Figure 1.
Extent of study area, ecoregions and reporting regions used for conversion analysis.
Figure 2.
Sequence of core spatial analyses used in study.
The three primary elements of the analysis are shown in sequence. The “change detection” step provided the full set of areas to classify in the “conversion classification.” Some lands where a change was detected but were not actually converted were removed from the analysis as false conversions. Converted lands were removed from the habitat data for the “status assessment”, which quantified the proportion of habitats under various types of protection. The year of the data used in FMMP overlays between time point 1 and time point 2 varied by survey area. Nineteen of the thirty-six survey areas spanned the period from 1984–2008, five spanned the period 1984–2006; and the remaining twelve covered various years with an average of seventeen years across them. The most protective conservation management status was assigned to land if multiple statuses existed, in order of precedence: fee ownership, easement, Williamson Act enrollment.
Figure 3.
Area (Ha) of land cover types on land converted from rangelands during the study period.
Converted areas were mapped using the California Department of Conservation's Farmland Mapping and Monitoring Program data (1984–2008) and classified using the National Agriculture Imagery Program imagery from 2009. The development categories (shown in gray) account for 49% of total area converted, agricultural conversions account for 40% and various other conversions account for about 10%.
Figure 4.
Regional conversion patterns by major type.
The primary type of conversion for each region was variable, but can be explained partly by the existing land use in the region. For example, the more developed Sacramento Metro and Bay Area regions saw the majority of the converted land end up as residential and commercial development, while the majority of conversions in the San Joaquin Valley and Central Coast regions were to intensive agriculture classes. Conversion data are from an analysis of Farmland Mapping and Monitoring Program data, and land cover assigned using the National Agriculture Imagery Program imagery for 2009.
Figure 5.
Conversion patterns by major type.
The converted rangelands spanned a large geographic area. In some areas large protected area complexes were created where conversion was less widespread, possibly enabled by lower land prices (A). Agricultural conversions were more common adjacent to existing cropland (B). Conversions to developed land uses are dominated by new housing at lower densities at higher elevations in the Sierra Nevada foothills (Madera, Fresno, Butte counties) and at higher densities in the San Francisco Bay Area and near Sacramento. The areas in the Central Coast around Atascadero and Arroyo Grande experienced a large amount of conversion from a variety of sources (C).
Table 1.
Rate of conversion of rangeland for years up to 2008 and for 2008–2010 based on FMMP data.
Figure 6.
Conservation status of rangeland habitats.
Over 60% of the total area in rangeland habitat have some protective status against various types of conversion with the majority provided by enrollment in the Williamson Act which prevented conversion to non-agricultural uses, but was defunded starting in 2009. This chart is for the portion of the study with rangeland habitats. WA = Williamson Act.
Table 2.
Area (Ha) by conservation status for California rangeland habitat types.