Warming and the Great Lakes Region
the opening scene of Holling Clancy Holling's classic children's
a young boy stands at his cabin door in the Nipigon country
north of Lake Superior. It is late winter, and the season's
first flock of Canada geese is flying overhead. "Geese!"
he cries. "They come back too soon!"
words, written by Holling nearly 60 years ago, have a familiar
ring today. For the geese — and many other birds —
now come back "too soon" to the Great Lakes region
on a regular basis. In Holling's home state of Michigan,
at least 15 bird species have advanced their spring arrival
dates in the upper peninsula by one to eight weeks since
Some researchers believe the birds are responding to long-term
changes in climate that may be due to global warming. In
fact, scientists have noted similar changes in other parts
of the world. A study in England, for example, found that
many birds there laid their eggs an average of 19 days earlier
in 1995 than in 1971.
warming could reduce the habitat available for
cold water fish such as trout and salmon in lakes
levels in the Great Lakes could drop significantly,
affecting wetlands, water quality, recreational
facilities, and shipping.
may change, with some species shifting their range
northward or dying out, and other trees moving
in to take their place.
species such as the Kirtland's warbler could lose
and other waterfowl could lose breeding habitat.
in the timing of migration and nesting could put
some birds out of sync with the life cycles of
their prey species.
researchers are concerned that such behavioral shifts could
be harmful for some birds. Insect-eating migratory birds
that return too early in the spring might have trouble finding
food, especially during late-season snowfalls and cold snaps.
Similarly, birds that lay their eggs earlier might have
poor nesting success if their young hatch before favored
prey species become available.
are not the only organisms responding to changes in the
climate. Scientists reported in 1997 that plant growth in
northern latitudes has increased by more than 10 percent
since 1981 due to longer growing seasons. The growing season
in latitudes where the effect is strongest — including
the northern Great Lakes region — may have lengthened
by 8-16 days. This sounds like a change for the better,
but it will take time to see the effects.
respond to environmental trends in complex ways. Scientists
have not yet determined how the longer growing seasons and
warmer temperatures might affect competition among tree
species in a forest, or what the changing climate might
mean for northern plants that are near the southern end
of their geographic range.
Great Lakes-St. Lawrence basin, which includes the five
Great Lakes, the St. Lawrence River, and their surrounding
watersheds, contains 20 percent of the world's freshwater.
The basin covers 295,000 square miles and includes huge
forests and wilderness areas, rich agricultural land, lakes,
streams, rivers, mineral deposits, and a world-class fishery.
It also is home to a diverse range of plants and wildlife,
including endangered and threatened species such as the
Canada lynx, gray wolf, peregrine falcon, Kirtland's warbler,
and Karner Blue butterfly.
portions of Minnesota, Wisconsin, Illinois, Indiana, Michigan,
Ohio, Pennsylvania, and New York, plus the Canadian provinces
of Ontario and Quebec, the basin is home to more than
one-tenth of the population of the United States and one-quarter
of the population of Canada.
The region supports a multibillion-dollar
outdoor recreation and tourism industry, with a number
of popular national parks and recreation areas such as
Isle Royale National Park; Voyageurs National Park; Superior
National Forest; Indiana Dunes National Seashore; the
Boundary Waters Canoe Area Wilderness; and Quetico, Algonquin,
and Killarney Provincial Parks in Canada.
If scientists' projections are accurate,
global warming could bring substantial changes —
both positive and negative — to the region and its
inhabitants in the years ahead.
Birds, plants, and other forms of life
in the Great Lakes region have always been exposed to
changes in climate and weather. But the changes underway
now, and those projected for the future, are different.
Climate scientists believe the Earth will experience an
average rate of warming during the next 100 years that
will be faster than any seen in the last 10,000 years.
For the Great Lakes region, that means the next century
could bring one of the greatest environmental transformations
since the end of the last ice age, perhaps rivaling the
dramatic changes wrought by humans after Europeans settled
the region nearly 400 years ago.
