Desertification, definition and its effect

desertification, the process by which natural or human causes reduce the biological productivity of drylands (arid and semiarid lands). Declines in productivity may be the result of climate change, deforestation, overgrazing, poverty, political instability, unsustainable irrigation practices, or combinations of these factors. The concept does not refer to the physical expansion of existing deserts but rather to the various processes that threaten all dryland ecosystems, including deserts as well as grasslands and scrublands.

1. The Intergovernmental Panel on Climate Change  (IPCC) will publish its special report on  climate change and land . The report,  written by  hundreds of scientists and researchers from across the world, dedicates one of its seven chapters solely to the issue of desertification. The combined impact of climate change, land mismanagement and unsustainable freshwater use has seen the world’s water-scarce regions increasingly degraded. This leaves their soils less able to support crops, livestock and wildlife. Desertification

2. Defining desertification In 1994, the UN established the  United Nations Convention to Combat Desertification  (UNCCD) as the “sole legally binding international agreement linking environment and development to sustainable land management”. The Convention itself was a response to a  call  at the UN  Earth Summit  in Rio de Janeiro in 1992 to hold negotiations for an international legal agreement on desertification. The UNCCD set out a definition of desertification in a  treaty adopted  by parties in 1994. It states that desertification means “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities”.

3. So, rather than desertification meaning the literal expansion of deserts, it is a catch-all term for land degradation in water-scarce parts of the world. This degradation includes the temporary or permanent decline in quality of soil, vegetation, water resources or wildlife , for example. It also includes the deterioration of the economic prod uctivity of the land – such as the ability to farm the land for commercial or subsistence purposes. Arid, semi-arid and dry sub-humid areas are known collectively as “drylands”. These are, unsurprisingly, areas that receive relatively little rain or snow each year. Technically, they are defined by the UNCCD as “areas other than polar and sub-polar regions, in which the ratio of annual precipitation to  potential evapotranspiration  falls within the range from 0.05 to 0.65”.

4. In simple terms, this means the amount of rainfall the area receives is between 5-65% of the water it has the potential to lose through evaporation and  transpiration  from the land surface and vegetation, respectively (assuming sufficient moisture is available). Any area that receives more than this is referred to as “humid”. Where the world’s drylands are identified by different grades of orange and red shading. Drylands encompass around 38% of the Earth’s land area , covering much of North and southern Africa, western North America, Australia, the Middle East and Central Asia. Drylands are home to approximately  2.7 billion people    90% of whom  live in developing countries.

5. Drylands are  particularly susceptible  to land degradation because of scarce and variable rainfall as well as poor soil fertility. There are numerous ways in which the land can degrade. One of the main processes is erosion – the gradual breaking down and removal of rock and soil. This is typically through some force of nature – such as wind, rain and/or waves  – but can be exacerbated by activities including ploughing, grazing or deforestation.

6. A loss of soil fertility is another form of degradation . This can be through a loss of nutrients, such as nitrogen, phosphorus and potassium, or a decline in the amount of organic matter in the soil . For example, soil erosion by water causes global losses of as much as  42m tonnes of nitrogen and 26m tonnes of phosphorus  every year. On farmed land, this inevitably needs to be replaced through fertilisers at significant cost. Soils can also suffer from salinisation – an increase in salt content – and acidification from overuse of fertilisers. Then there are  lots of other processes  that are classed as degradation, including a loss or shift in vegetation type and cover , the compaction and hardening of the soil, an increase in wildfires , and a declining water table through excessive extraction of ground water.

7. Climate Change and Desertification

8.  Desertification is a type of land degradation in which a relatively dry land region becomes increasingly arid, typically losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors. Desertification is a significant global ecological and environmental problem ( ARID: Lacking moisture,especially having insufficient rainfall to support trees or woody plants ) Desertification

9. CATEGORIES OF DESERTIFICATION Light Desertification: In this type of desertification, a very slight damage occurs in vegetation cover and soil. This damage does not affect the biological capacity of the environment and can be neglected . Moderate desertification : A medium degree of damage of vegetation cover occurs and formation of small sand dunes and salinization of the soil which reduces production by 10- 25%.

10. Severe Desertification : In this type, spreading of weeds and unwanted shrubs in the pasture at the expense of desirable and wanted species occurs as well as increasing of the erosion activity which affects the vegetation cover and reduces production up to 50%. Very severe desertification: In this type of desertification, composition of active naked great sand dunes occurs and formation of many grooves and valleys and the salinization of the soil which leads to soil degradation.It is the most serious type of desertification.

11. Causes of Desertification There are 4 main factors in desertification • Drought • Over grazing •Over cultivation • Trees used for fuel and shelter

12. Drought – A long period without rainfall. Causes crops to die. Lack of food. May have to move to find food.

13. Overgrazing – Too many animals grazing on the land. Animals eat all the vegetation. Vegetation fails to grow. Soil is exposed to rain and wind. Soil is washed or blown away.

