Grassland

An Inner Mongolian Grassland.

Grassland is the term given to land dominated by natural or sown grasses (Poaceae) and herbaceous (non-woody) plants (also known as forbs). Some grasslands are definitively dominated by herbaceous species, however the majority of the world's grasslands are savannas and show a range of woody plant and grass co-dominance. In temperate latitudes, such as north-west Europe, grasslands are dominated by perennial species, whereas in warmer climates annual species form a greater component of the vegetation<<fact>>. Grasslands are very varied and can be found in most terrestrial climates. Grassland vegetation can vary in height from very short, as in chalk downland where the vegetation may be less than 30 cm high, to quite tall, as in the case of North American tallgrass prairie, South American grasslands and African savannah.

Grassaland, shrubland and desert environments cover two-thirds of the world's land surface <<fact>>. In countries where modern agriculture has not destroyed wild grasslands, the greatest diversity of grazing animals and predators on the planet calls these open habitats their home<<fact>>. Grassland habitats appeared on Earth some 70 or 80 million years ago<<fact>>.

As flowering plants, grasses grow in great concentrations in climates where annual rainfall ranges between 10 and 39 inches <<fcat>>. The root systems of perennial grasses and forbs form complex mats that hold the soil in place. Mites, insect larvae, nematodes and earthworms inhabit deep soil, which can reach 20 feet underground in undisturbed grasslands on the richest soils of the world. These invertebrates, along with symbiotic fungi, extend the root systems, break apart hard soil, enrich it with urea and other natural fertilizers, trap minerals and water and promote growth (Chadwick 1995). Some types of fungi make the plants more resistant to insect and microbial attacks.

Climate and grasslands

Grasslands receive about 380 to 900 mm (15 to 36 in) of rain per year<<fact>> compared to deserts, which receive less than 300 mm (12 in) and tropical rainforests, which receive more than 2,000 mm (80 in)<<fact>>. While extreme temperatures may occur in some grasslands, normally they range between -20 to 30 degrees Celsius<<fact>>. Tropical grasslands have dry and wet seasons, but remain warm all the time<<fact>>. Temperate grasslands have cold winters and warm summers with rain or some snow. Since grasses die back above ground annually<<fact>>, the soil and the sod protect the roots and the new buds from the cold of winter or dry conditions.

Grassland biodiversity and conservation

The true grasslands are those where wild-plant communities naturally occur<<fact>>. 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<<fact>>. 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<<fact>>, 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<<fact>>. 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.

==Human impact and economic importance Grasslands are of vital importance for raising livestock for human consumption and for milk and other dairy products.

Grassland vegetation remains dominant in a particular area usually due to grazing, cutting (such as for hay), or natural or man-made fires, all discouraging colonisation by and survival of tree and shrub seedlings<<fact>>. Fire was used in North America by the Native Americans as a means of maintaining grassland<<fact>>. Some of the world's largest expanses of grassland are found in African savannah, and these are maintained by wild herbivores as well as by nomadic pastoralists and their cattle, sheep or goats<<fact>>.

Grasslands may occur naturally or as the result of human activity. Grasslands created and maintained by human activity are called anthropogenic grasslands. Hunting peoples around the world often set regular fires to maintain and extend grasslands, and prevent fire-intolerant trees and shrubs from taking hold. The tallgrass prairies in the American Midwest may have been extended eastward into Illinois, Indiana, and Ohio by human agency. Much grassland in north-west Europe developed after the Neolithic Period, when people gradually cleared the forest to create areas for raising their livestock.

Types of grassland

Tropical and subtropical grasslands

These grasslands are classified with tropical and subtropical savannas and shrublands as the tropical and subtropical grasslands, savannas, and shrublands biome. Notable tropical and subtropical grasslands include the Llanos grasslands of northern South America.

Temperate grasslands

Mid-latitude grasslands, including the Prairie of North America, the Pampa of Argentina, calcareous downland, and the steppes of Europe. They are classified with temperate savannas and shrublands as the temperate grasslands, savannas, and shrublands biome. Temperate grasslands are the home to many large herbivores, such as bison, gazelles, zebras, rhinoceroses, and wild horses. Carnivores like lions, wolves and cheetahs are also found in temperate grasslands. Other animals of this region include: deer, prairie dogs, mice, jack rabbits, skunks, coyotes, snakes, fox, owls, badgers, blackbirds, grasshoppers, meadowlarks, sparrows, quails, and hawks.

Flooded grasslands

Grasslands that are flooded seasonally or year-round, like the Everglades of Florida or the Pantanal of Brazil, Bolivia and Paraguay. They are classified with flooded savannas as the flooded grasslands and savannas biome and occur mostly in the tropics and subtropics.

