Most of Northern California's kelp forest ecosystem is gone, replaced by widespread 'urchin barrens' Northern California's kelp forest ecosystem is gone, replaced by widespread "urchin barrens." March 17, 2021 Satellite imagery shows that the area covered by kelp forests off the coast of Northern California has dropped by more than 95%, with just a few small, isolated patches of the bull kelp remaining. Species-rich kelp forests have been replaced by "urchin barrens," where purple sea urchins cover a seafloor devoid of kelp and other algae. A new study led by U.S. National Science Foundation-funded researchers at the University of California, Santa Cruz documents this dramatic shift in the coastal ecosystem and analyzes the events that caused it. The decline was not gradual but rather an abrupt collapse of the kelp forest ecosystem in the aftermath of unusual ocean warming along the U.S. West Coast starting in 2014, part of a series of events that combined to decimate the kelp forests.