Late 20th century land change in the Central California Valley ecoregion

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Language

English

Bibliographic Citation

The California Geographer 48: 27-59

Notes

This research challenges two general assumptions of land-cover change in California's Central Valley ecoregion. They are (1) the primary land-cover change occurring in urbanization of agricultural lands, and (2) that the ecoregion experienced a rapid decline in farmland between 1973 and 2000. Our findings indicate that while urbanization is significant, it is secondary to conversions occurring between agriculture and rangelands (grasslands/shrublands). Furthermore, we estimate that farmland increased in area over the study period, expanding from 71.6% of the ecoregion in 1973 to 72.4% in 2000, a net increase of 357 New agricultural lands were often found at the ecoregion periphery in the form of nut orchards and grapes, indicating a general shift away from traditional low-risk and low-value field crops to high-risk and high-value specialty crops. Rangeland is estimated to have declined by nearly 20%, from 19.2% of the ecoregion in 1973 to 15.4% in 2000, while developed lands increased from 6.5% to 9.0% over the same time period. Changes between agriculture and rangeland accounted for over 70% of all estimated change, while changes directly associated with urbanization accounted for approximately 14% of all identified land-cover change. Across all land-cover classes, we estimated that 12.4% of the ecoregion changed from one land-cover type to another during the 27 -year study and that the period of highest change was between 1973 and 1980. Many drivers may explain these results, including the influence of regional climate variability and drought. This research suggests that drought, if severe enough over an extended number of years, has the potential to significantly influence rates and types of regional land-cover change. Understanding these coupled human-environment relationships has implications for monitoring biogeochemical systems, natural resources, and ecosystem services at local to regional scales.

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Late 20th century land change in the Central California Valley ecoregion