societies the nuclear family is based on clear complementarity of the sexes in subsistence activities. Women are food collectors because they must not leave their children, who are their inescapable responsibility, whereas men may spend long periods away from their families hunting large game or fishing, if the technology makes this possible. Prior to the invention of such distinctly male-associated hunting devices as spears, bows, nets, and traps, both sexes may have collected food in so similar a way that they were no more differentiated than were the higher primates. If so, there may have been a long transitional stage when some type of matrifocal kin group persisted. The hand ax, which was long the principal weapon, may attest to men’s role in protecting the group but not specialization in hunting, for its use was in close combat.

Settlement patterns and the adaptive process

A culture that is introduced into a wholly new environment must adapt in some ways to local conditions, but only empirical research can determine whether the adaptations are unalterably fixed or whether there is latitude for variations. In some instances, the case for narrow limits of variation seems clear. Simple societies that exploit only sparse and scattered resources obtained by food collecting must obviously fragment into small groups, for members of the society are in competition with one another. More abundant resources, such as rich areas of vegetable foods, large game herds, fisheries, or intensive farming, may permit variation in some features and thus allow latitude for borrowing or for local innovations.

There can, however, be no a priori conclusions: whether a society is dispersed over its land or clustered in large settlements may result from adaptive factors, from historical patterns, or from both. The Indians of California and the Northwest Coast had very similar native population densities, but the dispersed acorns and game in California led to considerable dispersal of the villages, whereas the rich salmon fisheries of British Columbia and Alaska required the people to concentrate on the main streams in fairly large settlements. Similarly, agricultural areas dependent upon irrigation concentrated the population within the network of canals. On the rainless and barren deserts of coastal Peru, the people had to live in dense settlements along or near the rivers. The large communities on the coasts of British Columbia and Peru, however, were parts of unlike sociocultural systems. Each developed from a different historical background, and each had a distinctive local adaptation; there were fisheries on the Northwest Coast and intensive, irrigation farming together with ocean resources in Peru.

A dense population supported by a rich economy is not always concentrated in large centers. The native agricultural peoples of the northern Andes of Colombia and the Araucanian Indians of the central valley of Chile had very similar population densities, but the northern Andean peoples were organized in strong, class-structured chiefdoms with communities of five hundred persons or more, whereas the Araucanians were dispersed in many closely spaced villages, each a patrilineage of no more than one hundred persons. This contrast is not explained by farm productivity or other technological factors involved in maintaining large communities. The northern Andean chiefdoms were the result of a diffused cult-complex of temples, priests, warriors, and human sacrifice, which may have originated in Mesoamerica but was re-adapted to the diversified environment of high mountains and deep valleys. Presumably, the Araucanians could have supported chiefdoms, but the nucleating factors were absent. A limited pastoral nomadism based on llama herding may have been an ecological deterrent to community growth, Although this factor did not inhibit the development of states and empires in Peru.

Nontechnological features of culture may also affect the adaptive arrangements through the external social environment of the society. Peaceful interaction of societies through marriage, trade, visiting, and participation in ceremonies, games, and other activities may take various patterns within the limits imposed by the environment. Intergroup hostilities, however, may have a decisive influence, because fear of warfare often causes peoples to cluster in compact settlements that are not required by subsistence patterns and sometimes do not give optimum access to resources. Thus, the palisaded villages of parts of the Amazon some-what inhibited farming of the frequently shifting slash-and-burn farm plots. To judge by the pre-history of the Pueblo Indians, the nature of farming permitted considerable variation. Early settlements were small and widely scattered, but in later periods the population declined as the settlements became large and tightly nucleated. This was the result of increased precariousness of farming in an area that had frequent droughts and was inhabited by marauders. In Tanganyika, people did not dare disperse along the fertile lands near the waterways until colonialism largely eliminated warfare. Throughout much of history, warfare has been a major factor in the interaction of culture and environment.

Exploitation of an environment by means of certain cultural devices may also drastically affect the environment, which again reacts upon the culture. In native California, as in many other areas, the Indians deliberately fired the grass in order to kill seedlings of brush and trees and thus increase the grazing land for game. Deforestation, overgrazing with concomitant soil erosion, the damming and rechanneling of rivers, drainage of swamps, and conversion of rural areas to urban or suburban land-use patterns also alter the environment. In such instances as the firing of grasslands, the development of irrigation works, or reclamation of swamps, the culture increases its basic resources. In others, such as overgrazing, lack of conservation, or the exhaustion of basic minerals, the culture destroys or impairs certain aspects of its local foundations.

Cultural variables versus holism

Although the culture of any society constitutes a holistic system in which technology, economics, social and political structure, religion, language, values, and other features are closely interrelated, the different components of a culture are not similarly affected by ecological adaptations. Technology, which exemplifies progress in man’s control of nature, tends to be cumulative. A language, unless replaced by another one, slowly but continuously evolves into divergent groups of languages. Humanistic and stylistic cultural manifestations may retain their formal aspects during social transformations but acquire new functions. Societies change through a series of structural and functional transformations.

Social structures respond most clearly to environmental requirements. This basic structuring is related most immediately to cooperative productive activity, and it is manifest in community and band organization and in essential kinship systems. Among simple societies, any interpersonal or inter-familial arrangements necessary for survival in particular areas are virtually synonymous with social organization. Because food collecting, such as in the case of seed gathering, is competitive, societies in unproductive environments tend to become fragmented into nuclear family units. Societies of hunters are more productive under cooperative arrangements and attain various patterns of cohesion. Societies that depend primarily upon farming tend to have permanent community organization, whether in dispersed or nucleated settlements, because cooperation in such activities as clearing plots and irrigation projects facilitates production. Increase in productivity is delimited by the environmental potentials, crops, and farm methods, but it may lead to larger communities and to internal specialization of role and status.

Productive increases achieved by social cooperation and improvements in exploitative technology became the bases of the transformation of small, homogeneous societies into larger societies that were internally specialized by occupational role and social status. Structural aspects of cooperation are reasonably well known, but quantitative statements of productivity, potential and actual surpluses, manpower hours that might be available for pursuits other than production of basic necessities, numbers of persons engaged in special occupations, and other measurable activities are rarely available. These serious lacunae in our data leave open the question of the part that sheer quantities of people and things played in the transformations from simple to complex societies.

Even within the category of culture subsumed under social patterns, it cannot be assumed that all features are equally fixed by a given ecological pattern. Among simple societies, residence, kinship, and subsistence patterns are more fundamental and less alterable or variable than clans, moieties, religious and secular associations, and other elaborations which are secondary embroideries on the basic social fabric. Distributional evidence in many parts of the world clearly shows that such elaborations have diffused widely across different kinds of environments and to fundamentally different social structures adapted to use of the environments. In the Southwest, for example, matrilineal clans occurred among the western Pueblo farm villages and the seminomadic pastoral Navajo, and moieties were a secondary adjunct of the patrilineal hunting bands in southern California and some of the eastern Pueblo agriculturalists.

A final problem concerning the response of different aspects or components of culture to adaptive processes is whether old or traditional forms may acquire new functions. Among the Sonjo of Tanganyika, the men’s age-group that served as warriors in precolonial times now spends several years performing wage labor in the new nonmilitaristic, cash-oriented context. Clan-owned or lineage-owned land and traditional types of ownership and inheritance of herds may persist under production for an outside market. Although traditional structures and trait-complexes tend to perpetuate themselves in all stages of cultural development, the evidence seems clearly to indicate that the new functions of the changing context eventually alter old forms beyond recognition, or that these forms wither and are replaced by new ones.

Levels of sociocultural integration

The adaptations of a complex or highly developed society differ in many ways from those of a simple society. The internal specialization that developed after the agricultural revolution and more so after the industrial revolution has affected the adaptive processes of the local segments of states and nations. Land use has increasingly reflected the importance of external economic institutions rather than local subsistence goals. Trade, improved transportation, mechanization, and other factors related to industrialization have made each local social group a more highly specialized and dependent part of the larger sociocultural system. There is a tendency toward monocropping in areas best suited to production of crops for external markets and toward specialization of local extractive industries, such as mining, oil, and timber, which have little intrinsic value to the local subsociety. Larger sociocultural systems have also created metropolitan and industrial centers and set aside special recreational areas.

Owing to technological achievements, the impact or conditioning effects of nature upon society are far less direct and compelling in a complex society than in a simple one. Culture increasingly creates its own environment. Foods and other necessities can be transported, water diverted, and electric power transmitted great distances. Reasonable comfort can be provided even for those who live for a time in Antarctica.

In a more fundamental sense, however, the distinction between primitive and developed societies is not merely one of social complexity or of technological knowledge. Among primitive peoples, the family, extended kin group, or fairly small village or band adapts directly to its own territory. Among more complex societies, there are suprafamilial and supracommunity institutions that are impersonal in that they do not involve the total cultural behavior of the people connected with them. State economic institutions—corporations, for example, that extract new materials and manufacture and distribute the products—serve the varied needs of the many subcultural groups within the state. They also extend the interaction of culture and environment far beyond state boundaries through the exploitation of distant resources and through extensive commerce. These vast economic extensions of the more developed societies penetrate local societies, and by creating new uses for land and other resources and imposing outside political and economic patterns, they fundamentally transform the local societies.

Within a modern, complex state, there is increasing specialization of land use within environmental potentials, but distinctiveness of local subcultures is partly leveled by the impact of national influences. The subcultures of ranchers in Nevada, sugar-cane workers in Puerto Rico, tea-plantation workers in Kenya, and other subsocieties who live on the land are shaped by the outside economic institutions to which they are linked, as well as by the local environment. As technology develops and sub-societies become more dependent upon the larger society, direct adaptation to the local environment decreases. The way of life, or subculture, of business executives of New York City, for example, has become dichotomized: in part it is derived from their highly specialized occupational role in a city and in part from their residence in suburbia, where the family and neighborhood culture differs from that of their profession and neither is closely adapted to the local environment. Even more remote from direct environmental impact are certain urban institutions found in contemporary Nevada, where the divorce, gambling, and entertainment complexes are linked to special aspects of the total national culture rather than to the semideserts of the Great Basin.

Some substantive applications

The concept of cultural ecology may be clarified by a number of substantive applications. These cases range from simple to complex societies, from the most elementary level of sociocultural integration to higher levels.

The precursors of man lacked culturally derived devices for killing game and for gathering, storing, and preparing food. They were food scavengers, and any food they collected was preserved without culturally prescribed techniques. Because animals can best forage a known habitat, they may have lived in groups or bands that were somewhat territorially delimited. Any social structuring was probably biologically oriented around the male’s dominance and protection of the group and the female’s role of caring for the young.

