WHAT IS DESERTIFICATION
‘’There have always been tensions and conflicts between agricultural and pastoral practices but desertification has accentuated them.’’
Desertification is a form of degradation that occurs on dry lands, which results in the loss of biological productivity. Desertification causes another type of biome to turn into a desert biome because of changes of all sorts. The word ‘desert’ itself is derived from the Latin word ‘desertus’, which has the meaning, ‘to desert,’ ‘to abandon.’ The clear implication is that a desert is an area too barren and desolate to support human life. The term ‘desertification’ was almost abandoned and was supposed to be replaced by the term, ‘land degradation’, because it gave only a vague idea about the issue. But since the term already got out there and was already a commonly used term, it was kept. The term ‘land degradation’ itself is considered as a vague term because, a land can be degraded so that it’s function is changed.
According to the United Nations Environmental Program, all areas of land in which the ratio of total annual precipitation to potential evapotranspiration ranges from 0.05 to 0.65 should be considered vulnerable to desertification. Such regions constitute some 40% of the global terrestrial area.
A huge issue that many countries have is the fact that there are large pockets of land that are going through the process of desertification. Desertification changes the land’s vegetation and it makes it unable to support life and the area becomes like a desert. An area becomes desertified due to climatic variations and human interference. About half of the Earth’s ice-free land surface is drylands, and these drylands cover some of the world’s poorest countries. Desertification is a major international concern. It has affected 36 million square kilometre of land.
According to the United Nations Convention to Combat Desertification, the lives of 250 million people are affected by desertification, and as many as 135 million people may be displaced by desertification by 2045, making it one of the most severe environmental challenges facing humanity. The UNEP sponsored projects in the early 1980s to plant trees along the edge of the Sahara, with the aim of warding off the invading sands. While there are places where the edge of the desert can be seen encroaching on fertile land, the more pressing problem is the deterioration of the land due to human abuse in regions well outside the desert.
An area’s resemblance to a desert does not make it a permanent desert if it can recover from its damaged state, and, in any case, the modes of human subsistence and levels of consumption differ greatly from place to place.
EFFECTS OF DESERTIFICATION
Desertification, in short, is when land that was of another type of biome turns into a desert biome because of changes of all sorts. A huge issue that many countries have is the fact that there are large pockets of land that are going through a process that is known as desertification.
Another thing Overgrazing is the major cause of desertification worldwide. Other factors that cause desertification include urbanization, climate change, overuse of groundwater, deforestation, natural disasters, and tillage practices in agriculture that make soils more vulnerable to wind. Desertification affects topsoil, groundwater reserves, surface runoff, human, animal, and plant populations. Water scarcity in drylands limits the production of wood, crops, forage, and other services that ecosystems provide to our community.
According to UNESCO, one-third of world’s land surface is threatened by desertification, and across the world, it affects the livelihood of millions of people who depend on the benefits of ecosystems that drylands provide. Desertification is another major environmental concern and a significant barrier to meeting basic human needs in drylands and is being constantly threatened by increases in human pressures and climatic variability. In this article, we’re going to give you an idea as to what are the causes of desertification, the effects that desertification has, and what we can do in order to deal with the problem at hand. Let’s take a closer look at all of these topics.
other main effects are:
Sand and dust storms — There has been a 25% increase in global annual dust emissions between the late nineteenth century to present day. The increase of desertification has also increased the amount of loose sand and dust that the wind can pick up ultimately resulting in a storm. For example, dust storms in the Middle East “are becoming more frequent and intense in recent years” because “long-term reductions in rainfall promot[ing] lower soil moisture and vegetative cover” and dust storms can contribute to certain respiratory disorders such as pneumonia, skin irritations, asthma and many more.They can pollute open water, reduce the effectiveness of clean energy efforts, and halt most forms of transportation.
