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Giant Sequoia Trees Face "Drying" Times

Posted by Diane Banegas, U.S. Forest Service in Forestry
Feb 21, 2017
U.C. Berkeley biologists Cameron Williams and Rikke Naesborg measuring the trunk diameter of a giant sequoia
U.C. Berkeley biologists Cameron Williams and Rikke Naesborg measure the trunk diameter of a giant sequoia in Giant Forest, Sequoia National Park. Photo credit: Anthony R. Ambrose

“A mature Giant Sequoia can use 500-800 gallons of water every day during the summer,” said Anthony Ambrose, a tree biologist at U.C. Berkeley. “That’s a lot of water necessary for just one tree.”

For the first time in at least 125 years, Giant Sequoias in the southern Sierra Nevada Mountains of California are showing significant amounts of “dieback” in their foliage due to several years of drought.

The U.S. Forest Service contributed emergency funding to a collaborative research project involving scientists from U.C. Berkeley, Sequoia and Kings Canyon National Parks, U.S. Geological Survey, and Carnegie Airborne Observatory to examine the effects of the current historic drought on Giant Sequoias.

If they get adequate water and nutrients, Giant Sequoias can live to be well over 3,000 years. They are the largest single-stem tree species in the world, with respect to wood volume and mass, and they grow best in a climate of snowy winters and dry summers. A big decline in snow pack in California over the last few years is a major reason for the observed dieback.

Log meadow in Giant Forest, Sequoia National Park
Log meadow in Giant Forest, Sequoia National Park. Photo credit: Anthony R. Ambrose

“What’s happening above ground is only half the picture,” noted Ambrose, one of the lead scientists on the project. He wants a much better handle on how below-ground conditions correlate with what they see above ground. For example, scientists do not yet know why a tree near a wet meadow can show dieback while a tree on dry ridgetop looks green and healthy.

Ambrose and his colleagues intend to construct a “vulnerability map” for the Giant Sequoias using a combination of traditional ground-based monitoring and data collected aerially by the Carnegie Airborne Observatory. The map will reveal which stands of trees are the most susceptible to drought conditions, allowing managers to prioritize those stands most in need of prescribed fire, mechanical thinning, or other treatments.

Prescribed fire is the most cost-effective way to remove brush and tree species that compete against the Giant Sequoias for limited water and soil nutrients; the sequoias’ thick bark protects them from fire while species that grow in their shade, such as white fir, go up in flames. Irrigation is another potential management tactic, although practical constraints will necessarily limit its application to small isolated areas.

“Obviously, given the water needs of Giant Sequoias, we cannot water an entire forest during periods of extended drought,” Ambrose said.

NOTE: For an interactive look at USDA's work in conservation and forestry over the course of this Administration, visit

U.C. Berkeley biologist Cameron Williams ascending a giant sequoia to collect leaf samples
U.C. Berkeley biologist Cameron Williams ascends a giant sequoia to collect leaf samples in Giant Forest, Sequoia National Park. Photo credit: Anthony R. Ambrose
Category/Topic: Forestry

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Timothy Johnson
Feb 17, 2016

Preserving the Red Woods has to be priority ONE! Yes research into the basic reasons for the decline is important but if it's global warming we need to Stop and solve that also! Could reseeding the trees to higher elevations be an answer?

Kim Dement
Feb 18, 2016

So if we can build a pipeline for oil, why in the heck wouldn't we build a pipeline to save our forests and maybe, just maybe, save ourselves in the process. BUILD A "WATER" PIPELINE FROM NEW YORK TO SAN DIEGO, AND START NOW!

Feb 21, 2016

One mature giant sequoia uses 500-800 gallons of water a day that will seriously effect our water supply, doesnt seem to make sense...

Feb 22, 2016

And that is a pipeline for oil...not water...where would we plan on getting the water from? Unless we can develop an extremely fast and cheap way to convert salt water; but then we would be seriously depleting our oceans...

Feb 22, 2016

It is a matter of $$. If industry can build petroleum and gas pipelines all across the US, the govt. could as well. Requires resolve. Source the water off of the reservoirs on the upper Missouri River. Sure this was probably looked at. Hard to get the $2 billion or more funded I suppose.

Feb 24, 2016

I wonder the importance of cloud-water input to this ecosystem. Since this big tree also absorbs water by foliage uptake, it is very possible decline cloud-water level that has an influence.

Tree High
Apr 05, 2016

The situation definitely required immediate action. It is disheartening to hear that the Giant Sequoia trees are facing crown dieback. This magnificent tree species needs to be preserved. We hope scientists and arborists identify the reason for drying and measures to handle it best.

May 03, 2017

i love sequoia trees! They never fail to amaze me.

Marci Mansfield
Nov 03, 2017

Hi, I'm the art director for "Your National Forests" magazine produced by the National Forest Foundation. I'd love to get the original high resolution file of the photo of UC Berkeley biologist Cameron Williams to use in the next issue for an article about unique trees on National Forests.
Would you kindly email me and let me know if this is possible? Many thanks!!

Lara Mendoza
Oct 11, 2019

I am wondering if too much water is being diverted to agriculture from the rivers which run through there. It would add to draught in parks.