When culture provided more efficient techniques for survival, the essential human biological facts of sex, age, and kinship continued to affect the nature of society but were patterned in various ways by cultural ecological adaptations. Where the principal resource was seeds, roots, fruits, insects, small mammals, or shellfish, which occur sparsely, food gathering was necessarily competitive rather than cooperative because the yield decreases with the number of families that exploit the same site. If the local occurrence of principal resources varied each year, as it did among the Shoshoni Indians of Nevada, a multifamily society of permanent composition was not possible. Each Shoshoni family was linked with other families through intermarriage, through largely fortuitous association at a winter campsite, and through brief cooperation during antelope and rabbit hunts wherever there happened to be game. There were no bands of constant membership and no claims to territory or to resource areas. These families were not free wanderers, however, for any human society more effectively exploits a territory familiar to it.

The Chilean archipelago is completely unlike the Great Basin, but the erratic occurrence of shellfish, which was the principal food of the Alacaluf Indians, was functionally similar to Great Basin resources in preventing the formation of permanent social units larger than the nuclear family. That the nomadic, food-collecting family was the irreducible social unit in both cases is a function of the biological factors underlying marriage, division of labor, and child rearing. The independent nuclear family, however, is rarely reported ethnographically, and its occurrence in history is an empirical question rather than a matter of deduction from evolutionary principles.

Many societies fragment seasonally into family units of food collectors, but if the resources are sufficiently abundant and their whereabouts is predictable, the same families maintain contact with one another in loose groups that associate for supra-familial activities. Examples are the Indians of California, who subsisted on acorns, and the Indians of Lake Superior and the upper Paraguay River, who gathered wild rice. It appears that such groups tended to consist of extended families or lineages, although the evidence is not clear on this point.

Hunting generally requires cooperation, but there are various kinds of hunting societies, each reflecting special ecological adaptations. The Central Eskimo, whose population density was one person to 250 square miles or more, lived in small, some-what isolated family clusters. Since some cooperation was necessary in arctic hunting, nuclear families could not well have survived alone.

In societies that hunted large herds of bison, the concentrated resources supported bands of several hundred persons that exceeded the size of traceable lineages and consisted of many unrelated kin groups. The clans among certain Plains Indians were fictitious kinship extensions and an embellishment of the basic subsistence group. The Plains bands were more tightly integrated than the hunting bands of Canada, because game herds were larger, cooperative hunts were more highly developed, and warfare, especially after horses were acquired, became a major factor. By contrast, hunters of small and less-migratory game herds cooperated in bands of thirty to sixty persons who constituted a patrilineal lineage that controlled territorial resources, married outside the band, and brought wives to the husband’s band.

The basic social structure of these types of bands is essentially an interfamilial arrangement that is a necessary—or an optimum—organization for survival, depending on the conditions. A historical explanation that they originated elsewhere and were introduced to the areas through diffusion or migration is not credible, especially in the case of the patrilineal hunting bands that occurred in South Africa, Australia, Tasmania, southern California, and Tierra del Fuego. Each is a special kind of evolutionary development.

Societies of early farmers seem also to have been small, except where intercommunity warfare forced the people to concentrate in protected villages, and each probably consisted of lineages that tended to bud off as long as land was available. Although few analyses of the ecological adaptations of such farmers have been made, several types are suggested. In tropical rain forests such as the Amazon basin, where root crops were staples, slash-and-burn cultivation together with rapid soil exhaustion required the frequent shift of plots and sometimes villages. In addition, dietary needs made riverine protein foods of major importance, and canoe transportation facilitated the concentration of the population along rivers. In temperate areas, such as the United States, there was a marked contrast between the small villages of woodland farmers, who contended with prairie sods or forests, and the river-bottom farmers, as in the Mississippi system, whose fertile soils, once cleared of vegetation, supported large communities that were able to adopt the temple-mound complex from Mesoamerica.

In several temperate, and areas, early farming was restricted to flood plains or to the rainy high-lands. Increased population density in the valleys—made possible by irrigation in such cases as Peru —led to theocratic and militaristic states, whose power extended over wide areas, and to urban centers, which were the containers of civilization. It is not now clear to what extent trade, based upon increasingly specialized local production in adjoining areas, religious cults, and militaristic controls regimented the people to achieve maximum production and fill special statuses and roles.

Animal domestication entailed other kinds of ecological adaptations. Herds require more land for subsistence purposes than farming, have to be tended and moved about, and may be subject to theft. Claims to exclusive grazing areas were difficult to enforce until barbed wire was mass-produced in the last century. Cattle stealing and consequent intergroup hostility could therefore develop, as they did among many cattle breeders of east Africa. Free-roaming livestock, moreover, is a threat to crops, and until recently, farmers had to fence out the animals.

When societies became mounted, for example, the horse or camel nomads, other special adaptations occurred. They became more efficient hunters or herders and could transport foods a greater distance, thus extending their areas of exploitation and permitting larger social aggregates to remain together. They could also engage in predatory activities against one another and their settled neighbors. Mounted predators even created several ruling dynasties in the empires of the Middle East, China, and India.

After the agricultural revolution, the development of supracommunity state- or imperial-level institutions extended the areas of resource exploitation beyond those occupied by any of the subsocieties that were welded into the larger sociopolitical unit. Each local subsociety, although adapted in some measure to its terrain, became a specialized part of a new kind of whole to which it contributed different foods, raw materials, products, and even people—all for state purposes.

The industrial revolution enormously expanded the areas of exploitation through its improved transportation, mass manufacturing, communications, and economic and political controls. Its technology also gave importance to many latent resources. Modern nations and empires embrace highly diversified environments and draw upon areas beyond their political boundaries. Their technology may modify environments to meet their cultural needs, and, above all, any localized subsociety reacts to a complex set of state institutions, to a diversified social environment, and to a large number of goals other than survival. Although people necessarily live in particular places, members of highly industrialized nations must be viewed as increasingly nonlocalized to the extent that their behavior is determined by a great overlay or elaboration of cultural patterns that are only remotely connected with particular environments and are even minimizing some of the child-rearing and economically complementary functions of members of the nuclear family. It can be imagined that nuclear power, hydroponic and synthetic food production, and other technological developments might create wholly artificial environments, as in a permanent space station.

Julian H. Steward

[See alsoCulture, article onCultural adaptation; Evolution, articles onHuman EvolutionandCultural Evolution. Other relevant material may be found inHunting and gatheringandKinship.]

BIBLIOGRAPHY

Barth, Frederik 1956 Ecologic Relationships of Ethnic Groups in Swat, North Pakistan. American Anthropologist New Series 58:1079–1089.

Helm, June 1962 Ecological Approach in Anthropology. American Journal of Sociology 67:630–639. → Includes a review of the literature of cultural ecology.

Lattimore, Owen (1940) 1951 Inner Asian Frontiers of China. 2d ed. Irvington-on-Hudson, N.Y.: Capital.

Sahlins, Marshall D.; and Service, Elman R. (editors) 1960 Evolution and Culture. Ann Arbor: Univ. of Michigan Press.

Steward, Julian H. 1955 Theory of Culture Change: The Methodology of Multilinear Evolution. Urbana: Univ. of Illinois Press.

Washburn, Sherwood L. (editor) 1961 Social Life of Early Man. Viking Fund Publications in Anthropology, No. 31. Chicago: Aldine.

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Ecology

ECOLOGY.

Ecology is commonly seen as a lineal descendant of traditional natural history extending back to such classical figures as Aristotle, Theophrastus, and Pliny. Notable persons in this tradition include the Swedish botanist, Carl von Linné (Carolus Linnaeus; 17071778), who coined the phrase "economy of nature" in 1749. Gilbert White (17201793), a British cleric, made astute ecological observations of his parish in The Natural History and Antiquities of Selborne (1789). Charles Darwin's (18091882) work on evolution, published in 1859, was acknowledged as the stimulus for coinage, in 1866, of the term ecology. Henry David Thoreau (18171862), poet and naturalist, in 1860 anticipated a key phenomenon of ecology, and its name, in an article, "The Succession of Forest Trees." In 1864 George Perkins Marsh (18011882), an American diplomat, anticipated the environmental crisis that was widely recognized a century later, in his book Man and Nature in America, which described the deleterious impact of humans on the earth.

The ubiquity of such observations was explicit in the observations of the historian Clarence Glacken (1967), who said that ecological theory originated in the design argument of nature and that every thinker from the fifth century b.c.e. to the end of the eighteenth century had something to say about one or more of the ideas about environments. Even this extended attribution omits consideration of the detailed, and commonly insightful, traditional natural history knowledge of nonliterate aboriginal cultures the world around. The premier British ecologist Charles Elton dubbed ecology as scientific natural history in 1927. Increasing recognition of the extended history of ecological insights, anticipating a formal science of ecology, called up the apt term protoecologist (protoecology) in 1983.

Origins

The undisputed source of the term ecology is the eminent German zoologist, Ernst Haeckel (18341919), who coined it in 1866. It is well to revert to Haeckel's expanded definition in 1869 as translated by Allee and others:

By ecology we mean the body of knowledge concerning the economy of naturethe investigation of the total relations of the animal both to its inorganic and to its organic environment; including above all, its friendly and inimical relations with those animals and plants with which it comes directly or indirectly into contactin a word ecology is the study of all those complex interrelations referred to by Darwin as the conditions of the struggle for existence. (Allee, 1949)

Haeckel's definition illustrates the continuing tendency to distinguish animal and plant ecology. His emphasis on Darwinian evolution was echoed by numerous early ecologists, and later historians, and persists as evolutionary ecology.

The term ecology appeared sparingly in the scientific literature until the 1890s. In 1893 the president of the British Association for the Advancement of Science described ecology as a branch of biology coequal with morphology and physiology and by far the most attractive. Also in 1893, the Madison Botanical Congress, a large meeting of professional botanists, formally adopted the term ecology. A chair of ecological botany was established at Uppsala University in Sweden in 1897, and in 1904 Oscar Drude, a German plant geographer, described the sudden recognition of ecology in a talk at a Congress of Arts and Sciences at the Universal Exposition in St. Louis. Charles E. Bessey, a prominent American botanist, commented in 1902 that ecology had become a fada slight exaggeration, as the "fad" was largely confined in America to a few Midwestern universities and state agencies. The first named textbook of ecology was published in Danish by a Danish botanist, Johannes Eugenius Bülow Warming, in 1895; and the first doctorate in ecology in the United States was granted to Henry Chandler Cowles in 1898 by the University of Chicago for his work on the dunes of Lake Michigan.

