Climate Change Impacts On The Great Lakes
Climate change is causing significant and far-reaching impacts on the Great Lakes and the Great Lakes region. In
recent years, our planet has experienced some of the warmest temperatures ever recorded, record-breaking weather
extremes, powerful storms, increasing tragic flooding from rising sea levels and associated storm surge, huge
wildfires, and continued melting of glaciers and polar sea ice. The accelerating pattern of changes in the Earth’s
climate is affecting the Great Lakes. Here, we draw on the array of existing research to assess how the shifting global
climate impacts the unique Great Lakes region.
The Great Lakes have an enormous impact, seen and unseen, on the 34+ million people who live within its Basin.
These millions of people rely on the freshwater lakes for drinking water, fisheries, recreation, and commerce and
industry. The Great Lakes contain 5,500 cubic miles of freshwater, one of the very largest freshwater resources in the
world. The Great Lakes support one of the world’s largest regional economies similar to those of whole developed
nations. Agriculture, industrial manufacturing, fishing, and recreation together form an economic engine. Regional
fisheries alone represent a $7 billion per year industry. Tourism generates $16 billion more.
Heavy human use over the past two centuries has taken its toll in the forms of habitat loss and fragmentation,
influxes of invasive species, and polluted air, water, and sediments. Soil and nutrient runoff from agricultural
fields and concentrated animal feedlot operations (CAFOs) imperil water quality and wildlife populations in many
parts of the basin, threatening public and wildlife health and the economic vitality of the region. Climatic changes
now underway further stress these ecosystems, alternatively raising and lowering lake levels and threatening
the region in new ways.
NEW DATA: Climate-driven shifts in deep Lake Michigan water temperatures
signal the loss of winter
A long-term study just published in Nature
Communications from NOAA reveals a warming trend in deepwater temperatures that foreshadows
profound ecological change on the horizon. While less visible than the loss in ice cover and increasing lake
surface temperatures, this latest index of climate change adds to the growing evidence of climate change
impacts in the region.
"Lake Michigan’s deep waters are warming and the study shows that winter is vanishing from them,” said NOAA
GLERL’s Eric Anderson, the study’s lead author. As climate change has gradually delayed the onset of
cooler autumn weather over the past three decades, the deep waters of Lake Michigan have reflected this
change by showing shorter winter seasons.
This key finding may indicate some dramatic changes in the foreseeable future, as an increase in a lake’s
overall water temperature can lead to permanent changes in the water’s seasonal mixing patterns. This
would inevitably disrupt the structure of its entire food web — a change that could have negative
impacts on fisheries and recreation.
The duration of seasonal ice cover decreased in most areas of the Great Lakes between 1973 and 2013, while
summer surface water temperature (SWT) increased in most areas between 1994 and 2013. (a) The map shows the
rate of change in ice cover duration. The greatest rate of decrease in seasonal ice cover duration is seen near
shorelines, with smaller rates occurring in the deeper central parts of Lakes Michigan and Ontario, which rarely
have ice cover. (b) The map shows the rate of change in summer SWT. The greatest rates of increase in summer
SWT occurred in deeper water, with smaller increases occurring near shorelines.
The Great Lakes sustain remarkable populations of fish and habitats for wildlife. More than 170 species of fish
live in the lakes, streams, rivers, and connecting waterways. Trout, sturgeon, walleye, lake whitefish and other
varieties of fish are once again becoming plentiful among the five Great Lakes. The basin’s ecosystems support
wolves and moose while providing resting and breeding grounds for large flocks of migratory birds and
waterfowl. More than 3,500 species of plants and animals use its large network of streams, lakes, inland
wetlands, coastal marshes and forests. Many of these species are rare or are found nowhere else.
The Great Lakes are large enough to themselves influence weather in the region. The Lakes moderate
temperatures throughout the year, helping to cool nearby lands in the summer and warm them in winter. Their
humidity feeds cloud cover and precipitation both over the lakes and downwind. That causes both “lake effect”
snowstorms, and summer rainfall that provides ideal growing conditions for orchards in Michigan’s “fruit belt.”
Climate change presents challenges to the Great Lakes, with complicated effects and inter-relationships.
