Protecting One of the World’s Largest Sources of Freshwater

Protecting One of the World’s Largest Sources of Freshwater

The Great Lakes and the St. Lawrence River make up one of the largest surface freshwater ecosystems in the world. Government entities in Canada and the United States have forged an agreement to apply uniform laws throughout this water system to protect it and make it a sustainable resource.


5 - 8


Biology, Ecology, Conservation, Geography


Great Lakes Satellite View

The Great Lakes-St. Lawrence River watershed, which accounts for about 84 percent of North America's freshwater, is threatened by pollution, invasive species, and urban development.

Photograph by Planet Observer
The Great Lakes-St. Lawrence River watershed, which accounts for about 84 percent of North America's freshwater, is threatened by pollution, invasive species, and urban development.

The Great Lakes–St. Lawrence River watershed is one of the world’s largest freshwater ecosystems. It contains about 84 percent of all the freshwater in North America, and is also home to about 30 million people. The watershed makes up lands in both the United States and Canada. Due to the sheer size of the watershed and the volume of water, protecting this valuable resource is a daunting task. To this end, the federal governments of the United States and Canada, as well as the governments of eight U.S. states and two Canadian provinces, are charged with different aspects of watershed protection. In December of 2005, to foster cooperation in this task, they jointly signed the Great Lakes–St. Lawrence River Basin Sustainable Water Resources Agreement.

The waters of the Great Lakes and the St. Lawrence River are important for commercial and recreational fishing. One of the biggest threats to the system comes from invasive species—organisms introduced from other parts of the world that thrive because they have no natural predators in their new environment. As the invasive species multiply, they crowd out the native species. One of the main threats to the species of the watershed has been the zebra mussel, which originated in Russia. Zebra mussels have contributed to habitat destruction and the decimation of native species, and they are estimated to have caused about four billion U.S. dollars’ worth of damage to the watershed. Zebra mussels outcompete native mussel species for food and space, which disrupts the natural nutrient cycles of the ecosystem.

Another valuable part of the ecosystem is the shoreline and coastal wetlands. These areas are important for recreational uses, residential sites, and wildlife habitats. Wetlands are particularly important as they provide a buffer between open water and land. Wetlands also prevent coastal erosion, serve as breeding grounds for many species, and absorb pollutants and sediments, keeping them out of the lakes and river. Destruction or modifications of these areas can lead to greater shoreline erosion and water pollution. The destruction of wetlands can also harm the native plant and animal populations and increase the numbers of invasive species in the area. The water resources agreement helps communities lessen the damaging effects of development while allowing for reasonable and sustainable growth along shorelines.

Perhaps one of the hardest tasks of the water resource agreement is the control of pollution. With such a large area and wide diversity of land and water uses, there are a great number of pollutants that can end up in the water. Each kind of pollutant requires a different scheme for its control. The most complex pollution problems are associated with industrial sources. Throughout the watershed, different types of industries generate a wide variety of wastes. These wastes range from heavy metals to organic chemicals, and they have varying effects on the watershed’s ecosystem. Many pollutants are concentrated in the tissues of the fishes that live in the watershed, which can make them dangerous for human consumption. The water resources agreement aims at ensuring that the different government entities enforce uniform laws to protect this freshwater system from harmful human influences. With uniform laws, everyone living in the watershed benefits by having cleaner water.

Due to the large amount of agriculture in the watershed, soil erosion and runoff pollution from farms is a significant problem. With soil erosion, valuable topsoil is washed away from farms and into the watershed. This causes degradation of the land and can result in excessive sedimentation in the waterways. Fertilizers and pesticides used on the land also cause environmental problems. Fertilizers can drain off the land and end up in the water, leading to excessive growth of plants and algae, which clogs waterways and kills fish. Pesticides can harm the plants and animals that live in the lakes and river. They can hinder the growth of fish and even kill them or make them unsafe to eat. The water resource agreement works to implement better management practices that minimize soil erosion and runoff throughout the watershed by regulating agriculture, development, and industry.

Urban development is yet another environmental problem for the ecosystem. Development destroys natural habitats and introduces nonnative species. It is possible for some of these nonnative species to become invasive species. Land development also increases the amount of area covered by impervious surfaces, such as streets and sidewalks, which add to runoff when it rains. This increased runoff carries trash, oil, and other pollutants into waterways. Because these types of pollutants come from widespread areas, they are difficult to manage. The water resources agreement addresses the problem of urban growth by providing guidelines for sustainable development that minimizes the impact on natural resources while promoting economic growth.

One of the biggest goals of the Great Lakes–St. Lawrence River Basin Sustainable Water Resources Agreement is to raise awareness about the watershed. Protecting this valuable resource is a balancing act between safeguarding the livelihoods of all those who live and work in the area and keeping the waters clean and the ecosystem healthy.

Media Credits

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Tyson Brown, National Geographic Society
National Geographic Society
Production Managers
Gina Borgia, National Geographic Society
Jeanna Sullivan, National Geographic Society
Program Specialists
Sarah Appleton, National Geographic Society, National Geographic Society
Margot Willis, National Geographic Society
Clint Parks
Roza Kavak
Last Updated

October 19, 2023

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