Montane grasslands

High-altitude grasslands located on high mountain ranges around the world, like the Páramo of the Andes Mountains. They are part of the montane grasslands and shrublands biome, and also constitute alpine tundra.

Polar grasslands

Similar to montane grasslands, arctic tundra can have grasses. However high soil moisture means that few tundras are grass-dominated today. However, during the Pleistocene ice ages, a polar grassland known as steppe-tundra occupied large areas of the Northern hemisphere.

Xeric grasslands

Also called desert grasslands, these are sparse grasslands located in deserts and xeric shrublands ecoregions.Grasslands have great biological diversity and stability; they are able to resist plant disease and drought. As such, they represent invaluable genetic banks. This diversity is being studied by scientists around the world and consequently uncovering chemical and biological secrets. Agriculture and other food production will profit from this emerging knowledge.

Benefits of Grasslands

Wheat, corn, oats, barley and rye – the bases of most human diets – are domesticated types of grasses bred from wild plants. As annual species 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<<fact>>. 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<<fact>>. Wild plant genes have proven valuable in producing hardier varieties of domestic strains through cross-breeding <<fact>>

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. 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 <<fact>>Eastern gama grass, for example, native to the American prairie, needs far less water than conventional crops <<fact>>.

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.

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. The purple coneflower (Echinacea purpurea), for example was used by Native Americans for many medicinal purposes <<fact>>, and compounds within it have been found to kill insects <<fcat>>.

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 neuro-degenerative 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

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 <<fact>>. 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).

Preserving dry grasslands

While there are treaties and international campaigns to save wetlands and forests, grassland and desert preservation has been accomplished on a national and regional basis. Some countries, including the United States, Russia, Mongolia and China, have set aside large areas of deserts, but grasslands are still considered prime grazing and farmland, an impediment to their protection. An international treaty such as the Ramsar Convention on wetlands protection (see Aquatic Ecosystems chapter) would help protect many remarkable and unique grasslands and deserts. Many have been designated as UNESCO World Heritage Sites under the World Cultural and Natural Heritage Convention for their "outstanding universal value" and/or Biosphere Reserves by the Man and Biosphere Programme. This has provided an incentive for protection, although unprotected land rarely receives such designations, which tend to be given to national parks or reserves.

The 1994 Convention on Desertification, a treaty drafted by the United Nations, attempts to slow the current trends turning grassland and shrub into desert. The treaty was negotiated at the urging of African nations attending the 1992 Earth Summit in Rio de Janeiro that requested funds for environmentally sustainable agricultural practices based on traditional methods in dryland areas (Pitt 1993). The United Nations estimates $10 billion to $22 billion will be needed annually over the next 20 years to finance the rehabilitation of land and arrest the desertification processes (Simons 1994). This treaty is one of the first to mandate cooperation with local communities and design methods incorporating input from local people. In late 1996, the Convention went into force, although the United States still had not ratified it. Estimates of the funding needed to slow the expansion of deserts rose to $43 billion by 1996.

One positive development is the designation of the Great Gobi National Park of southwestern Mongolia. The United Nations Development Programme, as part of a worldwide project financed by the Global Environment Facility organization, established a Mongolian biodiversity program with help from the Mongolian government (Possehl 1995). The United Nations agency has helped finance the park, one of the largest in the world, by funding the salaries of rangers who patrol on camels (Possehl 1995). The park is dotted with oases greened by poplar and tamarisk trees, waterholes and shrub vegetation. It has been divided into two sections that cover over 17,000 square miles. This commitment to conservation on the part of such a poor country is extremely laudable.

These hotspots once covered 5,266,009 square kilometers, 30 percent of the entire land area. One region not included above, the Caucasus area between the Black and Caspian Seas of Central Asia, is part grassland and part temperate forest (Mittermeier et al. 1999). All of these ecosystems have been drastically reduced from their former size. The Mediterranean Basin's original dry ecosystems once covered 2,362,000 square kilometers, but they have been reduced to 110,000 square kilometers, 4.7 percent of the original area; only 1.2 percent remains of the Brazilian Cerrado (Mittermeier et al. 1999). None of these ecosystems is more than 27 percent of its old size. Only 154,408 square kilometers – 3 percent – of the original 5,266,009 square kilometers are protected; these areas represent 7 percent of intact portions of these ecosystems (Mittermeier et al. 1999).

While this seems to paint a dark picture of grassland and dryland preservation, much good is also being done. The identification and biological surveys of these areas of high diversity are major first steps. Many of these regions have been ignored both by conservationists and the nations where they are found. Once governments are informed of the biological importance and threats to these regions, many begin to set aside national parks and reserves.

