Landscape Change in the San Joaquin Valley of California—
Pre-European Settlement to 2000

Natural Communities, 1885, 1912, 1945, 1977, and 2000

The San Joaquin Valley, including the Tulare Basin, is an area approximately 40,000 square kilometers (16,000 square miles) south of the San Joaquin/Sacramento Delta between the California coast range and the Sierra Nevada. Before the settlement of Europeans, the valley contained a vast mosaic of upland and freshwater ecosystems that supported a diverse collection of species including many endemic to the region.

After the gold rush of the 1840s, settlers began to arrive and cultivate lands along the fertile east side of the valley. Early irrigation development began by direct diversions from larger streams fed by spring snow runoff from the Sierra Nevada. Cattle ranchers also began diverting water from streams to irrigate pastures. By 1880, a railroad line through the valley provided the means to export agricultural products to market.

By the early twentieth century, groundwater pumping technology advances and private canal construction led to an increase in lands under irrigation. Intensive pumping heavily impacted groundwater levels in many areas. Following the great depression, the Central Valley Project was established to provide a stable source of water for irrigation. The project, encompassing 35 counties and an area approximately 500 miles long and 100 miles wide, was the largest water project ever undertaken at the time. The landscape had evolved from islands of irrigated farmland to mostly irrigated farmlands with large island blocks of natural lands.

By 1977, the Central Valley Project was delivering water supplies from the San Joaquin River to east-side farmers through the Friant-Kern Canal. On the west side of the valley, the Central Valley Project and the California State Water Project opened up new lands for irrigation. Urban development increased after World War II. Many natural lands of the valley floor remained in isolated, fragmented patches, and connectivity between many of these more natural areas was lost.

In the late twentieth century, the rate of loss of natural lands slowed, but isolation and fragmentation continued. Remaining natural lands, for the most part, cannot be economically farmed and are under pressure from continuing urban expansion and land conversion to large-scale dairies. However, some lands are being conserved through public acquisition and private conservation easements, and some farmlands with perched water tables and contamination problems are being withdrawn from production.