Issue 61
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Weather Trivia |
Great Lakes St. Lawrence Basin:
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From the heartland of North America, freshwater travels 3000 kilometres through the Great Lakes, the St. Lawrence River, and into the Gulf of St. Lawrence. Taken all together as a single unit, this is the Great Lakes St. Lawrence basin, a unified ecosystem and a true marvel of nature. Its complexity of functions creates a delicate balance which scientists are only just beginning to understand. The Great Lakes St. Lawrence water system is one of the world's largest. Approximately 15 million Canadians and 30 million Americans call the basin home. With so many people and so much economic activity in the basin it is little wonder that it has come under threat from industrial, municipal, and agricultural pollution, invasive species, toxic contaminants and loss of biodiversity. |
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Although our footprint is often local, the impacts can reverberate throughout the ecosystem. The loss of a species, a farm's contaminated run-off, a city's untreated sewage, the introduction of an invasive species, or a stretch of eroded shoreline are all serious problems individually. Taken together, their cumulative environmental impact on the basin represents a considerable threat to the ecosystem's health. Going with the Flow
The Great Lakes St. Lawrence basin contains about a quarter of the Earth's freshwater reserves. What happens here impacts the environmental processes of the entire North American continent. Still, pollution concerns are too often focussed on local activities, with each part of the ecosystem managed in isolation. Historically there has been little consideration of how activities in one part of the ecosystem may impact another. This separation obscures the full picture of the basin's health, especially since roughly 40 per cent of pollution in the St. Lawrence originates upstream in the Great Lakes. The Great Lakes and its connecting channels are like steps descending from Lake Superior at 183 metres above sea level to the Atlantic Ocean. Lake Ontario, the last stage before the St. Lawrence River, sits at about 74.7 metres. Water from Lake Superior flows into Lake Huron via St. Marys River. The broad and deep Straits of Mackinac link Lakes Michigan and Huron, which flow through the St. Clair River, Lake St. Clair and the Detroit River before emptying into Lake Erie. The water travels from here through the Niagara River and the Welland Canal into Lake Ontario before flowing to the Atlantic Ocean through the St. Lawrence River. The Great Lakes and the St. Lawrence River form a single hydrological system and any changes will also be felt downstream. The water levels and flows are influenced by many factors and variations are normal. However, extreme and prolonged shifts, such as climate change and human interventions like dam building and man-made islands, cause dramatic and permanent changes to level and flow in the entire ecosystem, upsetting the delicate equilibrium in the process. The Ecosystem Approach |
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