One spring day in 2006, a grizzly bear emerged from hibernation in Wyoming's Bridger-Teton National Forest, just outside Grand Teton National Park. The unromantically named Grizzly 399 became a sensation with tourists and photographers for her propensity to linger near roadways in the park with her three cubs. She dutifully taught her young how to hunt elk calves; two years later, the young bears set out to make their way in the world.

One was shot by a poacher near the tony town of Jackson. The trio's young male, Grizzly 587, wisely headed for the expansive wildlands of the 3.4-million-acre Bridger-Teton, where he put his calf-hunting skills to work on the abundant elk population. But he soon discovered an easier type of calf to feed on amid the thousands of cattle grazing the public lands at the headwaters of the Upper Green River. After twice being relocated for preying on livestock, 587 was killed in 2013 by state wildlife managers.

Over the past 30 years, grizzly bears have made a heartening comeback in the 22-million-acre Greater Yellowstone Ecosystem. Once numbering over 50,000 and ranging from the Mississippi River to the Pacific Ocean, grizzlies were listed as an endangered species in 1975, when only 136 remained in Yellowstone. That protection allowed the bears' population in the Yellowstone area to rebound to over 700 today.

Because of that growth—and, possibly, the diminished availability of whitebark pine nuts and cutthroat trout, two of the bears' foundational foodstuffs—grizzlies are now radiating out from Yellowstone into areas they haven't inhabited for generations. In the Upper Green River watershed, the snow-mantled Wind River and Gros Ventre Ranges rise above a fertile valley of aspen grasslands and willow-hemmed creeks. But in addition to some of America's finest wildlife habitat, the Upper Green also has 170,643 acres of public grazing lands, where bears that repeatedly kill cattle are "removed from the population." In October 2019, after 20 years of debate and countless delays, Bridger-Teton National Forest granted a 10-year extension of grazing permits with no additional measures taken to protect bears.

A burgeoning grizzly population combined with an abundant, nearly defenseless food source makes the Upper Green the largest grizzly killing field in America. Each year, the number of conflicts with bears increases by 9 percent, a trend government biologists predict will continue. The US Fish and Wildlife Service has repeatedly increased the allowed "take," or killing, of grizzlies on Upper Green allotments. The previous limit was 11 bears over a three-year period, but new regulations announced last fall allow for 72 grizzlies to be killed over 10 years.

"It's so egregious, we could not believe it," says Bonnie Rice, the Sierra Club's Greater Yellowstone senior campaign representative. "This is a threatened species. These are public lands. And they're not requiring any conflict-prevention measures. They're just increasing the incidental take."

Rice has been promoting grizzly-friendly rules for grazers since 2014. But Bridger-Teton officials have resisted implementing requirements—even when proposed by their own biologists—that ranchers in the field carry bear spray and dispose of livestock carcasses, which grizzlies can smell from over 10 miles away. Other potential solutions include using guard dogs, installing electric fencing, bunching livestock together at night, and not grazing vulnerable calves in grizzly habitat.

On March 31, 2020, the Sierra Club joined with the Center for Biological Diversity in a lawsuit to force Bridger-Teton to implement bear-protection measures; a separate lawsuit by the Western Watersheds Project seeks to end the killing of bears that prey on grazing livestock. Jonathan Ratner, the project's Wyoming director, points out that Bridger-Teton's own forest plan dictates that grazing allotments be managed for the benefit of wildlife and habitat. "The idea that we are killing endangered species to protect someone's private profit is absurd," he says.

On the other side of those lawsuits is Albert Sommers, a Republican Wyoming state representative, whose family has been grazing cattle in the Upper Green since 1902. Each summer he takes his cattle to their mountain pasture in the oldest continually operating cattle drive in Wyoming. His natural, native-grass-fed beef is sold regionally with the slogan "Grizzly tested, wolf approved."

Sommers is the head of the Upper Green River Cattlemen's Association, which has joined with federal agencies to defend against the lawsuits. If the grazing leases were eliminated, he says, "I'd be losing my way of life and the community that we built for 100 years." The first grizzly predation of his cattle, he says, occurred in 1993. Before then, he lost an average of 2 percent of his calves every summer. Now he averages 12 percent. "It's a financial toll, but we don't have a lot of options," he says. "There's just simply not enough private pasture to pull our herds back into."

Despite the bears' threat to his livelihood, Sommers says, "I don't know how you couldn't see the beauty in that animal. They're just trying to earn a living, and we're just trying to earn a living. And at times the way we both earn a living kind of runs into each other."

Meanwhile, as the bruins increasingly push out from the Greater Yellowstone Ecosystem, mortalities are spiking—more than 80 percent of them caused by humans. For the isolated population of Yellowstone grizzlies to survive in the long term, biologists say, they'll require even more territory and more genetic diversity. If things go poorly, they might end up like Grizzly 587, who is now mounted for display at the Jackson Hole Historical Society. As for Grizzly 399, the great matriarch, she emerged from hibernation last May at the grand old age of 24, unusually old to reproduce, with a near-miraculous brood of four playful cubs, her largest litter yet.

This article appeared in the November/December 2020 edition with the headline "The Killing Field." It has been corrected.

This article was funded by the Sierra Club's Our Wild America campaign.