Download Destruction of grasslands

Study of Grasslands
What is grassland?
Grassland is an area where the annual rainfall is insufficient to support a luxuriant growth of
trees, but is still high enough so that deserts are not formed. Grasslands are however not
restricted to low rainfall areas. Several grassland types form either clearings in different forest
types or are located on hill slopes with patches of forests along nala courses and depressions as
in the shola region of South India. Grassland ecosystems form Himalayan pastures, the terai
grassland of the foothills, semi-arid grasslands of Western and Central Inndia, in scrublands of
the Deccan Plateau and in the Shola forests of the Western Ghats, Nilgiri and Annamalai ranges.
Thus depending on the quantity of rain, there are tall, medium and short grasses. Natural
grasslands have a variety of grasses, forbs (small plants) and herbs. These differ according to
the different grassland types.
The true grasslands are those where wild-plant communities naturally occur. This is where
grasslands have remained undisturbed by agricultural improvement. In many parts of the
world, examples that have escaped agricultural improvement (fertilising, weed killing,
ploughing or re-seeding) contain many species of wild plants - grasses, sedges, rushes and
herbaceous species - 25 or more species per square metre is not unusual. However, such
examples, such as original North American Prairie or lowland meadows in the UK, are now rare
and their associated wild flora equally threatened. Associated with the wild-plant diversity of
the "unimproved" grasslands is usually a rich invertebrate fauna; also there are many species of
birds that are grassland "specialists" - for example snipe, or the Great Bustard. Agricultural
grasslands are usually poor in wild plant species due to the original diversity of plants having
been destroyed by cultivation, the original wild-plant communities having been replaced by
sown monocultures of cultivated varieties of grasses and clovers, such as Perennial ryegrass
and White Clover. In many parts of the world "unimproved" grasslands are one of the most
threatened habitats, and a target for acquisition by wildlife conservation groups or for special
grants to landowners who are encouraged to manage them appropriately.
There are two broad types of grasslands in the world: Tropical Savannah and Temperate
Grassland.
Tropical Savannah
Tropical Savannah occurs in Africa, Australia, South America and Indonesia. Rainfall of 50 to 130
centimetres a year is concentrated in six to eight months with drought the rest of the year. Soils
are usually very thin, supporting only grasses and forbs (flowering plants), with only scattered
trees and shrubs. Differences in climate and soils create many variations in the plant
communities and animal species throughout the Savannah. In many areas, the grasslands have
been burned to maintain a healthy grass crop for grazing animals. In some areas the Savannah
has been expanded by cutting the forest and burning the area each year to prevent the return
of trees.
Temperate Grasslands
Temperate grasslands have less rainfall (25 to 90 centimetres) than tropical grasslands and a
much greater range of temperatures from winter to summer than Savannah. There are two
broad types of grasslands in temperate latitudes: Prairie and Steppe.
Prairie grasslands
Prairie grasslands are found across the globe. They have a variety of names in other parts of the
world: pampas in South America, veldt in South Africa and puszta in Hungary. These areas have
deep, rich soils and are dominated by tall grasses; trees and shrubs are restricted to river
valleys, wetlands and other areas with more moisture. Over the years the native grass species
on the extensive areas of level ground have been ploughed and fields seeded. Many of these
grasslands have been lost to cereal crops.
Steppe grasslands
Steppe grasslands receive only 25 to 50 centimetres of rainfall each year and the grasses are
much shorter than those on prairie grasslands. They are also not as widespread, occurring only
in Central and Eastern Europe, Northern Eurasia and Western North America.
Significance of Grasslands
Wheat, corn, oats, barley and rye – the bases of most human diets – are domesticated types of
grasses bred from wild plants. No longer perennial, they must be planted each year and have
become extremely vulnerable to disease, insect predation and drought. They are grown in
monocultures, fields of a single species that often have insect pests or diseases sweeping
through them. Moreover, soil that is artificially fertilized and sprayed with pesticides and
herbicides lacks the millions of invertebrates, fungi and other creatures that make wild
grassland soil rich and resistant to insect pests and disease. Wild plant genes have proven
valuable in producing hardier varieties of domestic strains through cross-breeding (Chadwick
1995).
Many perennial wild plants have the potential to become food plants because of their natural
resistance to insects and drought. These grains would not have to be replanted each year,
which is a great benefit because plowing causes erosion and requires great amounts of energy.
Maize, a type of corn closer to wild strains, is a major food source in Latin America and
elsewhere. It is one of the most photosynthetically efficient grain crops in the world, able to
transform the sun's energy into food very effectively (Viola and Margolis 1991). Grown in North
America and Europe mainly as livestock fodder, it has great potential as a human food source.
The Land Institute of Salina, Kansas, is working to discover new perennial grasses that might be
sources of food (Chadwick 1995). Eastern gama grass, for example, native to the American
prairie, needs far less water than conventional crops (Chadwick 1995).
Native peoples have traditionally utilized a wide variety of wild grassland and dryland plant
seeds for food and other purposes, and many of these plants represent potential food sources.
