Prime Farmland Lost to Land Idling, Habitat Conversion, Urbanization

Posted on Monday, June 30th, 2014 by

With California’s final cap-and-trade budget including funding for agricultural land conservation, it is increasingly important to understand the dynamics of farmland trends in the state. The more we know about land use trends, the more we can work to ensure that threatened farmland is adequately protected through the most appropriate tools and policies.

The Farmland Conservation Strategy Act, AB 1961, aimed to do just that. Co-sponsored by CalCAN, the Community Alliance with Family Farmers, and American Farmland Trust, the bill would have required counties with significant agricultural resources to inventory their farmland, define their goals and policies to conserve farmland and mitigate for its loss, and publish that information on the county website. However, heavy opposition from the California Building Industry Association led to AB 1961’s failure to get out of the Assembly Appropriations Committee.

Despite this setback, a state program provides critical data on the status of farmland in the state. The California Department of Conservation (DoC) recently released the 2008-2010 Farmland Conversion Report. This report collects data from the Farmland Mapping and Monitoring Program (FMMP), which uses geographic information systems (GIS) mapping to document changes in the location and extent of California’s farmland.

Here, we summarize some of the report’s findings and consider their implications for California agriculture.

Urbanization Linked to Farmland Conversion

About 70 square miles (44,504 acres) of farmland was impacted by urban development between 2008 and 2010, 39 percent fewer than was seen during the 2006-2008 period and the lowest recorded in the FMMP’s history. Slowed urbanization in most counties reflects the impacts of the recession; the next lowest two-year rate of urban development occurred during a significant 1990s recession.

In Southern California, urbanization slowed by 45 percent–but the region still accounted for nearly 44 percent of statewide urbanization. Riverside County led the state in overall urbanization, followed by San Diego and Los Angeles. However, leading the state in acreage converted from irrigated farmland to urban uses was Kern County, followed by Tulare and Fresno, three key agricultural counties in the San Joaquin Valley.

30 percent of the land converted to urban uses was previously used for dryland farming and grazing, and some of it might have previously been left idle. Meanwhile, one-quarter (11,104 acres) of the land converted to urban uses had previously been classed as irrigated farmland. Of the irrigated acreage converted to urban uses, Prime Farmland was impacted at more than twice the rate of other farmland categories. The remaining 45 percent of new urban land was converted from either natural vegetation or vacant lands.

Irrigated Land Converted to Dry Farming and Left Idle

Photo Courtesy of USDA-NRCS
Photo Courtesy of USDA-NRCS

According to the DoC, California lost 168,039 acres of irrigated farmland from 2008 to 2010, 61 percent of which was classified as Prime Farmland. This includes loss from urbanization, land idling, habitat conversion, as well as low density rural development. Fresno County, home to more than 2,000 farms, led the state in the conversion of nearly 46,000 acres of agricultural land, and Kern County, another top agricultural county, followed with a loss of 29,000 acres.

Land idling and the conversion of highly-productive agricultural land to dry land grain production played the largest roles in irrigated land conversion, which points to water scarcity issues. The Sacramento-San Joaquin Delta and southern San Joaquin Valley counties exhibited the largest impact from land idling.

However, as we have previously reported, the USDA’s most recent Census of Agriculture suggests that California acreage increased slightly, by 204,306 acres, from 2007 to 2012.

The discrepancy between the Census and DoC numbers is likely because of differences in reporting methodologies and what lands are included in the Census categories. DoC uses aerial imagery and county-reported land management data, while the Census of Agriculture collects self-reported data.


During the development slowdown brought on by the 2008-2010 Great Recession, farmland conversion was dominated by land idling and the reversion of irrigated agriculture to dry farming techniques. Trends point to water availability as a prominent driver of agricultural land use change.

Conversion disproportionately impacts Prime Farmland, which is characterized by the highest-quality soils and is fundamental to California’s food production. Between 1984, when the FMMP began collecting data, and 2010, Prime Farmland losses were nearly 662,000 acres, larger than the size of Yolo County.

Although it only accounted for 6.5 percent of the total irrigated farmland lost between 2008 and 2010, urbanization accounts for the vast majority of farmland lost since data collection began. Between 1984 and 2010, 1.1 million acres of farmland have been lost to urbanization. The DoC attributes the slowed rate of urban development to the recession, which indicates that urbanization will pose a larger threat to farmland conservation as the economy recovers and revitalizes development.


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