Dust and sand storms can have a negative effect on the climate which can make desertification worse. Dust particles in the air scatter incoming radiation from the sun. The dust can provide momentary coverage for the ground temperature but the atmospheric temperature will increase. This can disform and shorten the life time of clouds which can result in less rainfall.
Food security — Global food security is being threatened by desertification and overpopulation. The more the population grows, the more food that has to be grown. The agricultural business is being displaced from one country to another. For example, Europe on average imports over 50% of its food. Meanwhile, 44% of agricultural land is located in dry lands and it supplies 60% of the world’s food production. Desertification is decreasing the amount of sustainable land for agricultural uses but demands are continuously growing. In the near future, the demands will overcome the supply.
Vegetation patterning — As the desertification takes place, the landscape may progress through different stages and continuously transform in appearance. On gradually sloped terrain, desertification can create increasingly larger empty spaces over a large strip of land, a phenomenon known as “brousse tigrée”. A mathematical model of this phenomenon proposed by C. Klausmeier attributes this patterning to dynamics in plant-water interaction. One outcome of this observation suggests an optimal planting strategy for agriculture in arid environments.
CAUSES OF DESERTIFICATION
The immediate cause is the loss of most vegetation. This is driven by a number of factors, alone or in combination, such as drought, climatic shifts, tillage for agriculture, overgrazing and deforestation for fuel or construction materials. Vegetation plays a major role in determining the biological composition of the soil. Studies have shown that, in many environments, the rate of erosion and runoff decreases exponentially with increased vegetation cover. Unprotected, dry soil surfaces blow away with the wind or are washed away by flash floods, leaving infertile lower soil layers that bake in the sun and become an unproductive hard pan. Many scientists think that one of the most common causes is overgrazing, too much consumption of vegetation by cattle or other livestock.
Scientists agree that the existence of a desert in the place where the Sahara desert is now located is due to a natural climate cycle; this cycle often causes a lack of water in the area from time to time. There is a suggestion that the last time that the Sahara was converted from savannah to desert it was partially due to overgrazing by the cattle of the local population.Researchers from Hacettepe University have reported that Saharan soil may have bioavailable iron and also some essential macro and micro nutrient elements suitable for use as fertilizer for growing wheat. It has been shown that Saharan soil may have the potential of producing bio available iron when illuminated with visible light and also it has some essential macro and micro nutrient elements. In this study the impact of various growth media on development of some bread wheat and durum wheat cultivation have been investigated. As a four different nutrient media, Hewitt nutrient solution, illuminated and non-illuminated Saharan desert soil solutions and distilled water have been utilized. Shoot length (cm.seedling-1), leaf area (cm2 seedling-1) and photosynthetic pigments have been determined. The results of this study indicate that wheat varieties fed by irradiated Saharan soil solution gave comparable results to Hewitt nutrient solution.
Overpopulation is one of the most dangerous factors contributing to desertification. Human populations are increasing at exponential rates, which leads to overgrazing, over-farming and deforestation, as previously acceptable techniques are becoming less sustainable. Climate change is likely a major contributing factor in the desertification process, as simulations suggest the greenhouse effect may increase the spread of deserts by as much as 20%. There are multiple reasons farmers use intensive farming as opposed to extensive farming but the main reason is to maximize yields.By increasing productivity, they require a lot more fertilizer, pesticides, and labor to upkeep machinery. This continuous use of the land rapidly depletes the nutrients of the soil causing desertification to spread.
AREAS EFFECTED BY DESERTIFICATION
Dry lands occupy approximately 40–41% of Earth’s land area and are home to more than 2 billion people.It has been estimated that some 10–20% of dry lands are already degraded, the total area affected by desertification being between 6 and 12 million square kilometres, that about 1–6% of the inhabitants of dry lands live in desertified areas, and that a billion people are under threat from further desertification.
Four areas effected by desertification
- Irrigated croplands, whose soils are often degraded by the accumulation of salts.
