|
Overview
Among the most endangered ecosystems today are the world's grasslands. Threats
menacing them include overgrazing, soil erosion, urbanization, and
replacement of natural vegetation with agricultural fields and tree
plantations. When native grasslands disappear, so do the unique
plants and animals that depend on them. Also at risk, are unique
human cultures and lifestyles specially adapted to them: Mongolian
nomads, Argentine Gauchos, and American cowboys all have developed
distinctive ways of thriving in the challenging conditions of the
world's grasslands, whether we call them prairies, pampas, veldts,
or steppes. The preservation of both our cultural and our natural
heritages, therefore, depend upon how successfully we can preserve
the natural grasslands that support both.
Learning Objectives
Students will be able to:
- Identify some of the threats confronting natural grasslands
worldwide.
- Describe some of the distinctive cultures and lifestyles that
have developed as adaptations to grassland conditions.
- Describe measures that people are taking to preserve grassland
ecosystems and the cultures that depend on them.
Pre-Viewing Activities
-
Introduce the following key terms to the students:
Pampas — the vast plains of southern South America, chiefly
in Argentina, but also in Uruguay, southern Brazil, and southeastern
Paraguay
Veldt — the extensive grasslands of South Africa
Prairie — grasslands, especially in the interior of North
America
Steppe — the plains of interior Eurasia
Savannah — a grassland with scattered trees, typical of
East Africa
erosion — the carrying away of soil by wind, ice, water
and animals
carrying (grazing) capacity — the amount of animals that
can be supported by a piece of land or body of water
sedimentation — the deposition of eroding soil onto land
or into water
- To familiarize students with the areas in the program segments,
use a wall map, desk map or an atlas and have students locate
- Shanghai
- Inner Mongolia
- Kenya
- Lake Baringo
- Buenos Aires
- New Mexico
After the students have found each of these locations,
begin a discussion to discover what they already know about these regions. Have
the discussion center on environmental problems that are familiar to
the students.
Post-Viewing Discussion
Inner Mongolia
- What weather conditions create the grasslands in Inner Mongolia? (Answer:
Hot and dry summers, long, cold winters. These typically create
grasslands worldwide.)
- Why do the people who live on the Mongolian grasslands roam around
instead of living in one place? (Answer: They move in search of
grass to feed their animals.)
- How do they live when roaming on the grasslands? (Answer: They
live in mobile tents and carry everything they need with them.)
- What is motivating people to overgraze the grasslands? (Answer:
China is undergoing an economic boom, and increasing numbers of people
want to buy meat and milk. The herders want to take advantage of
the demand for their animals, so they want to raise as many as possible.)
- What pressures are threatening the traditional Mongolian nomadic culture? (Answer:
Environmental deterioration, notably soil erosion, is making it difficult
to make a living. Increasing educational and employment opportunities
in cities and town lure young people away from the traditional nomadic
way of life.)
Kenya
- Why is the erosion occurring? (Answer: Overgrazing the land destroys
the vegetation that holds the soil in place.)
- What is causing the overgrazing? (Answer: Significant human population
growth around the lakes, leading to increased numbers of animals. Fewer
people living a nomadic lifestyle, more people living year-round in villages. This
forces livestock to focus their grazing on small areas close to villages,
rather than spreading out over a wider area.)
- What are some people doing about soil erosion? (Answer: They
are planting native grasses and other plants which will hold the soil
in place and provide fodder for stock.)
South Africa
- What are some ways in which the natural grasslands of South Africa
(the Veldt) are ecologically important? (Answer: Habitat for over
800 species of wildflowers, 360 species of birds, and many wild mammals. Grasslands
also absorb rainwater and release it gradually to streams, rivers, and
lakes. This greatly reduces the risk of extreme cycles of floods
and droughts.)
- What are some ways in which people use the grasslands? (Answer:
The grasslands provide natural medicines and grazing for livestock.)
- What is the unemployment rate in rural South Africa? (Answer:
Over 60%.)
- What happens to many of the trees? (Answer: They are sent to
Japan, Australia and the United States to make paper and pulp.)