The Great Lakes region has tracked global increases in temperature and outpaced trends in some parts of the
contiguous United States. Between 1901-1960 and 1985- 2016, the Great Lakes basin has warmed 1.6°F in annual
mean temperature, exceeding average changes of 1.2°F for the rest of the contiguous United States. By the end
of the 21st century, global average temperatures are expected to rise an additional 2.7°F to 7.2°F, depending on
future greenhouse gas emissions, with corresponding changes in the Great Lakes region.
A warmer atmosphere holds more moisture, increasing the frequency and intensity of heavy rain and snow
events. Overall U.S. annual precipitation increased 4% between 1901 and 2015, but the Great Lakes region saw
an almost 10% increase over this interval with more of this precipitation coming as unusually large events. In the
future, precipitation will likely redistribute across the seasons. We expect wetter winters and springs, while
summer precipitation should decrease by 5-15% for most of Great Lake states by 2100.
These increases in precipitation will likely increase flooding across the Great Lakes region. In cities with
abundant roofs, concrete, and other impermeable surfaces, this will likely 2 damage homes, roadways, and
other infrastructure. In rural areas, intense rains and melting snows will increase runoff and erode soils. In rural
areas, increased flooding will also cause soil erosion. In combination with more unpredictable precipitation and
warmer temperatures, these effects could seriously curtail Midwestern agricultural production
Climate change is causing more extreme weather across the United States. Heat waves have become more
common since the 1960s while extreme cold temperatures have generally decreased. Intense summer storms
occur more often as temperatures rise.
Extreme weather events have already taken their toll on the Midwest. The 2012 Midwestern heat wave and
drought caused more than $30 billion in economic damage, 123 deaths, and harmful long-term health impacts
across most of the central and western United States.
Extremely warm days (above 90°F) will increase for states bordering the Great Lakes, especially in the southern
parts of the region. By century’s end, the region will experience 30 to 60 additional days each year of these
extremely warm temperatures. Areas within the Great Lakes Basin will see an increase of 17 to 40 extremely
warm days as annual average temperatures continue to rise.
Meanwhile, in states surrounding the Great Lakes, the number of extremely cold days (with temperature less
than 32°F) will decrease significantly. Lake effect snowfalls could be even more dramatic, particularly across the
Lake Ontario snowbelt in upper western areas of New York state where three- and four-feet snowstorms are
Changes in seasonal precipitation are already affecting farmers in Midwestern states, with planting delays
caused by spring flooding and excessively wet soil conditions. Delayed planting puts crops at greater risk
during hotter and drier conditions later in the growing season, and that increases the demand for irrigation to
mitigate crop losses. Hot temperatures interfere with pollination in corn and other crops, thereby reducing yields.
Yet, even with increased water management in agricultural watersheds, climate change will likely reduce crop
yields for both soybean and maize by 10% - 30% by mid-century in the southern parts of the Great Lakes
watershed. Soybean and maize production will likely move northward.
In the summer, high temperatures and heat waves cause poorer air quality, which harms public health,
especially for the most vulnerable people – the elderly and children with asthma. For the many millions of people
living in urban areas across the Great Lakes states, heat waves and summer air pollution events increase the
risk for heat related illness, respiratory diseases, and death.
Projected increases in extreme precipitation will likely exacerbate flooding, especially in winter, spring, and
during summer thunderstorms. Extreme winter rain events in 2017 and 2018 led to serious flooding. Rain events
exceeding 6 inches now occur regularly, exceeding the capacity of culverts and storm sewers to handle runoff.
Under-resourced communities in low-lying, flood-prone areas have become vulnerable to infrastructure damage,
transportation barriers, and displacement from homes due to these intensified floods.
Climate change will likely threaten drinking water quality and place great stress on water infrastructure. For
example, in southern Wisconsin, extreme precipitation could rise by 10% to 40%, overloading water treatment
infrastructure, increasing sewer overflows, and increasing the quantity of water born pathogens flowing into
streams, rivers, and Lake Michigan.
