Another 27 million trees died in California last year due to the lingering effects of drought, according to new aerial survey data from the U.S. Forest Service. That brings the total number of trees killed statewide to a staggering 129 million since 2010. In a typical year, about one million trees die across California. But beginning in 2014, that number began ticking up as aerial surveyors with the U.S. Forest Service started to notice entire hillsides turning yellow, brown and orange.