Argentina
- Why is the pampas perfect for raising cattle? (The weather is
constant — mild and moist.)
- What is the chief threat to the pampas? (Answer: Conversion to
croplands. This wipes out native vegetation, puts more insecticides
and fertilizers into the environment, and reduces water storage in spongy
grassland soils.)
New Mexico
- What are people trying to do with the Gray Ranch? (Answer: Maintain
an environment that will prove healthy for wildlife, livestock, and a
traditional way of life far into the future.)
- What are some measures being implemented to bring this about? (Answer:
Maintaining native vegetation, restricting the numbers of livestock that
roam the ranch so that they do not overgraze, using fire to remove alien
plant species and to encourage new and nutritious plant growth, employing
traditional ways of managing the ranch.)
Special Projects
-
To help your students learn where the major biomes
of the world are found, divide the students into
work groups and assign to each a biome (tundra/alpine;
coniferous forest; deciduous forest; tropical rain
forest; grassland/Savannah; desert) to research. Each
group should prepare a map showing where in the
world each biome is found and present some animals
typical of each. Results may be presented
on a poster or an oral presentation, or each group
can combine efforts to prepare a large world map
for the classroom wall or the hallway, decorated
with pictures of wildlife cut out from magazines
or downloaded from the internet.
-
To compare the life found in fields, pastures,
or grasslands in your neighborhood with other local
ecosystems such as forests, have your students
carry out a mini-transect study. The students
will tie a string five meters long to two sticks
and stake them into the ground in each habitat
being compared. Then they will carefully
survey the plants and animals they find. A
range of field guides are available to your students
to help them identify what they find.
-
To see the effects of soil erosion, take your
students on a neighborhood stroll to compare the
soil in both eroded and intact sites. Have
your students consider the following:
- Differences in soil color, texture, and moisture.
- Plant life in each site.
- Reasons why erosion occurred in one site and
not the other.
- Which soil evidently contains a higher percentage
of decomposed plant material.
- Which soil evidently contains more worms and
other soil fauna.
- Which habitat is healthier.
- Have a discussion with your students about human
carrying capacity. Ask them how humans can raise
their carrying capacity, (e.g. irrigation, plant breeding,
fertilization) and how humans can decrease it (e.g.
desertification, soil erosion). What will happen
if human populations continue to increase and human
carrying capacity decreases? Do your students
know of examples around the world that look like this?
- As an extension, ask your students to consider vanished
civilizations, such as ancient Mesopotamian city-states,
classic Mayan, and the Anasazi of the American Southwest. Many
scientists now believe that environmental degradation,
notably deforestation and soil degradation, contributed
to their demise. What archaeological evidence
would your students expect to find if significant environmental
degradation did, indeed, occur?
- Ask a farmer to visit your class and discuss how
he or she works to conserve soil. Have their
crop yields been increasing, decreasing, or remaining
the same, and why? Or, ask an agricultural extension
agent to speak with your students. What soil
conservation problems occur in your neighborhood, and
what can people do to solve them? What can your
students do?
- With the help of an agricultural extension agent,
have your students prepare a soil conservation demonstration
plot on school property. If your school is in
the Midwestern United States, have your students prepare
a plot of native prairie plants. Agricultural
extension agents, the local land grant college, or
local environmental or nature study organizations may
be able to help. You may be able to have your
school property warrant registration as an official
wildlife habitat. Contact the National Wildlife
Federation (see listing below) for information about
its Backyard Wildlife Habitat program.
- To compare the water retention capacity of eroded
and healthy soil, collect a sample of each. Then
take two one-liter clear plastic bottles and cut off
the bottom. Insert each bottle into a clear glass
jar and fill each about two-thirds full with one of
the soil samples. Now, take a container of water
and gently pour into each bottle. Have the students
compare the quantity and clarity of the water that
comes out the other end.
-
Have your students compose travel
brochures describing the various grasslands worldwide
and the cultures (e.g. Mongolian nomads, Gauchos,
African pastoralists, American cowboys) found there. The
brochures should accurately present what the discriminating
eco-tourist can find and do in these places. Your
students can use images cut from magazines or downloaded
from the Internet.
|