Interactions Between Urban Development and Spatial Distributions of Specialty and Commodity Crops in S.E. Michigan, 1992-2001

Abstract

Agriculture is being displaced by development throughout the United States. Because agricultural activities vary among crop types and farm operations, and because agricultural competes for space with urban land uses at the urban-rural fringe, it is important that we understand the spatial dynamics of agriculture in this area, where conversion to development is most acute. In particular specialized crops, such as fruits and vegetables, are important because they promote biodiversity and provide more diverse food products than commodity crops. I developed a model to test the idea, from the von Thünen model of agricultural land rents, that specialty crops are more likely to be located lost the process of urbanization than commodity crops. Because historical data on the locations of farms by crop type do not exist at a resolution finer than counties, I used dasymetric mapping to estimate locations of specialized crops in 1992 and then analyze their loss by 2001. The study area for this analysis was the ten-county region of Southeast Michigan. A regression analysis showed that specialized crops were significantly more likely to be located where there was less development and more agriculture in an area, higher population density and nearer distance to water. These relationships were then used to create a suitability surface for specialty agriculture in 1992. Specialized and Commodity designations, for which land areas were available at the county level, were then allocated to agricultural areas identified in a land-cover data product, and those that were lost between 1992 and 2001 were identified. The tabulated results showed that the entire region experienced a higher rate of loss specialized crops compared with commodity crops, with the loss happening more rapidly in the urban-rural fringe than in exurban areas. This application of dasymetric mapping could be used as a model to investigate agricultural dynamics of other urban areas.