Almost 90 years after the National Park Service formally began its work to preserve our national parks "unimpaired for future generations," and nearly 30 years after the enactment of the Endangered Species Act, park plants and animals remain threatened.

   Species as varied as the Hawaiian silversword, New England cottontail, boreal toad, and piping plover teeter on the brink of extinction. Hundreds of Florida panthers once roamed the swamps and pinelands of southern Florida. Today only a few of the large cats still inhabit the Everglades and Big Cypress. Grizzly bears in the lower 48 states occupy only about 2 percent of their historic range. Wolves in the lower 48 survive mostly as isolated or reintroduced populations.

   Since passage of the Endangered Species Act in 1978, nearly 250 species of plant and animal have become extinct, half of them in the past 20 years. The U.S. Fish and Wildlife Service lists more than 1,800 species in the United States and other nations as threatened or endangered. Of these, 398 occur in U.S. national parks, and hundreds more are being considered for listing.

The National Park System includes some of the most complete and naturally functioning ecosystems in the country, and habitat preserved within park boundaries affords many species an oasis of survival. But even park wildlife is in jeopardy. 

   Faced with threats ranging from pollution to poaching, invasive species to habitat loss and fragmentation, these islands of life we call our national parks may not be enough to ensure the survival of the plants and animals that live in them.

   The boundaries of most large national parks were created primarily to protect scenery, not ecosystems. This shortcoming of the national parks became clear in 1987, when biologist William Newmark published in the journal Nature the results of his study of carnivores, hoofed animals, and rabbits in 14 national parks in the western United States and Canada. He discovered that 43 percent of his study species had become extinct in the areas he surveyed.

   "Only the largest North American park assemblage, the Kootenay-Banff-Jasper-Yoho park assemblage (20,736 sq. km.), still contains an intact historical mammalian assemblage," he wrote. Thirteen of the 14 parks in the study had lost some of their mammals.

   Most important, Newmark found that the older and smaller a park is, the more species it loses. Small park size speeds the rate of extinction because smaller parks start with smaller, more vulnerable wildlife populations. Moreover, if wildlife populations on lands surrounding parks die off, park animals become isolated from others of their kind. 

The parks become prisons, disrupting the full range of natural behaviors. Young animals are unable to disperse in search of mates and unoccupied territories and may die without reproducing.

   Migratory mammals may be unable to reach seasonal feeding or breeding grounds outside the parks. As species populations shrink or disappear within national parks, we lose the fundamental building blocks upon which entire park ecosystems depend.

   Biologist Allen Cooperrider wrote in "Landscape Linkages and Biodiversity" about the failure of parks and other protected lands to protect biodiversity:

"Current preserve systems in the United States are of limited effectiveness by themselves because most were not established to preserve biodiversity. . . . Most of the national parks and monuments of the nonforest West . . . were designated because of their spectacular geological features. Similarly, until recently most designation of wilderness areas and wild rivers has been based upon desirability for primitive recreation such as backpacking and canoeing. This policy has resulted in a disproportionate number of alpine wilderness areas and white-water wild and scenic rivers."

   Many protected lands, including national parks, are not large enough to support viable wildlife populations. "Our oldest and largest national park in the West, Yellowstone, is not large enough to contain viable populations of many species, thus necessitating the need for management based on the 'Greater Yellowstone Ecosystem,'" Cooperrider wrote. Similar problems plague new national marine reserves under the protection of the National Park Service.