¹Nature Conservancy of Canada, Ontario RegionRR#5, 5420 Highway 6 North Guelph, ON N1H 6J2
²Natural Heritage Information Centre 300 Water Street, 2nd Floor, North Tower P.O. Box 7000, Peterborough, ON K9J 8M5
³The Nature Conservancy, Great Lakes Program,101 East Grand River Lansing, MI 48906

*Corresponding author: daniel.kraus@natureconservancy.ca

Abstract

   Lake Huron has the largest collection of freshwater islands in the world. These islands are a significant contributor to the biodiversity of the region. In this paper, we give preliminary results of a project that assembles mapping of over 23,000 islands and island groups and provides the most comprehensive biodiversity assessment of islands in Lake Huron to date. The number, extent and configuration of many islands, particularly small, low-lying systems, is very dynamic depending on lake-levels. Islands in Lake Huron can be divided into three general groups: 1) limestone and dolostone islands associated with and surrounding Manitoulin and Drummond Islands and the Bruce Peninsula, 2) dense archipelagos of small nearshore Precambrian Shield islands in eastern Georgian Bay and the North Channel and, 3) small groups of low-erodible islands in Saginaw Bay.
All three of these island groups are important for supporting colonial nesting waterbirds, endemic species and communities, and migratory birds. Lake Huron islands have been somewhat buffered from anthropogenic change due to their isolation and therefore support a rich and diverse sets of species and communities. Primary threats to island communities include development and invasive species. Threats are generally greater in many of the southern island regions where fewer islands are protected. Results from this project can be used to set priorities for conservation of key sites with high biodiversity values and conservation urgency.