The Sahel stretches across Africa, about 15 degrees north of the equator. Satellite measurements of vegetation reveal it as a transition zone between the sands of the Sahara and the jungles of the Congo. This map shows vegetation in the final two weeks of June 2005, near the end of the dry season in the Sahel. Dark green indicates dense vegetation, while light green and beige indicate sparse vegetation and barren land.
When we think of desertification, we first think about prolonged drought conditions. Desertification can also be the result of degradation of the soil in an area as the most recent definition includes the permanent loss of fertility in an area. All of the choices below result in soil degradation leading to desertification EXCEPT
A) The buildup of salts in irrigated soils due to evaporation.
B) The presence of rocky fields that have been tilled but not planted.
C) Overfarming or drought can change the soil so that rain no longer penetrates.
D) Deforestation results in erosion: nutrient-rich top soil blows or washes away.