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Prairie
Profiles
The Prairie
Ecosystem
The North American prairie is one of the most endangered ecosystems on
earth--perhaps even more endangered than the South American rain forest or the
old growth forests of the American northwest. The grasslands of North America
began to form about 20 million years ago, but in some areas, up to 99 percent
of the prairie has been destroyed in just the last 125-150 years.
The formation of the prairie
The area known as the
Great Plains was once the greatest grassland on earth and covered over a
quarter of the continental U.S. along with portions of southern Canada and
northern Mexico. The prairie stretched from the Rocky Mountains eastward for
over 800 miles, and extended more than 3000 miles from north to south. The
plains were created from sediment washed out of the Rockies over millions of
years which mixed with rubble from glaciers, and windblown deposits of silt,
sand and clay which now rests on the bed of what was once a shallow inland sea.
The Rocky Mountains also intercepted the flow of moist air from the Pacific,
and dried out the interior of the continent, which favored grasses over
trees.
Receding glaciers formed thousands of shallow depressions
across the Northern Plains. These wetland areas, known as prairie potholes,
range in size from 1/5th of an acre to 25 acres. Cattails and rushes comprise
the dominant emergent plants, and floating plants such as water lilies and
duckweed are also common. Although the pothole region comprises only 10 percent
of North America's waterfowl breeding areas, it produces over half of the
continent's duck population. Besides serving as breeding and watering sites for
wildlife, potholes collect rain and flood waters, which are released slowly,
helping prevent floods and erosion. Today, many areas of prairie potholes have
been drained, primarily to create farmland.
Fire was an important
element both in forming and maintaining the prairie. In the eastern prairie,
there is enough rainfall to support trees as well as grasses. Fire undoubtedly
helped the tallgrass prairie from being taken over by trees. Prairie fires
destroy tree seedlings, but burn only the uppermost part of grass plants. The
roots are unharmed, and in a short time, the plant will grow again. The ashes
then act as fertilizer for the grass.
Native Americans called fire
"red buffalo" since the roaring flames sounded like a stampeding herd. They
recognized its value and regularly set fires in order to lure game to areas
where tender new sprouts of vegetation attracted grazing animals within days
after a burn.
Tallgrass prairie
The tallgrass prairie
is found in the easternmost third of the Great Plains. It receives the most
rainfall, averaging 30-40 inches a year. The tallgrass prairie is predominantly
made up of Indian grass, switchgrass, and especially, big bluestem, which can
grow up to 12 feet high and half an inch a day. The tallgrass prairie is the
most lush, with much taller and denser grasses than the western prairies. An
acre of intact tallgrass hosts somewhere between 200 and 400 species of native
plants--3 out of 4 of them wildflowers. Each week from April through September,
about a dozen new kinds of flowers come into bloom. An acre of good tallgrass
may have 5 to 10 acres of leaf surface and produce 5000 pounds of forage a
year. Grazing cattle typically gain 2-3 pounds a day on these grasslands.
Today, what was once the tallgrass prairie is now the "corn belt", and not
surprisingly, 99.9 percent of the original tallgrass prairie has been
destroyed.
Mixed-grass prairie
West of the tallgrass
prairie, rainfall decreases to about 23-30 inches a year. The soil is less
productive and native grasses don't grow as tall. This section is known as the
mixed-grass prairie and is basically a transition zone between the tall grasses
of the Midwest and the very short grasses that lie just east of the Rocky
Mountains. Typical grasses of the mixed-grass prairie are little bluestem,
green needlegrass and prairie dropseed. Today, this area of the U.S. comprises
the "wheat belt".
Shortgrass
prairie
The far western prairie in the shadow of the Rockies is the
shortgrass prairie. Here, rainfall averages only about 15 inches a year, and
this region is dominated by drought tolerant plants that grow only 6-12 inches
high. The dominant grasses are blue gamma and buffalo grass. Sagebrush and
other shrubs are numerous and cactus are fairly common. The Rocky Mountains
intercept rain-laden clouds coming from the Pacific, resulting in the Rockie's
rain shadow to the east. Today, the shortgrass prairie is predominantly used
for cattle grazing.
