The Great Lakes hold about 21% of the world’s surface freshwater and 84% of North America’s supply, making them one of the most significant natural resources on the planet. Their importance extends well beyond water volume: the lakes anchor a regional economy worth trillions of dollars, support unique ecosystems found nowhere else, regulate the climate for millions of people, and hold deep cultural significance for Indigenous nations who have lived along their shores for thousands of years.
A Freshwater Supply With No Equivalent
No other freshwater system on Earth comes close to the Great Lakes in scale. Lakes Superior, Michigan, Huron, Erie, and Ontario together contain roughly six quadrillion gallons of water. That single resource provides drinking water for tens of millions of people across eight U.S. states and two Canadian provinces. In a world where freshwater scarcity is a growing concern, the sheer concentration of drinkable surface water in one connected system gives the Great Lakes outsized global significance.
A $3 Trillion Regional Economy
If the U.S. Great Lakes region were its own country, its economy would rank among the largest in the world. The region generates $3.1 trillion in gross domestic product, employs 25.8 million people, and supports $1.3 trillion in wages. That economic output spans manufacturing, agriculture, shipping, tourism, and fishing, all tied directly or indirectly to the lakes themselves.
Maritime commerce alone moves enormous value through the system. In 2022, cargo shipped through the Great Lakes-St. Lawrence Seaway totaled 135.7 million metric tons, valued at $26.1 billion. That waterborne trade supported over 241,000 U.S. and Canadian jobs and generated $36 billion in economic activity. Iron ore, grain, limestone, and coal are among the primary goods transported, feeding steel mills and power plants across the industrial Midwest.
Fisheries Worth $7 Billion a Year
The Great Lakes support roughly 180 native fish species, including walleye, lake trout, whitefish, northern pike, and muskellunge. Commercial, recreational, and tribal fisheries combined are valued at more than $7 billion annually and support over 75,000 jobs. Lake whitefish, walleye, yellow perch, and ciscoes form the backbone of the commercial harvest, while recreational fishing draws enormous participation. Over 1.8 million anglers fish the Great Lakes each year, spending nearly $2.2 billion on trips and equipment.
Biodiversity Found Nowhere Else
The Great Lakes aren’t just big. They’re biologically distinctive. The system’s size, depth variation, and geographic span create a range of habitats, from deep cold-water zones in Lake Superior to shallow wetlands along Lake Erie. That variety supports over 200 globally rare plants and animals. More than 40 species are found exclusively in the Great Lakes basin, existing nowhere else on the planet.
Coastal wetlands, dunes, and tributaries serve as breeding grounds for migratory birds and nurseries for fish. These habitats act as natural filters too, cleaning water as it moves through marshes and shoreline vegetation before reaching the open lakes.
How the Lakes Shape Regional Climate
The Great Lakes function as a massive climate buffer for the surrounding region. Their water absorbs heat slowly in spring and summer, keeping nearby areas cooler than inland locations. In fall and winter, the lakes release stored heat, keeping coastal temperatures warmer than they would otherwise be. This moderating effect is measurable: mean minimum temperatures across the basin are higher in every season compared to areas farther from shore.
The most dramatic climate effect is lake-effect precipitation. Cold winter air passing over relatively warm lake water picks up moisture, producing heavy snowfall on downwind shores. Cloud cover in winter increases by roughly 25% in areas downwind of Lakes Superior and Michigan. In summer, the effect reverses. The cooler surface water of Lakes Michigan and Huron reduces cloudiness by about 10%, creating sunnier conditions along their shores.
This climate moderation is especially valuable for agriculture. The lake effect extends growing seasons in coastal areas, which is why Michigan’s western shoreline supports fruit orchards, vineyards, and other crops that would struggle to survive just 50 miles inland. Nearly a quarter of the Great Lakes basin’s land area is used for agriculture, covering about 172,000 square kilometers.
Tourism and Recreation
The Great Lakes coastline stretches over 10,000 miles, offering beaches, dunes, lighthouses, and harbor towns that draw visitors year-round. Michigan alone saw over 113 million visitors spend more than $22 billion in a single year. Boating, swimming, kayaking, sport fishing, and winter activities along the lakeshores contribute billions more across the other seven states that border the system. For many communities along the lakes, tourism is the primary economic engine.
Cultural Significance for Indigenous Nations
Long before European contact, the Anishinaabek peoples, including the Ojibway, Odawa, and Potawatomi, built their lives around the Great Lakes. The lakes and surrounding lands provided food, shelter, medicines, and spiritual grounding for thousands of years. The relationship between Indigenous nations and the lakes is not historical in the past-tense sense. It is ongoing and legally protected.
The Treaty of Washington in 1836 was a pivotal moment. Leaders from six Ottawa and Chippewa tribes in Northern Michigan signed the agreement to avoid forced removal westward, ceding millions of acres of ancestral land but retaining rights to hunt, fish, and gather throughout the region. Those treaty rights are still exercised today. Tribal fisheries operate on the lakes, and Indigenous communities remain active stewards of the ecosystem, often leading conservation efforts rooted in generations of ecological knowledge.
Federal removal policies during the 1800s forced many communities into impossible choices to remain in their homelands. The cost was enormous, measured not just in land but in disrupted burial traditions and scattered ancestors. For the tribes still living in their ancestral territory, protecting the Great Lakes is inseparable from protecting their identity and sovereignty.
Threats to the System
The same qualities that make the Great Lakes valuable also make them vulnerable. Invasive species are among the most persistent threats. Zebra mussels alone cause $300 to $500 million in annual damages to power plants, water systems, and industrial infrastructure across the region. Sea lamprey, a parasitic species that devastated native fish populations in the mid-20th century, still requires about $20 million a year in control efforts.
Nutrient pollution, particularly from agricultural runoff, fuels toxic algal blooms in Lake Erie that can contaminate drinking water for entire cities. Climate change is warming lake temperatures, reducing winter ice cover, and shifting precipitation patterns in ways that stress both the ecosystem and the communities that depend on it. The interconnected nature of the five lakes means a problem in one part of the system can cascade through the rest, making coordinated management across two countries and multiple jurisdictions both essential and complicated.