Huntington Beach Central Park is a haven for wild birds. Once of the reasons is areas of untrimmed vegetation such as this. Unfortunately, the park has recently been invaded by Polyphagous Shot Hole Borers. These small beetles bore tunnels (galleries) into the trees then plant fungus for their young to feed on. The fungus eventually weakens and kills the trees. As a result, the park service has had to remove a significant portion of the trees.
This is supposed to be the work of the invasive Polyphagous Shot Hole Borers. The hole borers are small beetles that bore holes into the trees and then plant fungus in the holes for their grubs to feed on. The fungus may continue growing until it weakens and kills the trees. The beetle is an invasive species that has broken out in multiple locations in Orange County, and decimating trees at each.