If a Nipigon boy in the year 2050 were
to place a small carved wooden canoe into the headwaters
of Lake Superior, his Paddle-to-the-Sea
might eventually reach the ocean just as the one in Holling's
book did. But the sights and sounds along the way —
the fish in the brooks, the trees lining the marshes,
even the shape of the shorelines — might be very
different from what Holling painted and described in 1941.
The Earth's climate has changed in
the past, and will continue to change naturally in the
future. Ice ages, long warm periods, and short-term fluctuations
in temperature and precipitation are all elements of the
global climate's natural variability.
Today, the average global temperature is rising. Is that
natural? Some of the temperature increase can be explained
by natural factors. But many scientists believe that a
portion of the warming trend may be caused by humans.
Human activities are creating a buildup of greenhouse
gases — primarily carbon dioxide, methane, and nitrous
oxide — in the atmosphere. The heat-trapping property
of these gases is undisputed. Although scientists do not
know exactly how the Earth's climate responds to increases
in greenhouse gases, they do know that the current warming
trend is consistent with changes that would be expected
from the increase in greenhouse gases.
Scientists generally believe that the burning of fossil
fuels and other human activities are the primary reason
for the increased concentration of carbon dioxide in the
atmosphere. Fossil fuels burned to run cars and trucks,
heat homes and businesses, and power factories are responsible
for almost 99 percent of U.S. anthropogenic carbon dioxide
emissions and about 20 percent of our nitrous oxide emissions.
Of the carbon dioxide emissions, industrial activity accounted
for 33 percent in 1997. Personal and commercial transportation
accounted for 30 percent, and residential and commercial
energy use accounted for 19 and 16 percent, respectively.
Increased agriculture, deforestation, landfills, industrial
production, and mining also contribute a significant share
of carbon dioxide, methane, and other greenhouse gas emissions.
Average global temperatures at the Earth's surface have
increased 0.6-1.2°F since the late 19th
century. The 10 warmest years in the 20th
century all occurred in the last 15 years. Snow cover
in the northern hemisphere, floating ice in the Arctic
Ocean, and the areas covered by mountain glaciers have
all decreased. Globally, sea level has risen 4-10 inches
during the past century. Worldwide precipitation over
land has increased by about 1 percent, and the frequency
of extreme rainfall events has increased throughout much
of the United States.
Although it is impossible to predict future changes in
climate with certainty, many scientists believe that the
continued addition of greenhouse gases to the atmosphere
is likely to raise the Earth's average temperature by
several degrees in the next 100 years. Rising global temperatures
are expected to raise sea level and change precipitation
and other local climate conditions. Changing regional
climate could alter forests, crop yields, and water supplies.
It also could threaten human health and harm birds, fish,
and many types of ecosystems.
Can We Expect?
Global warming could cause lake levels
in all the region's lakes, including the Great Lakes,
to drop substantially. Climate change probably will reduce
the habitat available for cold water fish, such as trout
and salmon, in lakes and streams. Wetlands also may be
vulnerable to changes in climate. Forests and other ecosystems
in the Great Lakes region may be transformed as the climate
warms. Depending on the magnitude of changes in temperature
and precipitation, northern tree species such as balsam
fir may migrate northward or die out, with other tree
species such as maple moving in to take their place. Habitat
for endangered species such as the Kirtland's warbler
could be lost as forests change.
in the Lakes
The Great Lakes, their connecting channels,
and the St. Lawrence River form the largest fresh surface
water system on the planet. The lakes cover more than
94,000 square miles and hold an estimated 6 quadrillion
gallons of water, 95 percent of the U.S. freshwater supply.
The Great Lakes and other lakes and streams in the region
are famous for their recreational fishing and boating
With global warming, the water temperatures
of the Great Lakes and smaller lakes in the region could
increase because of the warmer summer air temperatures
and longer ice-free season. Warmer temperatures could
degrade water quality by decreasing dissolved oxygen in
the water and increasing the growth of algae.