14. Over cultivation Many crops being grown on the land year after year. No rotation of crops. Crops take all the nutrients from the soil. The soil becomes infertile and nothing can grow. Because there are no crops to protect the soil the soil is again easily eroded by the wind and rain.

15. REMOVAL OF TREES FOR FUEL AND SHELTER There are few trees in the desert and their roots hold the soil together. When the trees are removed for firewood or to build shelter the roots die and the soil becomes loose. Yet again this means the soil can be easily blown or washed away.

16. COUNTER MEASURES & PREVENTION FOR DESERTIFICATION 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. The culture of prevention requires a change in Governments’ and peoples’ attitudes through improved incentives. REFORESTATION. FIXATION OF SOIL. CONTOUR TRENCHING. FARMER-MANAGED NATURAL REGENERATION. MANAGED GRAZING

17. REFORESTATION •Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation. Reforestation can be used to improve the quality of human life by soaking up pollution and dust from the air, rebuild natural habitats and ecosystems, mitigate global warming since forests facilitate bio sequestration of atmospheric carbon dioxide, and harvest for resources. •The term reforestation is similar to afforestation , the process of restoring and recreating areas of woodlands or forests that may have existed long ago but were deforested or otherwise removed at some point in the past

18. •Reforestation of large areas can be done through the use of measuring rope (for accurate plant spacing) and dibbers, (or wheeled augers for planting the larger trees) for making the hole in which a seedling or plant can be inserted. Indigenous soil inoculants (e.g., Laccaria bicolor ) can optionally be used to increase survival rates in hardy environments

19. FIXATION OF 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 . •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 tillage are then used to still allow the planting of crops . •Enriching of the soil and restoration of its fertility is often done by plants. 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

20. CONTOUR TRENCHING •Contour trenching is an agricultural technique that can be easily applied in arid subareas to allow for water and soil conservation and to increase agricultural production. •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.

21.   FARMER-MANAGED NATURAL REGENERATION • Technique that has produced successful results for desert reclamation. • Its a simple and low-cost method has enabled farmers to regenerate some 30,000 square kilometers . 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.

22. MANAGED GRAZING •A method proposed to restore grasslands by using 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

24. Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services  (IPBES), “land degradation is almost always the result of multiple interacting causes”. Such as deforestation , overgrazing of livestock , over-cultivation of crops and inappropriate irrigation ; the latter includes natural fluctuations in climate and global warming as a result of human-caused greenhouse gas emissions. Then there are underlying causes as well, the IPBES report notes, including “economic, demographic, technological, institutional and cultural drivers”. Mix of causes

25. ( Recent research  shows that this is because the “lapse rate” – the rate that air temperatures decrease with height through the atmosphere – is experiencing larger decreases over the ocean than land. This results in smaller increases in surface ocean temperatures compared to the land surface as global temperatures rise.) the land surface has warmed by approximately 1.7C.

26. Local and global impacts Dr Alisher Mirzabaev , a senior researcher at the  University of Bonn  and a coordinating lead author on the desertification chapter of the IPCC land report Climate change interacts with the other human drivers of degradation, such as “unsustainable land management and agricultural expansion , in causing or worsening many of these desertification processes”, The productivity , loss of biodiversity , increasing chances of wildfires in certain areas. Naturally, these will have negative impacts on food security and livelihoods, especially in developing countries .”

27. Stringer says desertification often brings with it “a reduction in vegetation cover , so more bare ground, a lack of water, and soil salinisation in irrigated areas ”. This also can mean a loss of biodiversity and visible scarring of the landscape through erosion and the formation of gullies following heavy rainfall. “Desertification has already contributed to the global loss of biodiversity”, adds  Joyce Kimutai  from the  Kenya Meteorological Department . Kimutai , who is also a lead author on the desertification chapter of the IPCC land report. “Wildlife, especially large mammals, have limited capacities for timely adaptation to the coupled effects of climate change and desertification.”

28. For example, a  study   of the Cholistan Desert region of Pakistan found that the “ flora and fauna have been thinning out gradually with the increasing severity of desertification ”.   study  of Mongolia found that “all species richness and diversity indicators declined significantly” because of grazing and increasing temperatures over the last two decades. Degradation can also open the land up to  invasive species  and those less suitable for grazing livestock, says Michaelides “ In many countries, desertification means a decline in soil fertility , a reduction in vegetation cover – especially grass cover – and more invasive shrub species . the consequences of this are less available land for grazing, and less productive soils . Ecosystems start more drought tolerant shrubs lost grasslands and more bare soil is exposed to sun light”

29. “Where food security and livelihoods are intimately tied to the land, due desertification. Examples are many countries in East Africa – especially Somalia, Kenya and Ethiopia – where over half of the population are pastoralists relying on healthy grazing lands for their livelihoods. In Somalia alone , livestock contributes around 40% of the GDP [Gross Domestic Product].” The  UNCCD estimates  that around 12m hectares of productive land are lost due to desertification and drought each year. This is an area that could produce 20m tonnes of grain annually. In Niger, for example, the costs of degradation caused by land use change amounts to  around 11% of its GDP . Similarly in Argentina , the “ total loss of ecosystem services due to land-use/cover change, wetlands degradation and use of land degrading management practices on grazing lands and selected cropland s” is equivalent to  about 16% of its GDP .

