Mapping Exurban Development: Can Road and Census Data Act as Surrogates?

Abstract

Exurban development, characterized by low-density residential development, is one of the leading anthropogenic causes of land transformation. A major obstacle to studying this phenomenon is a lack of spatially explicit data. In this article, two commonly employed indirect approaches that use readily available road and census data as surrogates of exurban development are examined for their ability to delineate exurban development across large spatial extents. The study area is the heterogeneous exurban region of Peterborough County, Ontario, Canada. Comparing correlations between road density–based maps, dasymetric dwelling-count maps, and the reference data at multiple scales produced mixed results. Of the two methods, road density generally performed better, except when the census units were of relatively small size. Overall, the results highlight the way in which heterogeneity within a large study area can greatly obscure surrogate relationships that may be evident at smaller spatial extents, where conditions are relatively more homogeneous, making the use of these indirect methods challenging for large spatial extents. In particular, the geographic and historic context of the study area significantly influences the effectiveness of these methods, which should therefore be used with caution in mapping exurban development.