Scientist discover critical role sea otter play in climate change

Sea otters are cuddly, cute and playful, but a recently published report from the University of California at Santa Cruz claims they could hold one of the keys to mitigating climate change.

Two scientists from UCSC have demonstrated the crucial role that sea otters play in the health of kelp forests, one of the ocean’s great carbon sinks. If we want to sequester more carbon from the atmosphere, they say, we need more otters. Chris Wilmers, professor of Environmental Studies at the university, says predators have a greater impact on the environment that scientists once realized.

“When otters eat sea urchins, which are their main diet for instance, we see kelp forest bounce back to life,” he said. “And my research has also focused a bit on climate change and so I thought I wondered if there was a connection between the two.”

Wilmers said decades of research have shown that a vibrant otter environment leads to a vibrant kelp forest, and without the otters, the kelp disappears.

“What’s novel about this study is that we looked at how that influences carbon,” he said. “And what we found is that there’s a dramatic draw-down of carbon from the atmosphere when you have sea otters and all that underwater kelp using that carbon.”

Wilmers and his co-author, Jim Estez, have focused most of their research to-date on the Aleutian Islands, as well as the rest of the North American coast south to the U.S.-Canada border, near Seattle. In that area, the sea otter population is declining, as killer otters switch their diets for reasons not yet fully understood.

“The theory is that killer whales used to eat primarily the large baleen whales,” he said. “And after World War II, there was a tremendous increase in whaling which depleted most of the large baleen whales over much of the north Pacific. So by the 70s or 60s there were very few baleen whales remaining.”

The whales, the theory goes, switched to harbor seals, which they depleted, so they switched to fur seals. They depleted the fur seals and switched to feeding on Steller sea lions, which they depleted and led the whales to feed on otters. Where there were once hundreds of thousands of sea otters, scientists believe just a few thousand remain.

“There’s been a sort of chain of cascading events that initiated back in the 1950s with heavy whaling,” Wilmers said.

Wilmers said their research shows that sea otters are, indirectly, responsible for removing between between $205 and $400 million worth of atmospheric carbon.

That price is based on the costs of carbon on the European markets. Wilmers hopes that as those markets mature, people will be willing to spend money, but perhaps less than the cost of the carbon, to develop a natural solution to carbon sequestration — namely paying to reintroduce sea otters to areas where they no longer exist.

“Most of the carbon cycles don’t incorporate animals — they incorporate plants, certainly — but animals have been largely overlooked because it’s been assumed that they are bit players in the carbon cycle,” he said. “Ecologists more generally should be looking the world over for roles that animals might be playing in other kinds of ways in other kinds of ecosystems that influence the carbon cycle.”