10.4. THE IMPORTANCE OF SOIL

Terrestrial ecosystems depend on soil. Without soil, there would be no agriculture, for instance. The proper use of soil and conservation measures are necessary to protect it from degradation. The destruction or degradation of soil creates a serious loss because recovery is a very slow process.

	• The loss of vegetation especially trees and shrubs, leaves the soil unprotected against erosion and reduces the soil's ability to retain water.
	• Sediments are washed away by the rain.

Soil degradation has three main causes:

• Pollution. When toxic substances (Hg, Pb, etc.) are accumulated in the topsoil, they are absorbed by plants, making them unsafe for food.
• Soil compaction. It is the loss of porosity. Rock particles get closer together, reducing the water and air content. Agricultural vehicles and deforestation lead to soil compaction.
• Salinization. Whether due to natural causes or improper irrigation, the consequence is a buildup of mineral salts in the topsoil.

Desertification consists of a complete loss of soil, generally produced by erosion. It can be caused by natural factors (extreme weather events) or human activities (e.g. deforestation).