The American bald eagle still exists today thanks to the Endangered Species Act.

Nearly a half-century ago, Congress passed the Endangered Species Act by a vote of 92-0 in the Senate, and 355-4 in the House. Republican President Richard Nixon said the legislation “provides the federal government with needed authority to protect an irreplaceable part of our national heritage, threatened wildlife. … Nothing is more priceless and worthier of preservation than the rich array of animal life with which our country has been blessed.”

As the Trump administration continues to roll back America’s commitment to conservation, we should fear that it will succeed in turning the federal government away from its responsibility to protect species from extinction. The administration recently denied petitions to list 25 wildlife species as endangered.

As Kathleen Hartnett-White, who is a Senate-vote away from becoming the administration’s chair of the Council on Environmental Quality, put it, the Endangered Species Act is “economically harmful” and a “formidable obstacle to development.” So perhaps it should not have come as a surprise when Interior Secretary Ryan Zinke announced he would reopen areas of sage-grouse habitat to mining, as well as oil and gas leasing. Zinke, along with the U.S. Forest Service, also plans to revisit the state-federal sage grouse conservation plans that successfully led the U.S. Fish and Wildlife Service to decide not to list the grouse as threatened or endangered.

Some critics are encouraging a rewrite of the law itself, arguing that the ESA has failed, because relatively few of the already listed species have been brought to “recovery.” Many states also want more control over determining when a species should be listed, or removed, from the list, and in identifying “critical habitat” for the survival of a listed species.

The Endangered Species Act has prevented some important and iconic species from going extinct, including bald eagles, the Yellowstone grizzly and gray whales. The primary impediment to recovery has always been a lack of resources. A recent study found that most listed species with recovery plans received less than 90 percent of the amount of money needed for their recovery, and that overall funding for the act has declined since 2010. Only sufficient funding from Congress—not changes in the law itself—can fix this problem.

Critics also complain that “consultations”—the required reviews of projects that may harm listed species or their habitat—are costly and time-consuming, and that they increase uncertainty in project planning. In December, the Trump administration announced plans to change the rules governing endangered-species consultations and critical-habitat designations. Yet a recent review of all Fish and Wildlife Service consultations from January 2008 through April 2015 found that no project was stopped or extensively altered due to reviews. On average, approvals took only 14 business days. The 10 percent of consultations that required further review took 61 days. In virtually all cases, the agency acted within the time limits set by the law.

Although determining whether a species is in danger of extinction is based solely on biological grounds—as it should be—economic factors are already considered in identifying habitat that is critical for the survival of a species. In 2015, Wyoming Republican Gov. Matt Mead, as chair of the Western Governors’ Association, launched a review of how the Endangered Species Act was working. One outcome was a Western Governors’ policy statement supporting “all reasonable management efforts to conserve species and preclude the need to list a species under the ESA.”

The 2015 Fish and Wildlife Service decision not to list the greater sage grouse as threatened or endangered illustrates the benefit of this approach. That decision, based on state and federal land-management plans, initiatives by public-land users, and voluntary efforts by private landowners across the remaining 11-state range of the grouse, was a victory for conservation. It proved the wisdom of the authors of the act, who understood that the key to conserving imperiled species was protecting the ecosystem on which a species depended.

As Democratic Washington Gov. Jay Inslee put it: “What is a bird without a tree to nest in? What is an Endangered Species Act without any enforcement mechanism to ensure their habitat is protected? It is nothing.”

Yet the act seems to work best when it encourages voluntary measures to protect habitat. The flexibility built into it has permitted innovative conservation measures that benefit the species, the public-land users and the private landowners who implement those measures. In many instances, federal funding and technical assistance is available to help defray landowner costs and encourage collaborative conservation efforts.

As the rate of extinctions and the loss of biodiversity accelerates, the act is essential for keeping vulnerable species alive. Unfortunately, if President Trump’s administration and Republican leaders in Congress have their way, the Endangered Species Act itself could be extinguished.

Jim Lyons is a contributor to Writers on the Range, the opinion service of High Country News. He is a lecturer at the Yale School of Forestry and Environmental Studies and a senior fellow at the Center for American Progress in Washington, D.C.