The world's furriest animals, sea otters eat sea urchins and crabs, consuming a quarter of their body weight each day and supporting kelp forests in the North Pacific. When sea otters are lost, sea urchins clear cut kelp, destroying habitat for fish, invertebrates and other mammals. If sea otters return, they cut back urchins so kelp flourishes again. By eating crabs, they protect slugs and snails who scrape algae off seagrass so it can absorb more sunlight. Otters thus help both ecosystems pull carbon from the air and store it in kelp and seagrass. A 2012 study found their presence in a large area between Alaska and British Columbia means that ecosystem can store more carbon than is emitted by a million passenger cars for a year.