The designation of reserves of temperate grassland and dryland by governments such as the United States, Canada, Argentina, Chile, Mongolia, Russia, Central Asia and China has protected portions of these ecosystems being destroyed by livestock grazing, agriculture and new human settlers. Some of the largest of these reserves have been set aside to preserve the Asian steppe. In addition to Tibet's Chang Tang Reserve, the Chinese government set aside a 6,000-square-mile area, the Taxkorgan National Reserve, an international sanctuary where Afghanistan, Pakistan, Russia and China meet (Goddard 1995).

Ecosystem protection, a relatively new concept just now gaining acceptance, may become a major means of protecting the Earth's diversity. Reserves often fail to protect wide-ranging species that migrate out of them, and isolation may cause key ecological components of an ecosystem to die out, causing a biological collapse. In the United States, an organization of biologists and conservationists has urged protection of the Yellowstone Ecosystem, a mosaic of savannah, temperate forest and mountain environments surrounding Yellowstone National Park. The size of the park does not allow movements of its wildlife outside the park, such as the migrations of American bison (Bison bison), dispersal of grizzly bears (Ursus arctos) or the reintroduced gray wolf (Canis lupus), because cattle ranches and other private property now surround the park. Another even more ambitious proposal aims to link Yellowstone with other federal lands in the United States and Canada north to the Yukon, purchasing private lands where necessary, to create a wide corridor of undeveloped land. This would allow herd migrations and movements of carnivores to link them with other populations, while protecting the environment and species diversity. Such programs would help ensure permanent conservation of the region. A similar proposal in southern Africa would create a vast park system, stretching from southeastern South Africa north to Kenya, so that wide-ranging grazing animals and their predators could migrate freely.

The benefits to society of such preservation are significant. Ecotourism has a potential to make such projects pay for themselves. This industry is growing astronomically and yields far more income than consumptive uses of nature, such as trophy hunting, logging and mining. Likewise, use of video cameras in parks and reserves connected via satellite to the Internet for pay-per-view has emerged as a potentially enormous source of income for the funding of biological studies, national park expenses and land preservation.

Many organizations and scientific bodies have made great steps within the past decade to alert the public about the need to preserve these threatened grassland and dryland ecosystems. Books on the beauty and wild fauna and flora of the Serengeti, Tibet's steppe, and America's prairies, as well as films and television programs, are educating people about these beautiful areas.

Within the past decade, the protection of remaining grassland, as well as its restoration, has taken hold in the United States, sponsored by states, private organizations and the federal government. Many student projects have involved propagation of native grassland plants for restoring these habitats. The establishment of the country's first tallgrass national park has been a recent highlight of these trends.

Worldwide, a similar effort is needed to restore these magnificent habitats. Grasslands have been "so massively transformed by the hand of man that one is hard put to find any landscapes in them that match the original," and if "ever a biome needed a champion, it is the grassland", Warwick Tarbotoni once said (Africa--Environment & Wildlife, November 2000). The rich variety of plants and animals native to grassland and shrubland ecosystems is being preserved in parts of the world as more people gradually see these environments not as grazing land for livestock or potential farmland, but as vital to the preservation of diversity of their region.

To preserve dryland from overgrazing by livestock, new approaches are being explored. Portions of Saudi Arabian desert have been fenced off from livestock on an experimental basis, and native plants reemerged from long dormancy, covering the sand in green. Much of this region (and the Sahara) is sandy desert; herds of camels, sheep and goats owned by nomadic people are allowed to graze year-round, eliminating the seedlings that attempt to regenerate. In an innovative approach to helping desert people survive without destroying deserts in the process, several villages in southern Africa have agreed to fence their livestock and stop gathering wood for firewood. They will use methane gas fuel generated from animal dung for their cooking and heating needs. These villages have also been supplied with electricity from solar roof panels and small wind turbines. Without furnishing a solution to the needs of desert inhabitants who depend upon their livestock, one cannot expect these people, many of whom live on the edge of poverty and hunger, to preserve desert vegetation. Solar collectors, solar-powered stoves, technology to produce methane from livestock dung and information on water conservation should be provided by international conservation organizations and governments through foreign aid.

See also

• Coastal plain
• Dambo
• Desert
• Field
• Flooded grasslands and savannas
• Flood-meadow
• Meadow
• Pasture
• Plain
• Plateau
• Prairie
• Savanna
• Steppe
• Taiga
• Tundra
• Veld
• Water-meadow
• Wet meadow