30. At the  UN Conference on Sustainable Development  in Rio de Janeiro in 2012, parties agreed to “strive to achieve a land-degradation neutral world in the context of sustainable development”. This concept of “ land degradation neutrality ” (LDN) was subsequently  taken up by the UNCCD  and also  formally adopted  as  Target 15.3  of the  Sustainable Development Goals  by the UN General Assembly in 2015 . The idea of LDN, explained in detail firs t to avoid land degradation , second to minimise it where it does occur, and thirdly to offset any new degradation by restoring and rehabilitating land elsewhere. The outcome being that overall degradation comes into balance – where any new degradation is compensated with reversal of previous degradation.

31. “Sustainable land management” (SLM) is key to achieving the LDN target, says  Dr Mariam Akhtar-Schuster , co-chair of the  UNCCD science-policy interface  and a review editor for the desertification chapter of the IPCC land report. “Sustainable land management practices, which are based on the local socio-economic and ecological condition of an area , help to avoid desertification in the first place but also to reduce ongoing degradation processes.” SLM essentially means maximising the economic and social benefits of the land while also maintaining and enhancing its productivity and environmental functions. This can comprise a whole range of techniques, such as rotational grazing of livestock, boosting soil nutrients by leaving crop residues on the land after harvest, trapping sediment and nutrients that would otherwise be lost through erosion, and planting fast-growing trees to provide shelter from the wind.

32. “ Stringer agrees that there’s “no silver bullet” to preventing and reversing desertification. And, it’s not always the same people who invest in SLM who benefit from it, she explains: “An example here would be land users upstream in a catchment reforesting an area and reducing soil erosion into water bodies . For those people living downstream this reduces flood risk as there is less sedimentation and could also deliver improved water quality.” However, there is also a fairness issue if the land users upstream are paying for the new trees and those downstream are receiving the benefits at no cost, Stringer says:

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34. Dust storms in the Middle East, for example, “are becoming more frequent and intense in recent years”, a  recent study  found. This has been driven by “long-term reductions in rainfall promoting lower soil moisture and vegetative cover”. However, Stringer adds that “further research is needed to establish the precise links between climate change, desertification and dust and sandstorms”. Dust storms can have a huge impact on human health,  contributing to  respiratory disorders such as asthma and pneumonia, cardiovascular issues and skin irritations, as well as polluting open water sources. They can also play havoc with infrastructure, reducing the effectiveness of  solar panels  and  wind turbines  by covering them in dust, and causing disruption to  roads, railways and airports

35. Climate feedback Adding dust and sand into the atmosphere is also one of the ways that desertification itself can affect the climate, says Kimutai . Others include “changes in vegetation cover, surface albedo (reflectivity of the Earth’s surface), and greenhouse gases fluxes”, she adds. Dust particles in the atmosphere can  scatter incoming radiation  from the sun, reducing warming locally at the surface, but increasing it in the air above. They can also affect the formation and lifetimes of clouds,  potentially making rainfall less likely  and thus reducing moisture in an already dry area. Soils are a very important store of carbon. The top two metres of soil in global drylands, for example, store an estimated  646bn tonnes of carbon  – approximately 32% of the carbon held in all the world’s soils.

36. Research shows  that the moisture content of the soil is the main influence on the capacity for dryland soils to “mineralise” carbon. This is the process, also known as “soil respiration”, where microbes break down the organic carbon in the soil and convert it to CO2. This process also makes nutrients in the soil available for plants to use as they grow.

37. Solutions Limiting global warming is therefore one of the key ways to  help put a break on desertification  in future, but what other solutions exist? The UN has  designated  the decade from January 2010 to December 2020 as the “United Nations decade for deserts and the fight against desertification”. The decade was to be an “opportunity to make critical changes to secure the long-term ability of drylands to provide value for humanity’s well being”. What is very clear is that prevention is better – and much cheaper – than cure. “Once desertification has occurred it is very challenging to reverse”, says Michaelides . This is because once the “cascade of degradation processes start, they’re hard to interrupt or halt”.

38. Stopping desertification before it starts requires measures to “ protect against soil erosion , to prevent vegetation loss , to prevent overgrazing or land mismanagement” “All these things require concerted efforts and policies from communities and governments to manage land and water resources at large scales. Even small scale land mismanagement can lead to degradation at larger scales, so the problem is quite complex and hard to manage . ” The potential impacts of desertification on health include : higher threats of malnutrition from reduced food and water supplies; more water- and food-borne diseases that result from poor hygiene and a lack of clean water; respiratory diseases caused by atmospheric dust from wind erosion and other air pollutants; the spread of infectious diseases as populations migrate.