Challenges to the Great Lakes

Pollution threatens Great Lakes health

Every day, we drink water from the lakes and depend on the ecosystems it supports.  But widespread pollution threatens the lakes’ health – and ours.  The pollution comes from many sources.

From the air:
Air pollution causes mercury contamination in the Great Lakes region.  Mercury is a by-product of burning coal in coal-fired power plants – which produce the energy we use to power our homes and workplaces.  Particles of mercury end up the in the air – and fall back to earth and pollute Great Lakes waters. 

From sewage and runoff:
Untreated sewage and runoff dump bacteria into the Great Lakes, leading to swimming bans and illness for those who enter Great Lakes waters.  Fecal coliform and E. coli bacteria from animal feces, dirty diapers, failing septic systems and sewer overflows lead to higher levels of bacteria.

From dumping chemicals and toxins:
When companies, factories and individuals dump chemicals and other toxins into the Great Lakes, they negatively impact water quality for decades.  Although the chemicals PCBs and DDT were both banned in the 1970s, they still linger in the sand, clay, silt and organic matter found at the bottom of the lakes and other regional water bodies.  Newer substances, such as mercury and PBDEs, are being dumped to this day.  Chemical pollution causes a chain reaction throughout the Great Lakes food system.  Bottom feeders, such as tiny crustaceans and insect larvae, can absorb some of these chemicals into their bodies.  Fishes eat the bottom feeders – and the chemicals they contain. Eventually, waterfowl and even humans eat the fishes, passing the chemical exposure higher up the food chain.  This is a process called ‘biomagnification,” and it harms animals and humans.

Non-native animals and plants are overtaking our region

Invasive species can cause irreversible harm to native plant and animal species in the Great Lakes region. More than 180 invasive fishes, plants, viruses and other organisms have settled in the Great Lakes basin, such as sea lamprey, zebra mussels and hydrilla.  New species arrive at a rate of one every eight months. By altering habitats, outcompeting local wildlife for shelter and food, and reproducing unchecked without any natural predators, invasive species harm many economically and ecologically valuable species that have survived here for millennia.

Invasive species arrived in the Great Lakes as a consequence of human activity, both intentional and unintentional. Most invasive species arrive to the Great Lakes via ballast water from ocean-going ships. Even the tiniest microscopic organisms found in this ballast water can take hold and cause a significant disturbance in the lakes.

The stakes are high, and local, state and national governments are spending billions of dollars each year in an attempt to contain invasives.  But, the best way to deal with invasive species is to stop them from coming in the first place.  Asian carp – a commonly used name for silver carp and bighead carp – is the most recent, much-discussed threat to the Great Lakes.  For up-to-the-minute information on the situation with Asian carp and the lakes, visit

Conserving water = conserving the Great Lakes

The Great Lakes are a one-time gift from glaciers that melted tens of thousands of years ago.  Though these great expanses of water may appear to be a never-ending resource, each year only 1 percent of Great Lakes water gets replenished.

Increasing demands for water put the Great Lakes at risk.  Over time, lake levels are falling, and local communities have seen their groundwater supplies diminish – which negatively impacts the streams and wetlands that are key parts of the Great Lakes ecosystem.  However, we know exactly how to preserve this precious resource, and it’s simple: use less water.  

Crucial habitats are disappearing from the Great Lakes region

The Great Lakes are more than water — they include the land that surrounds them, known as the Great Lakes drainage basin or watershed. Water flows into the Great Lakes from all the lands and waterways within the basin — a true balance between land and water. The choices we make in our communities about how we protect land resources within the Great Lakes basin affect the future of the lakes themselves.

Wetland areas in the Great Lakes basin help keep our lakes and rivers clean, help prevent floods and provide important breeding grounds for fishes, waterfowl and a host of other animals.  More than two-thirds of Great Lakes fish species spawn in wetlands, and many rely on nearshore vegetation for food and shelter. When we lose this habitat, we lose more than places for our families to fish, boat and hike — we lose critical homes for area wildlife.  In some areas of the Great Lakes region, more than 90 percent of our wetlands have been lost.

Now that you've learned about the issues facing the Great Lakes, learn how you can help keep the Lakes Great.

How you can help

Small changes can make huge differences - learn how you can help keep the lakes great with these tips from Shedd Aquariums Great Lakes Conservation team

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