Estimating the Loss of Perennial Woody Vegetation to Cropland in California using 20 Years of Landsat Image Analysis

The progressive loss of perennial woody vegetation to cultivated land use throughout California has the potential to compromise native wildlife habitats and natural bio-control agents for cropland pests. In this study, satellite image products from the NASA Landsat sensor were compared from 1992 to 2012 to map the full spatial extent and the detailed geographic patterns of woody vegetation loss in all valley growing regions of the state. Counties the highest woody cover area converted to cropland were led by Riverside and Imperial in southern-most California and Siskiyou in northern-most California. On a statewide basis, the most common crop types into which woody cover was converted were alfalfa and hay, fallow, grapes, wheat, and almonds. Spatial autocorrelation analysis carried out within a 15-km diameter circular buffer zone centered on selected growing areas showed strongly clustered patterns of converted woody cover, indicating that entire woodland and shrubland corridors and connectors have been lost to cultivated land uses over the past two decades.