Grassland currently covers 40% of the earth’s
surface. They are the most endangered of all the
planet’s biomes.
Generally located in the center of
continents, grassland survival depends on great
seasonal temperature extremes, naturally occurring
fires, grazing by herbivores and low precipitation as
well as droughts.
Grasslands provide functions
essential to the overall biodiversity of the planet.
Two very important factors in the biodiversity of the
biomes surrounding the grasslands is the storage of
ground water and carbon. Grasslands store
approximately 1/3 of the terrestrial ecosystems global
stock of carbon. Carbon is important in the fixation
of atmospheric carbon dioxide in the
carbon cycle . Storage of carbon may be reduced if
grasslands continue to be overgrazed, cleared for
development and mined for resources.
Other important
uses of the grasslands are the economic benefits such
as tourism drawn in by the native habitats of birds
and wild herbivore and plant species. Grasslands
provide flora used to make many of our prescription
drugs. Domestic animals provide meat, milk, wool, and
leather products for humans. Wild herbivores present
in the grasslands provide prey for native predators.
Grasslands are divided into two categories: Temperate
and Tropical. They are endangered and threatened in a
variety of ways with a variety of resulting changes to
the grassland biomes.
Tropical Grasslands or Savannas
Tropical grasslands, also know as savannas,
consist of grasses as well as scattered trees and
shrubs. The grasslands of Africa are home to some 800
species of flowers and bulbous plants such as arum
lilies, 54 species of orchids, aloes, watsonias and
gladioluses. Rainfall is 20-50 inches per year falling
in a six to eight month concentrated period. The
rainfall is followed by a long drought that allowing
natural fires to occur. The fires supply birds with a
feeding ground as insects, mice and lizards are driven
from the area. The soil is porous with rapid water
drainage and a thin layer of humus, which provides
nutrients for the vegetation. A large number of plant
species compete for land space in the savanna with
only one or two types of grasses present.
Drier
savannas such as the Serengeti plains with
well-drained soils will grow Rhodes grasses and red
oat grass. Star grasses are present in East African
savannas. The western Uganda savannas have lemon
grasses. Tree density is kept in check with seasonal
fires and large grazing animals killing off many of
the seedlings. The overall biodiversity is kept in
check when the grasslands are undisturbed by
civilization or when the grasslands are preserved and
utilized without harming the natural processes.
South African Savanna
The temperate grasslands of Africa once covered
60% of the country. Warming trends around 3 million
years ago allowed trees and woody plants to invade the
grasslands. This converted it to a Savanna or tropical
grassland. Today only 16.5 percent of Africa is
grassland and is located only in South Africa. Sixty
to eighty percent of South African grasslands have
been irreversibly converted to non-native timber
plantations, coal and gold mines, urban sprawl and/or
cropland.
Tree plantations are being planted in Africa’s
grasslands to supply wood and pulp to other countries;
most of which have severely depleted their own tree
resources. When tree plantations are introduced, they
absorb the stored ground water thus depriving the
rivers and human water supplies. Rain is stored as
ground water in the grasslands. The water is released
slowly throughout the year through seepage zones
resulting in less immediate run-off and this prevents
erosion. Also threatened is the grassland’s water
supply that is needed for the long drought season.
When these essential water supplies are threatened,
rapid potentially irreversible soil depletion results.
Savanna species are then either threatened or become
extinct in these areas.
Pollution from high-sulfur coal burning is also a
threat to Africa’s savanna. Approximately 1 million
tons of sulfur dioxide is released into the atmosphere
each year. This is one of the highest rates in the
world. The grasslands absorb the pollution.
Mining is performed in opencast pits, which strip the
grasslands of native plant species.
Urban sprawl is the development of residential and
industrial properties, as well as road construction
and shopping centers. Africa’s economic heartland is
located in the grasslands consuming a large portion of
the land. Cropland is grassland that is converted into
farming area where row crops are planted and grassland
is eliminated. This is another threat to the savanna
of South Africa.
Temperate Grasslands
Grasses dominate the temperate grasslands; trees
and large shrubs are not present. Moderate rainfall
averaging about 20-35 inches in the late spring and
early summer, hot summers and cold winters, seasonal
drought and occasional fires are essential to the
preservation of the biological diversity of the
temperate grasslands. Temperate grasslands consist of
deep dark soil with fertile upper layers. Deep grass
root growth and decay result in the nutrient rich
soil. A few hundred species of flowers have been found
growing among the grasses of the temperate grasslands.
Coneflowers, goldenrods, and sunflowers are a few of
the species found. Corn, wheat, oats, rye, rice,
barley, millet and sorghum all originated in the
temperate grasslands.