- Rain-fed croplands, which experience unreliable rainfall and wind-driven soil erosion.
- Grazing lands, which are harmed by overgrazing, soil compaction, and erosion.
- Dry woodlands, which are plagued by the over consumption of fuel wood.
Irrigated crop lands
Nearly 2,750,000 square km of croplands are irrigated. Over 60 percent of these irrigated areas occur in dry lands. Certainly, some dry land areas have been irrigated for millennia, but other areas are more fragile. Of the irrigated dry land, 30 percent (an area roughly the size of Japan) is moderately to severely degraded, and this percentage is increasing.
The main cause of declining biological productivity in irrigated croplands is the accumulation of salts in the soil. There is an important difference between rainwater and the water used for dry land irrigation. Rainwater results from the condensation of water evaporated by sunlight. Essentially, rainwater is distilled seawater or lake water. In contrast, water used for irrigation is the result of runoff from precipitation. Runoff percolates through the soil, dissolving and collecting much of the salts it encounters, before finding its way into rivers or aquifers. When used to irrigate crops, runoff evaporates and leaves behind much of the salts that it collected. Irrigated crops need an average of 80 cm (about 30 inches) of water annually. These salts can build up in the soil unless additional water is used to flush them out. This process can rapidly transform productive land into relatively barren salt flats scattered with halophytes (plants adapted to high levels of salt in the soil).
Most salt-degraded cropland occurs in Asia and southwestern North America, which account for 75 and 15 percent of the worldwide total, respectively. In Asia, Iraq has lost over 70 percent of its irrigated land to salt accumulation. In Russia, much of the irrigated land located where the Volga River runs into the Caspian Sea may last only until the middle of the 21st century before the buildup of salts makes it virtually unusable. Such losses are not restricted to developing countries. In the United States, salt accumulation has lowered crop yields across more than 50,000 square km (19,000 square miles), an area that is about a quarter of the country’s irrigated land.
Rain-fed croplands
Dry lands also support rain-fed crops. Before cultivation, such areas were often vast grasslands. They now cover about 5 million square km (about 2 million square miles) and account for roughly one-third of all croplands worldwide. They receive less than 60 cm (about 24 inches) of rain each year, and thus they are at the margin of what farmers can use for crops without at least some irrigation. Rainfall can vary considerably from one year to the next, so those lands may experience droughts that often lead to crop failure. Globally, more than 2,000,000 square km (about 770,000 square miles) of rain-fed croplands are moderately to severely degraded, and each year about 1 percent of those lands is abandoned.
The crops grown on dry lands are annuals; each year they emerge from seed, mature, and die. Grains such as wheat and corn (maize) are annuals that account for roughly 85 percent of global food production. After these grains are harvested, the lands are left uncovered until the next planting season. During this time, the soil is vulnerable to erosion by wind and rain. Wind can whip up the unprotected topsoil to create severe dust storms. Such dust storms often transport the soils, along with the nutrients they contain, over long distances. Rainfall is scarce in dry lands, but when it does come it can be torrential. Heavy downpours often wash away the soils on bare ground or deplete them of their nutrients. In contrast, native grasslands contain a mix of mainly perennial species that inhibit erosion. Perennials live from year to year, have deeper roots to bind the soil, and do not leave the soils exposed for months on end.
Grazing lands
Desertification also occurs in range lands. Typically, the damage in those environments can be separated into damage to soil and damage to vegetation. The former is more important than the latter; however, large areas experience both. The process of soil damage and loss often begins with the activities of grazing animals. Grazing livestock sometimes consume plants down to the ground. This activity weakens the individual plant; with a reduction in tissues capable of photosynthesis, its growth is greatly inhibited. In addition, livestock herds may trample and kill vegetation by walking to and from permanent water sources. Trampling destroys plant roots that bind the soil together. When rains come to those grazing lands, rivulets often form along the walking paths and wash away unprotected topsoil. Also, the repeated movement of herds over one section of the landscape can compact the soil, hindering the development of plant roots.