Warmer waters in the region's lakes
and streams would reduce the size of favorable habitat
for trout, whitefish, and other cold water fish species.
A recent EPA study found that a warming of 4.5°F
over the next 70 years could cut the habitat of brook,
rainbow, cutthroat, and brown trout by one-fourth to one-third
nationwide. A 4.5°F warming
is slightly below the midpoint of the 2-8°F
range predicted by climate models for the year 2100; the
actual temperature change that occurs could be smaller
or greater. Chum, chinook, pink, and coho salmon would
experience similar habitat losses. According to the study,
Pennsylvania, New York, Ohio, Indiana, and Illinois would
collectively lose 86 percent of their habitat for rainbow
trout. These changes are expected to occur gradually over
the decades ahead as the climate shifts.
Would the Great Lakes basin be as popular
a fishing destination if classic northern cold water species
like pike, muskellunge, trout, and salmon became less
common? Recreational fishing certainly would continue,
but the experience might change.
Warmer waters also could affect the
timing and frequency of "overturning," in which
oxygen-rich surface waters sink and mix with other water
layers in the lake. The lakes currently turn over in the
spring and fall of every year. In a warmer climate, the
overturning may not occur every year in all lakes. Turnover
is the main way for deeper lake waters to become replenished
with oxygen. Without enough dissolved oxygen, cold water
lake fish and other species will be unable to survive
in their deepwater habitats.
If the climate warms, ice cover on
lakes and streams would not last as long as it does today.
Streamflows could peak sooner in the spring because of
earlier snowmelt and ice breakup. There already is evidence
that the annual rising and falling of some of the Great
Lakes occurs nearly a month earlier than it did 140 years
ago. Changes in the timing and volume of peak streamflow
also may affect fish and other creatures that live in
A warmer climate would lead to increased
evapotranspiration. (Evapotranspiration is the water lost
to the atmosphere by evaporation and transpiration combined.
Evaporation is the loss from open bodies of water; transpiration
is the loss from living plants.) Summer streamflows probably
would decrease, reducing the water quality. Freshwater
flow into the Great Lakes could decrease by 20 percent
with a 4°F warming (slightly
below the current mid-range estimate projected by climate
models), potentially reducing lake levels by a foot or
more. Because lake levels respond to hydrologic changes
in their drainage basins, the Great Lakes would respond
to global warming very differently than the oceans would.
Global warming will cause the oceans to rise as warm water
expands and freshwater from melting glaciers and ice sheets
enters the sea. Water levels in the Great Lakes, on the
other hand, are likely to fall.
Lower lake levels would reduce inputs
to hydroelectric power facilities, increase the concentration
of water pollutants, and require more dredging to maintain
Lake levels in the Great Lakes have
varied dramatically in the past due to natural variations
in the region's climate. For example, very low levels
occurred in the late 1920s, mid-1930s, and mid-1960s,
while very high levels occurred in the 1830s, 1880s, early
1950s, early 1970s, mid-1980s, and mid-1990s. The low
water levels in the 1960s caused significant losses in
hydroelectric power output, economic hardships for marina
operators and other lakeside recreational facilities,
loss of wetlands, and reductions in municipal water quality.
Global warming could increase the frequency and severity
of droughts in the Midwest, causing low lake levels to
occur more frequently.
In the region's smaller lakes, prolonged
drought from climate change could decrease the number
of lakes with suitable habitat for organisms such as crayfish
and snails. Drought also could decrease groundwater supplies
of silica, an essential nutrient for freshwater sponges
On the positive side, flood damages
could be reduced by lower lake levels. Global warming
also would lengthen the ice-free season for the Great
Lakes and St. Lawrence Seaway, with benefits for ship
navigation. Warm-water fish, both native and introduced,
could experience longer growing seasons and flourish in
a warmer climate.
