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Ecological Monitoring

Ecological Monitoring

Monitoring, research and indicators

Monitoring addresses important issues

State-of-the-environment reporting and social action


The goal of ecological monitoring is to provide information about changes to the structure and function of ecosystems for use in impact assessment, education, environmental protection, or management. Environmental monitoring involves repeated measurements of inorganic, ecological, social, and/or economic variables in ecosytems in order to detect changes over time and to predicting future change.

Human activities have the potential to impact both environmental and the ecological sensitive areas. To effectively understand these impacts, it is important to understand their dimensions and dynamics. Ecological monitoring identifies any damage an ecosystem may be experiencing. It assesses how affected ecosystems change over time. Finally, it seeks to determine what the best means of prevention or mitigation might be. Ecological monitoring relies on long term programs of monitoring and research to provide information about the the causes and consequences of ecological changes.

Humans and their societies have always been sustained by environmental resources. For almost all of human history the most important resources have been potentially renewable, ecological resources. Especially important have been animals that could be hunted, edible plants that could be gathered, and the productivity of managed, agricultural ecosystems. More recently, humans have increasingly relied on the use of nonrenewable resources that are extracted from the environment, especially fossil fuels and metals.

However, the ability of ecosystems to sustain humans is becoming increasingly degraded. This is largely because of the negative consequences of two, interacting factors: (1) the increase in size of the human population, which numbered more than 6.5 billion in 2006, and (2) the increase in the quantities of resources used by humans, especially people living in developed countries, such as those of North America and Western Europe.

Ecological degradation is important for two reasons: (1) it represents a decrease in the ability of Earths ecosystems to sustain humans and their activities, and (2) it represents damage to other species and to natural ecosystems. The role of ecological monitoring is to detect ecological degradation, to understand its causes and consequences, and to find ways to effectively deal with the problems.

Monitoring, research and indicators

The success of ecological monitoring depends on: (1) the astute choice of appropriate ecological indicators to measure and (2) successful data collection. Choosing appropriate indicators can be difficult because in many situations there are a diverse array of potential characteristics that may be quantified. Successful data collection can be expensive and difficult, and often requires measurements over long time periods in order to correctly identify trends.

Monitoring programs are often be integrated with scientific research. The ultimate goals of an integrated program of ecological monitoring and research are to: (1) detect or forecast changes to the ecology of a region, and (2) determine the causes and implications of those changes.

Monitoring involves the repeated measurement of ecological indicators. Changes in indicators are determined through comparison with their historical values, or with a reference or control situation. Often, monitoring may detect changes in indicators, but the causes of those changes may not be understood. To discover the causes of those changes, scientific research has to be undertaken.

For example, monitoring of forests might detect a widespread decline of a species of tree. In many cases the cause species decline are not known, but they may be related to an environmental stress, such as air pollution, insect damage, climate change, or forestry. They may also be related to ecological factors, such as changes in primary productivity, amounts of living and dead biomass, age-class structure of trees and other species, nutrient cycling, soilerosion, or overall biodiversity. In an ecological monitoring program designed to study the health of a tree species, well-chosen indicators would be measured to determine the cause of species decline.

Indicators used in ecological monitoring can be classified according to a simple model of stressorexposure-response:

(1) Stressors cause environmental and ecological changes, and are associated with physical, chemical, and biological threats to environmental quality. Stressors and their indicators are often related to human activities, for example, emissions of sulfur dioxide and other air pollutants, concentrations of secondary pollutants such as ozone, the use of pesticides and other toxic substances, or occurrences of disturbances associated with construction, forestry, or agriculture. Natural stressors include wildfires, hurricanes, volcanic eruptions, and climate change.

(2) Exposure indicators are relevant to changes in the intensity of stressors, or to doses accumulated over time. Exposure indicators might only measure the presence of a stressor, or they might be quantitative and reflect the actual intensity or extent of stressors. For example, appropriate exposure indicators of ozone in air might be the concentration of that toxic gas, while disturbance could be indicated by the annual extent of habitat change caused by forest fires, agriculture, clear-cutting, or urbanization.

(3) Response indicators reflect ecological changes that are caused by exposure to stressors. Response indicators can include changes in the health of organisms, populations, communities, or ecosystems.

Indicators can also take the form of composite indices, which integrate complex information. For reporting to the public, it is desirable to have composite indices of environmental quality, because complex changes can be presented in a simple manner. However, the design of composite indices of environmental quality or ecological integrity are controversial, because of difficulties in selecting component variables and weighing their relative importance.

