Soil and Change
- 11% of the world’s land is used to produce food.
- 99.7% of food comes from land.
- It takes 500 years for nature to replace one inch of topsoil.
- Agriculture (pesticides and fertilizers) is affecting the soil.
- Corn causes the most erosion (out of potatoes, tomatoes and lettuce) since a lot of pesticides etc. are involved.
- 50% of crop land in Iraq is salinized (highest percentage of salinized irrigated cropland).
- Increased irrigation does not necessarily help soil (manure, crop covering and agroforestry does).
- $400 billion - cost of soil erosion to the world annually. Erosion has claimed 30% of Earths fertile land in 40 years.
- Overgrazing is bad for soil (can’t overuse it).
- Fire returns fertility to the soil.
- Soil doesn’t like too much sun, and it needs water - an even balance is ideal.
- Climatic conditions have effects on soil.
- Soil can absorb and release CO2/methane as well.
- Soil needs to rest - it needs to regenerate (cant used all the time).
- Soil needs vegetation layer which protects it (especially arid soil) and can blow away (exposed to erosion) when the layer is gone.
Explain the causes of soil degradation.
Soil Degradation
The process of soil losing its fertility and nutrients becoming biologically dead (reducing in quality and quality)
Types of Soil Degradation
Wind and water
- Rain or wind blowing away the top soil and causing degradation
- The loss of humus and or plant/ animal life
- The loss of soil structure or change in permeability
- The change in the chemicals composition of soil. This could cause by acidification, chemical pollution or loss of nutrients.
Human Causes of Soil Degradation
Overgrazing
Allowing too much livestock to graze on a piece of land which means all the vegetation is eaten making the ground susceptible to wind and water erosion.
Overcultivation
If you farm land too intensively and don't have fallow (periods of not growing anything) periods then all the nutrients in the soil get used.
Deforestation
Cutting down trees which not only means the land will be receiving less nutrients, but it also means it is more vulnerable to erosion because there is no interception and less stability because the root systems have been removed.
Overpopulation
As the world population continues to grow (now nearly 7 billion) the demand for agricultural products (crops and meat) is increasing causing more land to be deforested, overcultivated and overgrazed.
Fertiliser and Pesticide Use
By using fertilisers and pesticides you can artificially increase yields of crops. However, the process is unnatural and prolonged periods of use can all naturally produced nutrients to be used and local water sources to become polluted reducing the ability of land to cultivate crops and therefore making it vulnerable to chemical degradation as well as wind and water erosion.
HYV and GM Crops
Like with fertilisers and pesticides, it is argued that HYV and GM crops have encouraged overcultivation, diminishing natural nutrients in the soil.
Industrial Pollution
Chemicals, metals and other pollutants leaked from industrial processes can chemical degrade soil making it useless or dangerous for farming. Acid rain caused by pollution can also cause soil degradation.
Unsustainable Water Use (aquifer depletion, unsustainable irrigation)
If aquifers or rivers are used unsustainably then areas can become increasingly arid as water resources are used up. A classic example of unsustainable irrigation happened in the Aral Sea (Irrigation and agriculture).
Toyotarisation
This is basically the increased use of 4x4s to travel across grasslands, deserts, etc. damaging topsoil and increasing wind and water erosion.
Conflict
During times of war biological and chemical weapons can be used which degrade the quality of the soil. During the Vietnam War large quantities of Agent Orange were used to defoliate forests. Much of the land in Vietnam is still degraded because of these 40 years on.
Discuss the environmental and socio-economic consequences of this process, together with management strategies.
Environmental
Desertification
The process of turning fertile land turning into a desert. As the soil becomes more degraded and has less nutrients it cannot support vegetation and effectively turns to desert.
Dust Storms
As soil becomes less stable because of the lack of vegetation it becomes much more vulnerable to wind erosion which can create large scale dust storms. Northern China is suffering from an increased frequency of dust storms as desertification takes place south of the Gobi Desert
Topsoil Erosion
The top layer of the soil often referred to as the humus layers is very nutrient rich. If the nutrients in this layer begin to reduce then it can support less vegetation and this layer become vulnerable to erosion starting a downward decline in the quality of the soil and reducing its ability to regenerate.
Socio-Economic
Reduced Crop Yields
As the soil becomes less fertile the amount of crops that it can support will reduce. The falling crop yields can lead to famine and starvation.
Conflict
With increasing soil degradation and reduction in agricultural output and available agricultural land conflict can arise over diminishing resources.
Famine
If the soil become degraded and cops begin to fail or the yields reduce in quantity then famine can happen. Famine is normally caused by a combination of factors, soil degradation, and drought and possibly a natural disaster or conflict, so if soil degrades it increases the potential of famine.
Increased Use of Chemicals
Fertilizer use may increase to compensate for the lack of natural nutrients. This increased can worsen the problem as overcultivation continues and pollute water courses.
Case Study – Loess Plateau in Alashan, China
- Loess Plateau was the cradle of Chinese civilization (used to be very fertile).
- It is the size of France (the area).
- Land has been arid for nearly 1000 years (land degraded).
- The land was prone to droughts and floods.
- The people became POOR.
- Sedimentation - soil/rock erodes, and transports into the yellow river, going down into the yellow river. This reduced the river quality, and got clogged up.
- We want to involve the local people in the infiltrating the water. They are intervening with the water cycle and the rain.
- They are building terraces to trap the water, stopping the water from going downstream, to further stop the erosion.
- Economic land and ecological land balance is being reformed.
- They reforest on the steep lands (plant trees). This brings diversity and water doesn’t run off. Little terraces around the trees to collect water.
- On the slightly flatter hill land, they use crops and proceed with agriculture.
- Now the huge land is fully forested. The ecosystem is back, fish are back in streams etc.
- The land is actually useful now; it is a good symbol of what we need to do to the land that is fading away by erosion.