Institutionalization

In Great Britain, plant ecology was initiated by botanical surveys done by members of hundreds of local natural history societies. Arthur S. Tansley, a pioneer British plant ecologist, suggested formation of the British Vegetation Committee, which brought the scientific leadership of the natural history societies together to study British vegetation.

Continental ecology was stimulated by the experience of European biologists in tropical colonies. Several of these, notably Drude, Andreas Franz Wilhelm Schimper, and Warming produced significant works of plant ecology that influenced British and American ecology.

Ecology in America was much influenced by early state-run natural history agencies, notably in the Midwest. Stephen A. Forbes was director of the Illinois State Laboratory of Natural History for many years, influencing numerous ecologists employed there as well as producing many of the most insightful ecological articles published before 1900. Edward A. Birge was director of the natural history division of the Wisconsin Geological and Natural History Survey and a pioneer in ecological studies of lakes. Bessey organized the Botanical Survey of Nebraska, which produced the major theorist of American plant ecology, Frederic E. Clements (18741945). American ecologists were influenced by federal surveys of the trans-Mississippi West. Ronald Tobey traced the development of plant ecology in the Midwestern grasslands, influenced by the developments of prairie agriculture and the Clements school of ecology.

Formal ecological societies were established in Britain in 1913 and in the United States in 1915. Academic ecology developed notably in Midwestern universities. In its century as a recognizable science, ecology acquired new and expanded significance. This is evident in the proliferation of journals of ecology. English language journals numbered four in 1940, increasing to twelve by 1980. The Institute for Scientific Information (ISI) included 102 journals under ecology in 2000, fifty of which had a clear reference to ecology in the title. The journal Ecology went from quarterly to monthly and the number of pages per year increased from approximately 750 in 1940 to about 2,250 in 2000. This proliferation of journals is a mixed blessing, making keeping up with the literature well nigh impossible at a time that ecologists are becoming involved in increasingly diverse enterprises.

Paradigms

Thomas Kuhn's concept of paradigm, introduced in The Structure of Scientific Revolutions (1962), changed the common view of how science progresses. A paradigm is a set of overarching principles and methods shared by a scientific community within which its adherents conduct "normal science." Science advances by changing its paradigms in revolutions.

The earliest putative ecological paradigm, the Clementsian organismic paradigm was a descendant of the traditional design or balance-of-nature concept, presuming a stable or equilibrium state as a norm. It is associated with Nebraska botanist Frederic E. Clements, who developed a concept of community or "association" as an organism or superorganism (1916). Clements envisioned the community as developing to converge on a "climax" or a stable endpoint determined by climate. This paradigm dominated early-twentieth-century ecology in America and was evident in major animal ecology references and general textbooks.

Some scholars describe a "revolution," or paradigm change, in ecology in the 1950s, with the revival and widespread acceptance of the "individualistic concept" of H. A. Gleason (1939). The shift from Clementsian ideas of equilibrium, homogeneity, and determinism to Gleasonian ideas of nonequilibrium, heterogeneity, and stochasticity greatly increased the difficulty of ecology and has dominated its recent development.

Another paradigm in ecology, population regulation, has a long natural-history tradition and was introduced into ecology in the 1920s, described by some as the "Golden Age" of theoretical mathematical ecology. Raymond Pearl resurrected the earlier "logistic curve" dN rN (K N ) and introduced it as a "law" of population growth. The equation includes r as the rate of population growth, K as the limiting maximum population, N as the number of individuals, and d signifying change. Subsequently the physicist Alfred J. Lotka, who joined Pearl's laboratory, and Vito Volterra, a mathematician, expanded the logistic to two species cases, especially competition. Mathematical population ecology persisted in the face of extended criticism and subsequent concerns about the basic equation. It remains to the present in much-elaborated forms with the assurance that populations at some scale are regulated but the mechanisms remain elusive.

Ecosystem

Early ecology recognized living (biotic) and nonliving (abiotic) aspects of nature but conventionally treated them separately. Environment acted on organisms, and organisms reacted on environment, according to Clements's familiar usage. The term ecosystem was coined by the British ecologist Arthur S. Tansley in 1935 to treat organisms and environment as a unit system. Tansley defined ecosystem as the whole system (in the sense of physics) including not only the organism complex, but also the whole complex of physical factors forming what we call the environment of the biomethe habitat factors in the widest sense.

Tansley's concept was particularly useful in aquatic ecology. It was used by Raymond Lindeman (1942) in a pioneer study of a lake ecosystem. Lindeman adapted the familiar food-chain, or trophic-structure concept of ecology and emphasized the energy and nutrient relations in a pyramid of production diminishing at higher levels and relating it to a succession of lakes. A major stimulus to ecosystem ecology was the influential textbook by Eugene Odum, Fundamentals of Ecology (1953).

The ecosystem concept was widely hailed as a new ecology in the 1970s, particularly when designated as "systems" ecology, which changed the emphasis in ecology from organisms to "ecoenergetics," the flux of energy in the ecosystem, along with the flow of chemicals through the ecosystem. Systems ecology flourished as ecology was turned into "big biology" by its first venture into heavily funded research in an International Biological Program (IBP) principally directed to formulating mathematical models of large-scale ecosystems. Another approach to ecosystems was the Hubbard Brook Program, begun in 1963, an intensive program of studies of a forested watershed, which examined nutrient flow and biomass accumulation. The program used computer simulations to model the complexity of natural ecosystems.

Opinions as to the merits of systems ecology in its philosophical and mathematical format vary, but the ecosystem persists as a major aspect of ecology and is frequently cited in the conservation, environmental, and even economic and political arenas. It is widely considered as producing ecosystem services, the valuable consequences of the multitudinous activities performed by biological systems to the great advantage of humans and often in spite of them. In 1988 "ecosystem" was designated "most important ecological concept" in a survey of members of the British Ecological Society, and it remains significant today.

Transecology

Ecology as a science developed largely in academia and in state, federal, and private conservation agencies until it came to the consciousness of the general public in the context of the environmental crisis of the 1970s in the guise of environmentalism. This is clearly evidenced in Mohan Wali's "Ecology Today: Beyond the Bounds of Science." Wali collected terms using "eco," "ecological," and "ecology" by professional ecologists and by nonecologists, and found that nonecologists use the term ecology as ideology, metaphor, allegory, myth, or gospel. Furthermore, while terms coined by professional ecologists numbered 276, those coined by nonecologists numbered over a thousand. Wali categorized the latter as General Ecologies (e.g., metaphysical ecology), Eco-business (e.g., eco-pornography), Eco-Health (e.g., gyn-eco-logical), Eco-types (e.g., eco-freak), Ecosport (e.g., ecogolf), Ecophilosopy (e.g., deep ecology), and Eco-religion (e.g., ecological sin). The problem for the unwary reader is that environmentalism is exceedingly diverse and for most of the users of these terms ecological science does not exist.

Another concern is the growth since around 1980 of environmental history, which takes a more encompassing view of environmental and ecological science and sometimes confounds it with ecologism, a loose construction of philosophy and ecology. Environmental history includes many works attending to the human environment with due cognizance of ecology and history. Other works, claiming to be histories of ecology, completely ignore the science and attribute diverse human and political foibles to ecology. One such cites no ecological science journals, but asserts that ecologists call for complete social and economic change. It links ecological ideas to Marxism, anarchism, Boy Scouts, anti-Semitism, fascism, and the German diseaseNazism.

The gross extension of the term ecology by nonscientists prompted the director of the public affairs office of the Ecological Society of America (ESA) to draft a letter to disclaim equating ecology and environmentalism, which, the letter said, diminished the credibility of ecology, and to urge members of the ESA to send it to offending publications such as the Wall Street Journal.

Complexity

Ecology has long been recognized as complex. One discouraged ecologist suggested, "ecology is not only more complex than we think, it is more complex than we can think." Ecology has assembled an extended body of information about the earth's ecosystems, but consensus on a general theoretical foundation remains elusive and some question its likelihood.

A notable effort to provide a theory of ecology was G. E. Hutchinson's formalization of the niche concept. A species niche is its response to all variables, biological and physical. Hutchinson influenced Robert MacArthur (1969), who pursued a theory of ecology predicated on competition that was widely accepted but subsequently questioned, as other factors such as predation and disturbance were shown to influence species relations.

An early consensus on "dynamic" ecology, focusing on the ubiquitous process of succession or change in ecosystems, regarded succession as "primary" if beginning on a previously unoccupied area, or "secondary" if following disturbance. This remains a factor in complex ecology. Disturbance by biotic or abiotic factors at varied intervals, intensities, or different area sizes is common and some disturbances (e.g., fire) are integrated into the development of an ecosystem, adding to its complexity.

One of the difficulties of assessing regularities in ecology is that ecological entities exist, and functions occur, at different scales of size, time, and rate, and the perspective of history is essential. Consideration of scale is widely evident in recent ecology, increasing its inherent complexity. The traditional ecological entities, population and community, are now expanded to metapopulations, populations of a species connected by migrations among them, and landscape ecology, an extended area including diverse communities. Taxonomic populations are also considered as guilds, species with similar functions apart from their systematic relations. At an extreme the biosphere, the whole-earth system, may be considered, and has been transformed into the GAIA hypothesis, treating the earth as an integrated superorganism transcending conventional ecology.

Another approach to ecological complexity is offered in hierarchy, an effort to deal with the scale problem in ecology. Ecological systems are considered as hierarchies in which processes at higher levels are predictable in some degree based on processes at lower levels. Some properties of the whole are said to be emergent and must be considered at the appropriate hierarchical level.

Evolutionary Ecology and Conservation Biology

Ecology was initially linked with Darwinian evolution. These ideas persist in evolutionary ecology, which explores the distribution and abundance of organisms and the control of their numbers, as in the interest in invasive species. Conservation biology is a following, overlapping discipline which focuses on the preservation of species incorporating genetic diversity. No feature of the earth is more striking than its enormous number of species. In ecological parlance number of species is called richness, number of species weighted by their proportionate abundance (number of individuals) is called diversity, and an amalgamation of all biological qualities is called biodiversity. In much ecological and common usage, however, biodiversity is simple number of species. Biodiversity has long charmed naturalists but in recent decades it has been considered a key ecological concept or paradigm and entered into environmental and political discourse as concerns grow about declining biodiversity. The emerging concern about loss of biodiversity has created urgency about its putative relation to stability and functioning of ecosystems.

Increasing recognition of the complexity of ecological systems called forth new mathematical considerations of fractals, chaos, and complexity. It led to the formation of a National Center for Ecological Analysis and Synthesis (NCEAS) on the West Coast of the United States. The NCEAS funds studies of large areas using meta-analysis of existing data and has had substantial impact on recent ecology.

