Conservatives and energy industry groups have railed against the ESA for years, but since January the Trump administration has been on the attack. The administration argues that onerous rules inhibit development and put the brakes on “energy domination.” Executive orders this year instruct agencies to rewrite ESA rules in ways that would speed approvals for fossil fuel projects without the environmental reviews the agency typically requires.

Burgum and other conservatives portray the law as broken, with rigid rules that have little to do with recovery. Scientists and legal experts point instead to the agency’s long-term funding problems and the political seesaw of priorities.

“We continue to wait until species are in dire straits before we protect them,” said David Wilcove, a professor of ecology and evolutionary biology at Princeton University. “That makes recovery far more difficult and expensive.”

The Endangered Species Act does work, experts agree. But it’s just as important to measure the act’s success in preventing the worst-case scenario for a species: extinction.

Since the ESA’s passage in 1973, only 26 species listed under the ESA have gone extinct while under federal protection. At least 47 species are known to have vanished from the wild while awaiting a listing.

“The ESA works more like a critical care unit than a hotel,” Wilcove said. “It’s as though we built a great hospital but never funded enough doctors or equipment.”

Arguably the ESA’s greatest success story is the bald eagle. Pesticides like DDT and the destruction of wetlands left just a few hundred nesting pairs in the lower 48 states by the 1960s. After DDT was banned and the bird was put under the ESA’s protection in 1978, its numbers began to climb, and in 2007 the bald eagle was the first species delisted under the Trump administration, with nearly 10,000 nesting pairs across the country.

American alligators and Steller sea lions are also among the many creatures that have made a comeback thanks to protections from the ESA.

One of the most common arguments against the ESA is that its protections apply to both public and private property.

The vast majority of listed species—more than two-thirds—rely on private lands for at least part of their habitat, and about 10 percent are found only on private property.

“If you have an endangered species on your property, your ability to use that land is going to be limited and you can be prosecuted,” said Jonathan Adler, a professor of environmental law at William & Mary. “That discourages people from being cooperative.”

In some cases, research has shown the rules may create “perverse incentives.” For example, one study on the red-cockaded woodpecker, a threatened bird found in the Southeastern U.S., found that timber was being harvested early in habitats with the bird, in an apparent effort to head off federal habitat restrictions.

Congress has tried to offer incentives like tax breaks and conservation easements, which pay landowners to maintain and protect certain habitats. But such programs have also been on the decline in recent years, many conservationists fear.

The Future of the ESA

Once considered a bipartisan priority, the Endangered Species Act is now one of the most litigated environmental laws in the country. For more than a decade, some in Congress have attempted to strip down its provisions, only to see their efforts reversed when the White House changes hands.

Today, experts fear the Trump administration’s unprecedented rollback of ESA protections—combined with a conservative-leaning Supreme Court—may have the effect of permanently scaling back the act’s scope, even when the current administration leaves office. They also worry that habitat loss and climate change continue to push ever more species toward the brink.

Andrew Mergen, a professor at Harvard Law School who spent decades litigating ESA cases for the government, argues the law’s focus should be on resources, not deregulation.

“The law has prevented extinctions,” he said. “The real challenge is the political will and funding to enable us to help them recover, not taking away the protections that keep them from going extinct.”

While the ESA’s battles play out in the courts and on the campaign trail, recent headlines have shown what’s possible. In July, the U.S. Fish and Wildlife Service announced that the Roanoke logperch, a freshwater fish, had been “delisted” from the endangered species register, because it has recovered enough to thrive on its own.

Burgum called it “proof positive that we no longer have the Hotel California situation” with the ESA.

But conservationists point out that those successes came from more than three decades of dam removals, wetland restoration and, in some cases, very expensive reintroduction programs that began well before Trump came to office.

“The optimistic part,” Wilcove said, “is that we know how to save species when we invest in them. The question is whether we’ll make that commitment.”