Dave Edwards has hiked in the Santa Monica Mountains for decades, but the view has changed in the past few years. Hundreds, if not thousands, of trees have died, leaving hillsides with gray and brown patches. Five years of drought has shortchanged trees on water and nutrients. Trees dried out and insects moved in. “It’s not just in the Santa Monica Mountains. It’s all over the state,” said Edwards, a volunteer with the Santa Monica Mountains Trails Council. “I have never seen it like this.”