Human Ecology

Early ecology had links with sociology. Patrick Geddes, British botanist-turned-sociologist, provided a classification of science in 1880 that included ecology in sociology. Much early plant ecology was called phytosociology, and a pioneer animal ecologist, Warder Clyde Allee, published Animal Aggregations: A Study in General Sociology in 1931. Early sociology at the University of Chicago was influenced by the ideas of the plant ecologist, Frederic E. Clements. An early animal ecologist, C. E. Adams, boldly anticipated convergence of animal and human ecology.

Both the British and American ecological societies were reluctant to engage in advocacy, and a president of the British Ecological Society said the society cannot have a corporate opinion on practical affairs lest its credibility over scientific aspects be damaged. Although many ecologists, notably Paul Sears in the United States and Arthur S. Tansley in Britain, were active proponents of environmental concerns and conservation, there was a common reluctance among ecologists and their societies to become involved in political affairs and public policy. Widespread recognition of the environmental crisis in the 1970s and the popularity of Earth Day emboldened many ecologists, their societies, and their journals to substantially change their position in respect to advocacy. In spite of reservations, ecologists and their organizations are increasingly becoming involved in matters of public policy if not politics.

One indication of increasing involvement of ecologists in public affairs is the Millennium Ecosystem Assessment, in which ecologists join with other scientists and social scientists from sixty-six countries to address the relations between ecosystems and human well-being on a global scale. These assessments (1) address the current and future capacity of ecosystems to provide services to humans, (2) determine human responses to changes in ecosystems, and (3) consider how assessments can be conducted at scales from villages, to river basins, countries, regions, and globally. It is clear that ecological science is becoming increasingly involved in the realm of public policy. Some ecologists have noted the failure of our educational system to train students to participate in science-policy discussions. Ecologists and economists, in order to change the status quo, are attempting to provide innovative courses.

An extremely difficult problem for contemporary ecologists is to respond to the suggestions that ecology extends beyond the bounds of science. This grandiose view of ecology is a contradiction of Ralph Waldo Emerson's assertion in "Nature" of an essence unchanged by human beings: "But his operations taken together are so insignificant, a little chipping, baking, patching, and washing, that in an impression so grand as that of the world on the human mind, they do not vary the result." Ecology confirms the fear that humans vary the result decisively.

See also Biology ; Environmental Ethics ; Environmental History ; Evolution ; Natural History ; Nature ; Wildlife .

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Robert P. McIntosh

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Ecology

Ecology


The term ecology is, etymologically, the logic of living creatures in their homes, a word suggestively related to ecumenical, with common roots in the Greek oikos, the inhabited world. Named in 1866 by German biologist Ernst Haeckel (18341919), ecology is a biological science like molecular biology or evolutionary theory, though often thought to be less mature. Ecosystems are complicated; experiments are difficult on these open systems, often large, that resist analysis. Ecology has nevertheless been thrust into the public arena, with the advent of the ecological crisis. Ecology has also become increasingly global, and still more complex, as when planetary carbon dioxide cycles affect climate change.

Ethics, policy, theology, and ecology

Ecology mixes with ethics, an ecological (or environmental) ethics urging that humans ought to find a lifestyle more respectful of, or harmonious with, nature. Ethics, which seeks a satisfactory fit for humans in their communities, has traditionally dwelt on justice, fairness, love, rights, or peace, settling disputes of right and wrong that arise among humans. Ethics now also concerns the troubled planet, its fauna, flora, species, and ecosystems.

American forester Aldo Leopold urged a new commandment in "The Land Ethic," a chapter in his 1968 book A Sand County Almanac : "A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise" (pp. 224225). Since the United Nations Conference on Environment and Development, held in 1992 in Rio de Janeiro, Brazil, the focus of environmental policy, often referred to as ecosystem management, has been a sustainable economy based on a sustainable biosphere.

Theologians have argued that religion needs to pay more attention to ecology, and perhaps also vice versa. Partly this is in response to allegations that Christians view humans as having God-given dominion over nature; they dominate nature and are responsible for the ecological crisis. An ecological theology may hope to find norms directly in ecological science, but often an ecological perspective rather freely borrows and adapts various goods thought to be found in ecology into human social affairs, such as wholeness, interrelatedness, balance, harmony, efficiency, embodiment, dynamism, naturalness, and sustainability.


Leading concepts in ecological science

Leading concepts in ecology involve ecosystems, succession of communities rejuvenated by disturbances, energy flow, niches and habitats, food chains and webs, carrying capacity, populations and survival rates, diversity, and stability. A main claim is that every organism is what it is where it is because its place is essential to its being; the "skinout" environment is as vital as the "skin-in" metabolisms. Early ecologists favored ideas such as homeostasis and equilibrium. Contemporary ecologists emphasize a greater role for contingency or even chaos. Others emphasize self-organizing systems (autopoiesis ), also an ancient idea: "The earth produces of itself [Greek: automatically]" (Luke 4:28). Some find that natural selection on the edge of chaos offers the greatest possibility for self-organization and survival in changing environments, often also passing over to self-transformation.

The stability of ecosystems is dynamic, not a frozen sameness, and may differ with particular systems and depend on the level of analysis. There are perennial processeswind, rain, soil, photosynthesis, competition, predation, symbiosis, trophic pyramids or food chains, and networks. Ecosystems may wander or be stable within bounds. When unusual disturbances come, ecosystems can be displaced beyond recovery of their former patterns. Then they settle into new equilibria. Ecosystems are always on historical trajectory, a dynamism of chaos and order entwined.

Michael E. Soulé and Gary Lease have demonstrated in their 1995 book, Reinventing Nature? Responses to Postmodern Deconstruction, that ecology as a science has not proven immune from postmodernist and deconstructionist claims that science in all its formsastrophysics to ecologyis a cultural construct of the Enlightenment West. Science is pragmatic and enables scientific cultures to get what they want out of nature; science is not descriptive of what nature is really like, apart from humans and their biases and preferences. According to this view, humans should make no pretensions to know what nature is like without them, but can choose what it is like to interact with nature, living harmoniously with it, which will result in a higher quality life. This fits well with a bioregional perspective. Environmental ethics is as much applied geography as it is pure ecology.

Some interpreters, such as Mark Sagoff, conclude that human environmental policy cannot be drawn from nature. Ecology, a piecemeal science in their estimation, can, at best, offer generalizations of regional or local scope, and supply various tools (such as eutrophication of lakes, keystone species, nutrient recycling, niches, succession) for whatever the particular circumstances at hand. Humans ought to step in with our management objectives and reshape the ecosystems we inhabit consonant with our cultural goals.

Other interpreters, such as David Pimentel, Laura Westra, and Reed Noss, argue that human life does and ought to include nature and culture entwined, humans as part of, rather than apart from, their ecosystems. Ecosystems are dependable life support systems. There is a kind of order that arises spontaneously and systematically when many self-actualizing units interactively pursue their own programs, each doing its own thing and forced into informed co-action with other units.

In culture, the logic of language or the integrated connections of the market are examples of such co-action. We legitimately respect cultural heritages, such as Judaism or Christianity, or democracy or science, none of which are centrally controlled processes, all of which mix elements of integrity and dependability with dynamic change, even surprise and unpredictability. We might wish for "integrity, stability, and beauty" in democracy or science, without denying the elements of pluralism, dynamism, contingency, and historical development.

Ecosystems, though likewise complex, open, and decentralized, are orderly and predictable enough to make ecological science possibleand also to make possible an ethics respecting these dynamic, creative, vital processes. The fauna and flora originally in place, independently of humans, will with high probability be species naturally selected for their adaptive fits, as evolutionary and ecological theory both teach. Misfits go extinct and unstable ecosystems collapse and are replaced by more stable or resilient ones (perhaps rejuvenated by chaos or upset by catastrophe).

This ecosystemic nature, once flourishing independently and for millennia continuing along with humans, has in the last one hundred years come under increasing jeopardyvariously described as a threat to ecosystem health, integrity, or quality.


Ecosystem management

Since the 1990s, emphasis has been ecosystem management. This approach appeals alike to scientists, who see the need for understanding ecosystems objectively and for applied technologies, and also to humanists, who find that humans are cultural animals who rebuild their environments and who desire benefits for people. The combined ecosystem/management policy promises to operate at system-wide levels, presumably to manage for indefinite sustainability, alike of ecosystems and their outputs. Such management connects with the idea of nature as "natural resources" at the same time that it has a "respect nature" dimension. Christian ethicists note that the secular word "manage" is a stand-in for the earlier theological word "steward." Adam was placed in the garden "to till and keep it" (Gen. 2:15).

Pristine natural systems no longer exist anywhere on Earth (the insecticide DDT has been found in penguins in Antarctica). Perhaps 95 percent of a landscape will be rebuilt for culture, considering lands plowed and grazed, forests managed, rivers dammed, and so on. Still, only about 25 percent of the land, in most nations, is under permanent agriculture; a large percentage is more or less rural, still with some processes of wild nature taking place. The twenty-first century promises an escalation of development that threatens both the sustainability of landscapes supporting culture as well as their intrinsic integrity.

Scientists and ethicists alike have traditionally divided their disciplines into realms of the "is" and the "ought." No study of nature can tell humans what ought to happen. This neat division has been challenged by ecologists and their philosophical and theological interpreters. The analysis here first distinguishes between interhuman ethics and environmental ethics. The claim that nature ought sometimes to be taken as norm within environmental ethics is not to be confused with a different claim, that nature teaches us how we ought to behave toward each other. Nature as moral tutor has always been, and remains, doubtful ethics. Compassion and charity, justice and honesty, are not virtues found in wild nature. There is no way to derive any of the familiar moral maxims from nature: "One ought to keep promises." "Do to others as you would have them do to you." "Do not cause needless suffering." No natural decalogue endorses the Ten Commandments.

But, continuing the analysis, there may be goods (values) in nature with which humans ought to conform. Animals, plants, and species, integrated into ecosystems, may embody values that, though nonmoral, count morally when moral agents encounter these. To grant that morality emerges in human beings out of nonmoral nature does not settle the question whether we, who are moral, should sometimes orient our conduct in accord with value there. Theologians will add that God bade Earth bring forth its swarming kinds and found this genesis very good. Palestine was a promised land; Earth is a promising planet, but only if its ecologies globally form a biosphere.

Environmental science can inform environmental ethics in subtle ways. Scientists describe the "order," "dynamic stability," and "diversity" in these biotic "communities." They describe "interdependence," or speak of "health" or "integrity," perhaps of their "resilience" or "efficiency." Scientists describe the "adapted fit" that organisms have in their niches. They describe an ecosystem as "flourishing," as "self-organizing." Strictly interpreted, these are only descriptive terms; and yet often they are already quasi-evaluative terms, perhaps not always so but often enough that by the time the descriptions of ecosystems are in, some values are already there. In this sense, ecology is rather like medical science, with therapeutic purpose, seeking such flourishing health.


