At a time when the federal government is rolling back public land protections at an alarming rate, a new study by Defenders of Wildlife and Tufts University finds those protections are crucial for vulnerable wildlife populations.

But it also underscores the point that relying on federal safeguards alone is not enough to conserve imperiled wildlife.

Habitat loss and altered landscapes are the primary cause of biodiversity loss, directly reducing population size and reproductive rates for many common and endangered species. After analyzing over three decades of satellite data to measure the amount of habitat lost by 24 imperiled animal species—from the gray wolf and desert tortoise to the California red-legged frog, Louisiana black bear and Florida scrub jay—across all major ecoregions in the lower 48 states, researchers found that species lost almost twice as much habitat (8.1%) on privately owned land than on federally owned land (3.6%). They also caution that their results likely underestimate losses on private lands because they did not include losses due to agricultural development. 

“Our analysis confirms the strength of federal regulations on federal lands to provide solid protections to habitat and wildlife,” says Michael Evans, senior data scientist at Defenders’ Center for Conservation Innovation. “But it also means that reduced protections on private lands—where protections are fewer and less easily enforced than on federal lands—undermine conservation efforts because species need private lands to survive, too.”

In fact, private lands encompass more than 80% of the habitat for more than half of all federally listed endangered and threatened species, according to the U.S. Fish and Wildlife Service. Further, habitat loss on private lands adjacent to protected areas can still threaten species by isolating populations from one another. And as climate change drastically transforms ecosystems, animals may respond by moving to new territories. For example, national parks are expected to lose up to 20% of mammal species as they try to adapt to changing environments.

The study’s findings also underscore the effectiveness of the Endangered Species Act (ESA)—the only U.S. law with the broad scope to provide enforceable habitat protection across all federal lands—finding that species experience significantly less habitat loss after they gained ESA protections. “We now have a much clearer picture of just how tied habitat preservation is to federal protection and the unique role the ESA plays.”

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