Desertification

Desertification

Overview
Desertification is the degradation of land
Land degradation
Land degradation is a process in which the value of the biophysical environment is affected by one or more combination of human-induced processes acting upon the land....

 in drylands
Drylands
Drylands is a Miles Franklin Award winning novel by Australian author Thea Astley. This novel shared the award with Benang by Kim Scott.-Awards:...

. Caused by a variety of factors, such as climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

 and human activities, desertification is one of the most significant global environmental problems.

Considerable controversy exists over the proper definition of the term "desertification" for which Helmut Geist (2005) has identified more than 100 formal definitions. The most widely accepted of these is that of the United Nations Convention to Combat Desertification
United Nations Convention to Combat Desertification
The United Nations Convention to Combat Desertification in Those Countries Experiencing Serious Drought and/or Desertification, Particularly in Africa is a Convention to combat desertification and mitigate the effects of drought through national action programs that incorporate long-term strategies...

 which defines it as "land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities"

The earliest known discussion of the topic arose soon after the French colonization of West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

, when the Comité d'Etudes commissioned a study on desséchement progressif to explore the prehistoric expansion of the Sahara Desert.

The world's great deserts were formed by natural processes interacting over long intervals of time.
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Encyclopedia
Desertification is the degradation of land
Land degradation
Land degradation is a process in which the value of the biophysical environment is affected by one or more combination of human-induced processes acting upon the land....

 in drylands
Drylands
Drylands is a Miles Franklin Award winning novel by Australian author Thea Astley. This novel shared the award with Benang by Kim Scott.-Awards:...

. Caused by a variety of factors, such as climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

 and human activities, desertification is one of the most significant global environmental problems.

Definitions


Considerable controversy exists over the proper definition of the term "desertification" for which Helmut Geist (2005) has identified more than 100 formal definitions. The most widely accepted of these is that of the United Nations Convention to Combat Desertification
United Nations Convention to Combat Desertification
The United Nations Convention to Combat Desertification in Those Countries Experiencing Serious Drought and/or Desertification, Particularly in Africa is a Convention to combat desertification and mitigate the effects of drought through national action programs that incorporate long-term strategies...

 which defines it as "land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities"

The earliest known discussion of the topic arose soon after the French colonization of West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

, when the Comité d'Etudes commissioned a study on desséchement progressif to explore the prehistoric expansion of the Sahara Desert.

History


The world's great deserts were 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
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...

, the largest 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.

Areas affected



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.

The Sahara
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...

 is currently expanding south at a rate of up to 48 kilometres per year.

Causes



Dryland ecosystems are already very fragile, and can rarely sustain the increased pressures that result from intense population growth. Many of these areas are inappropriately opened to development, when they cannot sustain human settlements.

The most common cause of desertification is the overcultivation of desert lands. Over-cultivation causes the nutrients in the soil to be depleted faster than they are restored. Improper irrigation practices result in salinated soils, and depletion of aquifers.

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. Overgrazing removes this vegetation causing erosion and loss of topsoil.

Desertification and poverty


At least 90% of the inhabitants of drylands live in developing nations, where they also suffer from poor economic and social conditions. This situation is exacerbated by land degradation because of the reduction in productivity, the precariousness of living conditions and the difficulty of access to resources and opportunities.

A downward spiral is created in many underdeveloped countries by overgrazing, land exhaustion and overdrafting of groundwater in many of the marginally productive world regions due to overpopulation
Overpopulation
Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...

 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. Because of these migrations into the cities, there are often large numbers of unemployed people who end up living in slums.

Countermeasures and prevention


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, even while they are socially and environmentally beneficial. Another issue is a lack of political will, and lack of funding to support land reclamation
Land reclamation
Land reclamation, usually known as reclamation, is the process to create new land from sea or riverbeds. The land reclaimed is known as reclamation ground or landfill.- Habitation :...

 and anti-desertification programs.

Desertification is recognized as a major threat to biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

. Some countries have developed Biodiversity Action Plan
Biodiversity Action Plan
A Biodiversity Action Plan is an internationally recognized program addressing threatened species and habitats and is designed to protect and restore biological systems. The original impetus for these plans derives from the 1992 Convention on Biological Diversity...

s to counter its effects, particularly in relation to the protection of endangered flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...

 and fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...

.