Ecology in classical religions

Is there ecological wisdom in the classical religions? Religion and science have to be carefully delineated, each in its own domain. One makes a mistake to ask about technical ecology in the Bible (such as the Lotka-Volterra equations, dealing with population size and carrying capacity). But ecology is a science at native range. Residents on landscapes live immersed in their local ecology. At the pragmatic ranges of the sower who sows, waits for the seed to grow, and reaps the harvest, the Hebrews knew their landscape. Abraham and Lot, and later Jacob and Esau, dispersed their flocks and herds because "the land could not support both of them dwelling together" (Gen. 13:2-13; 36:6-8). There were too many sheep and goats eating the sparse grasses and shrubs of their semi-arid landscape, and these nomads recognized this. They were exceeding the carrying capacity, ecologists now say.

Here academic ecologists can learn a great deal from people indigenous to a landscape for centuries. Such ecological wisdom might be as readily found with the Arunta in Australia, or with the Navajos in the American Southwest on their landscapes. This would be indigenous wisdom rather than divine revelation. Such wisdom is often supported more by mythology than by science. Such wisdom is also frequently mixed with error and misunderstanding.

Christian (and other) ethicists can with considerable plausibility make the claim that neither conservation, nor a sustainable biosphere, nor sustainable development, nor any other harmony between humans and nature can be gained until persons learn to use the earth both justly and charitably. Those twin concepts are not found either in wild nature or in any science that studies nature. They must be grounded in some ethical authority, and this has classically been religious.

One needs human ecology, humane ecology, and this requires insight more into human nature than into wild nature. True, humans cannot know the right way to act if they are ignorant of the causal outcomes in the natural systems they modifyfor example, the carrying capacity of the Bethel-Ai rangeland in the hill country of Judaea. But there must be more. The Hebrews were convinced that they were given a blessing with a mandate. The land flows with milk and honey (assuming good land husbandry) if and only if there is obedience to Torah. Abraham said to Lot, "Let there be no strife between me and you, and between your herdsmen and my herdsmen" (Gen. 13:8), and they partitioned the common good equitably among themselves. The Hebrews also include the fauna within their covenant. "Behold I establish my covenant with you and your descendants after you, and with every living creature that is with you, the birds, the cattle, and every beast of the earth with you" (Gen. 9:5). In modern terms, the covenant was both ecumenical and ecological.

See also Animal Rights; Autopoiesis; Chaos Theory; Deep Ecology; Ecofeminism; Ecology, Ethics of; Ecology, Religious and Philosophical Aspects; Ecology, Science of; Ecotheology; Feminism and Science; Feminist Cosmology; Feminist Theology; Gaia Hypothesis; Womanist Theology


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gumbine, r. edward. "what is ecosystem management?" conservation biology 8 (1994): 27-38.


leopold, aldo. "the land ethic." in a sand county almanac. new york: oxford university press, 1968.


northcott, michael s. the environment and christian ethics. cambridge, uk: cambridge university press, 1996.

pimentel, david; westra, laura; and noss, reed f., eds. ecological integrity: integrating environment, conservation, and health. washington, d.c.: island press, 2000.

rolston, holmes, iii. "the bible and ecology." interpretation: journal of bible and theology 50 (1996): 1626.


sagoff, mark. "ethics, ecology, and the environment: integrating science and law." tennessee law review 56 (1988): 77-229.

soulé, michael e., and lease, gary, eds. reinventing nature? responses to postmodern deconstruction. washington, d.c.: island press, 1995.

holmes rolston, iii

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ROLSTON, HOLMES. "Ecology." Encyclopedia of Science and Religion. 2003. Encyclopedia.com. 1 Oct. 2016 <http://www.encyclopedia.com>.

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Ecology

Ecology

Ecology is a branch of science that studies the ways in which plants and animals interact with one another and with their surroundings. Ernst Haeckel, a German zoologist, invented the word "ecology" in 1869. It comes from the Greek words oikos, which means "household," and logos, which means "discourse" or "study." In The Riddle of the Universe, Haeckel applied the term oekologie to the "relation of the animal both to its organic as well as its inorganic environment."

For many years, ecology was an obscure branch of biology. In the late twentieth century, however, as environmentalism became a popular movement, ecology moved to the forefront of public opinion and also rose to prominence as a discipline. Some of the late twentieth and early twenty-first centuries' thorniest problemsexpanding populations, food scarcity, and environmental pollutionwere and are essentially problems of ecology.

Ecologists study organisms in various kinds of environments by looking for patterns of interaction. An organism's environment includes both other organisms and physical surroundings. It involves relationships among individuals within a population and among individuals of different populations. These interactions among individuals, among populations, and between organisms and their environment form ecological systems, or ecosystems.

Background

The origins of ecology lie in the natural history studies of the Greeks, particularly the philosopher and scientist Theophrastus (c. 372-d. 287 B. C. E. ), a contemporary and friend of the philosopher Aristotle. Theophrastus first described the interrelationships among organisms and between organisms and their nonliving environment.

In the early twentieth century, botanists in Europe and America began to study communities of plants that seemed to depend on each other. The Europeans looked at the composition, structure, and distribution of plant communities. The American botanists studied how plant communities changed over time. Animal ecology developed along separate lines until American zoologists began to study the interrelation of plant and animal communities as a whole.

Around the same time, biologists began to study the interaction of predators and prey, competition among species, and territoriality (especially in nesting birds). Austrian zoologist Konrad Lorenz studied instinctive and learned behavior (such as imprinting in birds). In 1920 German biologist August Thienemann proposed the concept of trophic levels and energy flow in ecosystems. English biologist Charles Sutherland Elton developed the concept of ecological niches and trophic pyramids. Nutrient cycling was studied in the 1940s and 1950s.

Modern ecology is now based on the idea of the ecosystem, a well-defined unit including the organisms and the nonliving environment in an identifiable region. Ecosystems have several structured interrelationships, and they function by maintaining a flow of energy and a cycling of materials through a series of processes such as the food chain. Ecosystems become more complex as they mature. Complex ecosystems are more stable. The organisms in an ecosystem occupy a niche, which includes their feeding and other behaviors as well as their physical position in the ecosystem.

Subdivisions of Ecology

Ecology is a multidisciplinary science. It draws from such disciplines as plant and animal biology, taxonomy, physiology, genetics, behavior, meteorology, pedology (the study of soils), geology, sociology, anthropology, physics, chemistry, and mathematics. Plant ecology centers on a descriptive study of the relationships of plants to other plants and their environment. Animal ecology studies population dynamics, distribution, behavior, and the interrelationships of animals and their environment. Plant ecology can often focus on just the plants. Because, however, animals depend on plants for food and shelter, animal ecology must include plant ecology. This is particularly true in areas of applied ecology, such as wildlife management.

Even within one of the subdivisions of ecology, ecologists usually concentrate on particular taxonomic groups, so that there are fields of insect ecology or the ecology of large mammals. Other ecologists may study particular ecosystems, such as marine environments or tropical rain forests. In applied ecology, basic ecological principles are applied to the management of plants and animals. Applied ecologists also study the effect of humans on their environment and on the survival of other species. Theoretical ecologists develop mathematical models and computer simulations of particular practical problems.

The study of an individual organism in relation to its environment is known as autecology. The study of groups of organisms in relation to each other and to their environment is called synecology. Autecology is closest to the original concept of ecology. When an individual organism is studied, it is possible to change variables in a controlled way. Thus, autecology is an inductive, empirical science. Synecology is more descriptive and deductive.

There are several other subdivisions of ecology. Ecological geography is the study of the geographic distribution of plants and animals. Population ecology is the study of population growth, mortality, birthrates, competition, and predator-prey relationships. Ecological genetics is the study of the genetics and ecology of local races and distinct species. Behavioral ecology is the study of the behavioral responses and social interactions of animals to their environment. Community ecology is the study of groups of organisms in a community. Systems ecology is the analysis and understanding of the structure and function of ecosystems by the use of applied mathematics, mathematical models, and computer programs. Finally, pale-oecology is the study of the ecology of fossil organisms.

Methods

Ecologists work with living systems possessing numerous variables, so the techniques used by the other sciences are not directly applicable. It is obvious that an individual organism removed from its environment cannot be studied in the laboratory with any hope of learning about its relation to its environment. Ecologists must deal with many different variables, only a few of which can be controlled. Some of the variables are probably not known. Consequently, ecological measurements may never be as accurate or precise as measurements made in physics or chemistry.

In spite of these problems, statistical procedures and computer modeling are providing improved understanding of population interactions and ecosystem function. Computer modeling is becoming increasingly important in applied ecology, especially in the management of natural resources and of agricultural problems that have an ecological basis.

Several different modern techniques have improved the ecologist's ability to study animals in relation to their environment. Various techniques of telemetry can be used. For example, animals can be fitted with a radio transmitter and a global positioning system to provide a constant flow of information including body temperature, respiration, and position. Radioisotopes can be used to track nutrient cycling in an ecosystem. Laboratory microcosms can be constructed using living and nonliving material from natural ecosystems and can be held under conditions similar to those found in the field.

Interdependence in Nature

Ecology emphasizes the interaction between every organism with other organisms and with the natural resources in the environment, such as air, soil, and water. Nineteenth-century British naturalist Charles Darwin emphasized this interdependence in On the Origin of Species : "It is interesting to contemplate a tangled bank, clothed with plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp Earth, and to reflect that these elaborately constructed forms, so different from each other, and so dependent upon each other in so complex a manner, have all been produced by laws acting around us."

The well-established principles of ecology make it clear that humans cannot regard themselves as separate from and independent of the natural world. Nature is not just a place a person visits during a drive in the country. Changes made to the environment affect all the organisms in it. When vehicles and factories emit pollutants, plants and animals (including humans) are affected. Water contaminated by waste cannot support a mature, complex, stable ecosystem. Even the vast oceans cannot escape pollution.

Applications of Ecology

Early in the twentieth century, southern Ohio suffered massive flooding. To prevent a repeat of the disaster, residents in the area constructed large earthen dams across river valleys to contain floodwater. The dam slopes, however, were unstable and washed away easily. Ecologists were called on to devise a system for stabilizing the earthen dams. They recommended planting the fast-growing grasses alfalfa and clover. This was followed by planting bromegrass and Japanese honeysuckle. The combination of plants quickly produced a strong turf that was able to hold the soil and gravel in place.

