The Trump administration and Republicans in Congress have launched a new assault on the Endangered Species Act, the 1973 law credited with saving dozens of animals and plants. These include such icons as bald eagles, grizzly bears, and Florida manatees, and other species that many of us have never heard of—such as the Hidden Lake bluecurl, a small plant with delicate blue flowers that grows along a single lake in the San Jacinto Mountains of southern California. Earlier this month the bluecurl became the latest of dozens of species to be officially taken off the list, because officials determined that its population had recovered.

The sage grouse is in a way the opposite of the bluecurl. Its habitat stretches across 173 million acres of arid sagebrush steppe in the American West, and it has never been listed as endangered—even though its population is now thought to be less than 10 percent of what it was in the 19th century.

View Images Sage grouse need sagebrush to survive: It shelters them and feeds them, especially in winter. As economic development and invasive species have stolen ground from sagebrush, grouse numbers have declined by around 90 percent. Some conservationists argue the bird should be listed under the Endangered Species Act—which might place severe limits on ranching, oil-and-gas development, and other activities.

But the sage grouse, and the sagebrush ecosystem it depends on, has still been protected by the ESA. It was the threat of an ESA listing that drove state and federal officials and Western landowners to negotiate an historic compromise in 2015. Under that agreement, states and landowners and energy companies agreed to protect key bird habitat—and the federal government agreed not to list the bird, which might have forced far more drastic restrictions on development.

“We battled it out mightily,” Paul Ulrich of the Wyoming-based Jonah Energy told our writer, Hannah Nordhaus. “And then we put our interests aside and asked, ‘What is best for Wyoming?’”

View Images The Jonah Field, south of Pinedale, Wyoming, is one of the nation's most productive gas fields, with hundreds of wells. But the enormous flocks of sage grouse that used to nest there are now gone. The birds return to the same spots to mate and nest each year—even when roads and well-pads make those spots unsuitable.

Nordhaus and photographer Charlie Hamilton James are reporting a feature on sage grouse for the November issue of National Geographic, as part of a larger package on the conflict over western public lands. The photos accompanying this story were selected from that package.

The sage grouse compromise left some on both sides of the issue dissatisfied. Now the Trump administration plans to reopen several areas to development that had been set aside for the birds. It’s part of a broader effort to open western public lands to development, particularly for energy, and hand more control over them to the states.

On July 19, the administration proposed to limit the power of the ESA in several ways—for instance, by allowing regulators to consider the economic impact of listing a particular species before deciding whether or not to list it, as opposed to relying solely on the relevant science.

View Images Not far from the Jonah Field in southwestern Wyoming, a thousands cows and their calves cross the sagebrush sea, on the annual drive that takes them from summer to winter pastures. In some parts of the West, cattle grazing has allowed invasive and fire-prone cheatgrass to take hold, undermining the sagebrush ecosystem.

Meanwhile in Congress, Republican lawmakers have introduced more than two dozen bills over the last two weeks that would change the enforcement of the act. These bills would, among other things, remove federal protections for gray wolves in several areas, de-list the American burying beetle, whose presence in many oil-rich areas presents an impediment to drilling, and prevent grizzlies from being reintroduced into parts of Washington state.

Lawmakers say these changes are necessary to modernize the act and avoid over-restrictive rules, although a 2015 scientific analysis of the law suggests that it has essentially never out-right prevented development.