Humans have an unlikely ally in the fight against global warming: sea otters.
According to a new study out of the University of California Santa Cruz, the playful, foraging mammals play a vital role in managing kelp forests, which in turn are capable of absorbing large amounts of carbon dioxide. Sea otters prey on sea urchins, which, unchecked, can ravage kelp forests, but thriving sea otter populations help keep the urchins in check.
The study looked at 40 years of otter and kelp data from Vancouver Island to the Western Aleutian Islands in Alaska. The researchers found that in areas where otters flourished, so too did kelp. In fact, the kelp was able to absorb 12 times more carbon in areas that were not overrun by sea urchins. Giant kelp can grow as tall as 30 meters and kelp forests are provide important habitat for a number of fish species, including blue sharks.
"Right now, all the climate change models and proposed methods of sequestering carbon ignore animals," one of the study’s lead authors, professor Chris Wilmers said. "But animals the world over, working in different ways to influence the carbon cycle, might actually have a large impact.”
The study’s authors noted that the carbon sequestered by otter-aided kelp forests alone could be worth between $205 million and $408 million on the European Carbon Exchange, a market for trading carbon credits.
Populations of California sea otters, which once numbered around 15,000 along the Pacific coast, were decimated in the 18th and 19th centuries by hunters. In 1938, one lone colony of 50 otters discovered near Big Sur represented the entire population. Today that number has rebounded to almost 3,000 but the animal still faces threats, especially from parasites and infectious diseases which thrive in polluted waters. Otters, which depend on their fur coats for insulation, are also especially vulnerable to oil spills.
A decision is expected this December about whether to reopen a “no-otter zone” enforced by the Fish and Wildlife Service which extends from just North of Santa Barbara to the Mexican border in California. The zone was originally established in 1987 to help the fishing industry, and sea urchins have removed large swaths of kelp forest in the area.