Climate and Weather of the Great
Plains
The two most distinctive features of the climate and
weather of the Great Plains are range and variability. Plants and animals of
the prairie have evolved to be highly adaptable to extreme changes in their
environment. Winters in the northern Great Plains are the coldest in the
contiguous 48 states. Parts of Texas and Oklahoma can be as cold as states far
to the north. In contrast, summers on the Great Plains can be as hot as the
tropics. Fall and spring are transition periods with great fluctuations in both
temperature and precipitation. Much of the climate of the Great Plains is
controlled by three factors: continentally, air masses, and mountain
barriers.
Continentally refers to the great temperature ranges
associated with major land masses. Large bodies of water such as oceans heat
and cool slowly and maintain relatively uniform temperatures throughout the
year. On the other hand, land surfaces heat and cool quickly. Since the Great
Plains are located in the center of the North American land mass, far from the
moderating influence of major bodies of water, there is a great range of annual
temperature.
Air masses, the second control, are large bodies of lower
atmosphere, hundreds of square miles in size, that have fairly uniform
temperature and humidity taken from the surfaces over which they form. The
Great Plains are a battle ground of air masses: bitterly cold air out of the
north in winter; warm wet air from the Gulf of Mexico in the spring; and
occasionally hot, dry air from the Southwest in the summer. Unsettled weather
and precipitation often occur where air masses with different characteristics
collide--a front. The plains are also the windiest part of the country due to
the frequent air mass exchanges and the flat nature of the landscape. Air mass
movements are also influenced by mountain barriers. The Rocky Mountains
partially block moist air from the Pacific and contribute to the semi-arid
conditions of the western prairie in the "rain shadow" of the Rockies.
Plants of the prairie
The rich, deep soil of the
prairie was formed from sediment washed down from the Rocky Mountains, mixed
with rubble from glaciers, and windblown sand, silt, and clay. This combination
makes prairie topsoil--the layer of earth where minerals and other nutrients
are available for plant growth--some of the most nutrient-rich on earth. Forest
regions generally contain about 20-50 tons of topsoil per acre. On the other
hand, an acre of tallgrass prairie contains as much as 250 tons of topsoil.
The tough prairie sod is a great conserver of soil and water. Sod acts
like a giant sponge catching and holding rainwater. As a result, the amount of
water runoff from the prairie is small compared to land where there is no
strong network of roots to absorb the rain. The roots also bind the soil
tightly to the earth, protecting it against erosion. Prairie sod is so dense
that settlers once used it like bricks to build houses. A square yard of soil
just 4 inches deep may contain roots that would stretch for 20 miles if they
were placed end to end.
Grasses are the basic fabric of the prairie
since they are uniquely adapted for life in the open. Most plants grow from
their tips to add length. By contrast, grass grows from its base, emerging from
a bud at, or just under the soil where the sensitive growth tissues remain
protected from the elements and from grazing. In periods of extreme heat or
cold, grasses become dormant--they temporarily stop growing and using energy.
Roots of some grass species extend 10-15 feet deep into the soil, and can
extract moisture deep underground during dry periods.
Although
prairies may be grasslands in terms of sheer volume of vegetation, about three
out of every four plant species found there are wildflowers. Since wildflowers,
or forbs, must occupy the same space on the prairie as grasses, they have
adapted ways to guarantee their share of water and sunlight. Most forbs send
their roots deeper into the soil than grass roots, which allows them to tap
water the grasses cannot reach. To make sure they receive adequate sunlight for
growth, the shortest wildflowers bloom early in the spring before grasses have
time to grow and overshadow them. During summer and fall, forbs that stand as
tall or taller than grasses come into flower.
Many prairie wildflowers
have medicinal value to humans, such as the purple coneflower, or Echinacea.
This member of the sunflower and daisy family was used by Native American
tribes to treat ailments from ordinary colds to snakebite. In laboratory tests
the plant shows anesthetic, anti-inflammatory, and antibiotic properties and
increases the resistance of cell cultures to viruses. One compound it produces
appears to stimulate the immune system and another serves as a natural
insecticide. Echinacea is now widely available as an herbal supplement.
Destruction of the prairie
To the European
settlers of North America, the prairie was unlike anything they had ever seen.
The forests of the eastern U.S. were not unlike the forests of Europe, but the
Great Plains were a vast sea of unending grass. The mind set of many of these
settlers was to "tame" this wild, unknown land.