Despite nearly 400 years of forest
clearing, agricultural and industrial development, and
other human impacts, the Great Lakes basin still contains
vast tracts of forest. Boreal and northern mixed forestlands
such as those in the Boundary Waters Canoe Area Wilderness,
a million-acre wilderness in the Superior National Forest,
provide habitat for spectacular wildlife species such
as moose, black bears, and wolves. The region's forests
are a popular destination for backpackers, naturalists,
hunters, anglers, and wildlife photographers.
Trees and forests are adapted to specific
climatic conditions. As these conditions are altered,
forests will change. Global warming could cause forests
to undergo changes in species, geographic extent, health,
and productivity. If conditions become drier, the current
range and density of forests could be reduced and replaced
by grasslands and pasture. Even a warmer and wetter climate
would lead to changes; trees that are better adapted to
these conditions, such as oaks, would thrive. Under wetter
conditions, forests could become more dense. These changes
could occur during the lifetimes of today's children,
particularly if the changes are accelerated by other stresses,
such as fire, pests, and diseases, that could themselves
be worsened by a warmer and drier climate.
In Michigan, for example, changes in
climate could cause the extent of forested areas to change
little — or decline by as much as 50-70 percent.
The uncertainties depend on many factors, including whether
soil becomes drier and, if so, by how much. Hotter, drier
weather could increase the frequency and intensity of
naturally caused wildfires. The mixed aspen, birch, beech,
maple, and pine forests found in the northern part of
the state could be replaced over time by a combination
of grasslands, savanna, and hardwood forests of oak, elm,
and ash. The predominant hardwood forests in southern
Michigan could give way to pine and oak forests. These
changes could affect the character of Michigan forests
and the activities that depend on them.
In northern Minnesota, the boreal forests
in Voyageurs National Park and in the Boundary Waters
Canoe Area Wilderness could be replaced by mixed forests
better adapted to warmer conditions. Boreal forests are
what most people think of when they envision Minnesota's
remote north woods: small northern conifers such as tamarack,
black spruce, and balsam fir, in a landscape that typically
includes wetlands, bogs, and carpets of lichens and mosses.
According to one climate study, changes in the Great Lakes'
boreal forests could be apparent in the relatively near
future, between 2010 and 2040.
The world's boreal forests cover a
vast area 29 times the size of Texas, but they are rare
in the lower 48 states. The Great Lakes region contains
mostly transitional forests that include species typical
of both the Canadian boreal forests to the north and the
broadleaf deciduous woodlands to the south. But a few
regions of boreal or boreal-like forests occur near the
Canadian border. If climate change causes boreal species
to shift their range northward out of the United States,
some of the romance and evocative character of the northern
borderlands will be lost.
Whether we consider these changes to
the forests "good" or "bad" depends
on our individual perspectives. Some plants and animals
may benefit from climate change while others may be harmed.
An increase in wildfires might create new habitats for
some populations while eliminating habitats for others.
A decline in one species may make way for another species
to expand its range.
Can Be Done?
address the threat of climate change, first we have to
understand the risks. U.S. and Canadian scientists have
been studying potential impacts on the Great Lakes region
through programs such as the bi-national Great Lakes-St.
Lawrence Basin Project, the Canada Country Study, and
the U.S. National Assessment of the Potential Consequences
of Climate Variability and Climate Change.
of human-induced climate change also is an important strategy.
Some global warming probably will occur no matter what
we do, because some of it is natural. But also, humans
have become dependent on fossil fuels. The burning of
fossil fuels emits greenhouse gases, which may remain
in the atmosphere for years, decades, or even centuries,
exacerbating the natural warming. But we as individuals
can take action now to reduce our own consumption of fossil
fuels by improving energy efficiency and using alternative
energy sources. (See "Searching
People Can Do".)
Royale National Park
Holling noted in Paddle-to-the-Sea,
Lake Superior is shaped like the head of a wolf. The wolf's
eye is Isle Royale, the largest island in the world's
largest lake. This roadless 45-mile long island is part
of an archipelago off Lake Superior's northwestern shore.
