Millions of California’s Trees May Die due to Drought

Satellite data and laser-imaging technology has shown that about 888 million trees in California have experienced water losses due to the ongoing drought.

The new study from the Carnegie Institution for Science – published December 28 in the journal of the National Academy of Sciences – used a new and much better technique to assess the health of tree population in California. Ashley Conrad-Saydah, deputy secretary for climate policy at the California Environmental Protection Agency, said that it is a never-before-seen in-depth analysis of individual trees.

Gregory Asner, scientists in the Department of Global Ecology at Carnegie Institution for Science and his colleagues, used laser-imaging technology to analyse the water content of trees, while flying above them in an airplane.

In August 2015, researchers spent twelve days to collect their airborne observations on California’s forests. Based on the observations, they were able to find how much water was present in the trees. The researchers also wanted to know just how much the water content had changed over time, so they looked at satellite data collected over the past few years.

A new model that explained the link between the imaging data on tree water content and the satellite data was developed by the researchers, after they had compared the two types of data.

The study results showed that between 2011 and 2015, estimates of 888 million trees – that cover almost 40,000 square miles (about ten million hectares) – have experience water loss. About 58 million of those trees have experience losses of more than thirty percent of their canopy water, and approximately 412 million trees have lost up to ten percent of their water content.

The most suppressed in water content were the trees on slopes and trees crests, the researchers found. That may be because water usually rolls downhill. Forests in the Sierra Mountains were in the worst shape. However, the trees in the northern coastal forests and those around Los Angeles are also among the most vulnerable, according to Asner.

Although the results show great water loss in millions of threes, that does not mean that all of those 888 million will die in the near future, the researchers noted. Asner said that more research needs to be conducted to figure out which of the trees are likely to die.

Ashley Conrad-Saydah, Deputy Secretary for Climate Policy at the California Environmental Protection Agency, said that the newfound data can be used to look for areas in which trees are more susceptible to falling over. Falling trees can cause a lot of damage to properties and may even put human life at risk, Conrad-Saydah added.

Image Source: cdn.phys