Monitoring addresses important issues

Environmental monitoring programs commonly address issues related to changes in: (1) environmental stressors, for example, the chemical quality of water, air, and soil, and activities related to agriculture, forestry, and construction; (2) the abundance and productivity of economically important, ecological resources such as agricultural products, forests, and hunted fish, mammals, and birds; and (3) ecological values that are not economic resources but are nevertheless important, such as rare and endangered species and natural communities.

Monitoring programs must be capable of detecting changes in all of the above, and of predicting future change. In North America, this function is carried out fairly well for categories (1) and (2), because these deal with economically important activities or resources. However, there are some important deficiencies in the monitoring of non-economic ecological values. As a result, significant environmental issues involving ecological change cannot be effectively addressed by society, because there is insufficient monitoring, research, and understanding. A few examples are:

(1) Is a widespread decline of populations of migratory songbirds occurring in North America? If so, is this damage being caused by stressors occurring in their wintering habitat in Central and South America? Or are changes in the breeding habitat in North America important? Or both? What are the causes of these changes, and how can society manage the stressors that are responsible?

(2) What is the scope of the global biodiversity crisis that is now occurring? Which species are affected, where, and why? How are these species important to the integrity of the biosphere, and to the welfare of humans? Most of the extinctions are occurring because of losses of tropical forest, but how are people of richer countries connected to the biodiversity-depleting stressors in poorer countries?

(3) What are the biological and ecological risks of increased exposures to ultraviolet radiation, possibly caused by the depletion of stratospheric ozone resulting from emissions of chlorofluorocarbons by humans?

(4) What constitutes an acceptable exposure to potentially toxic chemicals? Some toxins, such as metals, occur naturally in the environment. Are there thresholds of exposure beyond which human emissions should not increase the concentrations of these chemicals? Is any increase acceptable for non-natural toxins, such as synthetic pesticides, TCDD, PCBs, and radionuclides?

These are just a small sample of the important ecological problems that have to be addressed by ecological monitoring, research, and understanding. To provide the information and knowledge needed to deal with environmental problems, many countries are now designing programs for longer-term monitoring and research in ecology and environmental science.

In the United States, for example, the Environmental Monitoring and Assessment Program (EMAP) of the Environmental Protection Agency is intended to provide information on ecological changes across large areas, by monitoring indicators at a large number of sites spread across the country. Another program has been established by the National Science Foundation and involves a network of Long-Term Ecological Research (LTER) sites (26 in 2006).

State-of-the-environment reporting and social action

The information from programs of environmental monitoring and research must be reported to government administrators, politicians, corporations, and individuals. This information can influence the attitudes of these groups, and thereby affect environmental quality. Decision makers in government and industry need to understand the causes and consequences of environmental damage, and the costs and benefits of alternative ways of dealing with those changes. Their decisions are based on the balance of the perceived costs associated with the environmental damage, and the shorter-term, usually economic benefits of the activity that is causing the degradation.

Information from environmental monitoring and research is interpreted and reported to the public by the media, educational institutions, state-of-the-environment reporting by governments, and by nongovernmental organizations. All of these sources of information help to improve ecological literacy, which eventually influences public attitudes. Informed opinions about the environment will then influence individual choices of lifestyle, which has important, mostly indirect effects on environmental quality. Public opinion also influences politicians and government administrators to more effectively manage and protect ecosystems.

See also Ecosystem; Indicator species; Population, human; Stress, ecological.



Elzinga, Caryl L., et al. Monitoring Plant and Animal Populations. Malden, MA: Blackwell Science Inc., 2001.

Spellerberg, Ian F. and Martin W. Holdgate. Monitoring Ecological Change. Malden, MA: Blackwell Science Inc., 2005.


US Environmental Protection Agency. Environmental Monitoring and Assessment Program (EMAP). September 14th, 2006. <> (accessed October 15, 2006).

National Science Foundation. The US Long Term Ecological Research Network. 2006. <> (accessed October 15, 2006).

