Like soil degradation, this is a global epidemic but one that is subtle, slow- burning, deadly— and of which nobody knows the true extent. Salinity can be either natural or manmade and affects about a tenth of the Earth’s land surface. Naturally salty areas don’t produce much food, but in the dry farming regions of the world, human- caused salinity— resulting mainly from removal of deep- rooted trees and poor design of drainage or irrigation— is spreading like a lethal crystalline shroud, taking much good land out of production. According to Michael Stocking, an expert in land degradation and sustainable land management, the 1990 GLASOD study put the area affected by salt at 4 percent of the world’s total land area, and 7 percent in Asia. The problem has undeniably become far worse since then, taking much valuable land out of food production, but no one really knows how much worse. Soil salinity may seem a lesser factor among the drivers of global food insecurity, but one of the hardest- hit regions is the Indus valley, breadbasket to both Pakistan and India, where it has been estimated that Pakistan alone sustains salt damage to around 40,000 hectares (about 100,000 acres) of irrigation land a year.11 Salinity is thus a potent ingredient in the cauldron of tensions over food, land, and water between these two nuclear powers.
Acidic soil is another time bomb. Each time a crop is harvested or a pasture grazed it removes certain elements, with the result that the soil turns gradually more acidic until it eventually reaches a point where food crops will not grow. This pro cess is hastened by the use of fertilizers, by legume rotations, by other human activities, and by acid rain. In intensive and prosperous farming systems surface soil acidity can be countered by applying lime or gypsum, but in countries where farmers cannot afford to do this— or where lime is not readily available— it becomes ever more difficult to sustain yields, even when growing acid- tolerant crops. The area of the world’s acid- affected farm soil is estimated to be around two million square kilometers (three- quarters of a million square miles). One of the worst manifestations of soil acidity occurs when tropical rainforests are felled, leaving soil so acid that few plants or trees can grow; after a brief year or two of farming, the area is colonized by short- lived grasses of little nutritive value and becomes what has been dubbed “the green desert.” Not only is this happening throughout Asia, where tropical forests have been cleared on a massive scale, but it could also potentially affect large expanses of Latin America and Africa if savannah and jungles were to be further cleared for farming. Acidity is thus one of the main environmental obstacles to unbridled expansion of agriculture in the great tropical river basins.
The arsenic epidemic in Bangladesh, West Bengal, and other Indian states, China, Chile, Cambodia, Laos, Burma, Pakistan, Nepal, Vietnam, Taiwan, Iran, Argentina, Finland, and the United States poisons around one hundred million people every day through toxic food and drinking water.13 This epidemic is due to the extraction of groundwater causing the sediments to dry and release soluble forms of arsenic; these then dissolve into the groundwater when the wet season recharges it. The toxic water is then used for house hold purposes and irrigating food crops. Industrial contamination of soil is a growing problem worldwide— and an emerging human health issue; some scientists link the rising global epidemic of cancers and degenerative diseases to the toxic cocktail of pollutants encountered in the home and in the air, water, soil, and food of city dwellers. This consists of heavy metals in the waste streams of mineral pro cessing and factories, spills and leaks of fuel and industrial chemicals, timber treatments, the overuse of agricultural pesticides and fertilizers, poor disposal of sewage, and industrial fallout from the air. Because cities, which produce most of these contaminants, are usually built in river valleys they have a tendency to pollute the best food-growing soil, either directly or through the movement of the toxic contaminants in groundwater and air. For example, in recent de cades it has been recognized that ozone emitted by industry in large cities damages crops growing downwind, shutting down the plants’ ability to turn sunlight into food energy. This can reduce yields by 10 percent or more.
Degradation and Desertification
