a) Why is the term “desertification” so hard to define? (10)
Desertification is so hard to define because nobody is actually that clear about what it really is. The word was coined by a Frenchman, Aubrville, in 1949 as he attempted to describe the change to more desert-like conditions in humid areas adjacent to the Sahara. However this definition has since been outdated and at the last survey now over one hundred different ones exist. The one which is currently accepted by most is according to the UN “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variations and human activities.” However even though this definition is broad enough to satisfy most other questions are still raised about it. For instance, can desertification occur in a non-dryland area? It might be argued that in parts of south east England there is the potential threat of desertification yet the climate is by no means dry sub-humid.
b) What are i) the prime causes of and ii) the most effective remedies for dryland degradation? (35)
i) One of the largest causes of desertification due to the knock on effects it has as much as its own actions, is the overgrazing of land. This has come about for several reasons. First both human and animal populations have increased with time which has put greater pressure on the land there is. This is due to increasing birth rates but also an advancement in medicine allowing a higher rate of survival for all species. This increase in population has lead to people being forced to lands they would not have originally chosen to graze on but have to due to the competition for space. The increase in people has also required an increase in livestock as many people in arid regions, for example the Sahel, are subsistence farmers and need to support themselves and families.
Whereas the herdsmen of old were also nomadic hence allowing the land to recover once they had moved on, there is now a certain amount of permanency to some grazing sites due to the sinking of wells which are intended for year round us meaning the crops can’t recover. This lack of vegetation means that the soil is not bound as well as it was resulting in increased wind and water erosion. The constant pounding of the herds’ hooves on the ground also has the same effect by compressing the substrate, increasing the amount of fine material and decreasing the amount of percolation again resulting in higher levels of erosion. The lack of vegetation also means that there is more evaporation due to reduced shade which draws the minerals and salts to the surface, increasing salinity and hence making it harder for plants to recover and grow there unless they are adapted to handle high levels of salt.
Overcultivation is another prime cause of desertification. There are several facets of overcultivation that can cause desertification. One stems from the intensification of farming which can result in shorter fallow periods, leading to nutrient depletion and eventually reduce crop yields. Another way is again through wind and water erosion. This is what caused the great “Dust Bowl” in 1930’s America. There was in the areas concerned an extensive amount of farming without crop rotation. This was fine until a drought arrived, turning the soil to dust and blowing it away. There would have been no problem if it had been left alone but the ploughing of the virgin topsoil killed all the natural grasses meaning that when drought did hit this was an entirely man made disaster. The dust blown away affected over 400,000km leaving up to 500,000 people homeless.
Deforestation is also another main cause. The removal of trees for grazing, cultivation or fuel, reduces the protection offered to the soil by tree cover. This will result in accelerated erosion and the breakdown of soil. The main reason for the increase in deforestation is the growth of population. Wood has many different uses for people, namely as a fuel, but it also has a valuable role in construction and as the population grows and due to the urbanisation / rural urban migration of many areas this is going to be an ever increasing factor, for example, it is very rare to find a tree within 90km of the Sudanese capital Khartoum. The World Bank has estimated that sustainably harvested fuelwood in arid areas can support just two thirds of the population.
Salinisation is another prime cause. Problems are caused by the wasteful use of water: by applying more than can be taken up by plants, through leakage from improperly lined drain canals, and as a consequence of inadequate drainage. The salt tolerance of most cultivated plants is relatively low meaning that salinisation results in a slump in productivity economically but also a lack of vegetation. Most irrigated land suffers from a degree of salinisation but poor techniques in LEDC’s such as Pakistan have cost it greatly. 80% of Pakistan’s cropland is irrigated and 35% of it suffers from salinity resulting in it losing 40,000ha of irrigated land per anum.
There is one other real cause of desertification and that comes under the category of climate change and variation. Within this I would class things such as drought, which on an isolated scale may not necessarily have a great effect but when working in synergy with the other factors can accelerate and indeed make far worse the process of desertification.
ii) The best two ways of countering desertification are through the provision of water and fixating and enriching the soil. Fixating the soil can be achieved through processes such as shelter belts, wood lots and windbreaks. Windbreaks are often trees and therefore increase the soil stability but also reduce the rates of evaporation, hence decreasing salinity. Enriching the soil can be achieved through planting Leguminous plants. Leguminous plants extract Nitrogen form the air and put it into the soil, making it more fertile. There are also some very high tech ways of countering desertification although these are mainly restricted to the mineral rich Arab nations as they can be hugely expensive. The first method is to spray petrol or nano clay onto crops as this stops them from losing water but also means that they don’t get blown away. Another method used which is again very expensive is to bulldoze dunes and spray them with hydrocarbons which prevents them from moving.
However, not all countries will have the technology or even be able to afford the methods suggested above. There are other basic ways however, one of which is to stack stones around a tree in a ring. This, in theory means that the morning dew will collect on the stones, watering the plant and keeping the area around it cool and fertile. Another method is to dig artificial grooves in the ground which will trap any rainfall but also loose seeds being blown around allowing them to germinate.
In parts of Africa the governments have also been advocating and providing solar ovens and basic wood burning cook stoves in order to reduce the amount of deforestation that is occurring. Several countries around the Sahel region have also set up programs showing people how to cope with advancing dunes by building sand fences (a technology used in the Middle East and North America also which work in a very similar way to snow fences) and how placing straw grids reduces wind velocity, therefore the rates of saltation and suspension. They also recommend planting trees on the windward sides of dunes as this restricts their movement.
In China there has been over the past few years a large movement for countering desertification as there is a fear that the dunes could potentially reach Beijing in the future. There has been a mass scheme launched for the planting of trees on act as windbreaks, stabilising and enriching the soil. It has become known as the “Green Wall of China” and already over 30 billion trees have been planted. By the time it is finished it will stretch over 5,700km. However the government is taking hugely draconian measures in this instance, drafting people in to come and plant trees rather than relying on volunteers. They have also taken it to extreme measures in other areas. For example in Langtougou, all people have now been banned from farming and retaining livestock. They are also banned from burning firewood, having to use compost, manure and waste instead as fuel. A similar approach has been adopted in parts of Africa with a green wall built from Senegal to Djibouti.
In 1995, a Frenchman called Jean Meunier created something which is known as BOFIX. There is a simple principle behind this which when used effectively can have the power to manipulate any dune no matter what the size. His idea was to creating localised eddying winds by planting semi-permeable fences, therefore disrupting the wind pattern and dismantling the dune. The second part of his plan was to plant trees on the areas where the dunes had collapsed to stabilise and enrich the soil there meaning the dunes were unlikely to occur there again. He conducted his original tests in Mauritania, where the capital city Nouakchott is in danger of being swallowed by dunes. Using the aforementioned ideas he has successfully been able to protect houses and roads by harnessing the incredible power of the wind.
In 2007, the UNCCD adopted a ’10 year plan’ to counter desertification which has become known as ‘the Strategy.’ They have four aims in this which are to:
i. Generate global benefits
ii. Improve livelihood of affected populations
iii. Enhance productivity of affected ecosystems
iv. Mobilize resources
As this only came into play so recently it is hard to see the effects it has had but hopefully in the future we will be witness to the good it is doing.