"They are massive organisms that have been growing for thousands of years," Ambrose adds. "When you get up into their enormous, complex crowns you feel like an ant."
Ambrose hopes the public can now experience part of what it's like to scale a rope up a 250-foot tall giant sequoia (Sequoiadendron giganteum) while planted safely on the ground. He and his colleague Wendy L. Baxter are featured in new 360 videos produced by National Geographic for Facebook.
The videos were shot in June in the storied Giant Forest of California's Sequoia National Park, home of the General Sherman and President trees.
"Our objective is to use virtual reality to bring people up in the canopy to see this unique, beautiful view," Ambrose says.
But the effort isn't just about adventure and scenery. Ambrose and colleagues have been studying the trees over the past year in an attempt to better understand how they're faring in California's drought, the worst in memory.
Since the state's drought began in 2012 a hundred million trees have died. Pine and fir trees have been hit particularly hard. Many of the trees have succumbed to invasive bark beetles due to their weakened state.
Since 2014, the giant sequoias—which live above 6,000 feet in the Sierra Nevada—have shown signs of drying. Leaves have been turning brown and trees have dropped up to half of their leaves.
"This had not been observed in the 125-year history of the park," Ambrose says. (See more photos of giant sequoias.)
Through their study of the giants, published in the journal Oecologia, the scientists have measured—for the first time—exactly how much water they require. During the summer, each tree pumps up around 2,000 liters of water from the ground, far more than anything recorded anywhere else, for any other species (the average for an adult tree is less than 400 liters). The team thinks that number could climb as high as 3,000 liters a day for the largest specimens during the hottest weather.
By closing their leaf pores, or stomata, and dropping some of their leaves, the sequoias have been able to weather the drought with surprising resiliency, Ambrose says. Very few of the trees have died. But their growth has likely slowed.
Sequoias on the edges of groves have seen the most impact, as have seedlings, which aren't as tough. That could impact the future of the next generation.
But overall sequoias have fared better than many other types of trees in California, a testament to their strength, their resistance to insect attacks, and their choice of habitat—high, cool mountain basins that tend to have good accumulation of groundwater from snowmelt.
Future of the Forest
The longer term future of the trees remains uncertain. Climate models predict that the Golden State will get hotter and drier in the coming years, with droughts likely to last even longer. And the long lifespan of the trees—3,000 years or so—makes for slow genetic adaption to change.
"At some point they are either not going to grow as well or the groves will shrink back," Ambrose says. (Learn how sequoias need fire.)
"Climate change doesn't bode well for the future of the forest."