Environmental Problems, Their Causes, and Sustainability 1

Areas of serious concernAreas of some concernStable or nonvegetative areasFigure 14-7 Natural capital degradation: global soil erosion. (Data from UN Environment Programme and theWorld Resources Institute)Soil expert David Pimentel estimates that worldwidesoil erosion causes damages of at least $375 billion peryear (an average of $42 million per hour), including directdamage to agricultural lands and indirect damageto waterways, infrastructure, and human health. Seehis Guest Essay on this subject on the website for thischapter.Some analysts contend that erosion estimates areoverstated because they underestimate the abilities ofsome local farmers to restore degraded land. The UNFood and Agriculture Organization (FAO) also pointsout that much of the eroded topsoil does not go far andis deposited further down a slope, valley, or plain. Insome places, the loss in crop yields in one area couldbe offset by increased yields elsewhere.Case Study: Soil Erosion in the United StatesToday; Some Hopeful NewsSoil in the United States erodes faster than it formson most cropland, but since 1987 erosion has beencut by about two-thirds.In the 1930s, several midwestern states lost largeamounts of topsoil as a result of poor cultivation practicesand prolonged drought (Case Study, next page).This taught the country some important lessons aboutthe need for soil conservation.The situation has improved dramatically sincethen. But according to the Natural Resources ConservationService, soil on cultivated land in the UnitedStates is still eroding about 16 times faster than it canform. Erosion rates are even higher in heavily farmedregions. An example is the Great Plains, which has lostone-third or more of its topsoil in the 150 years since itwas first plowed.Good news. Of the world’s major food-producingnations, only the United States is sharply reducingsome of its soil losses through a combination of plantingcrops without disturbing the soil and governmentsponsoredsoil conservation programs.The 1985 Food Security Act (Farm Act) establisheda strategy for reducing soil erosion in the UnitedStates. In the first phase of this program, farmers receivea subsidy for taking highly erodible land out ofproduction and replanting it with soil-saving grass ortrees for 10–15 years. In 2003, roughly one-tenth of U.S.cropland was in this Conservation Reserve Program(CRP).280 CHAPTER 14 Food and Soil Resources