Prairies of the Great Plains of North America
Road networks have resulted in the decline of the
Great Plains along with overdeveloping and over
grazing. Urban sprawl is another concern for this
area. Agricultural conversion takes place when farmers
plow up native prairie to do row crop agriculture. The
government provides crop subsidies to the local farmer
thus encouraging the continuing row crop agriculture.
The soil is stabilized with non-native species of
grasses resulting in the endangerment of the native
species. Poor land management practices results from
prioritizing livestock and other commodity production
and ignoring the mandates to manage the land for
biological diversity. The destruction of biodiversity
by the removal of native grasses is a result of over
grazing, drought relief assistance and aggressive
wildlife control. Native grassland species help to
improve crops and increase resistance to diseases.
Clearing of native vegetation for seeding of
non-native or introduced grasses severely endangers
these species and many have already become extinct.
Often wide-scale poisoning of predators is performed.
Having large herds of grazing livestock in an area of
prairie that did not evolve this way has negatively
affected 99% of the sagebrush-grass zone west of the
Rockies.
Steppes of Central Eurasia
Desertification is the largest threat to many parts of
the Steppes of Central Eurasia. It is defined as the
transformation of vegetated productive land into bare
and unproductive land. The conditions become
desert-like and many native species become endangered
or extinct. Due to the degrading soil conditions seed
germination becomes difficult and adds to the problem
of desertification. The main cause of this is
overgrazing. Because of the large numbers of livestock
confined to small grazing plots without rotation, the
soils become eroded and vegetation becomes sparse.
More than 900 square miles of land, including parts of
the eastern edge of the Qinghai-Tibet Plateau, parts
of Mongolia and land north of Beijing, China, are
degraded into desert each year. Millions of herders
and farmers work this land. Poor grazing planning is
the number one cause.
It is believed that the loss of
grasslands is a result of droughts becoming longer due
to the effects of global warming. Some scientists in
the Qinghai Province claim to have documented rising
temperatures and lower rainfall since the 1970’s.
Other scientists argue that it is land misuse due to
the rising population of people and livestock.
The Eastern Steppes of Mongolia are under the
threat of economic development. Valuable oil and gold
reserves lie beneath the grasslands and neighboring
resource hungry countries are ready to develop, mine
and drill. One concern is for the approximately 2
million gazelles that populate the area because
grazing patterns will be interrupted. The Eastern
Steppes of Mongolia are the last unspoiled grasslands
in the northern hemisphere covering 300,000 square
kilometers. Herding and farming is the economic
foundation for millions of people living in the
steppes.
Pampa of South America
The Pampa or temperate grasslands of South America are
threatened due to an excess of water. The excess is
not due to excess rainfall but the lack of
percolation, surface movement and evaporation. This is
believed by some researchers to be due to trampling by
beef cattle. The trampling causes increases in bulk
density by compaction of the soil surface. Seasonal
increases in sodium and over grazing are also believed
to be a cause of the soil changes leading to
endangerment of the Pampa. Another concern for the
Pampa is the conversion of grassland to croplands. It
has been as high as 76% in South America.
Projects such as restoration, reconstruction and
conservation are being put into effect to help keep
the grasslands of the world from becoming severely
transformed or even extinct. Reconstruction is the
planting of grasses and flowers onto land that had
native vegetation removed. Restoration is the removal
of non-native species of flowers and grasses and the
seeding and planting of species native to the specific
grassland. These species are usually obtained from the
native plants still surviving in the area.
Conservation is of course the objective for the
remaining unchanged grasslands. Conservation projects
are in place in some of grassland biomes around the
world, but only a small fraction of the individual
grasslands are included in the protected areas.
Article written by Earth Sister Barb Palatino
References:
http://www.pbs.org/earthonedge/ecosystems/grasslands1.html
http://www.wri.org/wr2000/grasslands_carbon.html
http://www.iowaprairienetwork.org/definitions.html
http://www.wri.org/wr2000/grasslands.html
http://www.buyhard.fsnet.co.uk/news_18.htm
http://www.wri.org/wr2000/grasslands_extent.html
http://www.wri.org/wr2000/grasslands_biodiversity.html
http://www.changemakers.net/studio/99october/jarmant1.cfm
http://www.sawac.co.za/articles/whoneeds.htm
http://www.nwf.org/grasslands/national_grasslands.htm
http://www.wri.org/press/page_grasslands_pr.html
http://www.snowcrest.net/geography/slides/biomes/grass.htm
http://www.nfw.org/grasslands/threattograsslands.html
http://www.ucmp.berkely.edu/glossary/gloss5/biome/grasslan.html
http://www.wri.org/wr2000/grasslands_food.html
http://www.tve.org/earthport/transscript/29an2001.html
http://www.unu.edu/unupress/lecture12.html
Journal of Range Management 41(6), November 1988
