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Habitat Restoration

Habitat Restoration

The human race is in a precarious situation as a result of its exploitation of natural ecosystems . Humans must balance their current resource needs with the future land-use needs of wildlife and people. As such, it makes sense to care for habitats by reducing damage to them and restoring those that have been damaged. With careful planning, healthy habitats can be maintained for people as well as wildlife. The goal of habitat restoration is to identify disturbed habitats and restore the native flora and fauna that occur there to ensure the continued use of the land by both wildlife and humans.

Historical Background

Habitat restoration is a recent concept in human history. It began in the early 1900s with the recognition that protective measures must be given to wildlife to ensure its survival. A historical landmark is the Pittman-Robertson Act of 1937, which funds wildlife research and habitat restoration. This act was financed by a tax on sporting arms and ammunition. Hunting and fishing continue to provide revenue for wildlife research today. The Endangered Species Act, which was enacted in 1973, provides protection for wildlife, and organizations such as the National Audubon Society and the Nature Conservancy play important roles in habitat acquisition, restoration, and protection.

The Importance of Habitat Restoration

Habitat restoration seeks to repair areas that have been subjected to habitat destruction. Habitat destruction is one of the primary factors involved in causing species of plants and animals to be threatened with extinction. Activities important to maintaining civilization such as agriculture, development, mining, oil drilling, logging, and road building alter natural ecosystems. Habitat destruction can be obvious, such as clearing old-growth forests for timber and draining wetland areas to use the land for raising crops, but it can also be more insidious. Habitat destruction alters the normal abundance and distribution of species in the habitat. All of these types of disturbances require restoration if the land is to be viable in the future.

Habitat restoration is important for reasons varying from aesthetic and recreational to economic and pragmatic. Wild lands and wilderness have aesthetic properties that help to maintain mental health for millions of people every year. Restoring habitats can facilitate the return of wildlife to disturbed areas for its own sake or for the sake of recreational activities such as hiking, hunting, fishing, and bird-watching. Returning disturbed land to health can add to existing habitats, making them larger and thereby helping to protect species against the dangers of small population sizes. Restoring areas that have been damaged through human use can allow an area to be used again for another purpose. For example, areas that have been mined are often acidic and have high heavy-metal concentrations, making it difficult for native plants to be reestablished in the area. Restoring these areas can help to make the habitat healthy again. In the future, the same land could be available for timber harvesting or recreational parkland, or as a wildlife refuge. Healthy forests and riparian zones help control erosion and maintain good water quality in streams and lakes. Reforestation and restoring damaged riparian zones helps ensure clean drinking water, control floods, and maintain healthy fish and amphibian populations.

Restoration Methods

Habitat restoration is accomplished through management, protection, and reestablishment of plants by returning abiotic factors (e.g., soil chemistry, water content, disturbance) and biotic factors (e.g., species composition, interactions among species) to historical levels. Properly restored ecosystems demonstrate the historical species diversity of the area instead of one species in monoculture. Reestablishing plants provides a food source for animals and thus helps restore animal populations.

In reestablishing plants, soil conditions are very important, because they will determine what will grow and where. Soil moisture and mineral content, aeration, and presence of microorganisms are important factors that must be considered. Most plants are associated with fungi called mycorrhizal fungi (also called mycorrhizae), an association that is integral to a plant's system for absorbing nutrients and water. These fungi associate with the roots of the plants and help in gathering and transporting nutrients and minerals to the plant. These symbiotic relationships are often species specific, and this makes them essential in reestablishing native plants. Without their symbiotic fungi, many native plants are weak competitors with nonnative species. Therefore, it is often necessary to introduce the correct mycorrhizal fungus into the plants through inoculation. In addition, members of the soil community such as bacteria and earthworms, which create healthy soil food chains and aid in soil aeration, respectively, may also be added to disturbed habitat. Knowledge of the appropriate fungus, bacteria, and worm species for each habitat is necessary. The organisms must also be available for inoculation. In severely disturbed or unique habitats, knowledge of the proper organisms may not exist, or the organisms themselves may unavailable, resulting in an inability to restore the habitat properly.

Situations where the native flora is intact but is not functioning normally because of human activities require management and protection to accomplish restoration. In some cases removal of dense underbrush and thinning young trees is necessary to restore a habitat to health. Another method to restore habitats is controlled fire. In habitats historically subjected to fire, some species require occasional fires to set seed and to thin out young trees that are otherwise stunted as a result of competing for limited resources. Without periodic fire the densely growing trees will be stressed and subject to pest outbreaks that do more damage than the fire.

Drainage patterns and soil water content can be altered to facilitate natural reestablishment of native vegetation. Large earthmoving machines can alter drainage patterns while smaller tools can help shape water movement in the soil. Wetlands can be restored by flooding drained areas. Once the water is in place, revegetation can proceed with species appropriate for the area. Waterfowl and wetland bird species may assist in seed dispersal from nearby wetlands.

