Checking in on the state of the Great Lakes

09 July 2020

The Great Lakes are a wonderful, powerful, and critical natural heritage resource. Containing 20% of the world's total fresh water, the Great Lakes offer a supply of clean drinking water, facilitate ship-borne trade, offer a multitude of recreational opportunities, and are an important fishery. They also represent an essential part of indigenous peoples' heritage and customs. Speaking about the Great Lakes, former Ontario Regional Chief Isadore Day described the "infinite connection" indigenous peoples have to water through ceremony, harvesting, and trade.



This Spring, the Governments of Canada and the United States released their State of the Great Lakes 2019 Highlight Report summarizing the overall health of the Great Lakes. This report, which is released every 10 years, serves as an important "check-in", itself drawing upon many more specific reports.  The 45 sub-indicator reports are included in the State of the Great Lakes 2019 Technical Report.  However, this report does not yet appear to be available online.

The Good News

Water quality, overall, is generally good and not declining.  Municipally treated drinking water met the relevant quality standards 99.8% of the time in Canada and 95% of the time in the U.S. between 2015 and 2017.   Further, monitored beaches in Canada were safe for swimming 82% of the days tested and, in the U.S., for 93% of the days tested between 2015 and 2017.  E. Coli contamination is the primary reason swimming is declared unsafe. E. Coli may be caused by precipitation overflow from wastewater treatment plants, runoff from land after rainfall, improper septic systems, and large flocks of birds.

Fish can be safely eaten (to an extent).  PCB levels in fish fillets have decreased in some species in some lakes (Michigan and Ontario) while remaining stable in the others.  Mercury levels have also generally declined in many species. Nevertheless, fish are still subject to consumption limits.  For example, Walleye (a.k.a. Pickerel) are commercially fished in Lake Erie and are currently in season.  Because of contamination risk, Ontario advises the general population should not have more than 16 meals per month of Walleye fillets from fish between 30 and 35 cm long, caught in Lake Erie's central basin.

Aquatic Habitat Connectivity, while only rated as "fair" or "poor", is improving. Aquatic habitat in the great lakes has been fragmented by dams, weirs, stream crossings and other human-built structures that limit water flow and hamper animal movement between the lakes and the rivers that drain into them. This improvement in connectivity is occurring across all of the lakes through habitat improvement work, dam removal, and crossing replacement.

Toxic chemical loads in wildlife are either unchanging or improving.  There has been a notable decline in toxins like polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and mercury in fish tissue and Herring Gull eggs since the 1970s.  Unfortunately, the decline in toxins appears to have ceased and amounts have remained relatively stable, but still above target levels, for the past decade.

The Bad News

Invasive species present a serious environmental threat.  Invasive plants and animals are disrupting biotic communities in the Great Lakes. For example, native fish remain subject to Sea Lamprey predation (though Lamprey populations have been cut through basin-wide control measures such as lapricide application). Invasive plant species like Phragmites, Purple Loosestrife and Garlic Mustard are now widely distributed and causing detrimental impacts.  Phragmites, for example, colonizes wetlands and creates a mat of root material which drives out native plants and creates vast monocultures.

Plant and animal habitat is not generally improving.  In general, the Report indicates that coastal wetland habitats and offshore aquatic food webs are in fair and unchanging condition.  While the condition varies depending on the lake and wildlife community being assessed, a lack of overall improvement is a matter of concern. Improvement has been seen in the coastal wetlands of Lake Superior, and the northern shorelines of Lake Michigan and Lake Huron. Degrading conditions in the sedimentation and nutrient loads have lead to declines in the conditions of coastal wetlands in Lakes Erie and Ontario. Aquatic food webs in the Great Lakes are all in either an unchanging or in a declining state due to increases in harmful bacteria and invasive mussel species. However, native Lake Sturgeon populations have improved throughout the Great Lakes thanks to habitat improvements, dam removals, and government regulation.

Nutrient loads are up again.  Efforts in the 1980s and 1990's reduced the high levels of nutrients, particularly phosphorus, that enter the lakes due to agricultural operations, urban runoff, and point sources such as sewage treatments plants.  Excess nutrient levels can cause harmful algal blooms, nuisance algae and hypoxic (low oxygen) areas, all of which can be detrimental to water quality and to aquatic life. The report indicates that this ground has been lost, noting a "resurgence" in nutrient-related adverse effects caused by changes in land use, invasive species, and climate.  Conditions are worst in Lake Erie, because it is the shallowest and warmest lake and because its shores are densely populated.  For, example, record-setting algal blooms were recorded in 2011 and 2015.  Total phosphorous load in 2011 was over 10,000 tons for the lake as a whole; almost as much as was recorded in 1974.  Lake Erie is now subject to a Binational Phosphorous Reduction Strategy.

Most ecological indicators are rated as "fair" or "poor".  While the Report notes that drinking water and beaches are generally in "good" condition, 6 of the other indicators (Fish consumption, Toxics, Habitat and Species, Nutrients and Algae, Groundwater and Watershed Impacts) are rated as "fair" and "unchanging".  Invasive species was rated as "Poor" with the situation "deteriorating".

The Unknown

A significant "question mark" in this report is the impact of climate change on the Great Lakes. The Report notes that the long-term data shows basin-wide increases in precipitation, surface temperature increases (in Lakes Huron, Superior and Michigan) and an overall reduction in ice cover in all lakes.  However, the report acknowledges the difficulty of establishing whether these changes are part of natural year-to-year variability or represent a long-term trend.  Nevertheless, the report makes clear that these changes can impact a fish spawning, coastal wetlands, water quality, and species migration. Indicia such as rainfall, water levels, ice cover, and water temperature will continue to be monitored.

Bottom Line

There has been improvement in the Great Lakes since the 1970s because of deliberate, regulation-based, pollution control underpinned by careful environmental monitoring and improvement work.   All of this effort is supported by international co-operation between national, state, and provincial governments. The Binational Phosphorous Reduction Strategy mentioned above is an excellent example of such cooperation. 


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