As depicted in John Steinbeck’s famous Dust Bowl–era novel The Grapes of Wrath, it brings great suffering to afflicted communities, often forcing them to abandon their farms. Today land degradation is no longer a local or even a regional issue— it is rapidly assuming the stature of a global crisis by virtue of its sheer scale. Soil degradation is not a sexy topic, yet it has been a silent force in dragging down crop yield improvement in recent de cades and is a cryptic contributor to low grain stocks, rising food prices, hunger, and global insecurity. In the 1980s and 1990s it was an issue of notable concern to many governments but, although the agencies and scientists who watch such things have continued to issue warnings, in recent times the world at large has tended to treat land degradation as a low priority.
In Asia, Africa, and South America, soil losses due to erosion average 30 to 40 tonnes per year for every hectare (13–18 U.S. tons/acre)— which is thirty to forty times greater than the rate at which soil naturally forms. On slopes and in severely degraded rangelands, the losses can be as high as 100 tonnes (110 U.S. tons) of soil per year. On Gondwana continents— India, Australia, Africa, and South America— soil formation rates are close to zero, so any loss amounts to mining the resource. To the question “Why should I care?” the simple answer is that degraded land produces less food and so contributes to rising prices as well as to conflict and refugee crises, thus affecting everyone. It also damages the environmental systems that support us by providing clean water, absorbing carbon dioxide, supplying timber, and supporting wildlife and wilderness.
A full generation has passed since the last major on- the- ground check was run on the health of the world’s farming and grazing lands, and its data are now long out of date, showing how an issue once high among international concerns has slipped into obscurity. At that time, the Global Assessment of Human- Induced Soil Degradation (GLASOD) study found that about 15 percent of the world’s total stock of land was degraded. The most severely affected regions were, in order: Eu rope (25 percent of land affected), Asia (18 percent), and Africa (16 percent). The main causes were loss of soil by wind or water, loss of fertility, physical problems, salinization, and industrial pollution.
More recently, the FAO has conducted a worldwide survey using satellite images— a completely different technique from that used by GLASOD— which mea sure “greenness” or the extent of vegetation cover to assess how much the land is capable of producing. This revealed that the degraded area had increased alarmingly during the period 1980–2003, by the end of which it accounted for almost a quarter of the world’s land surface. “Land degradation is cumulative— this is the global issue. The 1991 GLASOD assessment indicated that 15 per cent of the land surface was degraded; the present assessment identifies 24 per cent as degrading but the areas hardly overlap, which means that new areas are being affected. Some areas of historical land degradation have been so severely affected that they are now stable— at stubbornly low levels of productivity,” the researchers commented.
“Almost one fifth of degrading land is cropland— more than 20 per cent of all cultivated areas; 23 per cent is broadleaved forest, 19 percent needle- leaved forests, 20–25 per cent rangeland,” they added. The study also noted, on the more hopeful side, that 16 percent of land was displaying improved productivity, and that this was mainly in cropping areas— encouraging evidence that land degradation can be arrested and even reversed with the right sorts of farming practices.7 As seen from space by satellite, the most severely affected areas are • Africa south of the equator (13 percent of the world’s degrading area), • Indochina, Myanmar, Malaysia, and Indonesia (6 percent), • South China (5 percent), • North and Central Australia and parts of the Great Dividing Range (5 percent), • the South American Pampas (3.5 percent), and • high- latitude forests in North America and Siberia.
Changing Perspectives and Climate Urgencies
