The giant sequoias in the Sierra Nevada are one of America’s treasures, but for the first time in Sequoia National Park’s history, the trees are showing visible signs of exhaustion due to the drought.

On a hike last summer, a scientist noticed that the leaves of the giant sequoias were browning and more sparse than usual. This finding got ecologists thinking: Did the drought cause this?

“We’re just trying to get a better understanding of how giant sequoia trees respond to severe drought. We have very little understanding of … how severe of a drought it takes to kill a giant sequoia tree,” says Anthony Ambrose, a tree biologist at University of California, Berkeley.

Some of the sequoias in the park are over 3,000 years old and have faced many droughts in their lifespans. But perhaps this drought is too much for them.

To Measure Drought’s Reach, Researchers Scale The Mighty Sequoia

Photo credit: Ezra David Romero/Valley Public Radio