A Geospatial Index of Agricultural Vulnerability to Climate, Urbanization, and Socioeconomic Impacts in California

Ensuring the resilience of agricultural systems in the face of climate, land use and socioeconomic changes requires a sound understanding of the possible risks and uncertainties. We developed a geospatial index of agricultural vulnerability derived from 22 biophysical and socioeconomic variables, collected to assess specific dimensions of vulnerability that vary across California’s agricultural landscape. Each indicator variable was assigned to one of four sub-indices: 1) climate vulnerability, 2) crop vulnerability, 3) land use vulnerability, and 4) socioeconomic vulnerability. Principal component analysis was then used to integrate the variables within each sub-index into composite measures of vulnerability which were mapped statewide using a raster grid standardized at 12.5 km resolution. A ‘total agricultural vulnerability index’ was developed from the four sub-indices using an additive model. Agricultural regions that merit special concern due to high (1.5-2.5 S.D. above mean index value) or very high vulnerability (>2.5 S.D.) included the Sacramento-San Joaquin Delta, the Merced-Fresno corridor, the Salinas Valley, and the Imperial Valley. Main drivers of vulnerability in the Delta and Merced-Fresno regions included high rates of urban growth, frequent flooding, and soil salinity problems, while vulnerability in the Salinas Valley was due mostly to socioeconomic factors (e.g. high farm disaster payments and more migrant farm workers).  A combination of climate risks, namely high summer temperatures and low annual precipitation, and the above-mentioned socioeconomic factors resulted in high vulnerability in the Imperial Valley. Moderate vulnerability (0.5-1.5 S.D.) was found in most of California’s prime farmland, suggesting a broad need for rural communities to develop adaptation plans that account for location-specific vulnerabilities. As state agencies consider responses to climate change and urban sprawl through the implementation of “climate action plans” now required by California’s Global Warming Solutions Act (AB32), opportunities to balance agricultural adaptation and mitigation objectives should be prioritized.