Fur Seals Made a Tremendous Comeback. That Might Be a Problem.

The once-endangered species is now wreaking havoc on coastal vegetation, putting Antarctica at risk.

fur seal nestled in lush vegetation in Antarctica

This article was originally published by Hakai Magazine.

In the Antarctic, the fur-seal population is booming. Having rebounded from near eradication by hunters in the 18th and 19th centuries, Antarctic fur seals are making their way to new frontiers. Their recovery has been so successful that the animals are pushing beyond their known historical range, causing “unexpected terrestrial conservation challenges” for Antarctica’s fragile vegetation, a recent study warns.

Since about 2010, fur seals have been expanding from their hub centered on the island of South Georgia down the Antarctic Peninsula, reaching the southern side of Marguerite Bay. “That’s way farther south than we would have seen them before,” says Peter Convey, an ecologist with the British Antarctic Survey and the lead author of the new study. This expansion is led mostly by juveniles and nonbreeding males. When they haul out on land, these fur seals trample the fragile coastal vegetation that thrives on Antarctica’s limited ice-free terrain.

Convey points to the damage fur seals have caused on Signy Island, one of the South Orkney Islands, where the landscape, including the fragile mosses and lichens that grow there, has been heavily affected by seals. In 1977, says Convey, there were about 1,600 seals on Signy Island. By the mid-1990s, there were more than 20,000. Besides trampling vegetation, seals are also defecating and urinating near the island’s freshwater lakes, which has contributed to their eutrophication.

Convey and his colleagues are raising the issue to stimulate discussion. He’s concerned that the current plans overseeing Antarctica’s protection—managed by the multistate Antarctic Treaty—account only for human impacts on the continent. But for him, the seal’s impact far outweighs that of humans. Convey says the situation gets at a fundamental question: Is it the Antarctic Treaty’s job to protect the continent’s inhabitants from one another? “There’s no easy answer,” Convey says. But he believes it is a debate that has to be had.

Brian Silliman, a marine biologist at Duke University who wasn’t involved in the research, suggests that the seals’ expansion may be a case of recolonization into their full historical range. It’s common when looking at rebounding species to think they are “doing things that we thought they’re not supposed to do,” Silliman says. Studying populations at their nadir after decades of overhunting or loss can give a false impression of their previous range and behavior, he adds.

It is unclear what Antarctic fur-seal population levels were, or where exactly they were distributed, prior to historical overhunting. Convey, however, underlines that there is no evidence that seals have ever galumphed their way across these particular coastlines—even prior to their exploitation.

Convey is careful to stress that culling the seals isn’t and shouldn’t be on the table. Yet the question of how to respond to the ballooning fur-seal population is a management headache requiring difficult decisions. At its core, the situation asks whether Antarctica’s terrestrial ecosystems should be prioritized over its expanding fur seals.

Claire Christian, the executive director of the Antarctic and Southern Ocean Coalition, an NGO devoted to protecting Antarctica and its surrounding waters, says the Antarctic Treaty System has tough choices to make based on rather limited information. Identifying hot spots of vegetation that should be protected from errant fur seals may be one approach. Convey agrees this is a potential solution. But taking steps to safeguard this terrain—such as by installing fences—would be yet another human intervention with possibly unforeseen consequences. Fences have been deployed in some locations, with mixed success.

Another approach, Christian suggests, is to figure out what is needed to make this new normal thrive, “instead of trying to make it into what we want to see,” she says.

Ally Kristan, a marine biologist who studied rebounding populations on South Georgia while at Louisiana State University and was not involved in the research, is “very wary of implementing control methods on a population that has already been so vastly and disastrously affected by human impact.” Regardless of where they used to live, Kristan says, fur seals are now in an altered ecosystem because of past and current impacts. There is no way to return things to “normal,” she adds.

This lack of simple answers unites those concerned about protecting Antarctica with those working to manage changing environments elsewhere, such as in the Indian Ocean, where dwindling shark populations have allowed green sea turtles to rebound swiftly—and to go on to overgraze seagrass meadows. Along the West Coast of North America, recovering populations of sea otters have come into conflict with local people. As other marine predators recover, they may do similarly.

Inadvertently or not, humans have been picking ecosystems’ winners and losers for millennia. As populations recover from historical exploitation and struggle to adapt to already altered environments that are further changing because of anthropogenic warming, taking a hands-off approach is seeming less and less viable.