Endangered Species Handbook

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Grasslands, Shrublands, Deserts

Drylands of the World: NORTH AMERICA: Page 5

     Even the bits and pieces of grassland that these birds and other grassland wildlife occupy are swept by pesticides, herbicides and other chemicals used by modern farmers.  Crops planted in huge monocultures of one type only, such as corn, create an ecosystem lacking diversity.  The introduction in the 1940s of chemical pesticides, fungicides and other chemicals for widespread use was heralded by chemical companies as the ultimate answer to insect and weed pests and a boon to mankind.  Farmers wage constant battles on insects, but each year, more species of insects become immune to certain pesticides, and some insects have become immune to all known pesticides.  Pesticides kill beneficial as well as pest insects, upsetting ecological balances.  Many of the long-lived pesticides of the chlorinated hydrocarbon family, including DDT and dieldrin, enter water tables, persisting in the bodies of animals throughout the food chain.  Annual pesticide application in the United States is estimated at 750 million pounds, while the percentage of crops lost to pests has increased from 7 percent in the 1940s to an estimated 37 percent today. 
 
     Bird kills began to be documented from DDT use in the late 1940s, and water birds suffered mortality and reproductive failure.  DDT and its toxic relatives concentrate in aquatic plants, which are then consumed by small fish, and carnivorous fish accumulated extremely high doses.  Birds of prey at the top of their food chains who fed on these fish or waterfowl suffered complete reproductive failure, and several species, such as the Peregrine Falcon (Falco peregrinus) and the Bald Eagle (Haliaeetus leucocephalus), suffered population collapses in areas of high pesticide use. 
 
     Seventy percent of the United States grain production is fed to livestock; 45.5 million cattle are grazed in the Great Plains (Manning 1995).  Many of them graze in the 19 grasslands of the National Grasslands system administered by the Forest Service, which encompass 1,600,000 hectares (3,953,600 acres); 17 are located on the Great Plains, and two are in the Far West (Knopf 1988).  They are used primarily as grazing land for livestock, but native wildlife, including endangered species, persists there.  The Bureau of Land Management (BLM) and the U.S. Forest Service's National Grasslands are the major landowners in these areas, and both operate under legislation which mandates multiple use or, according the needs of wildlife and conservation, an equal consideration with those of humans.  The National Wildlife Refuge System also controls millions of acres of grasslands and drylands harboring endangered species.  Livestock grazing and exploitation for oil and minerals takes place on these refuges and, in many cases, they have not been managed in such a way as to preserve natural habitats and threatened species.


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