Strait, G. Carroll, The World and I
Developing and implementing sustainable agriculture methods for the world's huge degrading dryland regions are major tasks for the twenty- first century.
The face of desertification is bleak, barren, hopeless, and ancient. Humans have been destroying dryland ecosystems for thousands of years up to this very day. As with our remote ancestors, so, too, with us, their living descendants. We have often bungled the task of living sustainably in dryland areas, whether through herding animals or raising crops.
Put simply, millions of people are harvesting food from lands where water is scarce and productivity is declining. If enough water is available from rainfall or irrigation, they plant crops. If such water is not available, they herd animals. Additionally, if the drylands have woody plants, these are often harvested as fuel for cooking fires. To make the range safe for herding animals, they kill predators and harvest the wild grazers as a source of meat and diverse supplies. From an ecosystem-level viewpoint, people displace the wild herds of dryland grazing animals with domesticated cattle, sheep, and goats and place themselves at the top of the food chain, replacing the natural predators they have eliminated.
Through history, human land-use practices have been instrumental in converting large dryland regions to deserts. Perhaps the most striking example is that northern parts of what is today the Sahara Desert were once major grain-growing areas for the Roman Empire. When the region became too degraded, the Romans shifted to grazing animals on it, finally abandoning the land when it could no longer support herds.
Whether it appears on the steppes of Central Asia, in Africa's Sahel, or in the western United States, desertification is a serious threat to the livelihood of people who depend on the land. In countries where range-fed livestock and dryland crops provide a significant portion of food supply or exports, desertification is a threat not only to individuals and families but to the country. Desertification is a creeping global disaster. Yet it remains difficult to understand because it is so diffuse, nonspecific, and insidiously incremental. Furthermore, determining which changes are natural and which are human caused is difficult because little is kown about the long-term natural dynamics of arid lands.
The processes of desertification now afflict more than one-third of the planet's land surface as a biospheric disease whose overarching symptoms are loss of soil fertility and biodiversity. In desertification, natural processes that have built up soil fertility through thousands or tens of thousands of years are subverted. Fertile soils, with their richly diverse composition and pore structure, are reduced from complex, fertile, and tough to simple, infertile, and defenseless against the eroding forces of wind and water. Once-healthy flora and fauna die and are replaced by barrenness or, in some cases, a weed species.
Around the world, the story is similar. In regions where land productivity is visibly declining or already below any value for food production, some elders remember or have heard stories about when the grass was tall and plentiful. Often, within memory, wild game abounded. A recent article in the New York Times describes the plight of farmers on the eastern edge of the Qinghai-Tibet Plateau, where legend has it that grasses once reached as high as a horse's belly. A local farmwife is quoted as saying that "the pasture here used to be so green and rich, but now the grass is disappearing and the sand is coming." In New Mexico, some dryland areas that were covered with knee-high grass 100 years ago today are unable to support even minimal numbers of grazing livestock.
Limits and causes
In the global community, concerns about desertification reached an important threshold at the UN Conference on Environment and Development in Rio de Janeiro in 1992, when the Convention to Combat Desertification was formulated. …