Protected Areas in the United States Too Small, Disconnected to Preserve Biodiversity, Studies Find

In fragmented habitats, nearly half of all species are lost within 20 years

The US National Park System includes more than 400 sites spread across some 84 million acres. But few national parks are large enough to contain ecosystems. Two new studies reveal that America’s national parks and other protected public lands are too small and fragmented to sufficiently preserve the nation’s biodiversity. Often missing are conservation corridors linking islanded protected areas.

aerial photo of a landscape, visibly divided by cut and uncut areasChris Margules, National Science FoundationTwo new studies find that America’s national parks and other protected lands are too fragmented to preserve the nation’s biodiversity.

A recent study on habitat fragmentation reached startling conclusions for the country’s ecosystems. Conducted by two-dozen leading ecologists, the study focused on long-term habitat fragmentation experiments on five continents. The authors found that more than 70 percent of the world’s forests are within one kilometer of a forest edge, making them susceptible to degradation by suburban, urban, and agricultural pressures that intrude further into forests every day. These influences were found to reduce diversity of life by 13 percent to 75 percent in all areas studied, with the percentage increasing the closer the habitat to the edge. In fragmented habitats, nearly half of all species are lost within 20 years, and this downward trend continues over time.

“Large public lands like national parks are critical for conservation, but not sufficient. Larger connected areas of land need to be conserved,” the study’s lead author, Nick M. Haddad of North Carolina State University, explained in an interview. “The scope and scale of land needed to protect and preserve a variety of biodiversity is well beyond the area that the national parks encompass. Ideally, it would be great to enlarge national parks, but more realistically the size needed to protect biodiversity should connect other protected areas in conjunction with national parks.”

Haddad cited the Yellowstone to Yukon corridor as an example. “The 1,800 miles of lands stringed together consist of several national parks and other protected lands, creating a superhighway for wildlife to flourish,” he said. “With human population increasing and the resources those increases call for, there is a greater need for more conservation against these pressures. We need to take advantage of the parks and other public lands, think outside their boundaries to create resilience and resist the negative changes of a shrinking wilderness.”

A co-author of the paper, Clinton N. Jenkins, contributed to another similar paper published on April 2 entitled “US Protected Lands Mismatch Biodiversity Priorities.” There, researchers found that many areas with high concentrations of biodiversity in the United States are inadequately protected, especially when it comes to protecting unique species found only in specific geographical areas. “Most species are very small and endemic to very small geographical areas. These rare, narrowly distributed species, most often fish, reptiles, amphibians, are often overlooked when it comes to conservation,” Jenkins told me.

The study found that the states with the most endemic species — those unique to a defined geographic location — are in the Southeast. Despite accounting for 10.7 percent of the land area of the lower 48 states, just 7.8 percent of the country’s land conservation easements exist in this region. Priority areas to expand conservation cited in the paper are the middle to southern Blue Ridge Mountains, the Florida panhandle, the Florida Keys, and the southern section of the Sierra Nevada Mountains, among others.

According to the authors, habitat loss is the primary threat to the survival of a species, and the lands being conserved in the United States are not geographically configured to match the distribution of endemic and vulnerable species. “It is a biological defined trend that heavily fragmented habitats are too small to thrive in the long term. Multiple strategies to connect these priority areas need to be implemented such as better land management and more incentives to private landowners for conservation. Financial resources are most often directed to the most convenient areas to conserve or where the funding originated rather than what makes the most sense in protecting biodiversity. By redirecting the financial resources available to conservation to connect endemic rich areas large enough to protect ecosystems, it will make it much cheaper and easier to maintain those areas,” said Jenkins.

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