Changing Planet

Geography in the News: The Great Lakes’ Mounting Problems

By Neal Lineback and Mandy Lineback Gritzner, Geography in the NewsTM

The Great Lakes’ Mounting Problems

Recent news about an algae bloom on Lake Erie leading to Toledo, Ohio’s municipal water plants closing is just one of the many problems affecting the Great Lakes. Toledo’s 400,000 people were forced to purchase bottled water for two days, focusing the attention of the region on the beautiful Great Lakes’ water quality and environmental issues.

The five Great Lakes contain an astonishing 20 percent of the world’s above-ground fresh water. The surface area of the five lakes is 95,000 square miles (246,050 sq. km.), or nearly twice the size of North Carolina. The lakes contain six quadrillion (or six followed by 15 zeros) gallons (23 quadrillion liters) of freshwater, representing 95 percent of the surface water of the United States.

gitn_914_Great Lakes
Map by Geography in the News and
Boundaries and names shown do not necessarily reflect the map policy of the National Geographic Society.


Pleistocene glaciers, occurring between one million and 11,000 years ago, gouged the Great Lakes’ lakebeds as the glaciers moved southward from Canada, leaving huge reservoirs, some that are below sea level.

Historically, the Great Lakes’ water quality and use have been hotly debated. One of the major issues throughout the 1900s, continuing into the 21st Century, has been pollution. The lakes were both a source of water and a destination for industrial waste and municipal sewage in the 20th Century.

Over the years, major international environmental efforts between the United States and Canada cleaned up some of the worst problems. Some problems persist, however, including mercury and agricultural pesticide pollution. The latest issue with a major algae bloom on shallow Lake Erie was caused by nutrients from agricultural fertilizers and municipal waste.

One of the lakes’ additional, problems is invasive species — organisms found in ecosystems from which they did not originate. Many of these exotics out-compete, eat or otherwise harm native organisms.

Since the 1800s, more than 160 documented invasive species have entered the Great Lakes ecosystem from around the world, causing economic and ecological impacts. According to the Inland Seas Education Association, these non-natives deprive fish of food, cause blooms of toxic algae disrupt spawning areas and foul boats’ and drinking water intakes. On average one new invasive enters the Great Lakes every eight months.

Zebra mussel infestations in the Great Lakes illustrate the severity of the problems stemming from invasive species’ introduction and spread. This non-indigenous mollusk is an efficient filter feeder that competes with native mussels and impacts fish populations by reducing food and available spawning habitat.

The zebra mussel was inadvertently introduced into the lakes in the ballast water of ocean-going ships from the Black Sea as they traversed the St. Lawrence Seaway and the Great Lakes. Utility and manufacturing industries around the region, dependent on Great Lakes water for production, are expending substantial time and money cleaning intake and discharge pipes clogged by zebra mussels. The U.S. Fish and Wildlife Service officials estimate the economic impact to these industries will be $5 billion over the next decade.

Invasive plant and animal species enter new ecosystems in many ways, including some natural, but most are introduced with the help of humans. Invasive species stow away on every type of transport vehicle imaginable. Of course, these means are unintentional.

In other cases, humans may modify the environment in such a way that a species may be able to expand into new territories. When engineers built the Welland Canal in order to bypass Niagara Falls located between Lake Erie and Lake Ontario, the lamprey eel was able to migrate upstream into Lake Erie. Lamprey eels threaten Lake trout and whitefish fisheries by attaching themselves to adult fish and finally killing them.

Interestingly, however, some exotic species have been introduced intentionally into aquatic environments. Examples include pets that are released, involving aquatic fishes, snakes and turtles.

When native species disappear because of competition with or predation by invasive species, biodiversity in general declines. Loss of biodiversity can throw the entire ecosystem out of balance, causing disruptions that are likely to be permanent.

The range of problems impacting the Great Lakes is enormous, many of which are impossible to change. Nutrient pollution that created the latest algae bloom on Lake Erie, the shallowest and warmest of the Great Lakes, may be only partially controllable by controlling the nutrients entering the lakes. The algae problem, however, is further exacerbated by the warming of the Great Lakes’ water associated with global climate change, making total control even more difficult.

And that is Geography in the News.

