KAWA MULTIMEDIA PUBLICATIONS
Effects of desertification
1. Food shortages.
2. Reduction of livestock.
3. Loss of agricultural potential land.
4. Stagnation of development particularly in agriculturally oriented economies.
In most cases of desertification, there is a reduction in total species richness, an increase in the proportion of exotic (nonnative) plants, and a decline in overall biodiversity—the variety of life forms and the ecological roles they fill.
Once desertification starts, it often causes changes that accelerate the process. For example, desertification often results in a decrease in the amount of vegetation covering the land. With less vegetation providing shade, soil temperatures rise, accelerating the breakdown of organic matter in the soil and the evaporation of water.
Some soils may become compacted or crusted, reducing their ability to absorb the limited rainfall that occurs, which further reduces the amount of water available for plants.
The absence of vegetation also enhances runoff and erosion by water and wind. Erosion may form deep gullies, lowering the local water table (level of water within the ground) and making less water available for plants. Wind erosion blows away nutrients in the soil and may physically damage plants. Each of these effects makes plant growth more difficult and may further reduce the amount of vegetation covering the land, which in turn leads to more degradation.
For land managers, desertification is a downward spiral. As it proceeds, the impact of any downturn, such as a drought, may become catastrophic and result in loss of human lives due to lack of necessary resources, such as water. With diminishing productivity and profitability comes increased pressure to compensate for declines. Livestock grazers increase herd sizes, and farmers plant all available plots of land and continue to irrigate even though yields shrink. In the poorest regions where no other employment is available, rural populations turn to woodcutting and charcoal production, which lead to deforestation. This deforestation forces families to spend more time seeking firewood for domestic use, leaving less time for tending fields or animals.
Desertification has become a large-scale problem. Arid and semiarid regions, known as drylands, account for one-third of the world’s land area and support a combined population of about 900 million people. Soil degradation reduces crop output and is a major concern economically. About 70 percent of drylands are susceptible to degradation, 50 percent have been degraded to some degree, and 15 percent show extreme degradation where agricultural yields are less than half of their former level. Almost all the areas of extreme degradation are in the African Sahel from Senegal to Sudan, along the Mediterranean from Tunisia to Egypt, and in central and southwestern Asia from China to Syria.
Desertification can also have impacts that extend beyond the immediate degraded area. Wind-borne dust from the Sahel creates havoc with air traffic across western Africa, and sediment eroded from central China damages water control systems far downstream. Many regions are affected indirectly by desertification as they absorb waves of people uprooted by their inability to grow enough food or raise enough livestock. Such people, called environmental refugees, swelled the urban areas of the Sahel during the 1970s and 1980s. Moreover, migrations of environmental refugees may cross national boundaries and contribute to political friction within and between countries. This migration problem has occurred at various times, such as during the drought years from 1968 to 1973 when Mauritanian nomads fled into Senegal.
2. Reduction of livestock.
3. Loss of agricultural potential land.
4. Stagnation of development particularly in agriculturally oriented economies.
In most cases of desertification, there is a reduction in total species richness, an increase in the proportion of exotic (nonnative) plants, and a decline in overall biodiversity—the variety of life forms and the ecological roles they fill.
Once desertification starts, it often causes changes that accelerate the process. For example, desertification often results in a decrease in the amount of vegetation covering the land. With less vegetation providing shade, soil temperatures rise, accelerating the breakdown of organic matter in the soil and the evaporation of water.
Some soils may become compacted or crusted, reducing their ability to absorb the limited rainfall that occurs, which further reduces the amount of water available for plants.
The absence of vegetation also enhances runoff and erosion by water and wind. Erosion may form deep gullies, lowering the local water table (level of water within the ground) and making less water available for plants. Wind erosion blows away nutrients in the soil and may physically damage plants. Each of these effects makes plant growth more difficult and may further reduce the amount of vegetation covering the land, which in turn leads to more degradation.
For land managers, desertification is a downward spiral. As it proceeds, the impact of any downturn, such as a drought, may become catastrophic and result in loss of human lives due to lack of necessary resources, such as water. With diminishing productivity and profitability comes increased pressure to compensate for declines. Livestock grazers increase herd sizes, and farmers plant all available plots of land and continue to irrigate even though yields shrink. In the poorest regions where no other employment is available, rural populations turn to woodcutting and charcoal production, which lead to deforestation. This deforestation forces families to spend more time seeking firewood for domestic use, leaving less time for tending fields or animals.
Desertification has become a large-scale problem. Arid and semiarid regions, known as drylands, account for one-third of the world’s land area and support a combined population of about 900 million people. Soil degradation reduces crop output and is a major concern economically. About 70 percent of drylands are susceptible to degradation, 50 percent have been degraded to some degree, and 15 percent show extreme degradation where agricultural yields are less than half of their former level. Almost all the areas of extreme degradation are in the African Sahel from Senegal to Sudan, along the Mediterranean from Tunisia to Egypt, and in central and southwestern Asia from China to Syria.
Desertification can also have impacts that extend beyond the immediate degraded area. Wind-borne dust from the Sahel creates havoc with air traffic across western Africa, and sediment eroded from central China damages water control systems far downstream. Many regions are affected indirectly by desertification as they absorb waves of people uprooted by their inability to grow enough food or raise enough livestock. Such people, called environmental refugees, swelled the urban areas of the Sahel during the 1970s and 1980s. Moreover, migrations of environmental refugees may cross national boundaries and contribute to political friction within and between countries. This migration problem has occurred at various times, such as during the drought years from 1968 to 1973 when Mauritanian nomads fled into Senegal.