Part of the massive Tongass National Forest, Admiralty Island in southeast Alaska supports the largest concentration of bears anywhere in the world. Sustained by a wealth of salmon streams, isolated and protected by their environment, some 1,700 Alaskan brown bears are part of a unique circle of life that has played out here for centuries. Beginning in August, millions of salmon -- pink and chum, coho and sockeye -- return to the island to spawn, providing a feast for the bears, eagles, orcas, sea lions and even the trees themselves. As long as the salmon continue to arrive, all is well. But this year, for the first time, the salmon fail to arrive and the bears get a bitter taste of what the future may hold.