Everyone witnessing the historic California drought may have expected the alarming news. Scientists gathering data in Sequoia National Park are seeing unprecedented signs of stress in the ancient trees, some of which are 3,000 years old. Now scientists, ecologists, park service workers and visitors are paying close attention to see if there is any cause for alarm among some of the true natural wonders of world as the Giant Sequoias are beginning to show the effects of the dry weather.

The hearty trees, which often reach more than 300 feet high, are reportedly being stressed to the point that they are dying in frightening numbers. Representatives of the National Park Service and biologists from U.C. Berkeley are busy installing more sensors which they use primarily to track humidity and temperature; but now they’re finding much more than the usual amount of dead and dry branches. Giant Sequoias are unique among trees in that they require a specific habitat and flourish in California in a narrow elevation range, clustered in about 75 very dense groves on the western slope of the Sierra Nevada mountains. And this is where the drought is having its worst effect, a result of the extremely high temperatures, little rain and an almost nonexistent snowpack.

Although scientists are not predicting a mass extinction of the trees which so delighted naturalist John Muir and President Theodore Roosevelt that they would ultimately declare them as national treasures, their historic habitat is rapidly being transformed by a changing climate. Patches of brown, dead foliage are appearing more than in past years which is why scientists are taking stock of the most vulnerable groves so they can better manage the forest through the hotter, drier droughts expected in the future.

“They’re beautiful, majestic trees,” said Koren Nydick of the National Park Service. An ecologist, Nydick is part of a research team focused on the beloved behemoths. “People come from all over the world to see the Giant Sequoias.” The data that Nydick and her team is collecting is considered an important piece of information that will assist to give certain trees a share of the scarce underground water.

How thirsty is the average Giant Sequoia? “A single tree can require up to 800 gallons of water a day,” Nydick said.

Giant Sequoias tend to make everything else look small. They start out as tiny sapplings—like every tree—but are so sturdy that they simply outlast everything in the living world. Record specimens have measured about 56 feet in diameter. The oldest known Giant Sequoia was more than 3,500 years old.

“It’s really a humbling experience because you feel just so small in the face of this thing that’s so big and so old,” said Anthony Ambrose, a tree biologist at U.C. Berkeley. He said he has an emotional tie to the giant trees and recently collected foliage from 50 of them after he and his team retrieved monitors installed weeks earlier which measure temperature and humidity. “If there are some impacts from the drought or climate change, we want to understand that. The drought is definitely taking its toll on the trees, but thankfully it is not causing an abnormally high number of them to die.”