M. Weir / CalTrout Lake Pillsbury with Scott Dam in foreground. (M. Weir / CalTrout)

A sweeping plan to remove two century-old dams on Northern California’s Eel River promises to revive native fish runs – but it also raises alarms for the wildlife that has come to rely on the soon-to-vanish Lake Pillsbury. Pacific Gas & Electric’s decommissioning of the Potter Valley Project will drain Lake Pillsbury’s 2,000-acre reservoir in the Mendocino National Forest, transforming the landscape from a placid lake to a re-established river. This ecological upheaval is expected to create clear winners and losers in the region’s wildlife.

On the muddy banks of Lake Pillsbury’s north shore, a herd of tule elk has long grazed and watered in the reservoir’s basin . Reintroduced in the 1970s, the elk herd flourished alongside the man-made lake. Now experts fear these elk could be among the biggest losers when Scott Dam is torn down. PG&E’s own

environmental filings warn that the disappearance of Lake Pillsbury may leave the elk stranded in thick sediment or searching for new forage grounds once the water is gone . State wildlife officials have noted

that removing the dam will likely reduce the lush lakeside meadows the elk depend on for food, at least in the short term .

Other Lake Pillsbury residents of the wild are also at risk. The reservoir has been a prime hunting ground for bald eagles and ospreys that nest in the area. They swoop down to snatch fish from the lake’s calm surface – a food source that will dwindle as the waters recede . “The disappearance of Lake Pillsbury would erase a key hunting ground for ospreys and bald eagles,” PG&E cautioned in its decommissioning plan . With their fishing spot dried up, these raptors may be forced to relocate or go hungry until they can adjust to fishing in a fast-flowing river. The California Department of Fish and Wildlife has pointed out that both species rely on the lake’s fish, urging that their nesting sites and foraging needs be considered during the transition .

Even species deeper in the forest could feel the disruption. The dam removal process – involving heavy construction and the release of 12 million cubic yards of sediment – is expected to be noisy and chaotic. Sensitive creatures like the northern spotted owl, which nests in the nearby woods, might abandon their sites during the commotion . Migratory waterfowl that seasonally flock to the lake’s open waters will likewise lose a resting and feeding habitat when the reservoir is gone. In short, as one local official put it, life around Lake Pillsbury “will never be the same” after the calm lake is replaced by a raw, new river channel .

Against these losses stands a well-documented ecological gain: the restoration of a free-flowing Eel River and its native salmon and steelhead. For over a century, Scott Dam has blocked migrating fish from reaching the river’s headwaters. Its removal will reopen more than 300 miles of upstream spawning habitat for imperiled Chinook salmon, coho, steelhead trout and other species . Biologists say no single action would boost these fish populations more than removing this barrier . Historical records show the Eel River once teemed with salmon – up to 800,000 Chinook swam its waters each year – a number now plummeted to under 20,000 . Liberating the cold, high-quality streams above Lake Pillsbury could kickstart a dramatic recovery for these runs.

Conservation groups herald the dam removal as an overdue victory for the river’s entire aquatic ecosystem. “Dam removal will restore access to over 300 miles of spawning habitat for fish, improve water quality conditions and make downriver communities safer,” said Regina Chichizola of the group Save California Salmon . Removing the dams will not only allow salmon and steelhead to return, but also benefit other native aquatic species like Pacific lamprey. The Eel River’s flow will be set free to carry natural sediment and nutrients downstream once again, rejuvenating habitat conditions. Supporters note it will eliminate the accumulation of toxic methylmercury in the reservoir and improve water quality for all creatures downstream .

Significantly, draining Lake Pillsbury may also help knock back invasive predators. The reservoir’s warm, stagnant waters have been a breeding ground for non-native Sacramento pikeminnow, an aggressive fish that preys on juvenile salmon. These invaders spread throughout the Eel after being introduced to Lake Pillsbury decades ago. Research suggests the Potter Valley Project’s reservoirs allowed pikeminnow to gain a foothold; removing them will reduce the slow, warm habitat that gave them an edge over salmon . In essence, the native fish and insects adapted to a swift river will regain dominance over those suited to a lake.

PG&E’s decommissioning documents bluntly acknowledge the trade-offs ahead. The company describes an “unavoidable” shift “from a lacustrine to riverine environment” in the Lake Pillsbury basin – in plain terms, a peaceful lake giving way to a reconstituted river . That transformation, expected to begin as early as 2028 pending regulatory approval, will be jarring for local residents and wildlife alike. The utility’s filings cite “unavoidable adverse effects” on the area’s recreation and way of life, along with impacts to animals from elk to eagles.

Efforts are underway to soften the landing for the ecosystem’s losers. PG&E has committed to replanting the drained lake bed with native trees and plants to jump-start natural recovery . Over time, the barren mudflats should transform into verdant riverbank habitat. Ecologists say the returning river will carve new channels and create riffles, pools, and wetlands, gradually becoming a ribbon of habitat teeming with life. Tule elk may eventually find fresh meadows to graze along the young Eel River, once vegetation takes hold. Bald eagles and ospreys could adjust by hunting the river’s revived fish runs, or by ranging to nearby lakes.

Environmental groups argue that the short-term turbulence is a price worth paying to heal a river long held back. “This agreement… is good for the Eel River,” Trout Unlimited adviser Brian Johnson said of the dam removal plan, emphasizing the rigorous ecological safeguards built into it. California Trout’s Charlie Schneider called the project a major ecological win that will ensure salmon and steelhead have “clean, connected habitat after the dams come down” . The Eel River, projected to become California’s longest free-flowing river once the dams are gone, is poised for a renaissance that could resonate from tiny invertebrates to apex predators.

As the Potter Valley Project’s undoing moves forward, the region is bracing for a profound ecological shake- up. On one side, a lake ecosystem nearly a century in the making will vanish, leaving elk, eagles, and other creatures to cope with the loss. On the other, a living river will rise in its place, offering salmon and a host of native species a second chance to thrive. “Mother Nature bats last,” one local resident observed of the Eel River’s restoration. In the years to come, wildlife managers and tribes, anglers and hikers will watch closely to see which species sink or swim in the Eel’s next chapter – an era of renewal for some, and adjustment for others, in the ever-changing tapestry of this watershed.