Researchers from the U.S. Forest Service are documenting what they are calling an unprecedented die-off of trees in urban areas across Southern California.

Sycamores, willows, avocado and citrus trees are dying because of the drought, pests and disease infestations.

http://www.kpbs.org/news/2017/apr/26/us-forest-service-unprecedented-tree-die-hits-sout/