Sources: GITN 914, “The Great Lakes’ Invasion,”, Dec. 7, 2007; GITN #575, “The Greatest Lakes,” June 8, 2001;;

Co-authors are Neal Lineback, Appalachian State University Professor Emeritus of Geography, and Geographer Mandy Lineback Gritzner. University News Director Jane Nicholson serves as technical editor. Geography in the NewsTM  is solely owned and operated by Neal Lineback for the purpose of providing geographic education to readers worldwide.


Neal Lineback has written weekly Geography in the News (GITN) articles for more than 25 years (1,200 published articles) while he was Chair of Geography and Planning at Appalachian State University and since. In 2007, he brought his daughter Mandy Gritzner in as a co-author. She is also a geographer with a graduate degree from Montana State University. GITN has won national recognition and numerous awards from the Association of American Geographers, the National Council for Geographic Education and Travelocity, among others..
  • TC

    All of this is very true and to make matters worse the most dangerous threat to the native lake species is the Asian Carp which are rapidly making their way up the Chicago River. Currently they are only being kept at bay by an electric fence but inevitably some will find their way into Lake Michigan and spread from there.
    The Obama administration vehemently opposes all efforts by the states of Michigan and Wisconsin to damn the Chicago River to stop the thread which would destroy untold billions of dollars in tourism and sports fishing in all the Great Lakes.
    Obama has gone so far as to fight the neighboring states in court and he has the support of his former Chief of Staff now turned Chicago Mayor Rahm Emmanuel. This president proven to be quite myopic in his former understanding of protecting the environment. Once the carp make their way into the Great Lakes they will destroy the livelihoods of thousands of Americans and Canadians.

  • David McFarland

    I can help with the mercury. Stop burning coal. When you burn coal, mercury(the only liquid metal) is evaporated into the atmosphere where it cools off and re liquifies and then falls back into the lakes, land, and oceans. Very simple.

  • Mario Victirino

    Not sure about Lake Erie, but most of the Great Lakes had late ice melts due to the cold winter. But keep beatin’ that drum NG.

  • Ron

    If they pollute the Great Lakes they better not try to get the last drops from the Colorado River.

  • kurt

    I understand how invasive species work – heck, we humans are the ultimate invasive species…started with a few members in Africa, ultimately colonized and totally modified the whole world. So yeah, stuff comes in & we deal with it. Is it different than before? Yes. Is it worse? Depends on your reckoning of the plus/minus surrounding the whole situation. Would we be better as a united Earth if we didn’t allow ships from the Black Sea into the USA? Or should we just deal with the mussels? Or starlings. Or water hyacinths. Or pythons. Whatever – whats the big picture, not the tiny, narrowly focused picture?

    • Neal Lineback

      Any region’s plants and animals will eventually adjust to the arrival of an invasive species. Is the resulting adjustment what we want? For example, is kudzu a benefit to the economy? The best we can do is attempt to limit invasive species’ arrival and impacts, but we all know that once the “genie is out of the bottle” (or the invasive species is ensconced in a particular ecosystem), the best we can do is slow its advance and try to limit its impacts. Thanks for the comment.

  • Witzling

    Great Lakes contain less than 1% of worlds fresh water – 20% of readily available surface water. You must count aquifers

  • Tom Brian

    Warming lakes that were almost 100% frozen over last winter,
    are they warmer or colder? you got to decide.

    • Neal Lineback

      Exactly. (Good point. We should have clarified that in the article.) Lake Erie is the shallowest of all of the Great Lakes. Consequently, it is most likely to freeze during the winter and be warmer than the others during the summer. Summer is when the algae blooms occur when the water is warmest.

  • R. Right

    The algae problem, however, is further exacerbated by the warming of the Great Lakes’ water associated with global climate change

    Nonsense. Great Lakes water temperatures are down on every lake from last year, and far below average — particularly on Lake Superior, which was at just more than 50 degrees on Aug. 1, about 7.73 degrees below its long-term average for that day, and Lake Michigan, which at 62.78 degrees was 6.49 degrees below long-term average.

    I remember when National Geographic used to be a science magazine, instead of an agenda-driven government mouthpiece.

  • Tom Simmer

    The global warming dig was totally gratuitous. The points about municipal waste and agricultural run off are valid–and both need an intelligent analysis that we should be considering. Instead, NG has sunk again to relating it all to global warming—even knowing that the water in Lake Eire is colder now than average for this time of year. I challenge NG to show that it is worth more that lip service to the environment and publish an intelligent piece on the two REAL issues here.

  • Brandon

    How do we get them out of the water

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