The Great Lakes are struggling under the combined weight of many ailments, from invasive species and toxic chemicals to the nutrient runoffs that fuel Lake Erie's chronic algae problem. And in many cases, climate change is making it worse.
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Water levels in the Great Lakes have fluctuated since 1860. Over the last few decades, water levels have declined slightly for most of the Great Lakes (see Figure 1).
Climate change's hotter temperatures and society's diversion of water have been shrinking the world's lakes by trillions of litres of water a year since the early 1990s. A close examination of nearly 2,000 of the world's largest lakes found they are losing about 21.5 trillion litres a year.
According to the average of their simulation ensemble, by 2040–2049, the average annual water levels of Lake Superior, Michigan-Huron, and Erie are projected to increase by 0.19, 0.44, and 0.28 m, respectively, relative to 2010–2019 under the Representative Concentration Pathway (RCP) 8.5 scenario.
These lake surface temperatures are projected to rise by as much as 7°F by 2050 and 12.1°F by 2100. Higher temperatures, increased precipitation, and lengthened growing seasons are likely to result in increased production of blue-green and toxic algae in the lakes.
Pollution from over a century of intensive development remains in the sediment of many Great Lakes tributaries, harming fish and wildlife and leaving water unsafe for people. These sites are being cleaned up through the Great Lakes Legacy Act by the U.S. EPA in partnership with local, state, and private organizations.
No. People are not capable of changing things on that scale. We could easily pollute the water and make it undrinkable, but we can't drain the lakes, because there is just too much water there, and it's constantly refilled from too many sources, including rain and snow melt.
Yet in the past 200 years, the Great Lakes have been altered by invasive species, historic overfishing, tributary damming, habitat loss and climate change. As a result, the Lakes have lost several mid-level forage fish that were once the foundation of a healthy food web, as they provided food for top predators.
The Great Lakes are freshwater ecosystems. Traditionally, Lake Michigan, for example, has been a very low-salt lake, with levels around one milligram of chloride per liter of water. Over the years, due to our increased salt use, that level has steadily but gradually climbed up to 15 milligrams per liter.