Great Lakes ecoregion

This lake system contains the largest supply of freshwater in the world.

How the Great Lakes formed

During the last ice age, the mile-thick Laurentide ice sheet covered most of Canada and the northern contiguous United States. The massive weight and movement of this glacier gouged out the earth to form the lake basins. About 20,000 years ago, the climate warmed and the ice sheet retreated. Water from the melting glacier filled the basinsoffsite link, forming the Great Lakes. Approximately 3,000 years ago, the Great Lakes reached their present shapes and sizes. Today, the Great Lakes ecoregion contains a variety of habitats, including aquatic, forest, marsh, wetland, and dune ecosystems. Widely varying climate, soils, and topography support more than 3,500 species of plants and animals.

Researchers on NOAA's Research Vessel Storm pause above the Middle Island sinkhole in northern Lake Huron, off the coast of Alpena, Michigan. July 17, 2019.
Giant sinkholes are adding water to Lake Huron. Scientists ask: How much?
Despite some being more than 300 feet across and up to 60 feet deep, sinkholes aren’t likely contributors of large volumes of water, but just knowing the amount could help scientists get a more accurate reading on water levels across the Great Lakes.

Humans and the Great Lakes

Humans are also part of the Great Lakes system. Commercial and sport fishing, agriculture, recreation, tourism, manufacturing, and shipping are all important to the region. These activities create jobs and provide goods and services. The fishing industry extracts millions of poundsoffsite link of fish per year from the lakes. Farmers within this watershed produce corn, soybeans, hay, milk, and other food products. The area is also known for its industry that produces steel, chemicals, and other products. The shipping opportunities in the Great Lakes played a critical role in settlement of the region and development of industry. Today more than 200 million tons of cargo pass through its waters each year.

 IMAGE--WWII - Navy drone - shipwrecks-010920--USN--SQUARE -809x809
Searching for WWII-era aircraft lost in the Great Lakes
Did you know that there are about 120 World War II era aircraft lying at the bottom of Lake Michigan?

Threats to the Great Lakes

Threats to the Great Lakes' ecosystems, include invasive species, climate change, pollution, and habitat destruction. Climate change affects water temperatures, weather patterns, and lake levels. Pollutants from residential, agricultural, and industrial areas reduce water quality. Land development decreases the amount of wildlife habitat. Fish populations have been decliningoffsite link in recent years as a result of these threats and increased fishing pressure.

An aerial photo of northern Lake Michigan near Sleeping Bear Dunes National Seashore. NOAA scientists are teaming up with Viking Cruises to conduct research onboard Viking ships touring the Great Lakes starting in 2022.
NOAA teams up with cruise company for Great Lakes research
NOAA plans to expand its research in the Great Lakes region as the agency teams up with the travel company Viking to carry scientists aboard new expedition voyages.


The Great Lakes Literacy Principlesoffsite link provide a framework for educators teaching about the Great Lakes, helping teachers and students think about the Great Lakes as a system, rather than a set of unrelated parts. Thinking systemically can provide a greater understanding and help identify solutions to the issues threatening the region.

Updated February 2019