Environmental Problems, Their Causes, and Sustainability 1

According to the U.S. Department of Agriculture,since 1985 this program has cut soil losses on croplandin the United States by about two-thirds. And between1982 and 1997, the area of U.S. farmland with thegreatest potential for wind erosion and water erosiondecreased by nearly one-third. If lawmakers continueto support this program, it could eventually cut suchsoil losses as much as 80%.A second provision of the Farm Act authorizes thegovernment to forgive all or part of farmers’ debts tothe Farmers Home Administration if they agree not tofarm highly erodible cropland or wetlands for 50years. The farmers must plant trees or grass on thisland or restore it to wetland.These efforts to slow soil erosion are important.But effective soil conservation is practiced today ononly about half of all U.S. agricultural land and onabout half of the country’s most erodible cropland.Case Study: The Dust Bowl: AnEnvironmental Lesson from NatureIn the 1930s, a large area of cropland in the midwesternUnited States had to be abandoned becauseof severe soil erosion caused by a combination ofpoor cultivation practices and prolonged drought.In the 1930s, Americans learned a harsh environmentallesson when much of the topsoil in several dry andwindy midwestern states was lost through a combinationof poor cultivation practices and prolongeddrought.Before settlers began grazing livestock and plantingcrops there in the 1870s, the deep and tangled rootsystems of native prairie grasses anchored the fertiletopsoil firmly in place. But plowing the prairie tore upthese roots, and the agricultural crops the settlersplanted annually in their place had less extensive rootsystems.After each harvest, the land was plowed and leftbare for several months, exposing it to high winds.Overgrazing by livestock in some areas also destroyedlarge expanses of grass, denuding the ground.The stage was set for severe wind erosion andcrop failures; all that was needed was a long drought.One came between 1926 and 1937 when the annualprecipitation dropped by about almost two-thirds. Inthe 1930s, dust clouds created by hot, dry windstormsblowing across the barren exposed soil darkened thesky at midday in some areas; rabbits and birds chokedto death on the dust.During May 1934, a cloud of topsoil blown off theGreat Plains traveled some 2,400 kilometers (1,500miles) and blanketed most of the eastern UnitedStates with dust. Laundry hung out to dry by womenin Georgia quickly became covered with dust blownin from the Midwest. Journalists gave the worst-hitColoradoNew MexicoMEXICODustBowlKansasOklahomaTexasFigure 14-8 The Dust Bowl of the Great Plains, where a combinationof extreme drought and poor soil conservation practicesled to severe wind erosion of topsoil in the 1930s.part of the Great Plains a new name: the Dust Bowl(Figure 14-8).During the “dirty thirties,” large areas of croplandwere stripped of topsoil and severely eroded. Thistriggered one of the largest internal migrations in U.S.history. Thousands of farm families from Oklahoma,Texas, Kansas, and Colorado abandoned their dustchokedfarms and dead livestock and migrated toCalifornia or to the industrial cities of the Midwest andEast. Most found no jobs because the country was inthe midst of the Great Depression.In May 1934, Hugh Bennett of the U.S. Departmentof Agriculture (USDA) went before a congressionalhearing in Washington to plead for new programsto protect the country’s topsoil. Lawmakerstook action when Great Plains dust began seeping intothe hearing room.In 1935, the United States passed the Soil ErosionAct, which established the Soil Conservation Service(SCS) as part of the USDA. With Bennett as its firsthead, the SCS (now called the Natural ResourcesConservation Service) began promoting sound soilconservation practices, first in the Great Plains statesand later elsewhere. Soil conservation districts wereformed throughout the country, and farmers andranchers were given technical assistance in setting upsoil conservation programs.What Is Desertification, and How SeriousIs It? Decreasing Land ProductivityAbout one-third of the world’s land has lost someof its productivity from a combination of droughtand human activities that reduce or degradetopsoil.In desertification, the productive potential of arid orsemiarid land falls by 10% or more because of a combinationof natural climate change that causes prolongeddrought and human activities that reduce or degradehttp://biology.brookscole.com/miller14281