Bill Freedman

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Environmental Monitoring

Environmental monitoring

Environmental monitoring detects changes in the health of an ecosystem and indicates whether conditions are improving, stable, or deteriorating. This quality, too large to gauge as a whole, is assessed by measuring indicators, which represent more complex characteristics. The concentration of sulfur dioxide , for example, is an indicator that reflects the presence of other air pollutants. The abundance of a predator indicates the health of the larger environment . Other indicators include metabolism , population, community, and landscape. All changes are compared to an ideal, pristine ecosystem. The SER (stressor-exposure-response) model, a simple but widely used tool in environmental monitoring, classifies indicators as one of three related types:

  • Stressors, which are agents of change associated with physical, chemical, or biological constraints on environmental processes and integrity. Many stressors are caused by humans, such as air pollution , the use of pesticides and other toxic substances, or habitat change caused by forest clearing. Stressors can also be natural processes, such as wildfire , hurricanes, volcanoes, and climate change.
  • Exposure indicators, which link a stressor's intensity at any point in time to the cumulative dose received. Concentrations or accumulations of toxic substances are exposure indicators; so are clear-cutting and urbanization.
  • Response indicators, which shows how organisms, communities, processes, or ecosystems react when exposed to a stressor. These include changes in physiology, productivity, or mortality , as well as changes in species diversity within communities and in rates of nutrient cycling.

The SER model is useful because it links ecological change with exposure to environmental stress . Its effectiveness is limited, however. The model is a simple one, so it cannot be used for complex environmental situations. Even with smaller-scale problems, the connections between stressor, exposure, and response are not understood in many cases, and additional research is required.

Environmental monitoring programs are usually one of two types, extensive or intensive. Extensive monitoring occurs at permanent, widely spaced locations, sometimes using remote-sensing techniques. It provides an overview of changes in the ecological character of the landscape, often detecting regional trends. It measures the effects of human activities like farming, forestry, mining, and urbanization. Information from extensive monitoring is often collected by the government to determine such variables as water and air quality , to calculate allowable forest harvests, set bag limits for hunting and fishing, and establish the production of agricultural commodities.

Extensive monitoring usually measures stressors (such as emissions) or exposure indicators (concentration of pollutants in the air). Response indicators, if measured at all in these programs, almost always have some economic importance (damage to forest or agricultural crops). Distinct species or ecological processes do not have economic value and are not usually assessed in extensive-monitoring programs, even though these are the most relevant indicators of ecological integrity .

Intensive monitoring is used for detailed studies of structural and functional ecology . Unlike extensive monitoring, a relatively small number of sites provide information on stressors such as climate change and acid rain . Intensive monitoring is also used to conduct experiments in which stressors are manipulated and the responses studied, for example by acidifying or fertilizing lakes, or by conducting forestry over an entire watershed . This research, aimed at understanding the dynamics of ecosystems, helps develop ecological models that distinguish between natural and anthropogenic change.

Support for ecological monitoring of either kind has been weak, although more countries are beginning programs and establishing networks between monitoring sites. The United States has founded the Long-Term Ecological Research (LTER) network to study extensive ecosystem function, but little effort is directed toward understanding environmental change. The Environmental Monitoring and Assessment Program (EMAP) of the Environmental Protection Agency (EPA) studies intensive environmental change, but its activities are not integrated with LTER. In comparison, an ecological-monitoring network being designed by the government of Canada to study changes in the environment will integrate both extensive and intensive monitoring.

Communication between the two types of monitoring is important. Intensive information provides a deeper understanding of the meaning of extensive-monitoring indicators. For example, it is much easier to measure decreases in surface-water pH and alkalinity caused by acid rain than to monitor resulting changes in fish or other biological variables. These criteria can, however, be measured at intensive-monitoring sites, and their relationships to pH and alkalinity used to predict effects on fish and other fauna at extensive sites where only pH and alkalinity are monitored.

The ultimate goal of environmental monitoring is to measure, anticipate, and prevent the deterioration of ecological integrity. Healthy ecosystems are necessary for healthy societies and sustainable economic systems. Environmental monitoring programs can accomplish these goals, but they are expensive and require a substantial commitment by government. Much has yet to be accomplished.

[Bill Freedman and Cynthia Staicer ]



Freedman, B., C. Staicer, and N. Shackell. A Framework for a National Ecological-Monitoring Program for Canada. Ottawa: Environment Canada, 1992.


Franklin, J. F., C. S. Bledsoe, and J. T. Callahan. "Contributions of the Long-term Ecological Research Program." Bioscience 40 (1990): 509524.

Odum, E. P. "Trends Expected in Stressed Ecosystems." Bioscience 35 (1985): 419422.

Schindler, D. W. "Experimental Perturbations of Whole Lakes as Tests of Hypotheses Concerning Ecosystem Structure and Function." Oikos 57 (1990): 2541.

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