The California Drought’s Alarming Toll On Forests

New research using high-tech tools to measure the moisture in trees found that 120 million trees across nearly every part of California are at risk of dying. Predictions that trends of higher temperatures and decreased precipitation will continue in the future could transform the state’s forests.

California is littered with dead trees. Four years of drought have pushed countless lone pines and forests alike to the brink of collapse, turning entire swathes of mountains from verdant to withering rust.

The numbers began rolling in early last summer with a U.S. Forest Service survey that tallied the death toll at 12 million. By September the agency revised its count to 21 million trees statewide. Soon the California Department of Forestry and Fire Protection (CAL FIRE), weighed in with 29 million confirmed dead trees.

Even those grim numbers, gathered through conventional on-the-ground and aerial estimates, were upended by a high-tech assessment done by scientists with the Carnegie Institution for Science. Four dry summers and four winters with a dramatically reduced snowpack have taken a toll throughout the Golden State, and will likely kill 58 million trees due to severe water loss, said Greg Asner, a Carnegie Institution biologist who published his results online on December 28 in Proceedings of the Natural Academy of Sciences. As many as 120 million trees statewide are in jeopardy from loss of water in their canopies, he said.

The higher temperatures and reduced precipitation that contributed to the die-off are widely predicted to continue, leaving California’s forests poised for radical transformation.

“If drought conditions continue or reoccur, even with temporary reprieves such as El Niño, we predict substantial future forest change,” Asner and his co-authors wrote.

They spent the summer doing aerial surveys throughout the state using remote sensing and modeling techniques that allowed them to look beyond what the —> Read More