Stream habitats may also be restored through appropriate management. For example, flooding can be problematic for inhabitants of small streams, particularly the eggs and young of salmonid fishes in the northwestern United States. Large-scale timber harvesting can add silt to streams, and with fewer trees, heavy rains reach streams more rapidly and with more force. This can lead to the covering of fish eggs by silt, which suffocates them, and the removal of young fish and eggs from protected areas into the main stream channel, which results in increased rates of predation. Restoration projects aimed at redirecting the streambed to slow floods and the placement of in-stream obstructions such as large rocks and logs can prevent these problems while creating spawning habitat at the same time. Maintenance of adequate riparian zones can eliminate the need for such restoration measures by reducing the impact of floods.

Restoration Difficulties

Habitat restoration is difficult and problems are often encountered. Exotic and invasive species, problematic soils, and variation in populations can make habitat restoration a challenge. Exotic or invasive species may outcompete natives for nutrients in the early stages of restoration. Inoculation with mycorrhizal fungi can alleviate this by helping the natives absorb nutrients, but often the problem persists. This is because habitat destruction releases nutrients into the soil that may be used by the exotic species. Sometimes, fertilizers are added with the intent of helping the native species grow, but the excess nutrients encourage exotic species to grow instead. One solution to this problem is to limit the nutrients available to the exotic species by removing excess nutrients. Removing excess nutrients, not adding them, allows the native species to persist with assistance from their mycorrhizal associates, while not giving the invasive species the nutrients they require to compete with the natives. Subtle differences in moisture, altitude, slope aspect, and other variables over species' ranges may make some restoration projects difficult. Individuals of a species from one area may be difficult to establish in another area because they may be adapted to local conditions.

A caveat of habitat restoration is that to do it properly one must have a thorough understanding of the ecological requirements, both abiotic and biotic , for the species involved. Also necessary for proper restoration is an understanding of historical land-use patterns coupled with the knowledge of what locally similar, pristine habitat looks like. This knowledge can be difficult to collect and can require substantial investment of money, time, and energy. The result, however, is a better understanding of ecosystems, and with this, one can make educated decisions about how to restore habitats. Habitat restoration is important for the health of the planet and the human race, and continued research on ecosystems and restoration techniques is vital.

Restoration need not only take place in rural settings. Suburban gardens of native plants encourage beneficial native insects and bird species that can act as biocontrol for pests. Gardening with native species also conserves water, increases awareness and appreciation of regional diversity, and can create small islands of habitat for local species to use as gateways to larger habitat areas. This type of habitat restoration can be done individually on a local level and can turn the tide from wildlife in a sea of people to people in a sea of wildlife.

see also Ecosystem; Environment; Habitat; Habitat Loss.

Ryan I. Hill

Bibliography

Berger, John J., ed. Environmental Restoration: Science and Strategies for Restoring the Earth. Washington, D.C.: Island Press, 1990.

Decamps, H. "River Margins and Environmental Change." Ecological Applications 3(1993):441-445.

Ferris-Kaan, Richard, ed. The Ecology of Woodland Creation. London: Wiley, 1995.

Peterjohn, W. T., and D. L. Correll. "Nutrient Dynamics in an Agricultural Watershed: Observations on the Role of a Riparian Forest." Ecology 65 (1984): 1,466-1,475.

Prasse, Rüdiger, and Reinhard Bornkamm. "Effect of Microbiotic Soil Surface Crusts on Emergence of Vascular Plants." Plant Ecology 150 (2000):65-75.

Smith, Robert Leo, and Thomas M. Smith. Elements of Ecology, 4th ed. San Francisco:Benjamin/Cummings, 1998.

Urbanska, Krystyna M., Nigel R. Webb, and Peter J. Edwards, eds. Restoration Ecology and Sustainable Development. Cambridge, U.K.: Cambridge University Press, 1997.

Whisenant, Steven G. Repairing Damaged Wildlands: A Process-Oriented, Landscape-Scale Approach. Cambridge, U.K.: Cambridge University Press, 1999.

Yaalon, Dan H., and Richard W. Arnold. "Attitudes Toward Soils and Their Societal Relevance: Then and Now." Soil Science 165, no. 1 (2000):5-12.

Aldo Leopold (1886-1946), American forester, director of the Audubon Society (1935) and one of the founders of the Wilderness Society (1935), stated in A Sand County Almanac (1949) that land is a community in which all individuals depend on one another. For Leopold, "individuals" include soil, water, plants, and animals. This idea of mutually dependent individuals within a community has been the moral center of the modern ecosystem-centered environmental movement.

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