Habitat and Ecosystem Conservation - The Ecosystem Approach

Ecosystem conservation considers entire communities of species as well as their interactions with the physical environment and aims to develop integrated plans involving wildlife, physical resources, and sustainable use. Such an approach sometimes requires compromise between environmentalists and developers. This is the case for several Habitat Conservation Plans (HCPs) developed by the U.S. Fish and Wildlife Service in recent years. In Southern California developers and environmentalists had long battled over hundreds of thousands of biologically rich acres lying between Los Angeles and Mexico that were home to uncounted species of plants and animals. Developers wanted to build there, while federal regulators wanted to protect the habitat for wildlife. Haggling over small parcels of land had already cost significant time and money and caused frustration on both sides. A compromise resolution permitted developers to develop some large parcels of land while setting aside other large, intact regions as conservation areas. A similar agreement between developers and environmentalists was reached in the Texas Hill Country in 1996 and is effective for thirty years from that date. The Balcones Canyonlands Conservation Plan set aside 111,428 acres for ecosystem enhancement while allowing uncontested development of many thousands of acres of land in the central Texas corridor.

Endangered U.S. Ecosystems

In 1995 the first full review of the health of the American landscape was compiled by the National Biological Service and published by the U.S. Geological Survey (Reed F. Noss et al., Endangered Ecosystems of the United States: A Preliminary Assessment of Loss and Degradation, 1995). It is still considered the definitive study of U.S. ecosystem health. Although individual species had been studied previously, the health of the larger ecosystems had never before been considered. The study was based on surveys of state databases and the scientific literature. The report concluded that vast stretches of natural habitat, totaling nearly half the area of the forty-eight contiguous states, had declined to the point of endangerment. Ecosystems suffered in two ways. Quantitative losses were measured by a decline in the area of an ecosystem. Qualitative losses involved degradation in the structure, function, or composition of an ecosystem.

Of the ecosystems that had declined by over 70%, 58% were terrestrial, 32% were wetland areas, and 10% were aquatic. Forests, grasslands, barrens, and savannas dominated the list. (See Figure 3.1.) American ecosystems identified by the National Biological Service as suffering the greatest overall decline include grasslands, savannas, and barrens (55%), followed by shrublands (24%) and forests (17%).

The National Biological Service found that thirty-two American ecosystems had declined by more than FIGURE 3.1 Distribution of critically endangered, endangered, and threatened ecosystem types Reed F. Noss, Edward T. LaRoe III, and J. Michael Scott, "Figure 1," in Endangered Ecosystems of the United States: A Preliminary Assesssment of Loss and Degradationsm, U.S. Geological Survey, 1995, http://biology.usgs.gov/pubs/ecosys.htm (accessed April 4, 200698% and were classified as "critically endangered." Fifty-eight had declined by 85% to 98% and were classified as "endangered." Thirty-eight others declined by 70% to 84% and were listed as "threatened."

Endangered ecosystems were found in all major regions of the United States except Alaska. The greatest losses occurred in the Northeast, the South, and the Midwest, as well as in California. Native grasslands, needlegrass steppes, and alkali sink scrubs are among the communities that have declined most precipitously in California.