B5.2 Threats to Soil
Soils worldwide contain 1550 billion tonnes of organic carbon (to be compared with an atmospheric carbon pool of 760 billion tonnes and 560 billion tonnes of carbon in living organisms and plants).
Source: European Commission 2007
Contamination
The contamination of soil is when a material of some sort is introduced to the soil, resulting in a negative affect. Common soil contaminants include hydrocarbons (usually oil) and heavy metals.
Contaminants may enter the soil through deposition in rain, a deliberate application (such as fertilizer or flytipping waste) or though an accidental occurrence (spillage).
Compaction
Soil particles contain air between them. When soil is compacted, the air gaps are eliminated, which affects the ability of the soil to retain water. The reduction of air within the soil also affects the living organisms within it.
Water Erosion
The main problem associated with soil erosion is that the soil may be washed away. This may be washed into water courses causing pollution. It may also mean that the beneficial topsoil (containing the organic matter) is washed away, leaving soil of a poor condition that requires extensive soil conditioning to restore any function. Without the organic matter the soil will not be able to effectively bind chemicals or retain water.
Wind Erosion
Wind erosion reduces soil quality and production using a mechanism different from that of water erosion. Water erosion removes the soil en masse, while wind erosion takes the finer/lighter particles from the surface, leaving the larger (generally inert) particles behind. As a result, wind erosion removes topsoil and reduces the soil clay and silt content and the organic matter. Wind erosion also has an impact on crop productivity. It sandblasts emerging crops, reshapes the land surface, thereby making it difficult to traverse with wide agricultural implements, buries or undermines infrastructure such as fences and roads, and buries adjacent land with sand drift. This results in limiting the drifted land’s production in the short term. Off-site impacts include reduces visibility, causes unwanted dust deposits and raises airborne particulate levels, which can have adverse health effects.
Climate Change
The processes that occur in soil are affected by temperature, rainfall and the atmospheric content of carbon dioxide. Soil is therefore affected by the change in global temperature and weather.
Man-made Development
As we expand our cities, towns and villages, we are covering the soil with materials such as tarmac and concrete. This creates an impermeable layer on top of the soil. The soil can no longer absorb water, be used for crop production or support plant life and its associated biodiversity.