Sea Otters Are Climate Super-Heroes

Few other animals eat as much relative to their weight or play such a pivotal role in maintaining their environment, says Brent Hughes, a marine ecologist studying coastal habitats at Sonoma State University in California.

Now, scientists are studying how these marine mustelids may also be climate superheroes. Sea otters help ecosystems capture carbon from the atmosphere and store it as biomass and deep-sea detritus, preventing it from being converted back to carbon dioxide and contributing to climate change.

Scientists have made several important discoveries that help put these perpetually hungry, furry creatures in the climate super-hero category.

Sea otters play an indispensable role in kelp forests. The key is to do with sea otters' voracious appetites. In order to maintain their high metabolic rates, the mammals must eat constantly. Among their favorite foods are sea urchins, which are easy to catch and dense in calories. When sea otters are lost from an ecosystem, sea urchin numbers spike. The herbivorous urchins then basically clear cut the kelp, chewing through the holdfasts at their base and sending the rest of the giant algae to wash away. Along with it goes the habitat for numerous species, including fish, invertebrates and other mammals. When present, sea otters eat so many urchins that the invertebrate's population stays low, making them a "keystone" species - without their presence, the stability of the entire ecosystem can be lost.

Sea otters also benefit seagrass. In these zones, otters mostly feed on crabs. When the mustelids bring down the numbers of crabs, grazing organisms that the crabs eat rebound. These slugs and snails don't eat the seagrass; instead they scrape away the algae that grows on the grass, which allows the seagrass to absorb more sunlight and grow more efficiently.

And in both these ecosystems, otters might have the added benefit of storing carbon.

Ecologists have published a study on the potential for sea otter carbon sequestration in the North Pacific between the Aleutian archipelago and Vancouver Island. Using data on the rate of kelp growth and its density at sites with and without otters, they found that the presence of sea otters, covering 51,551 (19,900 sq. miles – an area about the same size as Costa Rica), is capable of storing 4.4 to 8.7 million tonnes of carbon compared to if an otter-free condition. That's more carbon than that emitted from a million passenger cars for a year.


Fun Fact: Did you know that sea otters hold each other’s paws when they sleep so they don’t drift apart?