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Impacts of Different Growth Scenarios in the San Joaquin Valley of California


In the next 40 years, the eight counties of the San Joaquin Valley are projected to double in population from 3.3 million to more than 7 million (Great Valley Center 2006). The region faces many challenges with respect to its capacity to accommodate this dramatic increase in population while maintaining its environmental infrastructure and preserving its diminishing natural resources.

In response to these growing pressures, Governor Schwarzenegger announced in June 2005 the formation of the California Partnership for the San Joaquin Valley (Partnership) to “…improve the economic well-being of the Valley and the quality of life of its residents” (Department of Business Housing and Transportation 2006a). This 26-member Partnership, led by the Secretary of the Business, Transportation and Housing Agency, is composed of eight state government members (primarily cabinet level appointees), eight local government members (primarily members of county boards of supervisor), eight private sector members (representing leadership in various business sectors), and two deputy chairs. The Partnership region includes San Joaquin, Stanislaus, Merced, Madera, Fresno, Tulare, Kings, and Kern Counties.

The Information Center for the Environment (ICE) at UC Davis supported the Partnership by providing geographic information system (GIS) data and growth allocation build-out scenarios. Based on input from the Partnership and the Great Valley Center, ICE developed and produced seven urban growth scenarios for the region that project popula¬tion to year 2050 using UPlan, a rule-based GIS urban growth model (Johnston et al. 2006). These scenarios were developed based on different goals (such as Compact—within current spheres of influence; Farmland Protection—prime farmland masked; Great Cities—create “mega-cities” in concentrated regions) and produced vastly different outcomes.

This paper discusses the seven growth scenarios and the implications of mapped future urban growth in the San Joaquin under those scenarios on a collection of biologically significant factors. A team of federal, state, and non-government organization biological experts selected 14 key biological layers crucial for protecting high value open space in the San Joaquin Valley. ICE combined the modeled urban growth output for the seven growth scenarios with the 14 biologically significant GIS layers. The growth scenarios reflect seven different policy directions that the region’s leaders may choose when planning for growth in the upcoming several decades. Results showed that depending on the scenario chosen (and hence the policy emphasis), the magnitude of biological resources likely to be lost varies significantly. The scenario with the least overall ecological impact is the Compact Growth Scenario (Scenario 3), with Scenarios 6 (New Cities) and 7 (Great Cities) also fairly low in relative impact. Scenario 4 (Prime Farmland Protection) resulted in the largest decline in the acreage of the 14 key biological data layers we examined. Scenarios 5 (I-5 to Highway 99 Exclusion), 2 (East/West Road Improvement) and 1 (Status Quo) also showed relatively high negative impacts.

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