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Greenfield Development

Where is open space being converted to development?

From the days of the first Native American settlements, human activity in the Bay Area clustered around San Francisco Bay. Over time, development of the region's 7,000 square miles of land spread inland from the Bay, and this trend accelerated markedly during the rapid economic expansion that followed World War II.


As this process of development claimed lands formerly reserved for other uses, Bay Area residents have come to regard undeveloped lands as a precious resource - and not only for their scenic value. Construction on undeveloped lands - referred to as greenfield - decreases the area of agricultural lands and increases the area covered by impervious surfaces. The loss of greenfield across the Bay Area tends to correlate with an increase in the overall number of vehicle miles driven, as people who settle on the newly developed lands often have to travel long distances to work.

Updated: april 2020


acres of natural land per year were urbanized between 2000 and 2016


The Bay Area consumed the fewest greenfield acres among the nation's largest 10 metro areas over the last 15 years


of greenfield around the Bay Area were developed between 2000 and 2016


Regional Performance

The pace of Bay Area greenfield development slowed by nearly a third from 2000 to 2016.

Between 2000 and 2010, the Bay Area’s urban footprint expanded by around 4,700 acres per year. In this decade, that figure has been cut in half, down to 2,000 acres per year. The latest data show greenfield development on the rise from 2014 to 2016, which could suggest a resurgence in demand for lower-cost housing in less-centrally located parts of the region.


Development across the Bay Area increased the size of the region’s developed footprint to approximately 790,200 acres in 2016, making it 17 percent larger than the footprint of 1990. Since 1990, greenfield development was most rapid between 1990 and 2000, when approximately 55,000 acres were added to the region’s developed area. Nevertheless, the Bay Area has grown denser over time, with the rate of population growth outpacing the rate of greenfield development since 1990.

Historical Trend for Bay Area Greenfield Development

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Regional Distribution

Regional greenfield development since 2010 has been concentrated in Alameda, Contra Costa and Santa Clara counties.

East Bay counties, along with Santa Clara County to the south, have accounted for nearly two-thirds of the Bay Area’s greenfield development since 2010. Development in these three counties largely has consisted of nonagricultural land converting to housing or retail. Meanwhile, Sonoma County has drastically reduced its share of greenfield development in this decade, accounting for just 5 percent of the region’s share since 2010 – down from 19 percent in the 1990s.

Historical Trend for Greenfield Development by County

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Local Focus

The Bay Area’s urban footprint grew in large part due to activity in eastern Contra Costa and southern Santa Clara counties.

Powered in part by significant development activity in Brentwood, Antioch and Oakley, a significant chunk of our region’s greenfield development from 1990 to 2016 occurred in eastern Contra Costa County. The 28,100 acres of greenfield development in the county represented 25 percent of all such development within the region during this period. Combined with similar activity around South San Jose, Gilroy and Morgan Hill, Contra Costa and Santa Clara counties together account for more than 40 percent of our region’s greenfield development in this 26-year timeframe.


Sonoma and Solano counties have accounted for the majority of greenfield development in the North Bay. In Sonoma County – where nearly 16,600 acres have been developed since 1990 – nearly all development can be attributed to the conversion of small parcels in unincorporated areas along the U.S. Route 101 corridor. This contrasts with the development pattern in Solano County, where new, multi-acre residential subdivision developments are much more common.


Marin County accounted for just 5% of Bay Area greenfield development from 2000 to 2016


of the region's greenfield development from 2010 to 2016 occurred in Santa Clara County

Greenfield Development Areas

Developed before 1990
Developed between 1990 - 2000
Developed between 2000 - 2010
Developed between 2010 - 2016
Year: 1990
Click on a shape on the map for more information.

National Context

Since 2000, the Bay Area has consumed the fewest greenfield acres among the 10 largest U.S. metro areas.

While the fast-growing Sunbelt metropolitan regions of Atlanta, Dallas and Houston absorbed land at a prodigious pace from 2000 through 2018 – with each expanding its urban footprint by around 40 percent – the acreage of developed land in the Bay Area expanded by just 10 percent (measured in terms of U.S. Census block groups). Indeed, the Bay Area’s developed footprint grew by the smallest number of acres — and the third-smallest percentage — of any of the nation’s 10 largest metro areas during this period. Only New York City and Los Angeles registered similarly small growth rates for greenfield development.

Metro Comparison for Greenfield Development (2000 - 2017)

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Sources & Methodology

Methodology Notes

For regional and local data, FMMP maps the extent of "urban and built-up" lands, which generally reflect the developed urban footprint of the region. The footprint is defined as land occupied by structures with building density of at least 1 unit to 1.5 acres. Uses include residential, industrial, commercial, construction, institutional, public administration, railroad and other transportation yards, cemeteries, airports, golf courses, sanitary landfills, sewage treatment, water control structures, and other developed purposes.

To determine the amount of greenfield development (in acres) occurring in a given two-year period, the differences in urban footprint are computed on a county-level. FMMP makes slight refinements to urban boundaries over time, so changes in urban footprint +/- 100 acres are not regionally significant. The GIS shapefile represents the 2014 urban footprint and thus does not show previously urbanized land outside of the footprint (i.e. Hamilton Air Force Base).

For metro comparisons, a different methodology had to be used to avoid the geospatial limitations associated with FMMP. U.S. Census population by census block group was gathered for each metro area for 2000, 2010, and 2015. Population data for years 2000 and 2010 come from the Decennial Census while data for 2015 comes from the 2015 5-year American Community Survey. The block group was considered urbanized if its average/gross density was greater than 1 housing unit per acre (a slightly higher threshold than FMMP uses for its definition). Because a block group cannot be flagged as partially urbanized, and non-residential uses are not fully captured, the urban footprint of the region calculated with this methodology is smaller than in FMMP. The metro data should be primarily used for looking at comparative growth rate in greenfield development rather than the acreage totals themselves.

Data Sources

Department of Conservation: Farmland Mapping and Monitoring Program
GIS Data Tables/Layers (1990-2016)

U.S. Census Bureau: Population Data
Population by Census Block Group (2000-2010)

U.S. Census Bureau: American Community Survey (5-year)
Population by Census Block Group (2000-2018)

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