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‚Äôs 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.‚ÄĚ
The study‚Äôs 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 ‚Äúno-otter zone‚ÄĚ 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.
By popular demand, this week we‚Äôre discussing sea otters, the smallest marine mammal.
Native to the northern Pacific Ocean from Russia to southern California, this charismatic critter was seriously overhunted for its fur ‚Äď almost to extinction. It has been protected by international law since 1911 and its population is starting to rebound, but it is still considered endangered. Now 90% of sea otters live off the coast of Alaska. Sea otters can sometimes be found in large groups of either males or females, known as rafts.
The sea otter can spend its entire life in the ocean, including sleeping anchored to kelp beds to keep from drifting away. Because it spends so much time in cold water and has no insulating fat, it relies on its fur, which is the densest of any mammal, to stay warm. It blows bubbles of air into this coat, with 100,000 hairs per square centimeter, to keep water from penetrating to its skin.
The pictures you‚Äôve seen are probably of sea otters floating at the surface, but they are highly adapted to life in the water. Sea otters have a large tail to steer and large hind feet that act as flippers. Sea otters can swim as fast as 9 kilometers per hour and stay underwater for almost six minutes while diving.
Sea otters also eat in the water, hunting invertebrates like mussels, snails and crabs. Otters often become "specialists" in one type of prey, depending on their skills and what is available. The otter stores its prey in skin pouches under its forearms while it returns to the surface, where it uses its chest as a table and pounds frees its tasty morsel using a rock. This makes it one of only a couple of non-primate mammals known to use tools. Sea otters often keep using the same rock for multiple dives, and have been observed washing their prey. Males are known to steal food from females.
Sea otters have voracious appetites; in fact, their hunger can be crucial to maintaining healthy ecosystems. In some areas, otters act as ‚Äėkeystone species,‚Äô which means that they keep populations of their prey, such as sea urchins, strictly under control. Without sea otters present, urchin populations could grow rapidly and eat entire kelp forests; with sea otters present, kelp can live long enough to form forests.
Threats to sea otters include oil spills, killer whale predation, which is increasing as other prey options are becoming scarcer; infectious diseases, particularly toxoplasma; and being caught as bycatch, particularly in fisheries that use gill nets.
Learn more about the sea otter and other fascinating animals at Oceana‚Äôs marine life encyclopedia.