California’s Central Valley is 430 miles long, situated between the Sierra Nevada and the Coast Range.

The massive Sacramento and San Joaquin Rivers converge to form the San Francisco Bay Delta, the largest estuary on the west coast, which flows under the Golden Gate Bridge and out into the Pacific Ocean. These rivers once produced millions of migrating salmon, steelhead and sturgeon and the Bay Delta is home to delta smelt and longfin smelt.

The Central Valley includes grasslands, chaparral and forested lands, but much of the valley has been converted to agriculture and cities.

The arid San Joaquin uplands in the southern part of the valley is home to the critically endangered San Joaquin kit fox, kangaroo rats and blunt-nosed leopard lizards. The wetter northern valley is home to vernal pools, giant garter snakes, red-legged frogs and river otters.

Federal and state wildlife refuges like the Sacramento National Wildlife Refuge provide some of the last remaining wetland habitat in the Central Valley and are critical to millions of Pacific Flyway birds that migrate through the region each year. 

California has more than 18 million acres of rangelands within and encircling the Central Valley and interior Coast Range. Most of this land is privately owned and managed for livestock production. Although conservation and ranching are often cast as conflicting, there is increasing science that shows that managed grazing on these Central Valley rangelands can result in healthier grasslands that provide clean water and important wildlife habitat. 


Habitat loss is the greatest threat to the Central Valley and its wildlife. Conversion of the land for agriculture, industry and housing have left only remnants of what was once thirteen million acres of wetlands, riparian areas, and grasslands. Dams, levees, diversions, groundwater pumping and pollution have reduced once mighty rivers to mere trickles in the summer, blocked salmon spawning ground, and produced toxic water conditions. Agriculture, people, fish and wildlife all need water, but climate change and increased agriculture and development have created intense conflicts over the Central Valley’s declining water supplies.

Defenders' Impact

Defenders led the effort to protect the Central Valley’s rare and unique habitats by working as part of the California Rangeland Conservation Coalition to protect privately owned rangelands in the Central Valley and inner coastal range.

Defenders has also been working to direct renewable energy projects onto lower value lands and away from the most sensitive wildlife habitat.

Defenders’ Rachel Zwillinger is the current chair of the Central Valley Joint Venture, a partnership among conservation organizations like Defenders and state and federal agencies that work together to make sure wildlife refuges like the San Luis National Wildlife Refuge receive enough water to support the wildlife that depend upon wetland habitats. We are exploring methods to ensure the full mitigation of the impacts of water transfers on the imperiled giant garter snake and other wildlife, with a focus on pushing the California Department of Fish and Wildlife to utilize its authority under the California Endangered Species Act.

After more than a decade of work by Defenders, the State Water Resources Control Board (SWRCB) voted in 2019 to adopt the strongest set of wetland protection rules in the country. Defenders is also working with a small group of NGOs and the Newsom Administration to negotiate voluntary agreements that could help the SWRCB update and implement the water quality control plan for the San Francisco Bay-Delta and its tributaries.

Our efforts against the California WaterFix project have included ongoing litigation over the U.S. Fish and Wildlife Service’s and National Marine Fisheries Service’s Endangered Species Act permits for the project, participation in the permitting process before the SWRCB, and education of lawmakers and the public regarding the ecological problems that the project would cause. Defenders is working to ensure that contaminated agricultural drain water management in the San Joaquin Valley includes safeguards for wildlife. 

California's Central Valley Blog Posts

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