Dunes of the Laurentian Great Lakes

Most dunes along the 16, 000-km long shorelines of the Laurentian Great Lakes formed after lake levels fell from highs at 5 to 3.5 ka. Foredunes develop during decadal scale variations in lake levels, forming during low and eroding during high lake levels. More permanent foredune plain complexes, with parallel dune ridges separated by swales, form on constructional shores. Transgressive and transitional complexes containing inland-migrating blowouts, parabolic dunes, and dune ridges occur on shores with high onshore sand drift potential and abundant sand supply. Vegetation cover is highest and wind energy and aeolian transport lowest in summer. Vegetation die back and high wind energy accompanying the passage of extratropical cyclones cause an autumnal increase in aeolian activity. Activity decreases as shoreline ice and surface snow develop during the winter. In the spring, niveo-aeolian structures collapse, vegetation increases, and storminess decreases. Great Lakes dune complexes host many ecological communities, including open dune communities, mesic forests and interdunal wetlands. The 34 million people living near Great Lakes shorelines generate heavy anthropogenic pressure. Two national governments, a Canadian province and seven US states have jurisdiction over Great Lakes shorelines, complicating the regulation of coastal activities.