Livestock can substantially alter plant communities. It may be obvious that these animals reduce plant populations through their grazing activities, but livestock can also change the composition of the plant community by consuming some species and leaving others alone. The grazing pressure placed on grasses and other edible species gives a competitive advantage to cacti and other inedible species. For example, in the southwestern United States, honey mesquite (Prosopis glandulosa) is a native shrub, but it can increase its range considerably when cattle overgraze grasslands. The resulting plant community supports few livestock and is a persistent one — that is, the extensive thickets of mesquite often prevent grasses from recolonizing their former range.
Dry woodlands
The fourth area of desertification is dry woodlands, which are greatly affected by the over consumption of firewood. Across large areas of Asia and Africa, the principal raw material for cooking and heating is wood. Firewood in these areas is often converted to charcoal in earthen kilns before it is used, because charcoal gives off less smoke than wood. The conversion process is often inefficient, however, with about 75 percent of the wood’s heating potential lost. In Africa and Asia a very rough estimate of the per capita consumption of firewood is about half a ton per year. Across large areas of dry land where total plant production is roughly two tons per hectare per year, a family of four would have to clear a hectare of land or more per year. Very often, such deforested areas are not replanted. As human population densities increase, one can imagine that they might consume more wood than the land could support and create a “fuel wood crisis.”
COUNTER MEASURES AGAINST DESERTIFICATION
Techniques and countermeasures exist for mitigating or reversing the effects of desertification, and some possess varying levels of difficulty. For some, there are numerous barriers to their implementation. Yet for others, the solution simply requires the exercise of human reason.
One proposed barrier is that the costs of adopting sustainable agricultural practices sometimes exceed the benefits for individual farmers, even while they are socially and environmentally beneficial. Another issue is a lack of political will, and lack of funding to support land reclamation and anti-desertification programs.
Desertification is recognized as a major threat to biodiversity. Some countries have developed biodiversity action plans to counter its effects, particularly in relation to the protection of endangered flora and fauna.
Reforestation
Reforestation gets at one of the root causes of desertification and is not just a treatment of the symptoms. Environmental organizations work in places where deforestation and desertification are contributing to extreme poverty. There they focus primarily on educating the local population about the dangers of deforestation and sometimes employ them to grow seedlings, which they transfer to severely deforested areas during the rainy season.The Food and Agriculture Organization of the United Nations launched the FAO Drylands Restoration Initiative in 2012 to draw together knowledge and experience on dryland restoration. In 2015, FAO published global guidelines for the restoration of degraded forests and landscapes in drylands, in collaboration with the Turkish Ministry of Forestry and Water Affairs and the Turkish Cooperation and Coordination Agency.
The “Green Wall of China” is a high-profile example of one method that has been finding success in this battle with desertification. This wall is a much larger-scale version of what American farmers did in the 1930s to stop the great Midwest dust bowl. This plan was proposed in the late 1970s, and has become a major ecological engineering project that is not predicted to end until the year 2055. According to Chinese reports, there have been nearly 66 billion trees planted in China’s great green wall. The green wall of China has decreased desert land in China by an annual average of 1,980 square km. The frequency of sandstorms nationwide have fallen 20% due to the green wall. Due to the success that China has been finding in stopping the spread of desertification, plans are currently be made in Africa to start a “wall” along the borders of the Sahara desert as well to be financed by the United Nations Global Environment Facility trust.
In 2007 the African Union started the Great Green Wall of Africa project in order to combat desertification in 20 countries. The wall is 8,000 km wide, stretching across the entire width of the continent and has 8 billion dollars in support of the project. The project has restored 36 million hectares of land, and by 2030 the initiative plans to restore a total of 100 million hectares.The Great Green Wall has created many job opportunities for the participating countries, with over 20,000 jobs created in Nigeria alone.
