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Great Lakes
The Great Lakes—Michigan, Superior, Huron, Erie, and Ontario—form the largest surface
freshwater system in the world. Together, they hold nearly one-fifth of the earth's surface
freshwater. The Great Lakes have over 10,000 miles of shoreline and serve as a drain more than
200,000 square miles of land ranging from forested areas to agricultural lands, cities and
suburbs.
The Great Lakes watershed includes some of North America's more fascinating wildlife such as
the gray wolf, Canada lynx, moose and bald eagle. The lakes themselves are home to numerous
fish, including lake whitefish, walleye, muskellunge and trout. Millions of migratory birds pass
through the region during their spring and fall migrations.
People Depend on the Great Lakes
The Great Lakes region has been home to Native Americans for nearly 10,000 years. The first
Europeans arrived in the 1600s and began to utilize the region for animal furs. It wasn't long
before more settlers were drawn to the region seeking farmland.
Today, over 35 million people live in the Great Lakes basin in Canada and the United States. The
Great Lakes are important sources of drinking water, irrigation, transportation and recreation
opportunities such as fishing, hunting, boating, and wildlife watching. The Great Lakes are a
critical component of the regional economy on both sides of the border.
Wildlife in the Great Lakes
The land surrounding the Great Lakes was once dominated by forests and grasslands interspersed
with wetlands. Many of the wildlife that still call the region home exist in the remnants of those
habitats, such as the gray wolf, moose, beaver and many bird species. The Great Lakes region is
important for many species of migratory and resident birds, particularly waterfowl, birds that
nest in colonies, and neotropical migrants.
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Fish: The Great Lakes are actually quite different from each other. Lake Superior, the largest of
the lakes, is cold and deep. Lake Erie is one of the smallest of the Great Lakes and is relatively
shallow and warm. Because of this variation, different numbers and varieties of fish and other
aquatic wildlife can be found in each lake. Walleye, yellow perch, lake sturgeon, brook trout,
lake whitefish, muskellunge, and introduced salmon species are among the many kinds of fish in
the Great Lakes. Some fish are undergoing restoration efforts, such as lake sturgeon and lake
trout.
Mammals: Many mammals, large and small, live in the Great Lakes region, including the gray
wolf, Canada lynx, little brown bat, beaver, moose, river otter, and coyote.
Birds: The Great Lakes region provides important breeding, feeding, and resting areas for many
birds including the bald eagle, northern harrier, common loon, double-crested cormorant,
common tern, bobolink, least bittern, common merganser, and the endangered Kirtland's warbler.
Threats to the Great Lakes
Pollution
Despite their great size, the Great Lakes are actually very vulnerable to pollution. The amount of
water entering and leaving the lakes each year is less than one percent of the total in the lakes.
Persistent chemicals that enter the lakes can remain for many years, with many building up in the
food web. The source of toxic pollutants includes decades of industrial waste, raw sewage
overflows, runoff from cities, and mining operations. Excess nutrients that throw the ecosystem
out of balance enter the lakes from agricultural runoff and untreated sewage.
Global Warming
The impacts of global warming are already being observed in the Great Lakes. Increasing air and
water temperatures mean increased evaporation from the lakes, declining lake levels and
worsened water quality. The Great Lakes are already highly stressed, and climate change will
worsen existing threats to the Great Lakes, including making the lakes more suitable for invasive
species, drying coastal wetlands that filter pollution, exposing toxic sediment pollution, and
increasing the number of intense storms leading to sewage overflows.
For information on the Great Lakes and Global Warming see the fact sheet "Overview of Recent
Research: Effects of Global Warming on the Great Lakes" or the report "Great Lakes Restoration
and the Threat of Global Warming"
Invasive Species
Invasive species have significantly changed the Great Lakes by competing with native species
for food and habitat. They foul beaches, harm fisheries, clog water infrastructure and lead to the
regional extinction of species. More than 180 non-native species have entered the Great Lakes,
and a new species is discovered every 28 weeks on average.
Most invasive species were transported in the ballast water of ocean-going ships.
However, Asian carp are threatening to take hold in the Great Lakes by swimming up artificial
channels that connect Lake Michigan to the Mississippi River system.
Sulfide Mining
A proposal to mine sulfide metals in public forests only miles from Lake Superior threatens
wildlife and water in the Great Lakes basin. Sulfide mining has a terrible record of destroying
streams and endangering public health. This dangerous form of mining threatens to destroy
pristine fish habitat, poison drinking water sources and pollute the Great Lakes.
National Wildlife Magazine:
Alien Invasion: A Great Lakes Dilemma
Great Lakes Primer
New Hope for Great Lakes Recovery
Greatest Lakes in the World
Resources:
The Great Lakes Atlas (EPA)
Healing Our Waters-Great Lakes Coalition
Sources:
The Great Lakes Atlas (EPA)
Great Lakes Basin Ecosystem Team (USFWS)
USGS Great Lakes Science Center