California Drought is Putting Tens of Millions of Trees in Danger, Even with El Niño

The California drought is still taking its toll. Now, scientists have announced that tens of millions of trees are in danger from this dry spell.

California's forests are home to the planet's oldest, tallest and most-massive trees. However, these trees may now be in danger due to the unprecedented drought that's swept the state. In addition to the persistently low rainfall that these forests have had to deal with, there have been high temperatures and outbreaks of the destructive bark beetle.

In order to see how much the drought has impacted the forests, the researchers used laser-guided imaging spectroscopy tools mounted on the Carnegie Airborne Observatory. Then, the scientists combined the CAO data with more-traditional satellite data going back to 2011.

So what did they find? The data revealed a progressive loss of water in California's forest canopies over the four-year span. Mapping changes in canopy water content tells scientists when trees are under drought stress and greatly aids in predicting which trees are at greatest death and fire risk.

"California relies on its forests for water provisioning and carbon storage, as well as timber products, tourism, and recreation, so they are tremendously important ecologically, economically, and culturally," said Greg Asner, one of the researchers, in a news release. "The drought put the forests in tremendous peril, a situation that may cause long-term changes in ecosystems that could impact animal habitats and biodiversity."

About 41,000 square miles of forest containing up to 888 million large trees experienced measurable losses of canopy water between 2011 and 2015. Of this group, up to 58 million large trees reached water loss thresholds that the scientists deemed extremely threatening to long-term forest health. Given the severity of the situation, even with increased precipitation due to El Niño, if drought conditions reoccur in the near future, there would be substantial changes to already weakened forest structures and systems.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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