Protected areas are parks, ecological reserves, and other tracts set aside from intense development to conserve their natural ecological values. These areas protect the habitat of endangered species, threatened ecological communities, or representative examples of widespread ecosystems, referred to as indigenous (native) biodiversity values. Some protected areas are intended to conserve places of scenic beauty, or sites of historical or cultural importance. Most protected areas are terrestrial, but since the late 1980s, increasing attention has been paid to marine areas as well. Human activities that do not severely threaten the ecological values being conserved take place in some protected areas. Examples of theses activities include, research, education, ecotourism, spiritual activities, even hunting, fishing, and timber harvesting.
The biodiversity of Earth is in a fragile state. An incredible number of plant and animalspecies are becoming endangered, while many others have recently become extinct. These devastating ecological changes result almost entirely from human activities. The primary cause of widespread endangerment and extinction of biodiversity is the conversion of natural ecosystems into city, industry, and agricultural land. The harvesting of species and ecosystems as natural resources, such as forestry, fisheries, and hunting, is also harmful. Global environmental changes may also prove devastating to biodiversity. Increasing concentrations of greenhouse gases in the atmosphere, resulting in a gradually warming climate, is an example of this type of change.
One way of mitigating the biodiversity crisis is to establish protected areas of land and water. In these areas, native species and natural ecosystems are maintained without exposure to severely threatening human influences. Protected areas are essential to conserve the habitat of endangered species, and ensure the existence of rare ecosystems.
The International Union for the Conservation of Nature (IUCN) recognizes six categories of protected areas:
- Category 1 is the highest level of protection. This category includes scientific reserves and wilderness areas. They are managed to maintain native species and natural ecosystems, although use for research may be allowed. These types of highly protected areas are often relatively small, and present in most U.S. states.
- Category 2 includes national parks and equivalent reserves. These are managed primarily to protect species and ecosystems, although outdoor recreation and ecotourism is usually permitted. Two famous protected areas in the United States are Yellowstone and Yosemite National Parks.
- Category 3 includes national monuments and geological phenomena. Sites of aesthetic or cultural importance are also included.
- Category 4 includes habitat- and species-management areas, intended to conserve conditions required in support of productive populations of hunted species.
- Category 5 includes protected landscapes and seascapes. It is intended to sustain recreational use of such areas by humans, while also accommodating the needs of most wild species and ecosystems.
- Category 6 includes managed-resource protected areas, which are primarily managed to yield a sustainable harvest of renewable natural resources (such as timber), while also accommodating the needs of native species and ecosystems.
In 1997, there were about 10,400 protected areas covering a total of 2.1 billion acres (841 million hectares) worldwide (IUCN categories 1-5; World Resources Institute, 1998). Of this total area, about 4,500 sites, amounting to 1.2 billion acres (499 million ha), were fully conserved (IUCN categories 1-3) and could be considered true protected areas.
Ideally, the numbers and sizes of protected areas should be designed to sustain all native species and natural ecosystems occurring within a jurisdiction (a municipality, state, or entire country). This should include terrestrial, freshwater, and marine species and ecosystems, and the goal should be long-term protection. To ensure there is adequate representation of all elements of indigenous biodiversity within a system of protected areas, the kinds of native species and ecosystems in the jurisdiction must be known. This knowledge makes it possible to accommodate all elements of ecological heritage within a comprehensive system plan for a network of protected areas.
The above criteria are for an ideal system of protected areas. No country has yet managed to designate a comprehensive system of protected areas, in which all native species and natural ecosystems are represented and sustained. An enormous amount of political will is required to set aside the amounts of land and water necessary to fully protect the native biodiversity of any region. Countries that have made the most progress in this regard are relatively wealthy, such as Australia, Canada, New Zealand, and the United States. But even in these cases, the systems of protected areas are highly incomplete.
Most of the existing protected areas are relatively small, or threatened by degrading influences occurring within their boundaries or surrounding area. It is doubtful the smaller protected areas will be able to sustain their present ecological values over the longer term, in the face of disturbances and other environmental changes. In addition, scientists are often unfamiliar with the ecological needs of endangered species and ecosystems, making proper management difficult.
The design of protected areas is an important field of research in conservation biology. The essential questions involve criteria for the size, shape, and positioning of protected areas to optimize their ability to protect biodiversity, while using funding as efficiently as possible. Conservation biologists recommend that protected areas be as large and numerous as possible. Other design aspects, however, are more controversial. Controversy over the design of protected areas involves the following key elements:
- Is it preferable to have one large reserve, or a number of smaller ones of the same total area? Conservation biologists identify this question with the acronym SLOSS, which stands for: single large, or several small. According to ecological theory, populations in larger protected areas should have a smaller risk of extinction, compared to those in smaller reserves. However, if there are populations in several different reserves, the redundancy might prevent extinction in the event of a catastrophic loss in one reserve.
- Reserves can also be designed to have less edge (or ecotone) habitat. This refers to transitions between ecosystem types, such as that between a forest and a field. Edge habitat is often penetrated by invasive species and predators, which can become important problems in some protected areas. In addition, many species require interior habitat for breeding; meaning they are intolerant of ecotones. Larger protected areas have proportionately more interior habitat, as do simple-shaped ones (a circle has the smallest ratio of edge to area).
- For many ecological functions to operate well, there must be connections among habitats. This is particularly true of the dispersal of plants and animals. This need can be accommodated if protected areas are linked by corridors of suitable habitat, or if they are clumped close together. However, corridors might also serve as conduits for invasive species and diseases.
The conservation of biodiversity in protected areas also requires the monitoring of key ecological values, such as the populations of endangered species and the health of natural ecosystems. It may also be necessary to conduct research to determine the appropriate kinds of management required, and to then implement that management. Management includes actions such as patrolling to prevent poaching of timber and animals, altering habitats to maintain their suitability for threatened species, and captive breeding and release of endangered species.
Most protected areas are connected to surrounding areas by movement of animals, the flow of water and nutrients, or by climatic influences. Protected areas are not isolated, rather, they are a part of a larger ecosystem. The protected area plus its immediate surrounding area, is referred to as a greater protected area, which is co-managed to sustain populations of native species and natural communities. In addition, the surrounding area may be managed to supply resources, such as timber, hunted animals, and mined minerals.
Eagles, P.F.J., and S.F. McCool. Tourism in National Parks and Protected Areas: Planning and Management. Wallingford, U.K.: CABI Publishing, 2004.
Managing Protected Areas: A Global Guide, edited by Michael Lockwood, et al. London: Earthscan, 2006.
Partnerships for Protection: New Strategies for Planning and Management for Protected Areas, edited by Sue Stolton and Nigel Dudley. London: Earthscan, 1999.