Reforestation
Reforestation
Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation....

 gets at one of the root causes of desertification and isn't just a treatment of the symptoms. Environmental organizations work in places where deforestation and desertification are contributing to extreme poverty
Poverty
Poverty is the lack of a certain amount of material possessions or money. Absolute poverty or destitution is inability to afford basic human needs, which commonly includes clean and fresh water, nutrition, health care, education, clothing and shelter. About 1.7 billion people are estimated to live...

. 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.

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 windbreak
Windbreak
A windbreak or shelterbelt is a plantation usually made up of one or more rows of trees or shrubs planted in such a manner as to provide shelter from the wind and to protect soil from erosion. They are commonly planted around the edges of fields on farms. If designed properly, windbreaks around a...

s. Windbreaks are made from trees and bushes and are used to reduce soil erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 and evapotranspiration
Evapotranspiration
Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...

. They were widely encouraged by development agencies from the middle of the 1980s in the Sahel
Sahel
The Sahel is the ecoclimatic and biogeographic zone of transition between the Sahara desert in the North and the Sudanian Savannas in the south.It stretches across the North African continent between the Atlantic Ocean and the Red Sea....

 area of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

.

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
Zai
Zai are Pashtun tribes in Pakistan and Afghanistan. The title of tribe end in Zai and the their clans end in Khel.Some of the Pashtun tribes:* Alizai* Ghilzai* Kakar* Kakazai* Khudiadadzai* Khulozai* Mohamedzai* Noorzai* Omarzai...

 or tillage
Tillage
Tillage is the agricultural preparation of the soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shovelling, picking, mattock work, hoeing, and raking...

 are then used to still allow the planting of crops.

Enriching of the soil and restoration of its fertility is often done by plants. Of these, the Leguminous plants which extract nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 from the air and fixes it in the soil, and food crops/trees as grain
GRAIN
GRAIN is a small international non-profit organisation that works to support small farmers and social movements in their struggles for community-controlled and biodiversity-based food systems. Our support takes the form of independent research and analysis, networking at local, regional and...

s, barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...

, beans and dates are the most important. Sand fence
Sand fence
A sand fence is a structure similar to a snow fence used to force wind blown, drifting sand to accumulate in a desired place. Sand fences are employed to control erosion and to recruit new material in desert areas....

s can also be used to control drifting of soil and sand erosion.

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 tress can be used to provide mulching for fields thusincreasing soil water retention and reducing evaporation. Additionally, properly spaces 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.

See also


  • Desert greening
    Desert greening
    Desert greening consists of any of a number of methods used to revitalize deserts. So far only arid and semi-arid desert are meant when using the expression...

  • Arid Lands Information Network
    Arid Lands Information Network
    Arid Lands Information Network is a Kenyan-based non-governmental organisation that seeks to exchange ideas and experiences among "grassroots change agents"...

  • Aridification
    Aridification
    Aridification is the process of a region becoming increasingly dry. It refers to long term change rather than seasonal variation.It is often measured as the reduction of average soil moisture content....

  • Deforestation
    Deforestation
    Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....

  • Ecological engineering
    Ecological engineering
    Ecological engineering is an emerging study of integrating ecology and engineering, concerned with the design, monitoring and construction of ecosystems...

  • Global warming
    Global warming
    Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

  • Green Wall of China
    Green Wall of China
    The Green Wall of China, also known as the Green Great Wall or Great Green Wall , will be a series of human-planted forest strips in the People's Republic of China, designed to hold back the expansion of the Gobi Desert...

  • Oasification
    Oasification
    In hydrology, oasification is the antonym to desertification by soil erosion; this technique has limited application and is normally considered for much smaller areas than those threatened by desertification....

  • Water crisis
    Water crisis
    Water crisis is a general term used to describe a situation where the available water within a region is less than the region's demand. The term has been used to describe the availability of potable water in a variety of regions by the United Nations and other world organizations...


External links



News
  • Fighting Desertification Through Conservation Report on a project to stop the advance of the Sahara in Algeria
    Algeria
    Algeria , officially the People's Democratic Republic of Algeria , also formally referred to as the Democratic and Popular Republic of Algeria, is a country in the Maghreb region of Northwest Africa with Algiers as its capital.In terms of land area, it is the largest country in Africa and the Arab...

     - IPS
    Inter Press Service
    Inter Press Service is a global news agency. Its main focus is the production of independent news and analysis about events and processes affecting economic, social and political development....

    , 27 February 2007