This story originally appeared on Hakai and is part of the Climate Desk collaboration.Elizabeth Ruiz parked the white pickup at the side of a winding road, climbed out of the cab, and looked around in disbelief at what was left of the narrow valley: How could any salmon have possibly survived? Once a redwood forest so lush that the land’s contours were lost in it, every ridge and gulley was now exposed, eerily radiant under the Creamsicle-orange sky. Patches of ground still smoldered from the Walbridge Fire, which had blazed through the valley seven weeks earlier, in August 2020.Ruiz, a biologist with the science agency California Sea Grant, adjusted their N95 mask for protection from the haze. Dark hair tucked under a hard hat, wading boots kicking up ash, Ruiz clambered carefully down the steep bank to Mill Creek. They were accompanied by a four-person field crew, all dedicated to saving a population of coho, one of the most endangered runs of salmon on the West Coast of North America. Even bird calls rarely disturbed the quiet. Nearly all the wildlife had fled.“It felt like we were at the end of the world,” Ruiz says, recalling that mild October day.It’s not as though this corner of California had been pristine before 2020’s record-setting fire season. Mill Creek is part of the Russian River watershed, which drains 3,900 square kilometers of Sonoma and Mendocino counties. It’s an hour’s drive north of San Francisco, near enough that early buildings in the city were crafted with redwoods hauled from this watershed. So much gravel has been mined from the river—some of it used to construct the Golden Gate Bridge—that in places the streambed dropped to the height of a two-story house. In the late 1950s and early 1980s, the US Army Corps of Engineers built dams on the Russian River to flood the Lake Mendocino and Lake Sonoma reservoirs, walling off fish habitat. Scattered throughout the watershed, 500 smaller dams also prevented coho from reaching important spawning tributaries. By 2012, vineyards and wineries had become the dominant industry in Sonoma County, part of the wider region the tourism industry calls “wine country.” The complex landscape of oak-dotted hills and steep canyons that was once a haven for locally adapted salmon and steelhead now lends local vino its distinctive terroir.A century ago, roughly 20,000 coho—a salmon species known for spawning in even the smallest creeks—would return to the Russian River and its tributaries in a typical year. By 1988, the number had fallen by 95 percent. In 2000, only six coho returned to spawn. Over the following three years, a coalition of county, state, and federal agencies brought the watershed’s last young coho into captivity at Warm Springs Fish Hatchery, near Lake Sonoma, 30 kilometers inland from the coast. The species has vanished or is on the cusp of disappearing in all but three places in central California, the southernmost limit of coho’s wild range. In the Russian River, the intervention was a moonshot attempt to keep the population alive.