The Great Lakes are the largest system of fresh water lakes in the world, shared by the United States and Canada. They make up 95% of the surface freshwater in the United States and have 10,000 miles of coastline (including connecting channels, mainland and islands)—more than the both the American Pacific and Atlantic coastlines combined.
While 20% of fresh water in all of the world’s lakes is in Canadian lakes, only 6.5% of the world’s renewable water supply is in Canada.
Toronto is located in Southern Ontario, on the northwestern shore of Lake Ontario, and features a broad sloping plateau intersected by an extensive network of rivers, deep ravines, and urban forest.
Below are six of the most pressing issues facing this precious and extremely fragile natural resource:
Iroquois and Huron First Nations lived on the shores of Lake Ontario sustainably for thousands of years before Europeans arrived. Where there were once 150 species of fish in the Great Lakes, species that are indigenous to the region are disappearing due to habitat loss and competition from invasive species, causing biodiversity to decline. When biodiversity declines, the entire ecosystem can be thrown off balance causing disruptions that have yet to be fully understood. Commercial fishing in Lake Ontario peaked in the late 1880s; 130 years later, government and NGOs are still working to restore the lake's native fish populations.
Nonpoint source (or NPS) pollution comes from many different diffuse sources and is extremely difficult to regulate and control; therefore, many experts believe that NPS pollution is the top hazard facing the Great Lakes today.
NPS pollution is mainly caused by runoff, when rain and snowmelt move over the land, picking up pollutants along the way and eventually dumping the pollutants into rivers and lakes. Some common NPS pollutants include fertilizers and pesticides from agricultural lands and homeowners; oil, grease and salt from highways; sediment from construction sites and eroding shorelines; and animal and human waste.
Invasive species are organisms that are found in ecosystems from which they did not originate. Many of them often out-compete, eat, or otherwise harm other native organisms (see disappearing native species).
The Great Lakes ecosystem has been severely damaged by more than 180 invasive and non-native species. Species such as the zebra mussel, quagga mussel, round goby, sea lamprey, and alewife reproduce and spread, ultimately degrading habitat, out-competing native species, and short-circuiting food webs.
Atmospheric pollution (or air deposition) is another form of nonpoint source pollution, though instead of polluting via runoff, the pollution falls from the sky. As water moves through the hydrologic cycle, it falls as rain or snow and then evaporates into the air from land and surface water. Pollutants emitted into the air, such as through smoke stacks, follow this same path, and can be carried through the atmosphere and deposited into waterways hundreds of miles away from its source.
Acid rain is the most well known form of atmospheric pollution.
The major sources of atmospheric pollution include coal-burning energy plants and waste incinerators. The combustion of fossil fuels and waste (such as from hospitals) produces large amounts of mercury in the air, a toxic chemical that is fatal to humans and animals in large quantities. Phosphorus and polychlorinated biphenyls (PCBs) are also transported to waterways via air deposition.
There are over 100 beaches on Lake Ontario alone. Each year, millions of people in the Great Lakes region are seeking the beach, but red flags and “no swimming” signs often crush hopes for a leisurely day spent by the water’s edge. While there are a number of reasons to shut down beaches for the public including dangerous waves or eroding dunes, the principal cause for beach closings and advisories is water pollution caused by elevated levels of bacteria.
The presence of certain bacteria such as E. coli indicates the presence of human or animal wastes in the water. If bacteria counts are high enough that there is a risk of illness, a “Water Quality Advisory” is issued.
Water and sand that are polluted with untreated sewage or with human and animal wastes may contain harmful bacteria or other disease-causing microorganisms (pathogens). These pathogens can afflict swimmers, kayakers, or surfers when they ingest the contaminated water or sand. Children are most at risk because they may put contaminated sand or water in their mouth.
When pollutants enter the waterway though a specific entry point, such as a drainpipe draining directly into a river, it’s called point source pollution. Industrial water discharges and sewage treatment plants are the main culprits of this type of pollution. Point source pollutants can include many different organic and inorganic substances, including human waste and toxic metals.
Point Source Pollution is easier to identify and control than Non-Point Source Pollution. Factories and sewage treatment plants are two common types of point sources. Factories, including oil refineries, pulp and paper mills, and chemical, electronics and automobile manufacturers, typically discharge one or more pollutants in their discharged waters (called effluents). Some factories discharge their effluents directly into a water body. Others treat it themselves before it is released, and still others send their wastes to sewage treatment