Over thousands of
years, the prairie flourished in natural balance. Then, in less than a century,
the grassland ecosystem was changed forever. John Deere invented the steel plow
in 1837, and farmers were finally able to bust the thick prairie sod and
replace native grasses with corn and soybeans. The Homestead Act was passed in
1860, allowing settlers to claim 160 acres of land for a $10 filing fee. Once
the claim had been occupied for five years, it became the settler's property.
As a direct result, over 400 million acres of prairie were converted to
farmland. Change began in the eastern prairies first, and by the early 1900s,
the tallgrass prairie had been converted to corn. Illinois, for example, which
is known as the "Prairie State" now has 3500 acres of remaining tallgrass
prairie--less than one ten-thousandth of the 37 million acres of grassland that
once covered the state.
Settlement spread westward after the Civil War
in 1865. The few pioneers who initially followed Lewis and Clark west became a
flood of people. The U.S. Army, who no longer had to worry about the threat of
the Confederacy, turned their attention to destroying Indians, or confining
them to reservations to make the west "safe" for settlers.
A major
factor in "controlling" Indians was to destroy the animal that provided them
with food, clothing and shelter--the bison. Bison were slaughtered by the
millions, and "bison trains" became popular. Trains crossing the plains would
stop when a bison herd was spotted and passengers would shoot the animals
without ever leaving the train, leaving the carcasses to rot on the prairie. By
1900, the 60 million bison that once roamed the Great Plains had dwindled to
one last wild band of 20. Fortunately, another 500 or so had been kept in zoos
or private herds, and these animals are the ancestors of most bison living
today.
 Millions of prairie dogs were poisoned
because they were believed to compete with grazing cattle. Today, less than 2
percent of their original habitat remains. The Mexican prairie dog is an
endangered species; the Utah prairie dog is listed as threatened; and the
status of the once most abundant species--the black-tailed prairie dog--is
being reviewed to see if it should be listed as a threatened or endangered
species. Audubon's bighorn sheep, the plains grizzly, plains wolf and Eskimo
curlew were all hunted to extinction.
The absence of fire also
contributed to the destruction of the prairie, since it allowed trees to take
over in former grassland areas. In areas not already converted to cropland, the
easternmost prairies were overgrown with forest.
Barbed wire became
readily available by the 1870s. Once settlers fenced their land and left
animals to graze the same rangeland continuously, vegetation deteriorated since
it was not allowed to recover. Wildlife requiring open range, such as
pronghorn, began to decline due to loss of habitat.
Few people
recognized the ecological sensitivity of the Great Plains or realized that
native grasses held the prairie soil together. Without native vegetation, winds
carried away topsoil planted with crops. This problem became evident during the
drought which caused the Dust Bowl and black blizzards of the 1930s when many
farmers lost their land. It wasn't until after this devastation that range
management and soil conservation practices were developed.
The Great
Plains once supported over 60 million bison--which had a combined weight
greater than that of every person alive in the United States and Canada
today--along with about 50 million pronghorn, an estimated 5 billion prairie
dogs, millions of deer and elk, and countless other species. Ironically, to see
thriving grasslands with huge, migrating herds of animals, Americans now must
travel to Africa.
Saving the prairie
Although much of the grassland of North America has been destroyed, there are
areas where original prairie still survives. Much of the western prairie was
never plowed, but was used for cattle grazing, so much more of it remains
intact than the eastern tallgrass prairie. Rising interest in protecting the
prairie may ensure that some of these areas will be saved.
Many people
are learning to imitate nature rather than control it. Ranchers are
experimenting with new ways of raising cattle, bringing back native grasses for
grazing in order to restore and preserve the soil. Bison ranching is gaining
popularity since bison meat is much leaner and healthier than beef. Bison graze
more efficiently than cattle and can better survive extremes in weather. Some
of the most important prairie-saving activities are happening in back yards and
school grounds across the country, where manicured lawns are being replaced
with native grasses and wildflowers to attract a variety of wildlife and
perhaps bring back just a small piece of the prairie.
Prairie Profiles
To learn
about some of the species that inhabit the prairie ecosystem, click on any of
the following:
Badger
Bison
Coyote
Golden Eagle
Western
Prairie Fringed Orchid
Burrowing Owl
Prairie Dog
Pronghorn
Prairie
Rattlesnake
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Copyright ©2005
Black-Footed Ferret Recovery
Implementation Team.
Web site Design Make Mine Magic inc.
Revised -- January 20, 2005
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