Kim Steinhardt knows where to find the sea otters. The author and otter aficionado has wandered the channels and sloughs along California’s coast to find the haunts of these threatened marine mammals.

On a recent fall afternoon, Steinhardt pulls up alongside a dirt road in Moss Landing, California, with a small group of Earthjustice staff. His hunch turns out to be right: Three sea otters – a mom, her pup, and an older male – play in the water of an inlet as part of a morning feeding routine, gliding along the surface and splashing away in the crisp sunlight. They crunch loudly on mussels clutched with tiny, furry paws. While the older male rests motionless on his back, the mother swims back and forth, balancing her pup as it goes along for the ride. If she momentarily disappears into a nearby culvert that runs beneath a road bridge, the pup emits a high squeak, growing ever more insistent until she reappears.

“At the turn of the 20th century, they were nearly extinct due to humans hunting them for their fur,” Steinhardt reflects. “We’ve come from that point to the numbers today, around 3,200. And that is a pretty small number for a population, in terms of sustainability. We have a long way to go.”

Steinhardt delivers this message to audiences up and down the California coast, and today he is helping Earthjustice spread the word further. If the sea otters had a spokesman, it would be Steinhardt; and if they had a lawyer, it would be attorney Andrea Treece.

The Earthjustice attorney watches with Steinhardt as the otters barrel roll in the salt water. The scene brings both joy and a sense of foreboding about the ability to protect these vulnerable creatures in the current political climate. Members of Congress have launched an assault on the Endangered Species Act, the federal law that helped California sea otters gain the foothold they needed to survive.

Asked what she would do without this key legal tool, Treece is direct: “That question keeps me up at night,” she answers. “It would be incredibly hard to protect these landscapes, seascapes and species without the Endangered Species Act.”

Treece is no stranger to the Moss Landing area. An avid scuba diver who also enjoys kayaking and paddle boarding, she has made weekend pilgrimages to nearby Elkhorn Slough, where otters can be safely observed from a distance that won’t disrupt them.

“When I moved out to California and experienced sea otters in person for the first time, I just fell in love with them completely,” Treece admits.

Sea otters have come a long way over the last hundred years, but federal safeguards must be maintained because the species is still very much at-risk of being lost.

From the 1750s to 1800s, fur traders killed hundreds of thousands of sea otters across the Pacific Rim. Along the coast of California, the Southern sea otter was presumed extinct until 1938, when a ranch owner in Carmel made the startling discovery that several dozen had managed to survive. Since gaining protection under the Endangered Species Act in 1977, sea otters have started to make a significant recovery.

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Nevertheless, Steinhardt argues that their recovery is still tentative.

“One oil spill of a significant size could actually take out the entire population,” he says. Oil tankers from Alaska routinely ship raw crude through their habitat. As a deadly example, the Exxon Valdez oil spill in Prince William Sound killed nearly 3,000 sea otters in Alaska. “But that number of sea otters–that is all we have, along this coast in California,” Steinhardt says.

“It would be incredibly hard to protect these landscapes, seascapes and species without the Endangered Species Act.”

In the early 1980’s, when the U.S. Fish and Wildlife Service hashed out a recovery plan for sea otters, it took the threat of an oil spill into account and sought to establish an experimental population around one of the Channel Islands off Santa Barbara to prevent this outcome. But when the shellfishing industry raised concerns about re-introducing the population of 140 otters into southern California waters, the agency hashed out a compromise. It established a “No Otter Zone” in all southern California waters other than around the experimental population.

Enforcement of the zone was tricky. “The idea was that if an otter swam from the experimental population into this No Otter Zone, the Fish and Wildlife Service would come and scoop it out of the water, and return it to either the experimental population, or the parent population on the Central Coast,” Treece explains.

Unsurprisingly, this plan didn’t work out very well. “Otters don’t look at maps,” Treece quips.

Over time, it became increasingly apparent that the No Otter Zone was harmful. “Otters tried to swim back to shore. They died from the stress of being captured,” Treece says. The Fish and Wildlife Service ended the No Otter Zone, but soon several shellfishing industry groups filed suit to reinstate the program. Earthjustice has beat back the effort in court so far, but must continue with an appeal process to secure a final victory.

“We intervened on the behalf of Fish and Wildlife Service to defend that decision, and really to defend the core purpose of the Endangered Species Act,” Treece says. The goal is “not just to help otters survive, but make them thrive, to the point where they can recover and be delisted from the Act.”

If it weren’t for the Endangered Species Act, legal victories like the one Treece will defend in court would be tough to secure. Yet a slew of proposals have cropped up in Congress that could weaken or undermine this landmark conservation law. Certain lawmakers, like Utah Republican Rep. Rob Bishop, has said he’d like to “repeal and replace” the Act, while Senate Republican John Barrasso of Wyoming has couched the attack with softer language, insisting the law should be “modernized.” Earthjustice has joined a broad coalition in defending the Act.

Otters are considered a keystone species because they have such an important role to play in their ecosystem. For example, they eat urchins that would otherwise devastate kelp forests. In turn, kelp forests support a vast array of marine life and help to absorb carbon dioxide, making them a buffer against climate change.

“In the case of the otter, if we lose the Endangered Species Act, and we lose otters, we lose kelp forests and sea grass meadows,” Treece says. “We could lose commercial fisheries that depend on both of those habitats. There could be a whole negative cascade, which I think many people don’t appreciate. They think it’s just protecting one thing at a time—but we’re really protecting an entire ecosystem.”