In many places, spring happens gradually. But in far-north Fairbanks, Alaska, birch and aspen trees often put their leaves out over a span of just 24-48 hours, a dramatic event known as "greenup." ...

Alaska's Cook Inlet was home to nearly 1,300 beluga whales in the late 1970s, but today the population hovers around 300. Despite almost two decades of recovery work, the whales aren't bouncing back.