Isle Royale is an International Biosphere Reserve and
is known worldwide as a living laboratory, the site of
the longest continuous ecological study of wolves and
moose. The Royal National Park has 400 islands, 165 miles
of hiking trails and 36 campgrounds, and is used by backpackers,
boaters, scuba divers, and anglers. Park waters contain
the most productive native fishery and the most genetically
diverse lake trout populations in Lake Superior.
the park staff's own summation, Isle Royale "offers
visitors a chance to experience wildness, seclusion, solitude,
and recreation. It restores the human spirit. It is a
wilderness to be entered on its own terms. It is an adventure."
who climb to Lookout Louise on Isle Royale have a spectacular
view of the island's heavily wooded north shore and the
Ontario mainland 20 miles away. In 50 or 100 years from
now, the view might be quite different. There still would
be plenty of trees, but the conifers that dominate the
north shore today might be largely replaced by deciduous
species such as the maples that today are more common
on the island's southwestern shore and interior.
moose on Isle Royale browse heavily on balsam fir, one
of the tree species that researchers believe may be strongly
affected by global warming. Balsam fir prefers colder
climates and may shift its range northward as the temperature
study published in 1999 found that changes in winter snowfall
affect the hunting behavior of wolves on Isle Royale,
which in turn affects the population density of moose
and ultimately the growth of balsam fir trees on the island.
In years of high snowfall, wolves hunt in larger packs
and kill more moose. With fewer moose, the growth of understory
balsam firs increases. This study concludes that changes
in climate can cause what ecologists call a "trophic
cascade," an impact that trickles down through the
food web with repercussions for the larger ecosystem.
National Park and the Boundary Waters
as all know is the last great wilderness area of its kind
on the continent," proclaimed the noted Minnesota
nature writer and conservationist Sigurd F. Olson in a
speech to the Izaak Walton League in 1929. "Nowhere
else can such beautiful lakes be found. Nowhere else can
you find them close together enough to make what is known
as a canoe country, and nowhere else is there so much
beauty concentrated in one spot as here. It is the last
area of its kind in the country."
was referring to Superior National Forest in Minnesota's
north woods, an area that includes popular recreational
areas such as Voyageurs National Park and the Boundary
Waters Canoe Area Wilderness.
National Park lies on the southern fringe of the Canadian
Shield. The park contains a classic boreal ecosystem,
with bogs, beaver ponds, swamps, lakes, and islands. The
nearby Boundary Waters Canoe Area Wilderness and Quetico
Provincial Park are famous canoeing and camping destinations.
in 1978, the Boundary Waters Canoe Area Wilderness has
changed little since the glaciers melted. With 1,500 miles
of canoe routes, nearly 2,200 designated campsites, and
1,000 lakes and streams, the Boundary Waters draws more
than 200,000 visitors each year.
wilderness areas provide visitors with exciting opportunities
to observe wildlife, catch fish, hear wolves, and spend
time in a landscape rich in the lore of the north woods.
study suggests that global warming could cause forests
in the southern portion of the Boundary Waters Canoe Area
Wilderness and the adjacent Superior National Forest to
shift from boreal evergreens such as spruce and fir to
northern hardwoods such as sugar maple. Under one computer
model scenario, a 400-year-old stand of balsam fir on
fertile, moist soil in the Boundary Waters would lose
two-thirds of its area by 2010, with sugar maples moving
in to take the place of the fir.
plentiful lakes and ponds in the Great Lakes region support
large numbers of ducks, geese, and other waterfowl. Will
they be affected by global warming? Unfortunately, the
answer appears to be yes. Waterfowl may be vulnerable
to changes in water quality, the availability of food
resources, and impacts on wetlands and other nesting habitats.
warming is expected to affect the prairie pothole region
of the north-central United States and south-central Canada,
where 50-80 percent of North America's ducks and other
waterfowl nest. The shallow prairie wetlands are vulnerable
to drought, and computer models indicate that global warming
is likely to bring stronger and more frequent droughts
to the prairie pothole region.
to one study, global warming could cause the number of
prairie ponds in the north-central United States that
hold water in the spring to drop from today's average
of 1.3 million to just 0.6-0.8 million by the year 2060.