Migratory waterfowl declined during the early part of the twentieth century. To reverse the trend, ecologists used banding and other techniques to study the migratory patterns and feeding habits. They discovered that springtime hunting was adversely affecting the population, but the major problem was the loss of breeding areas and resting areas. Wetlands were being drained across the northern prairies. Some of these wetlands were not well-suited for crops while others had stored water. Draining had reduced breeding and resting sites and contributed to downstream flooding.

Not all species in an ecosystem are of equal importance. Some, known as keystone species, are critical. For example, alligators in the Florida Everglades dig deep holes to collect mud and grass for nests. These holes become permanent ponds that survive periods of drought and provide a reliable source of water for many other species in the ecosystem.

Famous Ecological Mistakes

Well-meaning conservation efforts often turn out to be disasters when ecological relationships are not taken into consideration. To increase the number of deer in Grand Canyon National Park and the Kaibab National Forest, most American mountain lions or cougars (Puma concolor ) were hunted out in the early part of the twentieth century. With no cougar to keep their numbers in check, the number of deer increased dramatically.

The deer stripped the forest of all undergrowth. They even ate the lower branches from the evergreen trees in the forest as high up as they could reach by standing on their hind legs. This gave the forest an unnatural appearance. With food supplies exhausted, the deer became feeble and many died of starvation. To reverse the damage, deer hunting was allowed and the remaining cougars were protected. The forest and the deer herd slowly recovered.

The Future

All over the world, human activity is dramatically altering natural environments. Natural communities are being replaced with human-made communities. These altered communities, however, still obey the same ecological principles. If these human-made communities are to thrive, people must recognize the ecological principles at work and strive for complex, diverse, and mature ecosystems. People must also recognize the interdependence of humans and the natural world and that human activities can adversely alter the natural balance.

see also Ecosystem; Habitat.

Elliot Richmond

Bibliography

Billington, Elizabeth T. Understanding Ecology. New York: F. Warne, 1971.

Curtis, Helena, and N. Sue Barnes. Biology, 5th ed. New York: Worth Publishing, 1989.

Darwin, Charles. On the Origin of Species. Danbury, CT: Grolier Enterprises, 1981.

Haeckel, Ernst. The Riddle of the Universe, trans. Joseph McCabe. New York: Buffalo Books, 1992.

Miller, G. Tyler, Jr. Living in the Environment, 6th ed. Belmont, CA: Wadsworth, 1990.

Pringle, Laurence. Lives at Stake: The Science and Politics of Environmental Health. New York: Macmillan Publishing Company, 1980.

Purves, William K., and Gordon H. Orians. Life: The Science of Biology. Sunderland, MA: Sinauer, 1987.

Sharpe, Grant William. Interpreting the Environment, 2nd ed. New York: Wiley, 1982.

Sharpe, Grant William, Clare W. Hendee, and Shirley W. Allen. Introduction to Forestry, 5th ed. New York: McGraw-Hill, 1986.

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ecology

ecology, study of the relationships of organisms to their physical environment and to one another. The study of an individual organism or a single species is termed autecology; the study of groups of organisms is called synecology.

The Ecosystem

Within the biosphere—the total expanse of water, land, and atmosphere able to sustain life—the basic ecological unit is the ecosystem. An ecosystem may be as small as a tidal pool or a rotting log or as large as an ocean or a continent-spanning forest. Each ecosystem consists of a community of plants and animals in an environment that supplies them with raw materials for life, i.e., chemical elements and water. The ecosystem is delimited by the climate, altitude, water and soil characteristics, and other physical conditions of the environment.

The Food Web and Other Vital Cycles

The energy necessary for all life processes reaches the earth in the form of sunlight. By photosynthesis green plants convert the light energy into chemical energy, and carbon dioxide and water are transformed into sugar and stored in the plant. Herbivorous animals acquire some of the stored energy by eating the plants; those animals in turn serve as food for, and so pass the energy to, predatory animals. Such sequences, called food chains, overlap at many points, forming so-called food webs. For example, insects are food for reptiles, which are food for hawks. But hawks also feed directly on insects and on other birds that feed on insects, while some reptiles prey on birds. Since a severe loss of the original energy occurs with each transfer from species to species, the ecologist views the food (energy) structure as a pyramid: Each level supports a smaller number and mass of organisms. Thus in a year's time it would take millions of plants weighing tons to feed the several steer weighing a few tons that could support one or two people. The ecological conclusion is that if human beings would eat more plants and fewer animals, food resources would stretch much further. Once the energy for life is spent, it cannot be replenished except by the further exposure of green plants to sunlight.

The chemical materials extracted from the environment and elaborated into living tissue by plants and animals are continually recycled within the ecosystem by such processes as photosynthesis, respiration, nitrogen fixation, and nitrification. These natural processes of withdrawing and returning materials are variously called the carbon cycle, the oxygen cycle, and the nitrogen cycle. Water is also cycled. Evaporation from lakes and oceans forms clouds; the clouds release rain that is taken up by the soil, absorbed by plants, and passed on to feeding animals—which also drink directly from pools and lakes that catch the rain. The water in plant and animal wastes and dead tissue then evaporates and can be recycled. Interference with these vital cycles by disturbance of the environment—for example, by pollution of the air and water—may disrupt the workings of the entire ecosystem. The cycles are facilitated when an ecosystem has a sufficient biological diversity of species to fill its so-called ecological niches, the different functional sites in the environment where organisms can act as producers of energy, consumers of energy, or decomposers of wastes. Such diversity tends to make a community stable and self-perpetuating.

Climax Communities

A climax community is one that has reached the stable stage. When extensive and well defined, the climax community is called a biome. Examples are tundra, grassland, desert, and the deciduous, coniferous, and tropical rain forests. Stability is attained through a process known as succession, whereby relatively simple communities are replaced by those more complex. Thus, on a lakefront, grass may invade a build-up of sand. Humus formed by the grass then gives root to oaks and pines and lesser vegetation, which displaces the grass and forms a further altered humus. That soil eventually nourishes maple and beech trees, which gradually crowd out the pines and oaks and form a climax community. In addition to trees, each successive community harbors many other life forms, with the greatest diversity populating the climax community.

Similar ecological zonings occur among marine flora and fauna, dependent on such environmental factors as bottom composition, availability of light, and degree of salinity. In other respects, the capture by aquatic plants of solar energy and inorganic materials, as well as their transfer through food chains and cycling by means of microorganisms, parallels those processes on land.

The early 20th-century belief that the climax community could endure indefinitely is now rejected because climatic stability cannot be assumed over long periods of time. In addition nonclimatic factors, such as soil limitation, can influence the rate of development. It is clear that stable climax communities in most areas can coexist with human pressures on the ecosystem, such as deforestation, grazing, and urbanization. Polyclimax theories stress that plant development does not follow predictable outlines and that the evolution of ecosystems is subject to many variables.

Bibliography

See E. P. Odum, Fundamentals of Ecology (3d ed. 1971); R. L. Smith, ed., The Ecology of Man: An Ecosystem Approach (1971); P. A. Colinvaux, Introduction to Ecology (1973); R. M. Darnell, Ecology and Man (1973); T. C. Emmel, An Introduction to Ecology and Population Biology (1973); D. B. Sutton and N. P. Harman, Ecology: Selected Concepts (1973); K. E. F. Watt, Principles of Environmental Science (1973); D. Worster, Nature's Economy (1977); R. Brewer, The Science of Ecology (1988).

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Ecology

Ecology

Ecology is the study of the relationships of organisms with their living and nonliving environment. No organism exists entirely independently of other living and nonliving things around it. A cactus in the middle of the desert, for example, draws nourishment from the air and from the ground. It depends on sunlight for energy needed to grow. The cactus may be home to birds, lizards, and microscopic animals. Even relationships that seem to be stark and simple as that of the cactus with its surroundings involve complex ties that form the subject matter of ecology.

Ecological relationships are always reciprocal (shared) relationships. In the example of the cactus, elements of the physical environment, such as air and water, have an impact on the cactus. But, at the same time, the cactus affects its physical surroundings. For example, it releases water vapor and oxygen into the air, changing the composition of the surrounding atmosphere.

Living relationships are also reciprocal relationships. The cactus may provide food, shelter, and shade for animals that live in or near it. But animals also contribute to the life of the cactus, by distributing its seeds, for example.

The subject matter of ecology

Although mostly a biological subject, ecology also draws upon other sciences, including chemistry, physics, geology, earth science, mathematics, computer science, and others. As the impact of humans on the environment increases, the subject matter of ecology expands. Ecologists may be asked to decide whether a desert should be left in its natural state or opened to certain forms of human development. As a result, ecologists increasingly find themselves confronted with social, economic, political, and other nonscientific issues. Because it draws upon knowledge and information from so many disciplines, ecology is a highly interdisciplinary field.

Words to Know

Biosphere: The sum total of all life-forms on Earth and the interaction among those life-forms.

Community: A collection of populations that interacts with each other in the same geographic region.

Interdisciplinary: A field of investigation that draws upon knowledge from many disciplines.

Photosynthesis: The sequence of chemical reactions by which green plants convert carbon dioxide and water into starch and oxygen, using energy provided from sunlight.

That ecologists focus on biological subjects is apparent from the fact that most ecologists spend much of their time engaged in studies of organisms. Examples of common themes of ecological research include: (1) how organisms adapt to their environment, (2) how the numbers and distribution patterns of organisms in an area are influenced by environmental factors, and (3) changes in the number of organisms in a area over time and how the environment influenced these changes.

Energy and productivity

One of the major areas of interest in ecology is the flow of energy through an ecosystem. (An ecosystem, or ecological system, is a collection of communities of organisms and the environment in which they live.) The source of almost all life on Earth is energy from the Sun, in the form of sunlight. That energy is captured by green plants in the process known as photosynthesis. When herbivorous (plant-eating) animals consume plants, they incorporate solar energy stored in those plants into their own bodies. Later, carnivorous (meat-eating) animals consume the herbivores, and solar energy is passed another step through the living world. Eventually, plants and animals die and are consumed by organisms known as decomposers (or detritivores; pronounced de-TRY-tuh-vorz). The complex of ecological relationships among all of the plants, animals, and decomposers is known as a food web.

The ultimate goal of ecology

The ultimate goal of ecology is to understand the nature of environmental influences on individual organisms, their populations and communities, on landscapes and, ultimately, the biosphere (all life on Earth). If ecologists can achieve an understanding of these relationships, they will be able to contribute to the development of systems by which humans will be able to wisely use ecological resources, such as forests, agricultural soils, and hunted animals such as deer and fish. This goal is a very important one because humans are, after all, completely reliant on ecological goods and services as their only source of life support.