The Great Lakes have higher levels of E. coli bacteria than other U.S. coastal regions. This untreated effluent is a
public health hazard and economically costly to mitigate. Cities like Chicago have spent enormous sums to
protect against water pollution. Nutrients (primarily nitrogen and phosphorous) run off from farms into surface
waters during intense rain events. These excess nutrients threaten human health both directly (e.g., “blue baby”
syndrome) and 3 indirectly by contributing to toxic harmful algal blooms in shallow water bays of the Great
Lakes and the “dead zone” in the Gulf of Mexico that has decimated shell fisheries.
In 2011, Lake Erie experienced the largest harmful algal bloom in its recorded history, with peak intensity more
than three times greater than any previously observed blooms. In 2014, 500,000 people in the Toledo area were
without safe local drinking water supplies for 72 hours because of toxic algae blooms in western Lake Erie. Algal
blooms will likely become more frequent in the future as higher temperatures and heavy precipitation mix heavy
nutrient loads with warmer waters. These pollutants have dramatically raised the cost of water treatment.
Climate change has already increased bacteria levels in the Great Lakes, as the water warms earlier in the
spring and warming contributes to vertical mixing that changes lake ecosystems. Sewer overflows, the dumping
of ship ballast water, and nutrient runoff from agriculture and industry all contribute to growth of bacteria and
several invasive species in the lakes. Heavier rainstorms and warmer weather exacerbate these challenges.
Hundreds of new species of pathogenic bacteria, viruses, protozoa, and non-native species could be introduced
and flourish in the warming conditions, displacing local native species. While climate change may not directly
drive lake species extinct, the persistence of many native species will be threatened as they confront more
invasive species, species replacements, and proliferating pest and disease organisms.
Fish respond sensitively to water temperature, assembling in distinct cold, cool, and warm water groupings.
This means that warmer temperatures, seasonal weather shifts, and storms that bring a quick influx of water will
all affect fish species. The geographic ranges of fish, demographics within species, system productivity,
species-specific productivity, the spatial arrangement of species, and their physiological state and performance
will all change in response.
The Great Lakes region supports many species of mammals, birds, amphibians, reptiles, and
macro-invertebrates. As air temperatures increase and precipitation patterns shift, habitat conditions, soil
moisture, and other conditions will shift, thereby driving some wildlife species northward and others westward.
Individual species however, will respond in different ways to local conditions such as ice cover on lakes and
specific patterns of regional precipitation.
Among mammals, moose may be especially vulnerable to climate change. In Minnesota, moose populations
have already declined precipitously. Moose density is expected to also decline at southern parts of the Ontario
region and increase at northern extents. Milder winters increase overwinter survival in white-tailed deer allowing
them to expand northward into habitats historically dominated by moose.
With water levels falling and temperature rising, diseases like botulism will increase, spreading more disease
and killing more birds that consume fish. Birds could also suffer from phenological mismatch, as the insect
species they relied on for food hatch earlier with warmer springs or decline as vegetation shifts northward.
Shipping, Power Generation and Shorelines
Fluctuating lake levels resulting from climate change greatly affect the ability of ships to safely navigate shallow
portions of the Great Lakes’ channels and harbors. Both lower lake levels and higher water temperatures pose
technical challenges for power generation. Changing lake levels affect marinas, docks, and shoreline homes
and other buildings.
The Great Lakes Commission estimated that boating contributed approximately $9 billion to the Great Lakes
economy in 2003. Boating activities such as skiing could be affected by warming temperatures, shifts in the
length of seasons, and changes in lake levels.
It’s become common in recent years for beaches in Chicago and Michigan to close or be under swim advisories
because of bacterial contamination. Beach closures are expected to increase as heavy precipitation
exacerbates issues associated with runoff and pushes up bacterial counts as well as algal blooms and E. coli
We should not and cannot take the vast natural resources of the Great Lakes for granted. Allowing the Great
Lakes to be degraded through human activities, including climate change, is not an option. For economic,
aesthetic, recreational, and ecological reasons, the Great Lakes should be restored to be healthy, unpolluted,
and productive. We must reduce the effects of climate change on the Great Lakes.
Public support for protecting the Great Lakes is strong across the region. Scientific analyses clearly show that
climate change has already greatly affected the region and that these impacts will continue and expand as the p
ace of climate change accelerates. It is critical that we recognize the importance of one of the world’s most
abundant freshwater resources and ensure its protection for generations to come.
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