Find your local watershed

Impact on biodiversity

Unfortunately, when water is being managed to meet the increasing demands of humans, the needs of nature come second or are often left out of the equation altogether.

Pollution and aquatic species

While Canada does have extensive freshwater supplies, many of our waterways are becoming polluted from human development. Human and animal waste and chemical substances are being released into the natural environment at such a rate that waterways like the Great Lakes and the St. Lawrence River, for example, are having problems cleansing themselves of pollution and sustaining the life that once thrived there.

The health of aquatic ecosystems and the organisms that depend on them is being compromised by the waste from homes and industry, farm runoff and dams that reduce the natural flow of rivers, thereby raising the water temperature and trapping sediments.

Across the country, contaminants and environmental changes are negatively affecting aquatic species. Beluga whales in the Beaufort Sea are showing increased concentrations of mercury. Chemical pollutants in the Pacific are suspected of playing a role in altering the sockeye migration in the Fraser River. In Alberta, trout are at risk from the toxic effects of selenium.

In the Great Lakes, reproductive failure in lake trout has been traced back to organohalogens. Fish reproduction and energy storage suffer downstream of our nation's pulp-and-paper mills. Liver tumours in fish, a sign of exposure to polycyclic aromatic hydrocarbons, have been reported in the Great Lakes, the St. Lawrence River and Vancouver Harbour, according to research conducted by the NRC Research Press.


Wetlands are considered to be one of the Earth's most productive ecosystems, and 14 percent of Canada's land mass is wetland.

The term wetland refers to any land that is permanently or temporarily submerged in or permeated with water. By this definition, freshwater and saltwater marshes, wooded swamps, bogs, seasonally flooded forest, sloughs and peatlands are all considered wetland.

Wetlands are a critical part of the water cycle. For one thing, they buffer river-flow regimes, reducing peak flow during floods and maintaining flow in dry years. Wetlands also recharge groundwater, clean and remediate polluted water and provide habitat for fish, wildlife and, of course, humans. According to a study conducted by the David Suzuki Foundation, wetland and forest ecosystems provide the most valuable ecosystem services.

Unfortunately, it appears that wetlands are as endangered as they are valuable. Historically, wetlands have been drained or filled in to create farmland. Agricultural expansion is responsible for 85 percent of Canada's wetland loss. Urbanization crowds out wetlands too. Over 80 percent of the wetlands near major cities have been converted to farmland or turned into urban sprawl. In southern Ontario, more than 70 percent of wetlands have disappeared altogether, gobbled up by roads, farmland, housing and industry.

And wetlands are particularly vulnerable to climate change.

Canada's boreal forest

The boreal forest that carpets 60 percent of the country is more than a forest. It contains one-quarter of the world's wetlands, almost 80 million hectares of surface water, more than 80 percent of the world's fresh water, five of the world's 50 largest rivers and the largest remaining unpolluted lake on the planet, Great Bear Lake. However, Canada's boreal forest is under threat from development. Already, forestry, road building, mining, oil and gas extraction and hydropower are encroaching on this ecosystem.

Watersheds related to this theme

Here is a sample of the 543 affected ones: