According to a 2014 World Bank economic ranking, California has the eighth largest economy in the world. With its globally important economy and a population exceeding 38 million, the importance of its forests are sometimes overlooked or understated. How are the Golden State’s forests holding up during the drought period that began in 2012 and continues today?

That’s what researchers1 from the Department of Global Ecology at the Carnegie Institution for Science in Stanford, Calif., wanted to know. Their findings of the forest canopy water loss during the drought have just been published in the Dec. 28, 2015 issue of PNAS https://www.pnas.org/content/early/2015/12/22/1523397113.full.pdf

Going in the researchers knew the draught had severely reduced snowpack, soil moisture, ground water and reservoir levels, but needed to assess the impact of the draught on the health of the forests. The researchers used airborne laser-guided spectroscopy and satellite-based models to assess losses in canopy water content of California’s forests between 2011 and 2015. Approximately 10.6 million ha of forest containing up to 888 million large trees have experienced measurable loss in canopy water content during the drought period. Severe canopy water losses of greater than 30% occurred over 1 million ha, affecting up to 58 million large trees. Their measurements exclude forests affected by fire between 2011 and 2015. The researchers predict substantial future forest change if drought conditions continue or reoccur, even with the current temporary reprieve of El Niño.

1. Gregory Asner G, Brodrick P, Anderson C, et al. Progressive forest canopy water loss during the 2012–2015 California drought PNAS 2015, published ahead of print December 28, 2015.