Each year millions of Americans visit one or more of the nation's large system of nature reserves. These areas serve to protect, preserve, and showcase the natural beauty of the American landscape.
However, according to an article in the August edition of Ecological Applications, they are not accomplishing a critical task: preserving the biodiversity of plant and animal species present in the lower-48 states. The research demonstrates that despite covering approximately 420,000 square kilometers, America's arrangement of nature reserves fails to encompass the full range of the nation's biodiversity.
The research team, led by J. Michael Scott of the U.S. Geological Survey, Department of Fish and Wildlife at the University of Idaho, built upon past studies, some of which illustrated that as much as one third of vegetation types are not found within protected lands.
The team examined the distribution of ecological zones in comparison to the location of national parks, national forests, national wildlife refuges, and designated wilderness areas, Indian reservations, county parks, and other areas having permanent protection from conversion of natural land cover.
Their conclusion: nature reserves are unevenly distributed across ecological zones, and therefore preserve only a small portion of the plants and animals that call America home.
"The current network of nature reserves in the coterminous United States is the result of lands being set aside not in accordance with a well-thought-out ecological plan, but rather because the lands lacked value for commercial uses, human habitation, or because of scenic or recreational value," argues Scott, primary investigator for the study. "These 'lands nobody wanted' don't come close to representing the natural variation found in the U.S."
The authors divided the lower-48 states into three broad ecological domains: Eastern Humid Domain, Western Humid Temperate, and Dry Temperate domains. They then combined soil productivity data with elevation and land management information to identify 35 potential soil and elevation classes within the lower-48 states.
After breaking down the U.S. landscape by soil productivity, elevation, and broad ecological zones, the authors show that nature reserves are predominantly located in middle to high elevations in areas with less productive soils. For example, they found that 63 percent of the nature reserves have soil productivity classifications of 4 and 5, the two poorest classifications on a scale of 1-5. The richest soils tend to be at lower elevations, and these areas are often more developed for agricultural use, timber production, and residential development.
The authors contend that by disproportionately locating reserves in higher elevations with poor soil productivity, entire species of plants and animals who reside in lower and more fertile areas are left largely unprotected. For example, past studies have shown that the greatest numbers of amphibian and reptile species in the western United States are found below 2000 meters, while many reserves are confined to higher elevations.
This poses a challenge: In order for America's biodiversity to be preserved for future generations, the authors point out that the private sector must be encouraged to protect plant and animal species outside of designated reserves. "Past experience indicates that involving the private sector in creative strategies such as conservation easements, tax incentives, and other methods, can provide habitat crucial to U.S. species," says Scott.
There are signs that policy makers are heeding this call, as the recently passed Refuge Improvement Act of 2000 calls upon the U.S. Fish and Wildlife Service's National Wildlife Refuge System to be representative of the nation's ecosystems, giving the agency the authority to take measures to ensure better representation of species not currently under the purview of public lands.
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