A California ecosystem has gotten a big boost from an adorable, fluffy and hungry friend. At Elkhorn Slough National Estuarine Research Reserve, a newly-reinvigorated population of native southern sea otters has eaten so many invasive European green crabs that researchers say the otters have locally solved a problem that has plagued the West Coast for years. States are spending millions to protect their inland waterways from the tiny crabs. Though small – they reach only four inches in width – the invaders harm native wildlife and shoreline ecosystems. At stake are multi-million dollar shellfish industries for Dungeness, king crab and other species. But at the reserve, otters have almost wiped the crabs out, helping the estuary’s ecosystem come back into balance.