Measuring exurban change in the American West: A case study in Gallatin County, Montana, 1973–2004

Dispersed patterns of rapid rural, or “exurban,” growth in the American West are recognized as key threats to the region's biodiversity through habitat loss and fragmentation. Both planners and ecologists have responded with strategies to minimize the impact of these patterns—strategies which have appeared in local planning policies since the 1990s. This research examined the degree to which these changing policies were effective in changing subdivision patterns in Gallatin County, Montana. Using landscape metrics drawn from landscape ecology and urban sprawl literature, this study tracked changes in metrics across the 1973–2004 time period for regulated subdivision, major and minor, at several spatial scales. The results revealed several distinct trends: (1) major subdivisions became more “clustered” and less land consumptive, (2) minor subdivisions revealed the opposite trend and are recently consuming the more land, (3) distances from existing development decreased for major subdivisions, and (4) increasing numbers of parcels were near or within riparian areas. These findings indicated a differential impact of planning across scales and types of subdivision and a mixed success of planning in mitigating the environmental impacts of rural residential development.