Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Thousands flock to the Sequoia National Park each year to view the majestic trees that tower high above the forest.

But below, on the forest floor, there are signs of struggle as many Sequoia trees are shedding more leaves and foliage during the fourth year California’s devastating drought.

And the best way to analyze the health of the trees is to climb them, which is just what biologist Anthony Ambrose does.

#Berkeley scientist Anthony Ambrose ascends a giant Sequoia to study drought stress. Story tonight on @NBCNightlyNews pic.twitter.com/8o2TvBPYYI — Gadi Schwartz (@GadiNBCLA) September 5, 2015

"These trees are some of the most amazing organisms on the planet, they're these huge ancient beings, they have these massive beautiful crowns," Ambrose said.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

"The giant sequoia is undisputedly the world's largest tree," according to the U.S. Forest Service, which says that the tallest recorded Sequoia is 310 feet tall — about the height of the Statue of Liberty.

When Ambrose gets to the crowns of the trees, he collects data that lets him know how much water has made its way all the way from the parched ground to the soaring tree tops.

A biologist scales a Sequoia in Sequoia National Forest. NBC News

"The measurements that we've been getting of the amount of tension in the water in the foliage indicate they’re more stressed than we've ever measured before," he said.

Fortunately Sequoias are resilient.

Their ancient tree rings show they have survived infestations, prolonged droughts and fire through the centuries. But Nathan Stephenson, a Research Ecologist with the US Geological Survey said that when the Sequoias are showing stress, it means smaller trees, like pines, are in dire straits.

In a small nearby plot of forest being monitored by the U.S. Geological Survey, Stephenson said 1 in 4 trees have died.

The plot consists of pines, cedars and spruce trees, much less drought tolerant than the mighty Sequoia. With the increase in dead trees, the threat of fire becomes much greater.

Nearby, in the Sequoia National forest a wildfire dubbed the Rough Fire, has been burning for more than a month.

Smaller trees are succumbing to a triple threat of insect infestation, the lack of water and the fires.

But for now the Sequoias still appear to be growing as they have for thousands of years, and their stress is offering scientists a glimpse at how these forest patriarchs have evolved to survive.

"They're the monarchs of the entire planet kingdom," Ambrose said.