Endangered Species Handbook

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Grasslands, Shrublands, Deserts

Threatened Species

     Over the millennia, vast herds of hoofed animals grazed grasslands throughout the world.   In spite of their great numbers, they did not overgraze or destroy these habitats, migrating before the soils were robbed of nutrients and wild plants died out.  Natural grassland can support at least 30 species of large ungulates without being damaged, but can be destroyed by a single kind of domestic livestock grazed in large numbers.  Over the past few centuries, sheep, goats, cattle, yaks and other domestic livestock have greatly increased in number, either herded by nomads or grazing on private and public lands.  The effects on native wildlife, especially ungulates, have been catastrophic.  They have been crowded out of their habitats, and in many parts of the world, livestock has transmitted lethal diseases such as anthrax and rinderpest to wildlife, resulting in massive die-offs, endangering many species.  Some African antelope and zebras, for example, have been reduced to a tiny fraction of their original populations and survive only in reserves.   Even these reserves can become islands surrounded by development outside, which isolates the wildlife into zoo-like environments.  Such wildlife often becomes inbred and extinction-prone.  
 
     Just how many species native to grassland and dryland habitats are threatened has not been calculated by either the 1994 or 1996 IUCN Red List.  Only for birds have such analyses been made.   BirdLife International, in Birds to Watch 2: The World List of Threatened Birds (Collar et al. 1994), concluded 6.3 percent of all threatened birds were grassland species, and a slightly larger percentage, 9.3 percent, were native to shrub and desert.  Thus, 15.6 percent of the world's 1,111 threatened birds (173 species) inhabit grassland, shrub or desert (Collar et al. 1994).  This is a significant percentage of the world's birds, and it is evidence that these regions are under great siege from a variety of factors.  In the 2000 IUCN Red List (Hilton-Taylor 2000), only forest areas had more threatened birds than shrubland (about 22 percent) and grassland (15 percent).  Likewise, for 515 threatened mammals, grassland was the second most important type of habitat after forests, with approximately 18 percent of all threatened species.  Some 8 percent inhabited a shrubland (Hilton-Taylor 2000), and semi-desert and desert provided key habitats for many other mammals. 
 
     Loss of habitat is the primary threat to the species, but other causes include decreasing water tables and desertification, competition for food with livestock, and mining or other activities that completely eliminate habitats.  Hunting and persecution in these open habitats is another threat to grassland and dryland species.  Large mammals of open grasslands and deserts are highly vulnerable to hunting and persecution by nomadic herders who consider them unwelcome competitors for grassland. 
 
     The introduction of exotic plants has destroyed many bird habitats because some species are dependent on a certain type of vegetation for food or cover.  Some plants have been deliberately spread, and others were nursery and garden plants that spread to the wild.  Such introductions have been catastrophic in some areas, when exotic species of grasses and shrubs overtake native vegetation.  The latter type rarely provides habitat or food supply for resident wildlife.  In some cases, birds rely on a very specific type of habitat, such as grassland with scattered shrubs of native species.   Birds and other wildlife with such specialized requirements are highly vulnerable to disappearance due to human-caused changes.
 
     Off-road vehicles driven on fragile desert soils have destroyed habitats for a wide range of species.  They cause instant mortality to tortoises, lizards and other animals, crushing them under their wheels and destroying their underground burrows.  These vehicles kill slow-growing plants that are easily uprooted from the sandy soil.  Dryland plants anchor the soils and provide a lifeline of shelter and food for native wildlife.  Desert soils have thin layers of lichen on the surface that prevents soil particles from being blown away by the wind.  Trampling by livestock and crushing by vehicular traffic destroys this fragile soil cover, promoting erosion and devegetation.  In many parts of the Sahara, the Saudi Arabian Peninsula and portions of American deserts, off-road vehicles have eliminated virtually all vegetation, causing local extinctions of native wildlife.
 
     Building fences for livestock or agriculture has also proved lethal to millions of wild ungulates, preventing their natural migrations and causing mortality when they attempted to leap over them.  In Africa, Australia and North America, millions of animals have crashed into fences, subsequently dying from the collisions, starvation or dehydration as they were prevented from reaching vegetation and water.  Few governments have legislation or sufficient parkland to protect wildlife threatened by the great numbers of livestock now grazing throughout the world.  Grassland that once stretched from horizon to horizon has been converted to pasture and farmland in nearly every region of the world, leaving only bits and pieces of the original ecosystems.  As humans migrate into the last of this wild grassland, they are obliterating native plants and animals.  Should these trends continue, almost no native wildlife will remain outside national parks (Simon 1995).  Much ecological damage is being done to fragile ecosystems that were never ecologically suitable areas for livestock grazing and are unable to recover from overgrazing.


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