Another dryland plant native to the Americas and a staple food crop, the potato, has wild
ancestor species that contain natural insecticides. Certain varieties of potatoes produce high
levels of bitter, toxic glycoalkaloids, which make plants insect-resistant; native peoples of the
Andes have long removed these toxins by cooking the potatoes with clay (Viola and Margolis
1991). Domestic strains of potatoes are prone to disease, most tragically illustrated by the 19th
century famine in Ireland it caused.
Rainforest plants have been studied by scientists and pharmacological researchers for their
medicinal value over the past few decades, but many grassland plants have been used for
centuries by native peoples to treat various ailments. Extracts of the purple coneflower
(Echinacea purpurea), for example, native to tallgrass prairies of America, have been found to
be an effective treatment for symptoms of colds; they marketed as Echinacea in health food
stores and pharmacies in the United States. This plant was used by Native Americans for many
medicinal purposes (Madson 1993), and compounds within it have been found to kill insects
(Chadwick 1995). So popular is this plant that many collectors have threatened the species by
pillaging the last scraps of native grassland to dig up wild specimens that are reputed to have
greater potency than cultivated plants.
Another plant being commercially marketed for its health effects is goldenseal (''Hydrastis
canadensis''), a species of the buttercup family found in grasslands throughout eastern North
America. Native Americans used it as a tonic, an astringent and an insect repellent, as well as a
yellow dye. It is considered rare because its roots were overcollected (Niering and Olmstead
1979). Blue (great) lobelia (''Lobelia siphilitica''), a wildflower of eastern North America, was
given its scientific name based on its supposed ability to cure syphilis. While not effective
against syphilis, its root contains alkaloids that cause vomiting (Niering and Olmstead 1979).
Other American grassland plants used for medicinal purposes include feverwort (boneset),
prickly poppies, prairie larkspur, western ragweed and prairie goldenrod (Chadwick 1995). A
type of prairie nematode is being tested as a possible cure for Alzheimer's and other neurodegenerative diseases (Chadwick 1995).
American grasslands and shrub also home to Sassafras (''Sassafras albidum'') and Sarsaparilla
(''Aralia nudicaulis''), from which medicinal teas, beverages and infusions are made. Wild plants
of the cactus family have been used traditionally by Native Americans and Mexicans for food,
medicine and beverages. Some species, such as cactuses and baobabs, store water in their
stems or trunks. Aloes of many species in North America and Africa have been found effective
in treating burns.
Many wild species that have endured the extremes of weather for eons and have traits that
might be of great value to humans are in danger of disappearing altogether as humans take
over their habitats for agriculture and development. Without conservation, they may disappear
prior to discovery of their benefits.
Destruction of grasslands
Humans began adversely affecting natural grasslands some 50,000 years ago with the
introduction of livestock. Herders set fires to grassland to maintain it for grazing, but frequent
fires caused deterioration of these ecosystems and eliminated many native species of wildlife
that could not adapt. To protect their livestock, herders killed off competing wild ungulates and
persecuted predators and rodents, contributing to the decline of natural grassland ecosystems.
Many agricultural crops, especially those grown in arid regions, require artificial irrigation.
Sources include underground reservoirs, fed by rainwater that fell thousands of years ago, that
underlie many deserts and shrublands. Known as fossil aquifers, they have recently been
exploited through deep wells and are rapidly becoming depleted in portions of the Sahara,
Namibia, Saudi Arabia and the United States. The aquifer beneath the Great Sand Desert of Iran
has been pumped out, leaving only a low flow of brackish water (Allan and Warren 1993). In
Saudi Arabia, aquifers are being depleted by water used in wasteful forms of irrigation that
cause salinization of the soil. Heavy applications of water bring natural salts in the soils to the
surface, resulting in a surface soil covered with salt crystals that renders the soil sterile unless
the crystals are removed (Allan and Warren 1993). Salinization is destroying land in many parts
of the world, affecting more than 30 percent of all irrigated deserts (Allan and Warren 1993).
Grassland and dryland areas are among the most threatened of all habitats, according to an
appraisal of ecosystems and centers of biodiversity that has designated 200 ecoregions in the
world (Grove 1999). These include temperate grasslands and Mediterranean-type shrublands,
which are also rich in diversity (Grove 1999, Mittermeier et al. 1999). Conservation plans for
preserving many of these areas become ever more important as they disappear or are
degraded.
The misuse and overuse of grasslands has already turned millions of square miles into shrub
and desert. With the rise in human populations around the world, the process is accelerating.
Each year, an area the size of Texas turns to desert. The spread of deserts is threatening the
livelihood of the 650 million people who live in these arid regions (Ponting 1991). The global
warming climatic pattern may be accelerating this process. Studies in the early 1990s by the
United Nations Environment Programme (UNEP) estimated an area equal to North and South
America combined – about 8 billion acres (30,000,000 km²) of grassland and cropland – was in
danger of desertification worldwide(Pitt 1993). Since then, the problem has worsened. An
estimated 75 percent of Africa is already considered degraded (Simons 1994). Desertification
has claimed 39 percent of the 760,000 km² (188 million acres) of once productive grassland in
Mediterranean Europe and 82 percent of the 1,420,000 km² (351 million acres) of Western
Asia's productive steppe land (Goriup 1988).
