A federal appeals court ruled on Monday that Arctic ringed seals must be protected under the Endangered Species Act because of their reliance on the sea ice, which is rapidly disappearing as the planet warms.

The seals—named for the light-colored circles that dot their coats—build lairs on the surface of the sea ice to birth and protect their young. That puts them, like other species that rely on the ice, in a precarious position as it vanishes.

“This major victory gives ringed seals vital protections in the face of climate change and melting sea ice,” said Kristen Monsell, an attorney from the Center for Biological Diversity who argued the case.

Protecting the seals means guarding their habitat, and that could impinge on oil and gas operations along Alaska’s waters, which the state relies on for revenue. The protected status comes with a requirement that the federal government designate areas as “critical habitat” for the seals. That could complicate efforts by the industry—and by the state and federal government—to increase development in the area.

The ultimate protection for Arctic habitat requires ending the emissions from fossil fuel use entirely, an ambition that so far has eluded the world.

The Arctic has been seeing record lows in the extent of sea ice for this time of year. January 2018’s ice extent was even less than a year earlier, when it was at a record low for the month. There was roughly 42,500 square miles less ice this year than in 2017—an area of missing ice about the size of Virginia. And January’s ice extent is more than 5 million square miles below the historical average for the month from 1981-2010.

Alaska and the Oil Industry Push Back

Both ringed and bearded seals were protected by the National Marine Fisheries Service in 2012 based on long-term projections about the disappearance of Arctic sea ice. By 2100, the service found, the seals could be extinct.

The seals’ protected status saw almost immediate pushback by the state of Alaska and oil industry groups—the first phase of a protracted battle between conservation groups and groups that sided with the industry.

In the first round, the district court in Anchorage revoked the decision to list the seals as threatened, ruling that the projections about sea ice loss and the seal populations that the National Marine Fisheries Service relied on were speculative.

The Ninth Circuit Court of Appeals restored the protections in 2016 for the bearded seal before doing the same for ringed seals this week.

“Climate change models show the habitat of the Arctic ringed seals to be diminishing as sea ice recedes,” the judges wrote in their decision. “We hold that the decision here to list the Arctic ringed seal as threatened was also supported by the record and was not speculative.”

Survival Depends on Ice; Ice Is Declining

The Arctic ringed seal population appears to be in good shape—according to the IUCN Red List there are more than 1.4 million of them—but experts say those looks can be deceiving.

A 2007 study asked the question: If a marine mammal species that U.S. federal agencies monitors was to decline 50 percent over 15 years, would the agencies notice using their current practices? When it came to marine mammals that haul out onto ice, like the ringed seal, the answer was a resounding no.

“There was zero percent chance that the decline would be detected,” said Brendan Kelly, a University of Alaska Fairbanks researcher who studied ringed seals for more than 30 years. “We just don’t have good ways to count those animals in a way that is robust.

What is known is that the seals’ survival depends on sea ice.

Though a significant amount of sea ice remains, there’s no ambiguity about what’s happening in the Arctic, Kelly said. “This is massive habitat loss. You can’t maintain a species without it.”

The Fight May Not Be Over

With the bearded seals, the State of Alaska and industry groups sought to have protected status reviewed by the U.S. Supreme Court. The court in January declined to hear the appeal, but opponents to the seals’ protected status have signaled that they are not giving up their fight.  

“We still believe that the decision to list the bearded seal based on projections 100 years into the future was not supported by adequate science and contrary to any reasonable interpretation of the Endangered Species Act,” Cori Mills, a spokeswoman for the Alaska Department of Law said in a statement at the time.

“We will explore our administrative options to right this wrong for listing a species robust in health and numbers,” she said.