A Scheme for Evaluating the Impact of Development on the Geomorphic and Ecologic Process of Lake Michigan’s Coastal Dunes

Recent changes to Michigan’s Critical Dune Law initiated this study to create a science-based, public policy tool for evaluating a development’s impact on the geomorphology and ecology of Lake Michigan’s coastal dunes. These dunes are valued for their scenic beauty and diverse ecological communities. However, development pressures on them are increasing and the revised law requires that regulators consider the diversity, quality, and function of the dunes when reviewing Critical Dune building permits. Hence, our current scientific understanding of geomorphic and ecologic processes in the dunes was used to create this two-part decision-making flowchart. The first part evaluates a development’s impact on the dune’s physical processes in three categories: dune mobility, erosion by gravity, and pavement effects. The second part evaluates the change in the overall diversity of communities, changes in the composition of species making up a community, and changes in the connection between communities. Five development scenarios with different dune/ecology settings, house/road layouts and densities were evaluated. The amount of dune mobility, and, therefore, the amount of sand burial, especially in open dune areas, decreased with development. Ecologically, early pioneer and successional communities, including sensitive species, which are dependent on sand burial, were lost due to the resulting dune stability from development. Ecological changes in the back dunes were not as pronounced as these dunes have little to no dune mobility and are vegetated with near-climax to climax communities adapted to little to no dune mobility. The distance connecting similar ecological communities increased with development, very likely decreasing the likelihood of that community’s existence. Overall, this scheme is useful for assessing the impact of one development scenario versus another in different coastal dune settings. This method also shows promise in providing a science-based public policy tool for managing the coastal dunes