By Silke Schmidt
Sea otters are an unlikely ally for scientists trying to mitigate climate change. But they do a job that is surprisingly similar to that of an environmentalist working to protect the Amazon rainforest: helping trees to absorb carbon dioxide (CO2), which would otherwise be released into the atmosphere where it contributes to a warming climate.
Sea otters perform this job by having an appetite for sea urchins, which look like a miniature marine equivalent of a hedgehog. By munching on kelp forests, the spiky sea urchins can wreak havoc on this marine equivalent of a tropical rainforest, and thereby destroy a very efficient absorber of atmospheric carbon dioxide.
But with sea otters keeping urchin populations in check, kelp forests can thrive and capture lots of CO2. The otters are pretty smart in terms of how they actually eat the spine-covered sea urchins: they bite through the underside, where the spines are shortest, and then lick the soft contents out of the urchin’s shell – yum!
Up until recently, it was unknown just how much carbon healthy kelp forests are able to trap; however, a 2012 study changed this with some pretty surprising findings: scientists at the University of California-Santa Cruz demonstrated that the presence of sea otters allows kelp forests to store between 4.4 and 8.7 megatons more carbon than kelp forests without otter protection. This corresponds to annual carbon dioxide emissions from 3 to 6 million passenger cars!
The study provided yet another stunning figure: if the carbon that sea otters help to store in kelp forests were sold at the European Carbon Exchange, where companies releasing more carbon than the agreed-upon ceiling have to buy emission permits, it would cost between $200 million and $400 million. Think of this as the dollar value of the sea otters’ contribution to carbon storage in just the one particular habitat in which the study was performed: a 5,400 km area on the western coast of North America, ranging from the southern border of Canada to the Aleutian Islands in Alaska.
The dollar range provided by the researchers stems from the fact that only some of the kelp ultimately sinks to the deep ocean, where the trapped carbon can be stored for long periods of time; the remainder tends to wash ashore and decompose, releasing the carbon back into the atmosphere. The calculations assume that between 1% and 50% of all kelp may end up in the ocean depths.
So next time you are at the zoo watching a playful sea otter zip back and forth in its pool, remember to thank its ocean buddies for their huge help in maintaining carbon-storing kelp forests!