[See also Biome; Biosphere; Ecosystem; Environmental ethics ]

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ecology

ecology Ecology is the scientific study of the interactions that determine the territorial distribution and abundance of organisms. The term was first used scientifically in 1869 by the German biologist Haekel in a study of plant ecology. Darwin's theory of the evolution of species inspired the development of ecology. According to Darwin, evolution is driven by reproduction and inheritance on the one hand, and by natural selection on the other. Natural selection eliminates species least able to survive the struggle for existence because they fail to adapt to changing environments. An important aspect of the latter—alongside factors such as climate and topography—is the presence of other species competing for limited territory or other resources. However, unfettered competition is normally limited, as species are also interdependent, related to each other symbiotically in a ‘web of life’, the result of successful adaptation to each other and to the natural environment (although certain species are dominant). This equilibrium is temporarily upset when newly dominant species emerge. The concepts of invasion, domination, and succession have been used to analyse the stages of this process.

Ecological perspectives have had considerable influence well beyond the biological sciences, for example in medical epidemiology, the psychology of architecture and design, and human geography. Late-twentieth-century concern about the impact of human activities on the environment has resulted in new social and political ecology movements and the growing salience of so-called green issues generally—all of these being topics for sociological research. However, the main influence of ecological concepts on sociological theory occurred between the 1920s and the 1940s in the United States, initially through the development of urban ecology by Chicago sociologists. The ecological perspective was subsequently applied more widely and the terms human or social ecology have often been used in this context. Some human ecologists were critical of the emphasis placed by the early Chicago sociologists on competition between human groups for territorial advantage (based on a rather unidimensional view of Darwinian natural selection) and suggested a broader remit for study, namely, the form and development of different types of human community (not necessarily spatially bounded), with particular reference to the ways in which they adapt to their environments through co-operative and competitive social relationships.

The relationship between ecological theories and sociology has been limited, and is stronger in North America than in Europe, still influencing, for example, some American urban and rural sociology. Indeed, it has been claimed that the ecological perspective transcends any individual social science, as it deals with processes which underlie all these disciplines. Recent sociological theory is scarcely influenced by its particular use of the biological analogy, although the concern with adaption, interdependence, and equilibrium also characterizes structural-functional sociology.See also DARWINISM; ECOLOGICAL COMPETITION; ECOLOGICAL INVASION; ECOLOGICAL SUCCESSION; INVASION-SUCCESSION MODEL; NATURAL AREA.

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Ecology

Ecology

Ecology is the study of how plants, animals, and other organisms interact with each other and with their environment, or "home." The word "ecology" comes from the Greek word oikos, which means "home." Ecology is also the study of the abundance and distribution of organisms. An ecologist, for example, might try to find out why a species of frog that used to be common is now rare, or why fir trees are rare in a dry pine forest but common in a moister habitat.

Ecologists study living organisms in different ways. One might study a population, a group of individuals that can interbreed with each other; a community, the many species that inhabit an area; or an ecosystem, a community of organisms along with the nonliving parts of their environment. The nonliving parts, which ecologists refer to as "abiotic" components, include air, water, soil, and weather.

Population ecologists study what makes populations go extinct, what regulates populations at intermediate densities, and what makes populations increase in size. A major cause of extinction is loss of habitat or the break up of habitat into patches. Community ecologists study the relationships among different species; for instance, how groups of predators and prey affect one another.


Founded in 1915, the Ecological Society of America is a non-profit organization of scientists that aims to promote ecological science, increase the resources available for the conduct of ecological science, and ensure the proper use of ecological science in environmental decisionmaking by improving communication between the ecological community and policy-makers.


The study of ecosystems means examining how all the parts fit together. An example of this is carbon in the atmosphere, which is taken up by plants during photosynthesis. Animals eat the plants, or eat the animals that ate the plants, and then exhale the carbon as carbon dioxide. The carbon cycles through networks of organisms, the atmosphere, and the Earth itself. Another example are shellfish, which make their shells from carbon. These shells drop to the bottom of the ocean to form thick sediments. Millions of years later, geological processes lift them up as mountains. The study of ecosystems is truly the study of life on the Earth.

see also Community; Ecology, History of; Ecological Research, Long-Term; Ecosystem; Plankton; Population Dynamics; Theoretical Ecology

Jennie Dusheck

Bibliography

Ecological Society of America. <http://esa.sdsc.edu/>.

Molles, Manuel C. Ecology, Concepts and Applications. 3rd ed. Boston: McGraw-Hill, 1999.

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ecology

ecology Biological study of relationships of organisms to their environment and to one another. The term was coined (1866) by Ernst Haeckel. Ecologists study populations (groups of individual organisms), communities (different organisms sharing the same environment), or ecosystems (a community and its physical environment). The maximum population that can be sustained by a particular environment's resources is called its carrying capacity. Within the biosphere, natural cycles (carbon cycle, hydrological cycle, nitrogen cycle and oxygen cycle) are assisted when the biological diversity of species fills ecological niches. This diversity produces climax communities, and an extensive climax community is called a biome. Applied ecology is the practical management of natural resources and environments.

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Ecology

Ecology

Ecology is the study of organisms and their relationship to the environment. The field was born in 1866 when German biologist and philosopher Ernst Haeckel (1834-1919) created the precursor to the modern word "ecology" by combining the Greek words oikos, meaning "home," and logos, meaning "study," to create the word "oecology." Haeckel used this word to summarize the concept of natural selection and the struggle for existence that English naturalist Charles Darwin (1809-1882) had outlined in his ground-breaking work on evolution, On the Origin of Species.

In the early twentieth century, even before the modern word ecology had been invented, interest in what is now called plant ecology began to grow. American botanist and ecologist Frederic Clements (1874-1945) and others conceived the idea that plants would develop in an orderly succession of formations from pioneer species to a well-defined and stable group of species called a climax community. Clements believed that plant formations were like intact organisms with a predictable pattern of birth, growth, and death. Clements's ideas were quickly challenged. American botanist and plant ecologist Henry Allan Gleason (1882-1975) argued that the distribution of plants was the result of random events in the environment that combine to form an individual and possibly unique plant community. Partially in response to the rigid classification developed by Clements, British ecologist Arthur Tansley (1871-1955) in 1935 coined the word ecosystem to describe what he called a quasi organism. Tansley's concept of the ecosystem as a single physical unit containing both organisms and their environment is essentially the same to this day.

Plant Ecology

The concept of ecology may seem fairly simple, but in practice it is very complex. As the field developed, scientists soon found themselves unable to master the entire discipline, and even within the already narrowed field of plant ecology, subfields rapidly developed. Today, there are six major fields of plant ecology:

  • Population ecologists study the relationship of individuals of one species in a given area to each other and to their environment. A population ecologist might be interested in what environmental conditions limit the northern range of black spruce trees in the Canadian boreal forest.
  • Community ecologists study the distribution and abundance of groups of species and how they are influenced by biological and environmental factors. Community ecologists have studied the major associations of deciduous forests in the eastern United States and how the environment, in terms of climate, soils, and topography, controls this association.
  • Ecosystem ecologists study energy and matter transport through organisms (see below). This includes studies of how nutrients, energy, and biomass are cycled through ecosystems. The study area for ecosystem ecologists depends on the defined ecosystem and can vary from small ponds or tiny forest plots to the entire globe. Ecosystem ecologists are today conducting politically and economically important research on the global carbon cycle.
  • Physiological ecologists study how environmental factors such as light, temperature, and humidity influence the biochemical functioning of individual organisms. Physiological ecology and ecosystem ecology are very complementary; often ecologists have a hard time deciding if they are one or the other.
  • Landscape ecologists study the biological and environmental factors that influence vegetation patterns observed in a landscape. Landscape ecologists may study the factors controlling the boundary between forests and grasslands.
  • Human ecologists study the influence of human activity, both currently and historically, in controlling the distribution and abundance of organisms. Human ecology also examines the social and cultural factors that control the way humans exploit, alter, and manage the environment. Most ecological research has focused too much on natural ecosystems while pretending that humans do not exist. For example, an ecologist coming across the deciduous forest in New England today might assume that the forest always looked that way. In fact, the present pattern of forest distribution is the result of extensive human modifications by Native Americans, European colonists, and foresters.

Food Webs

In the 1950s the idea of the food web began to emerge in ecosystem ecology. Food webs and the related topics of trophic levels and energy flow are some of the most critical ecological concepts because they illustrate the connections between organisms that are required to maintain healthy ecosystems.

Energy flow refers to the way that energy is transformed through a food chain containing a series of levels, including plants, consumers, predators, and decomposers. Each step in the food chain is called a trophic level (from the Greek word trophikos, meaning "nutrition"). Primary producers (plants, algae, and photosynthetic microbes) are the base of food chains and are the lowest trophic level. They transform energy from the Sun into sugars. Primary producers thus make their own food and are called autotrophs ; all other organisms ultimately use the energy produced by autotrophs and are called heterotrophs . At the next trophic level, primary consumers (herbivores ) eat some of the sugars produced by primary producers. Secondary consumers (predators) consume primary consumers and other secondary consumers. Decomposers such as earthworms, maggots, fungi, and bacteria break down the carcasses of dead primary and secondary consumers and un-eaten primary producers.

The amount of living material (biomass) and energy in food chains has a specific ordering between trophic levels. Consider a simple example of an African savanna ecosystem consisting of trees and grasses (primary producers), gazelles and zebras (primary consumers), and lions (secondary consumers). If we check the trophic levels, we will find that primary producers have the most biomass, followed by primary consumers, and then secondary consumers. The amount of energy at each trophic level will follow the same pattern. This ordering of trophic levels forms a pyramid with primary producers at the bottom followed by primary consumers in the middle and secondary consumers on the top. More energy is required at the lower levels of the pyramid because during the transfer between trophic levels energy is lost through heat and waste products.

Most ecosystems on land follow the pyramid pattern. In the ocean or other aquatic systems, the opposite pattern may at times be true: at any one time, the biomass and energy of the primary and secondary consumers may exceed those of the primary producers. This is because photosynthetic algae have a very short life span. Even though they may have a low biomass at any one time, their biomass measured over the whole year will be larger than the biomass of the consumers.

The pyramid concept of trophic levels is consistent across many terrestrial ecosystems, but in reality the interactions among organisms are much more complex than in the African example. A food web is a network of connected food chains and is used to describe community interactions. Consider a food chain in the Rocky Mountains. Small aquatic plants are primary consumers in a stream ecosystem. Arthropods and fly larvae feed on the plants and are in turn consumed by trout. Bears eat the trout. But each part of this food chain is also connected to other food chains. Birds feed on plants and fish, while bears will also feed on roots, tubers, and rodents. The complete network of these connections forms an ecosystem food web.

