So many salmon once spawned each year in the Central Valley that humans all but lived on them, and chemical traces of the fish are still detectable in the soil, where the scavenged carcasses fertilized riparian vegetation.
“It was a salmon-based ecosystem,” said Peter Drekmeier, the policy director of the group Tuolumne River Trust.
All that has changed. California’s Chinook population has collapsed. The fish compete against agriculture, urban growth and climate change, and with their inland habitat mostly gone and the cold water they need to spawn a scarcer and scarcer resource, wild Chinook, especially in the San Joaquin River, face extinction. So do several other fish species, whose estuary habitat has been destroyed or drained dry by agricultural diversions. Reduced flows and higher water temperatures also cause frequent blooms of toxin-producing algae and cyanobacteria in the Sacramento–San Joaquin Delta—events that turn the water an electric green and which scientists consider serious threats to public health.