High Above the Canopy. California’s Drought and Its Trees

This year’s strong El Niño is bringing some much-needed rainfall to drought-stricken California. But much more is needed.

“While it is good news that drought improvement is predicted for California, one season of above-average rain and snow is unlikely to remove four years of drought,” said Mike Halpert, deputy director of at NOAA’s Climate Prediction Center. Halpert says about twice the normal amount would be needed to push California out of its drought.

New research is out this week highlighting the impact of the severe drought from 2011 to now. 58 million large trees in California suffered severe canopy water loss in the four-year period. And it wasn’t just the long periods of low rainfall. Scorching temperatures and a rise in the destructive bark beetle also threatened trees.

California drought and forest

The progressive forest canopy water stress from 2011 to 2015.

Carnegie’s Greg Asner underscores the importance of California’s forests. “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,” says Asner. “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.”

Asner’s team observed measurable canopy water loss in forests spanning nearly 41,000 square miles. 888 million large trees showed measurable impacts from the severe drought. 58 million of these trees reached levels of water loss researchers consider extremely threatening to long-term forest health.

El Nino is bringing a welcome change to weather patterns, but researchers are still concerned. If drought conditions come back soon, the situation would turn dire for the most affected trees.

How do you measure statewide water loss?

Lucky for Asner and his team, they didn’t have to hike across California to get the data they needed. Meet the Carnegie Airborne Observatory (CAO).

Carnegie Airborne Observatory

Researchers traded in their DSLR cameras for laser-guided imaging spectroscopy tools mounted on the CAO. The data from the CAO combined with satellite data going back to 2011 shows the full impact of the recent drought and its effect on the forest.

The advantages of having this kind of data are two-fold. One, researchers can see which trees are most at risk of death. Two, this data can also determine which areas are at the highest risk for forest fires.

Continuous monitoring of California’s forest is vital according to Asner. “Monitoring will enable actions on the ground to mitigate a cascade of negative impacts from forest losses due to drought, as well as aid in monitoring forest recovery if and when the drought subsides.”

The plane that made it possible

The Carnegie Airborne Observatory (CAO) is the brainchild of Greg Asner. Here it is taking off in May to begin observing the forests of California.

Instruments aboard the airplane capture forests in 3D at a resolution of 3.5 feet. The video of the Amazon rainforest below shows the height of the vegetation. You can see the tallest trees appear in red while low forest gaps show up as blue.

It’s incredible how technology like this can show us what’s going on with forests across the world.