The World Day to Combat Desertification and Drought is observed annually on June 17. It’s purpose is to highlight ways to prevent desertification and recover from drought. It was proclaimed on January 30, 1995 by the United Nations General Assembly resolution. Each annual celebration has a different theme such as Attainment of food security for all through sustainable food systems, Conserving land and energy, Combating land degradation for sustainable agriculture, Desertification and Climate Change,The Beauty of Deserts – The Challenge of Desertification, Women and Desertification, Social Dimensions of Desertification: Migration and Poverty, International Year of Deserts and Desertification (IYDD)
Desertification is defined as “the process of fertile land transforming into desert typically as a result of deforestation, drought or improper/inappropriate agriculture” and “land degradation in arid, semi-arid and dry sub-humid regions resulting from various factors, including climatic variations and human activities.” The world’s most noted deserts have been formed by natural processes interacting over long intervals of time. During most of these times, deserts have grown and shrunk independent of human activities. Paleodeserts are large sand seas now inactive because they are stabilized by vegetation, some extending beyond the present margins of core deserts, such as the Sahara, the largest hot desert. Desertification has played a significant role in human history, contributing to the collapse of several large empires, such as Carthage, Greece, and the Roman Empire, as well as causing displacement of local populations.Historical evidence shows that the serious and extensive land deterioration occurring several centuries ago in arid regions had three epicenters: the Mediterranean, the Mesopotamian Valley, and the loessial plateau of China, where population was dense (some of the population in England are really dense too).
Drylands 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 drylands 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 drylands live in desertified areas, and that a billion people are under threat from further desertification. As 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.
Desertification can be caused by a number of factors including man made overgrazing of a particular area by cattle and Overgrazing of drylands by poorly managed traditional herding is one of the primary causes of desertification. Wildebeest in Masai Mara during the Great Migration. Overgrazing is not caused by nomadic grazers in huge populations of travel herds, nor by holistic planned grazing.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, hi 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 hardpan.
At least 90% of the inhabitants of drylands live in developing nations, where they also suffer from poor economic and social conditions exacerbated by land degradation because of the reduction in productivity, the precariousness of living conditions and the difficulty of access to resources and opportunities. This creates a downward spiral in many underdeveloped countries by overgrazing, land exhaustion and overdrafting of groundwater in many of the marginally productive world regions due to overpopulation pressures to exploit marginal drylands for farming. Decision-makers are understandably averse to invest in arid zones with low potential. This absence of investment contributes to the marginalisation of these zones. When unfavourable agro-climatic conditions are combined with an absence of infrastructure and access to markets, as well as poorly adapted production techniques and an underfed and undereducated population, most such zones are excluded from development.Desertification often causes rural lands to become unable to support the same sized populations that previously lived there. This results in mass migrations out of rural areas and into urban areas, particularly in Africa. These migrations into the cities often cause large numbers of unemployed people, who end up living in slums.
There are many different types of deserts, and many different types of desert reclamation countermeasures and 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. Anti-sand shields and Jojoba plantations, have also played a role in combating edge effects of desertification and Techniques exist for mitigating or reversing the effects of desertification; however, there are numerous barriers to their implementation. One of these is that the costs of adopting sustainable agricultural practices sometimes exceed the benefits for individual farmers, 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 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. In 2012 The Food and Agriculture Organization of the United Nations launched the FAO Drylands Restoration Initiative 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.
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.
Another technique that is useful is contour trenching. This involves the digging of 150m long, 1m 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 done by plants. Of these, the Leguminous plants which extract nitrogen from the air and fixes it in the soil, 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.
The Bel-Air Research Center is 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 nutrients from the soil). An example of a promosing setup is Jujube combined with Glomus aggregatum. Farmer-managed natural regeneration (FMNR) is another technique that has produced successful results for desert reclamation. 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 methods are argued to be able to restore grasslands, thereby decreasing atmospheric CO2 levels as Restoring grasslands store CO2 from the air into plant material. Grazing livestock, usually not left to wander, would eat the grass and would minimize any grass growth while grass left alone would eventually grow to cover its own growing buds, preventing them from photosynthesizing and killing the plant. 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 mimick natural grazers and allowing the grass to grow optimally. while large herds are often blamed for desertification, prehistoric lands used to support large or larger herds and areas where herds were removed in the United States are still desertifying.