UNEP reported in 1986 that rangelands are turning to desert at an increasing rate: 85 percent
of rangelands in North Africa, 30 percent in Mediterranean Europe and 85 percent in Western
Asia (Goriup 1988). Some studies have projected that should present trends continue, within 30
to 40 years, over half of the African continent, much of Central Asia, the majority of southern
and eastern South America, most of central and western North America and about 90 percent
of Australia will become desert (Allan and Warren 1993).
Specimens of Grasslands
Each grassland type has its specific herbivores and carnivores. The grassland herbivores are
mostly fleet footed animals that live in herds. They tend to form herds as a protective
mechanism. Animal life in the grassland evolved along two lines: those that run, such as the
blackbuck, wolf and the cheetah; and those that burrow such as the hedgehog and the gerbil.
Running is useful in pursuit or flight. The fastest wild animals of the world live in open
grasslands.
Grasslands also have an enormous number of insects. These insects attract a large number of
predatory animals like the lizards and birds.
In the past grass covered areas were considered to be the ‘common property’
of a village community. Over-utilisation and misuse of these ‘common’ grazing
lands has led to their degradation. However due to our ever increasing population these
grassland are being converted into agricultural lands through the development of dams and
canals.
The Asiatic Cheetah that once roamed the Indian subcontinent is now extinct.
Asian lions are now restricted to a single Sanctuary in Gujrat. Ecologists estimate that more that
43% of the Indian subcontinent is in the process of changing from grassland to desert.
Himalayan pastures
We have the Himalayan pastures in the Himalayas, which extends upto the snowline. These
grasslands at the lower level are found along with coniferous or broad-leaved forests. The
Himalayan wildlife require both the forest and the grassland ecosystem. Several wild sheep and
goat such as the Goral are found here.
Terai grasslands
The Terai grasslands at the
foothills of the Himalayas consist
of tall elephant grass along with
Sal forest. The largest herbivore
of the Terai is the elephant. It requires an enormous amount of tall grass to feed on. The Terai
grasslands form the habitat of the Swamp deer, Wild buffalo and the Rhinoceros.
Semi-arid grasslands
The semi-arid grasslands of the Western and Central India are interspersed with thorn forests.
Some of the very important Indian animals such as the blackbuck, chinkara and endangered
birds like the Great Indian Bustard are found here. The apex predator of this ecosystem was the
cheetah which is now extinct in India.
Shola grasslands
The Shola grasslands are found in high rainfall areas in Southern India. They are located on hill
slopes with patches of forest that occur along the nala courses. The Nilgiri Thar is found only in
these grasslands. It is now highly endangered.
Grasses
Grasses are very often considered as small plants that are insignificant and do not have much
value. However in reality they are a very important plant species that have over 10000 different
types. They are found everywhere in deserts, in snow covered areas, in mountainous regions,
on the coasts and even in water. Most significantly the grains of grasses form the staple food of
people all over the world.
Grasses belong to a group of plants that have more than 10,000 species. Like other plats
grasses also have stems, roots, leaves, flowers and fruits.
The roots of the grass plants are fibrous and form a strong web under the ground, which makes
it difficult to pull the grass out. They thus hold the soil tightly and fo not allow it to get blown
away by the wind or washed away by water. Grasses thus play an important role in
conservation of soil and moisture.
The stems of the grass plants are called as culms. They are generally cylindrical, hollow and
jointed. Sometimes as in sugarcane, these culms may be filled with a soft tissue. The elongated
hollow sections are interspersed with compact solid sections called nodes. Unlike other plants,
grass stems grow from the nodes, not from the tops or the ends of the branches. This helps
grasses to grow rapidly even when they are grazed on by a variety of animals.
Some stems grow vertically. Others may trail along the ground. These are called as stolons.
Grasses also have rhizomes or underground stems which are an intricate part of their structure.
Rhizomes are brown in colour and also have nodes and internodes. Rhizomes are important as
they help grasses to hold on to the soil. They also play a major role in propagation as they send
up a large number of new shoots. They also play a very important role in the survival of grasses
when they are burnt, as they remain unharmed when the surface vegetation is burnt and
quickly send up replacements.
The leaves of grasses are ribbon like with parallel veins. The leaves encircle the stem above
each node in a sheath and then protrude out in different directions.
Grasses are flowering plants. The flowers are extremely small and do not have petals. They
normally occur in groups. These flowers are neither brightly coloured nor scented as they are
mostly pollinated by wind. They produce a very large number of seeds. The wind carries the
seeds to new locations. These seeds often have fine hair like structures. Animals also play an
important role in the dispersal of grass seeds. This can happen in many ways: by sticking to an
animal’s body as when the seed is pointed and by being eaten and left in animal
droppings. Some grasses have seeds that are attached to the plant very lightly. These seeds are
designed to be knocked to the ground by rain or passing animals.