Great Valley Grasslands State Park is a state park of California, United States, preserving a parcel of remnant native grassland in the San Joaquin Valley. Such a temperate grasslands, savannas, and shrublandsbiome was once widespread throughout the whole Central Valley.[1] The 2,826-acre (1,144 ha) park was established in 1982.[2] Largely undeveloped, it was formed by combining two former state park units: San Luis Island and Fremont Ford State Recreation Area.[3] Its chief attractions for visitors are spring wildflowers, fishing, and wildlife watching.[4]
Grassland Ecological Area
The park is part of the larger Grasslands Ecological Area (GEA), a 160,000-acre complex (65,000 ha) of federal, state, and private lands dedicated to wildlife conservation. In 2005, the GEA earned recognition as a Ramsar Wetland of International Importance, underscoring its status as California's largest remaining contiguous freshwater wetland system.[5] Located in the San Joaquin River Basin of the Central Valley, this diverse landscape encompasses a rich tapestry of habitats, from semipermanent and permanent marshes to riparian corridors, vernal pools, wet meadows, native uplands, and expansive grasslands.
The ecological significance of the GEA is particularly evident during winter months when it transforms into a crucial haven for migratory birds. Annually, the area hosts hundreds of thousands of waterbirds, including a wide variety of duck and goose species, alongside vast numbers of shorebirds. Beyond its role as a migratory stopover, the GEA serves as a sanctuary for numerous threatened and endangered species. This remarkable concentration of diverse ecosystems within the GEA fosters an extraordinary richness of flora and fauna, positioning the area as a cornerstone of California's biodiversity conservation efforts.[6]
Purple needlegrass (Stipa pulchra) –– California’s most widespread native grass, and named California’s State Grass in 2024. It is a perennial bunchgrass that can grow up to 3 feet tall with a deep root system, making it drought-tolerant and excellent for erosion control.[7]
California fescue (Festuca californica) –– a native perennial bunchgrass that is intermediate to long-lived. It grows to a height of 24-55 inches with tightly clumped bases and erect culms (stems).
Endangered plants:
Delta button celery (Eryngium racemosum) — an endemic and state-listed endangered species, primarily found in the Sacramento-San Joaquin River Delta region. It grows seasonally in flooded plains and swales, and is threatened by habitat destruction due to water regime alterations, land conversion, and invasive species.[8]
Hairy Orcutt grass (Orcuttia pilosa) –– a federally and state-listed endangered species that inhabits vernal pools and seasonal wetlands. Its population has drastically decreased due to habitat loss from agricultural conversion and urban development.[8]
Wright's trichocoronis (Trichocoronis wrightii) –– an endangered species found in meadows, freshwater marshes, and vernal pools within the park. It is considered a special-status species due to its limited distribution efforts and habitat requirements.[9]
California Tiger salamander (Ambystoma californiense) — an amphibian endemic to Northern California. It spends most of its life underground in rodent burrows and emerging during rainy seasons to breed in vernal pools and seasonal ponds. Adults can grow up to 7-8 inches in length and are characterized by their black coloration with yellow or white spots. The species faces significant threats to habitat loss and fragmentation due to agricultural and urban development, as well as introduced predators and hybridization with non-native salamanders, leading to its listing as endangered [10]
Vernal pool fairy shrimp (Branchinecta lynchi) — a fairy shrimp endemic to the vernal pools and swales in California’s Central Valley, coast ranges, and a limited number of sites in southern Oregon. The species produces drought-resistant cysts that can survive dry periods for years, allowing populations to persist in ephemeral habitats. Vernal pool fairy shrimp are filter feeders, consuming algae, bacteria, protozoa, rotifers, and bits of detritus. The species is listed as threatened primarily due to habitat loss and degradation from urban development, agricultural conversion, and invasive species that alter the vernal pool ecosystems.[11]
San Joaquin tadpole shrimp (Lepidurus packardi) — a tadpole shrimp endemic to California. The species inhabits vernal pools and seasonal wetlands in California’s Central Valley, where it contributes to the aquatic food web. It can enter a dormant state during dry periods, allowing it to survive in ephemeral habitats until water returns. The San Joaquin Tadpole Shrimp is endangered due to habitat loss from agricultural conversion and urban development, which have reduced its available breeding sites.[12]
Western spadefoot toad (Spea hammondii) –– a species endemic to California that inhabits lowlands, such as river floodplains and washes in the Central Valley and along the coast. It is found in grasslands and areas with shallow, temporary pools. Adult spadefoots spend most of their time underground, emerging mainly on rainy nights to feed extirpated from the 80% of its range in southern California due to agricultural expansion and urban development. This species is listed as a California Species of Special Concern and is under federal review for endangered status. Its fossorial lifestyle and need for both aquatic and terrestrial habitats complicate conservation efforts.[13]
Giant Garter Snake (Thamnophis gigas) –– an aquatic species endemic to wetlands in California’s Central Valley. It inhabits marshes, sloughts, ponds, small lakes, low-gradient streams, and other waterways, including agricultural wetlands such as irrigation and drainage canals and rice fields. The species has been negatively impacted by habitat loss and fragmentation due to urbanization, agricultural development, flood control, and water management practices. Federally listed as threatened, its survival depends on suitable aquatic habitats with vegetated banks and reliable freshwater sources.[14]
Proposal for closure
Great Valley Grasslands State Park faced significant challenges in January 2008 when it was one of 48 California state parks proposed for closure as part of a statewide deficit reduction program. This proposal underscored the ongoing financial pressures affecting California's park system. Ultimately, the threatened closures were avoided through budget adjustments, including reduced operating hours and cutbacks in maintenance across the state park system.[15] Since then, the park has not only remained open but has also become a focal point for renewed conservation efforts. As of 2024, California State Parks has initiated a comprehensive General Plan process for Great Valley Grasslands State Park, aimed at enhancing visitor experiences and addressing resource management needs.[16]