Food webs are usually more complex in ecosystems that have not been disturbed for a long time. Food webs in coral reefs and tropical forests have thousands of highly specific food chains. In these ecosystems, many animals are adapted to feed on one or only a few food sources. Disruption of a few elements can have serious consequences for the entire food web. By contrast, the tundra ecosystem was covered in ice until about 8000 B. C. E. In this ecosystem, there has been less time to evolve complex and specific food webs. Species tend to be interchangeable. Removal of one species or interaction does not usually seriously damage the health of the entire food web.

Advances in Ecological Research

Advances in the ecology field happen frequently. The following four examples from the late twentieth century show the breadth of the field as well as the need for ecologists to reach across disciplines.

Leaf Design.

There are thousands of kinds of leaves, ranging from tiny evergreen needles to enormous tropical leaves more than fifty centimeters wide. In spite of great diversity, leaves follow a strict set of rules. Long-lived leaves, such as ten-year-old spruce needles, have a low nitrogen concentration (this means low rates of photosynthesis) and thick, dense leaves that are highly resistant to herbivores. Short-lived leaves, such as blades of grass lasting only weeks or a few months, have a very high nitrogen concentration and thin, light leaves. Almost all leaves follow this pattern and are either long-lived with low rates of photosynthesis and a high resistance to herbivores, or short-lived with high rates of photosynthesis and herbivory. Intermediate levels of all three traits are also possible. This finding, drawn from hundreds of plants all over the world, helps to explain the appearance and physiology of leaves and is one of the most important ecological findings in recent years.

Ecosystem Carbon Storage.

Many ecologists wanted to know the total amount of carbon released or stored by ecosystems, but until recently, there was no way to accomplish this. Experimental meteorologists devised a method called eddy covariance to measure the amount of carbon dioxide entering or leaving an ecosystem. By adding up these numbers over the course of a day or year, ecologists can now determine if an ecosystem is storing more carbon through photosynthesis or releasing more carbon through respiration. They found that many forests are storing carbon, but that some, especially in the boreal forest, can release carbon due to slight changes in climate. This research is critical for understanding the carbon cycle and the potential for global climate change.

Impacts of Rising Carbon Dioxide.

Scientists have published hundreds of research articles on the response of plants in greenhouses or special enclosures to increased carbon dioxide (CO2) levels, but there had been no way to test the response of real ecosystems. Scientists at the Brookhaven National Laboratories developed the Free-Air CO2 Enrichment (FACE) system. FACE uses a circle of instruments that pump CO2 into the atmosphere to artificially increase the CO2 levels of a real ecosystem. The increased CO2 increased photosynthesis, supporting earlier greenhouse results showing that plants would respond to higher CO2.

Ecology and Natural Resource Management

Beginning in the early twentieth century, ecological theories began to be seriously considered in natural resource management. Unfortunately, results were not always good. In an application of Darwinian theory, U.S. Forest Service managers believed that by clearing old, unproductive forests and replacing them with young, vigorously growing forests they would increase forest health and productivity. Instead, throughout much of the dry inland Rocky Mountains foresters created dense thickets of fire- and insect-susceptible forests. Today, guided by modern ecological research, this policy is changing to include a focus on returning fire to the ecosystem and managing forests for the health of the entire ecosystem, not just human economics. This is called ecosystem management. In large part, it was the legal, political, and social pressures exerted by nonscientist citizen activists that caused this shift in natural resource management policy.

Ecological research has been used in many other ways to improve natural resource management. Due to ecological research showing the catastrophic effects of cyanide on river ecosystems, cyanide heap leach gold mining is now being restricted. Ecologists showed how DDT, an insecticide common in much of the world during the mid-1900s, was transferred through trophic levels until it reached toxic levels in secondary consumers. Millions of birds were killed before DDT was banned in most of the world. Ecologists found that large, interconnected populations of grizzly bears were required to ensure long-term breeding success of the species and natural resource managers are now designing migration corridors to link the remaining bear populations.

In short, there are very few areas of natural resource management that are unaffected by ecology. Critical developments include:

  • ecosystem management for recreation, water quality, and protection of endangered species, not just economic development
  • an increased awareness of public health consequences
  • attempts to reintroduce elements of ecosystems that had been removed by humans
  • consideration of the complex and sometimes fragile nature of food webs before making resource management decisions.

Role of Computer Modeling

Politicians, scientists, and natural resource managers are becoming more and more interested in complicated ecological questions over large regions. For example, the economically critical and politically sensitive issue of the global carbon cycle is being answered mostly by ecosystem ecologists. Clearly, it is impossible to measure the entire Earth. Another solution is required, and computer models have filled this need.

A computer model is a system of mathematical equations that ecologists use to represent the ecosystem or problem being assessed. Models do not duplicate reality; they are simplified systems that attempt to represent the most critical processes while ignoring all the details that are impossible to measure or extremely difficult to represent with mathematics. Ecological models range from detailed treatments of gas exchange for a single leaf to carbon cycle models for the entire globe. Developing a good model of the global carbon cycle is like trying to make the simplest possible car: you strip away everything you possibly can until the car stops running. Just as in a car you could probably remove the windows and the passenger seat but not the transmission or the engine, in a global carbon model, you can probably ignore individual species and hour-to-hour weather changes but not vegetation and climate.

Computer models have an extremely significant role in ecology. In fact, because so much in ecology is so difficult to measure except for the smallest plot, models are common in every field of ecology. Models are highly useful for testing scenarios. What will happen to stream flow and fish populations if 50 percent of trees are cut in a watershed? How will elk populations change if wolves are reintroduced to a particular area? How will the introduction of small controlled fires affect the potential for larger, highly destructive fires? How will forests respond if carbon dioxide levels double in the next one hundred years? These are just some of the ways that ecological models are used.

see also Biome; Carbon Cycle; Clements, Frederic; Ecology, Energy Flow; Ecology, Fire; Ecology, History of; Global Warming; Interactions, Plant-Fungal; Interactions, Plant-Insect; Interactions, Plant-Plant; Interactions, Plant-Vertebrate; Plant Community Processes; Savanna; Tundra.

Michael A. White

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Colinvaux, Paul. Ecology 2. New York: John Wiley & Sons, 1993.

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Kohm, Kathryn A., and Jerry F. Franklin, eds. Creating a Forestry for the 21st Century: The Science of Ecosystem Management. Washington, DC: Island Press, 1997.

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ecology

ecology The study of the interrelationships between organisms and their natural environment, both living and nonliving. For this purpose, ecologists study organisms in the context of the populations and communities in which they can be grouped and the ecosystems of which they form a part. The study of ecological interactions provides important information on the nature and mechanisms of evolutionary change. Advances made in ecology over the last 25 years have led to increased concern about the effects of human activities on the environment (notably the effects of pollution), which has resulted in a greater awareness of the importance of conservation.

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ecology

e·col·o·gy / iˈkäləjē/ • n. 1. the branch of biology that deals with the relations of organisms to one another and to their physical surroundings. ∎  (also human ecology) the study of the interaction of people with their environment. 2. (also Ecology) the political movement that seeks to protect the environment, esp. from pollution. DERIVATIVES: ec·o·log·i·cal / ˌekəˈläjikəl; ˌēkə-/ adj. ec·o·log·i·cal·ly adv. e·col·o·gist / -jist/ n.

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ecology

ecology The scientific study of the interrelationships among organisms and between organisms, and all aspects, living and non-living, of their environment. The German zoologist Ernst Heinrich Haeckel (1834–1919) is usually credited with having coined the word ‘ecology’ in 1866, deriving it from the Greek oikos, meaning ‘house’ or ‘dwelling-place’.

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ecology

ecology The scientific study of the interrelationships among organisms and between organisms, and between them and all aspects, living and non-living, of their environment. Ernst Heinrich Haeckel (1834–1919) is usually credited with having coined the word ‘ecology’ in 1869, deriving it from the Greek oikos, meaning ‘house’ or ‘dwelling place’.

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ecology

ecology The scientific study of the interrelationships among organisms and between organisms, and all aspects, living and non-living, of their environment. Ernst Heinrich Haeckel is usually credited with having coined the word ‘ecology’ in 1869 (as the German word Ökologie, from the Greek oikos, ‘house’, and logos, ‘discourse’).

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MICHAEL ALLABY. "ecology." A Dictionary of Zoology. 1999. Encyclopedia.com. 1 Oct. 2016 <http://www.encyclopedia.com>.

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ecology

ecology The scientific study of the interrelationships among organisms and between organisms, and between them and all aspects, living and non-living, of their environment. Ernst HeinrichHaeckel is usually credited with having coined the word ‘ecology’ in 1866.

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ecology

ecology (biol.) study of the relations of plants and animals with their habitat. XIX. — G. ökologie, f. Gr. oîkos house (used for ‘habitat’); see WICK2, -LOGY.

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ecology

ecology (bionomics) (ee-kol-ŏji) n. the study of the relationships between humans, plants and animals, and the environment.
ecological adj. —ecologist n.

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Ecology

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Ecology

Ecology: see ANIMALS.

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ecology

ecology •haji • algae • Angie •argy-bargy, Panaji •edgy, sedgy, solfeggi, veggie, wedgie •cagey, stagy •mangy, rangy •Fiji, gee-gee, squeegee •Murrumbidgee, ridgy, squidgy •dingy, fringy, mingy, stingy, whingy •cabbagy • prodigy • effigy • villagey •porridgy • strategy • cottagey •dodgy, podgy, splodgy, stodgy •pedagogy •Georgie, orgy •ogee • Fuji •bhaji, budgie, pudgy, sludgy, smudgy •bulgy •bungee, grungy, gungy, scungy, spongy •allergy, analogy, genealogy, hypallage, metallurgy, mineralogy, tetralogy •elegy •antilogy, trilogy •aetiology (US etiology), amphibology, anthology, anthropology, apology, archaeology (US archeology), astrology, biology, campanology, cardiology, chronology, climatology, cosmology, craniology, criminology, dermatology, ecology, embryology, entomology, epidemiology, etymology, geology, gynaecology (US gynecology), haematology (US hematology), hagiology, horology, hydrology, iconology, ideology, immunology, iridology, kidology, meteorology, methodology, musicology, mythology, necrology, neurology, numerology, oncology, ontology, ophthalmology, ornithology, parasitology, pathology, pharmacology, phraseology, phrenology, physiology, psychology, radiology, reflexology, scatology, Scientology, seismology, semiology, sociology, symbology, tautology, technology, terminology, theology, topology, toxicology, urology, zoology • eulogy • energy • synergy • apogee • liturgy • lethargy •burgee, clergy •zymurgy • dramaturgy

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"ecology." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 1 Oct. 2016 <http://www.encyclopedia.com>.

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