A full-grown giant sequoia is a thirsty tree. In the height of summer, the millenia-old behemoths, some of which grow upwards of 30 stories tall, can guzzle 500 to 800 gallons of water per day. They can also survive a variety of scourges that would fell an inferior conifer -- beetles, wildfires, storms. But scientists are worried the species may have met its match in the ongoing California drought.
Nate Stephenson, a research ecologist with the U.S. Geological Survey, was walking through the woods last year when he noticed some of the trees he'd been studying for decades had dropped most of their leaves. He joined forces with other researchers from the USGS, as well as from the National Park Service, U.S. Forest Service, Stanford University and the Carnegie Airborne Observatory, to launch a comprehensive health study on the sequoia.