This loss of habitat could reduce the average number of
ducks settling to breed in this area from 5 million birds
today to between 2.1 and 2.7 million. The Great Lakes
also serve as important staging areas for migratory waterfowl
and other birds. Changes in water levels and food availability
may affect migrants as they pass through the region.
can be done to protect the pothole region from the potential
effects of global warming? Scientists recommend that we
start by protecting the least drought-sensitive areas
so they are available to birds in the future as the climate
address the threat of global warming, the Great Lakes
and Upper Midwest states could improve the health and
resiliency of natural ecosystems, prepare for a changing
climate, and work to limit future global warming by reducing
greenhouse gas emissions.
to improve the health of the Great Lakes environment,
such as the Great Lakes Basin Compact and the remedial
action plans for the 43 Great Lakes Areas of Concern,
will help make the region's ecosystems more robust. A
healthy environment will be better able to withstand some
of the potential impacts of global warming.
U.S. Environmental Protection Agency's Great Lakes National
Program Office, located in Chicago, brings together federal,
state, tribal, local, and industry partners in an integrated
ecosystem approach to protect, maintain, and restore the
chemical, biological, and physical integrity of the Great
Great Lakes 5-Year Strategy, developed jointly by EPA
and its multistate, multiagency partners, provides a promising
agenda for management of the Great Lakes ecosystem: reducing
toxic substances, protecting and restoring important habitats,
and protecting human and ecosystem health.
action is occurring at every level to reduce, avoid, and
better understand the risks associated with global warming.
Many cities and states across the country have prepared
greenhouse gas inventories, and many are pursuing programs
and policies that will result in reductions of greenhouse
the national level, the federal government is working
in partnership with businesses, states, and localities
to address global warming while also strengthening the
economy. In addition, the U.S. Global Change Research
Program coordinates the world's most extensive research
effort on climate change.
What People Can Do
We all add greenhouse gases to the atmosphere whenever we
use energy from fossil fuels. Residential energy use accounted
for 19 percent of overall CO2
emissions from the combustion of fossil fuels in 1997, and
motor vehicle use accounted for approximately 20 percent.
Here are a few actions that people can take to reduce their
- Use mass
transit, carpool with friends, or ride a bike whenever
- When it's
time to replace the family vehicle, consider one that
gets more miles per gallon than your present vehicle.
- If you
have a small boat for fishing and recreation, run it
with "human power" when possible.
- When it's
time to replace an appliance, look for the Energy Star®
label identifying energy-efficient models.
- When buying
or building a new house, an Energy Star model gives
greater quality and comfort as well as lower monthly
costs. For more information, go to the Energy Star Homes
web site, www.epa.gov/homes.
- Buy products
that feature reusable, recyclable, or reduced packaging
to save the energy required to manufacture new containers
and reduce greenhouse gas emissions from landfills.
your company to join EPA programs such as Energy Star
BuildingsSM and Waste Wi$e recycling programs,
and to buy office equipment with the Energy Star label.
trees, which absorb carbon dioxide from the air.
others. Let friends and family know about these practical,
energy-saving steps they can take to save money while
protecting the environment.
scientific research and public discussion on global
warming and solutions such as energy efficiency and
U.S. Environmental Protection Agency's global
warming site includes
detailed information on climate change, impacts,
Lakes Information Network,
created by the Great
Lakes Commission, offers a wide range of information.
Great Lakes Atlas
is another excellent source of environmental and
economic information on the Great Lakes region.
Lakes Program coordinates
many environmental protection efforts in the basin.
latest U.S. National
Assessment of Climate Variability and Change
gives a detailed report
on the potential effects of global warming in
the United States.