Environmental Problems, Their Causes, and Sustainability 1

capita meat production more than doubled. It is likelyto more than double again by 2050 as affluence rises inmiddle-income developing countries and people beginconsuming more meat.Some analysts expect most future increases inmeat production to come from densely populated feedlots,where animals are fattened for slaughter by feedingon grain grown on cropland or meal producedfrom fish. Feedlots account for about 43% of theworld’s beef production, half of pork production, andalmost three-fourths of poultry production.In the United States, most production of cattle,pigs, and poultry is concentrated in increasingly large,factory-like production facilities in only a few areas.As many as 100,000 cattle may be confined to a singlefeedlot complex and 10,000 hogs may be crowded almostshoulder to shoulder in a giant barn.This industrialized approach increases meat productivity.But it has a number of harmful environmentaleffects. Animal wastes from such facilities are typicallystored in enormous open lagoons, which can rupture orleak and contaminate groundwater and nearby streamsand rivers. In 1999, for example, torrential rains fromHurricane Floyd caused a number of hog and poultrywaste lagoons in southeastern North Carolina to over-flow and spill their wastes into local rivers. Living neara feedlot or animal waste lagoon is also a nasal assault.Expanding feedlot production of meat will increasepressure on the world’s grain supply becausefeedlot livestock consume grain produced on croplandinstead of feeding on natural grasses. It will also increasepressure on the world’s fish supply becauseabout one-third of the world’s fish catch is used to feedlivestock. Livestock production also has an enormousenvironmental impact (Connections, below).What Are the Effects of Overgrazing?Eroding Soil and Fewer LivestockOvergrazing can lead to soil erosion and limitlivestock production.Overgrazing occurs when too many animals grazetoo long and exceed the carrying capacity of a grasslandarea. It lowers the net primary productivity ofgrassland vegetation, reduces grass cover, and whencombined with prolonged drought can cause desertification.It also exposes the soil to erosion by water andwind (Figure 14-20, left) and compacts the soil (whichdiminishes its capacity to hold water). Overgrazingalso enhances invasion of exposed land by woodySome Environmental Consequences of Meat ProductionThe meat-baseddiet of affluentpeople in developedand developingcountries has aCONNECTIONSnumber of harmfulenvironmental effects. More thanhalf of the world’s cropland (19% inthe United States) is used to producelivestock feed grain (mostly fieldcorn, sorghum, and soybeans). Livestockand fish raised for food alsoconsume about 37% of the world’sgrain production and 70% of grainproduction in the United States.Meat production uses more thanhalf the water withdrawn from theworld’s rivers and aquifers eachyear. Most of this water is used toirrigate crops fed to livestock and towash away animal wastes.According to Canadian scientistVaclav Smil, producing one calorieof energy in the flesh of a cow, pig,or chicken requires 11–15 calories offeed. The energy needed to producea single hamburger is enough todrive a small car about 32 kilometers(20 miles).About 14% of U.S. topsoil loss isdirectly associated with livestockgrazing. Cattle belch out about 16%of the methane (a greenhouse gasabout 25 times more potent thancarbon dioxide) released into theatmosphere. Also, some of the nitrogenin commercial inorganic fertilizerused to grow livestock feed isconverted to nitrous oxide, a greenhousegas released from the soil intothe atmosphere.Livestock in the United Statesproduce about 20 times more waste(manure) than is produced by thecountry’s human population. A singlecow produces as much waste as16 humans. Only about half of thisnutrient-rich livestock waste is recycledinto the soil. Manure washingoff the land or leaking from lagoonsused to store animal wastes can killfish by depleting dissolved oxygen.Chickens, pigs, and cows useabout 70% of the antibiotics consumedin the United States. Accordingto the World Health Organizationand the FAO, widespread useof antibiotics in the livestock industryis increasing the development ofmicrobes that are genetically resistantto widely used antibiotics. Thismakes it harder to fight infectiousdiseases in both humans and livestockanimals. In 2004, McDonaldsbegan requiring its chicken suppliersto stop giving their birds antibioticsto promote growth.Producing meat can also endangerwildlife species. According to a2002 report by the National PublicLands Grazing Campaign, livestockgrazing in the United Stateshas contributed to population declinesof almost a fourth of thecountry’s threatened and endangeredspecies.Critical ThinkingAre you willing to eat less meat ornot eat any meat? Explain.http://biology.brookscole.com/miller14295