Although there are many tactics used to control growth, ultimately, there is only one measure of importance in protecting farmland: efficient urban land use. In examining four communities in the Central Valley, we found large disparities in land use efficiency. Planners and researches often measure efficiency based on housing units built per acre of land. However, this statistic often misleads, as housing characteristics vary from market to market. What makes the most sense when determining the level of land use efficiency, is to look at the number of additional residents housed per converted acre of farmland. To evaluate the rates at which cities are converting farmland to urban uses, we will use four Central Valley cities as examples: Modesto (in Stanislaus County), Merced (in Merced County), Davis and Woodland (both in Yolo County). We chose these cities because each represents a distinguishable urban area of growth surrounded by farmland. While many cities have an option of what type of land to develop, these cities have little choice; virtually all of their converted land comes from farmland. The study areas represent not just the incorporated cities, but also the urban clusters in and around these cities. Although it varies from place to place, much of the growth and land use conversion happens beyond the city boundaries. We used census tracts to define the study regions, two of which are shown in the map to the right. Population data for each study are shown in table 1-1, while land use conversion data (in acres) are shown in table 1-2. Looking at the two datasets together yields the following results: * Modesto is adding 13 people per converted acre. * Woodland is adding 10.57 people per converted acre. * Merced is adding 8.4 people per converted acre. * Davis is adding 7.25 people per converted acre. At first glance, it is surprising that Davis — known for its progressive planning policies and work in farmland preservation — would make the least efficient use of converted agricultural land. Additionally, Davis's growth rate during the past ten years (25%) is the greatest of the four. Woodland, which lies only a few miles north of Davis, is adding more than three people per urbanized acre more than Davis. The difference here is likely explained by the difference in real estate markets. Davis has built high-end homes in subdivisions with large lots and open space requirements, while Woodland provides more mid-range and starter homes for Sacramento commuters. Merced is the poorest community of the four and has been hit hard by the closing of the Castle Air Force Base in 1995. Merced lacks the large development projects more common in the other cities, and has little in the way of growth control measures. It will be interesting to see what kind of effect the new University of California campus planned a couple miles east of town (see CP&DR Public Development, April 2001; Environment Watch, June 1999) will have on these numbers in the future. Modesto is, by a fair measure, the most "efficient" of the four. This efficiency can be seen in the large housing subdivisions of northern Modesto, which provide single-family homes on lots that are smaller than usual in the Central Valley. With its proximity to Bay Area job centers, Modesto's real estate market is strong, and the city has implemented some growth measures that keep lot sizes relatively small and developments clustered close together. This methodology could easily be applied to many other California cities and regions to help paint a more complete picture of farmland conversion rates throughout the state. Also, the methodology may be used in conjunction with population projections to predict the future rate of farmland conversion. Projections indicate that growth in California is not likely to slow anytime soon, and that much of this growth could occur in the Central Valley, making farmland conversion an issue of increasing concern. Erik Kancler is a research associate at Solimar Research Group.