The effects of land use and cultural development on the Lake Ontario ecosystem since 1750

Lake Ontario is the lowest in the chain of five Great Lakes which form part of the boundary between Canada and the United States. Although European exploration began as early as 1615, it was not until the mid-18th Century that permanent settlement began in the Great Lakes basin. Construction of the Erie Canal which links Buffalo with New York via the Hudson River, and its branch to Oswego, strengthened ties between settlements around the lower Great Lakes (lakes Erie and Ontario) and rapidly growing populations along the Atlantic seaboard. The coming of railroads greatly expanded these ties, and provided a direct link between Canadian settlements and the port of Montreal. Over the past 200 years, successive waves of immigrants entered the region, particularly from Europe.Cultural development has resulted in a wide range of environmental impacts throughout the Great Lakes basin. Impacts have been particularly severe in Lake Ontario. Major changes in water quality and the structure of biological communities have resulted from forest clearance, agricultural expansion, intensive fishing, industrial and urban development, and lake level control. Introductions of exotic species, inputs of nutrient and toxic contaminants, and the effects of climatic variation and modification of microclimates have all interacted such that it is often impossible to establish singular cause and effect. The effects of cultural impact became most severe during the early 1970s and prompted strong support for the International Great Lakes Water Quality Agreement (1972) between Canada and the United States. In response to this agreement and subsequent revisions, contaminant loadings have been greatly reduced. Present water quality is generally good in Lake Ontario although some persistent toxic substances remain a problem. Programs to restock the lake have also provided major benefits. Although much further work remains, Lake Ontario is undoubtedly a good example of successful large scale remedial actions.