Health of Great Lakes wetlands

Covering over 700 km2, wetlands along the shores of the Great Lakes, their connecting channels, and tributaries provide critical habitat for wildlife, including birds, mammals, fish, amphibians, reptiles, and a diversity of plants. They have suffered extensive loss and degradation over the past 200 years30, 31 and many have been greatly affected by pollution.32, 33 It is estimated that, by 1984, 35% of wetlands along the Canadian shores of lakes Erie, Ontario, and St. Clair had been lost,34 with greatest losses, 73 to 100% by 1979, occurring between Toronto and the Niagara River.35 Most conversion occurred from the late 19th to early 20th centuries when large wetlands were dredged for shipping and filled for industrial and urban development.36 Loss and degradation continue due to shoreline alteration, water level control, nutrient and sediment loading, invasive non–native species, dredging, and industrial, agricultural, and residential development.36-41 Upstream land practices also have an impact, particularly through run–off from agricultural lands and impervious surfaces.42-44

Recent surveys show that the health of wetlands is variable across the basin.40 Water Quality Index scores, one method of monitoring wetland health, indicate that for Canada, the lower Great Lakes, especially the western end of lakes Ontario and Erie, which are most heavily impacted by urbanization and agriculture, suffer the most degradation. Comparatively few sites in Canada in Georgian Bay, Lake Huron, and Lake Superior are degraded.45-48

Great Lakes Water Quality Index scores in Canada
Lakes Ontario and Erie and Georgian Bay, sampled 2006 to 2009 Lakes Superior and Huron, sampled 1998 to 2005
Map: Great Lakes water quality index scores in Canada. Click for graphic description (new window).
Source: updated from Chow–Fraser, 200645 with 2008 unpublished data collected primarily in eastern Georgian Bay and the North Channel by the author, and with unpublished 2009 data collected in lakes Erie and Ontario by Canadian Wildlife Service, Environment Canada, Ontario Region48
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