Soil restoration
Techniques focus on two aspects: provisioning of water, and fixation and hyper-fertilizing soil. Fixating the soil is often done through the use of shelter belts, woodlots and windbreaks. Windbreaks are made from trees and bushes and are used to reduce soil erosion and evapotranspiration. They were widely encouraged by development agencies from the middle of the 1980s in the Sahel area of Africa.
Some soils (for example, clay), due to lack of water can become consolidated rather than porous (as in the case of sandy soils). Some techniques as zaï or tillage are then used to still allow the planting of crops.Waffle gardens can also help as they can provide protection of the plants against wind/sandblasting, and increase the hours of shade falling on the plant.
Another technique that is useful is contour trenching. This involves the digging of 150 m long, 1 m deep trenches in the soil. The trenches are made parallel to the height lines of the landscape, preventing the water from flowing within the trenches and causing erosion. Stone walls are placed around the trenches to prevent the trenches from closing up again. The method was invented by Peter Westerveld.
Enriching of the soil and restoration of its fertility is often achieved by plants. Of these, leguminous plants which extract nitrogen from the air and fix it in the soil, succulents (such as Opuntia), and food crops/trees as grains, barley, beans and dates are the most important. Sand fences can also be used to control drifting of soil and sand erosion.
Another way to restore soil fertility is through the use of nitrogen-rich fertilizer. Due to the higher cost of this fertilizer, many smallholder farmers are reluctant to use it, especially in areas where subsistence farming is common. Several nations, including India, Zambia, and Malawi have responded to this by implementing subsidies to help encourage adoption of this technique.
Some research centres (such as Bel-Air Research Center IRD/ISRA/UCAD) are also experimenting with the inoculation of tree species with mycorrhiza in arid zones. The mycorrhiza are basically fungi attaching themselves to the roots of the plants. They hereby create a symbiotic relation with the trees, increasing the surface area of the tree’s roots greatly (allowing the tree to gather much more nutrient from the soil).
The bioengineering of soil microbes, particularly photosynthesizers, has also been suggested and theoretically modeled as a method to protect drylands. The aim would be to enhance the existing cooperative loops between soil microbes and vegetation.
Desert reclamation
As there are many different types of deserts, there are also different types of desert reclamation methodologies. An example for this is the salt flats in the Rub’ al Khali desert in Saudi Arabia. These salt flats are one of the most promising desert areas for seawater agriculture and could be revitalized without the use of freshwater or much energy.
Farmer-managed natural regeneration (FMNR) is another technique that has produced successful results for desert reclamation. Since 1980, this method to reforest degraded landscape has been applied with some success in Niger. This simple and low-cost method has enabled farmers to regenerate some 30,000 square kilometers in Niger. The process involves enabling native sprouting tree growth through selective pruning of shrub shoots. The residue from pruned trees can be used to provide mulching for fields thus increasing soil water retention and reducing evaporation. Additionally, properly spaced and pruned trees can increase crop yields. The Humbo Assisted Regeneration Project which uses FMNR techniques in Ethiopia has received money from The World Bank’s BioCarbon Fund, which supports projects that sequester or conserve carbon in forests or agricultural ecosystems.
Managed grazing
Restoring grasslands store CO2 from the air as plant material. Grazing livestock, usually not left to wander, eat the grass and minimize grass growth. A method proposed to restore grasslands uses fences with many small paddocks and moving herds from one paddock to another after a day or two in order to mimic natural grazers and allowing the grass to grow optimally. Proponents of managed grazing methods estimate that increasing this method could increase carbon content of the soils in the world’s 3.5 billion hectares of agricultural grassland and offset nearly 12 years of CO2 emissions.
One proponent of managed grazing, Allan Savory, as part of holistic management, claims that keeping livestock tightly packed on smaller plots of land, meanwhile rotating them to other small plots of land will reverse desertification; range scientists have however not been able to experimentally confirm his claims.
