Types of environmental degradation

There are many different types of environmental degradation. Some of the main types in Namibia are soil erosion, deforestation, bush encroachment, desertification and salinisation.

Soil erosion

Soil erosion is the gradual wearing away of soil by either physical breakdown or chemical solution which is then transported away by means of water, wind or ice to another location. Soil erosion is the leading cause of damage to our soils, leaving them barren and ultimately less productive.

It can take centuries to create just a few centimeters of soil and only a few moments to destroy the same few centimeters. Today the rate of erosion has been speeded up by human activities. Consequently making soil erosion an ever-increasing problem. Soil erosion results from the ways that people use the land. Practices such as tree felling cause deforestation, and can lead to soil erosion. The removed trees would usually guard the soil from rain and wind as their roots hold the soil in place. Additionally many land owners cut down trees to create space in which to plant crops and raise animals which eventually can lead to soil erosion.

Soil salinisation

This is a type of environmental degradation that is particularly common in naturally dry areas that undergo irrigation and do not allow for any fallow periods for the land to recover. Irrigation schemes are set up to provide a constant flow of water to dry lands so that crops can be grown. However when irrigation systems are badly designed the results can be disastrous. The irrigation causes the water-table level to rise bringing natural salts to the surface. The salts cause problems as they restrict the root activity of the plant and therefore slow down its growth. In areas with high rates of evaporation the salts become even more concentrated.

The final result is that the soils are too salty for plants to be able to grow in them and the degraded land has to be abandoned. Soils which have been affected by salinisation are very difficult and expensive to rehabilitate and often remain unused and abandoned.

Desertification

Desertification occurs when productive lands are turned into non-productive desert as a result of poor land-management. This generally occurs in semi-arid areas such as Namibia.

Deforestation

This is the permanent destruction of indigenous forests and woodlands which results in a loss of natural resources as well as a protective barrier for topsoil.

Bush Encroachment

Bush encroachment happens where woody vegetation gets so thick that it threatens farming lands. Bush encroachment happens because woody vegetation and grasses have different growth rates leading the woody vegetation to take over and dominate a piece of land. Before the introduction of domestic livestock, the balance between grasses and woody vegetation would have been kept in check by fires and game. This would have resulted in an African savannah dominated by grass with only a few scattered trees.

With the introduction of livestock the balance was upset. Most of the game was eliminated and selective grazers were brought in. Fire outbreaks have also been eliminated as far as possible due to human intervention. This means that grasses are heavily eaten but the trees which are usually controlled by fires, continue to grow. The result is a shift in the balance in favor of trees and woody vegetation.

Since the growth of grass is limited the soil is largely left bare making it especially susceptible to soil erosion by wind and water. The deposits of nutrients are therefore increasingly found only under trees and bushes, making it difficult for grasses to grow. Eventually the grasses cease to compete for water and die out. Most of Namibia's best farming lands are bush encroached.