Greenfield Development

Where is open space being converted to development?

Greenfield Development

Greenfield development refers to construction on previously undeveloped land and the corresponding expansion of our region’s developed footprint, which includes the extent of urban and built-up lands. The footprint is defined as land occupied by structures, with a building density of at least 1 unit to 1.5 acres.

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.

Regional Performance
The pace of Bay Area greenfield development slowed by nearly a third from 2000 to 2014.

The number of new acres of urban development in the Bay Area has decreased during each biannual period since 2002, marking a decade-plus-long trend of declining greenfield development. In the most recent period – from 2012 to 2014 – greenfield development occurred at one-fifth the rate it did during the 1990s. The slowing rate of urban expansion is no doubt influenced by the lingering effects of the Great Recession, but it also may reflect changing preferences among Bay Area homebuyers and the efficacy of cities’ and counties’ growth management strategies.

Development across the Bay Area increased the size of the region’s developed footprint to approximately 790,000 acres in 2014, making it 14 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, overall densification increased in the 1990s because while the addition of the newly developed acreage boosted the size of the developed Bay Area by 8 percent, population grew by 12 percent. Since 2000, densification of developed land has been even more intense as fewer acres of greenfield developed while population continued to grow at a steady pace.

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

East Bay counties, along with Solano County to the north, account for most of the Bay Area’s greenfield development since 2010, with large housing developments moving forward at the Bay Area’s eastern periphery. This reflects a slight shift from the urban development pattern seen in previous decades, when additional urbanization occurred in Santa Clara and Sonoma counties as well. Santa Clara County’s share of regional acres of greenfield development dropped from 20 percent in the 1990s to just 5 percent in the 2010 to 2014 period.

Marin County has a history of minimal greenfield development in recent decades. Between 2012 and 2014, 640 acres of the decommissioned Hamilton Air Force Base in Novato was converted to wetlands, resulting in a net decrease in urban land for the county. This is a relatively rare example of an urbanized area contracting as land is returned to nature.

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Historical Trend for Greenfield Development by County

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 development activity in Brentwood, Antioch and Oakley, a significant chunk of our region’s greenfield development from 1990 to 2014 occurred in eastern Contra Costa County. The nearly 24,000 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 42 percent of our region’s greenfield development in this 24-year timeframe.

Sonoma and Solano counties have accounted for the majority of greenfield development in the North Bay. In Sonoma County – where nearly 15,300 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.

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Greenfield Development Since 1990

Year: 2012

Click on an area of the map to see when it was developed.
Developed before 1990
Developed in the 1990s
Developed in the 2000s
Developed in the 2010s
National Context
Since 2000, the Bay Area has consumed the fewest greenfield acres among the top 10 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 2015 – with each expanding its urban footprint by around 40 percent – the acreage of developed land in the Bay Area expanded by 8 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.


Department of Conservation: Farmland Mapping and Monitoring Program

GIS Data Tables/Layers (1990-2014)

U.S. Census Bureau: Population Data

Population by Census Block Group (2000-2010)

U.S. Census Bureau: American Communicty Survey (5-year)

Population by Census Block Group (2000-2014)

Image: Flickr (Creative Commons license), Photographer: Pembina Institute, 2994480730_4fbebc392f_o.jpg

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.