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Sand dunes show the increasing desertification of the Tibetan Plateau, as land dries out and vegetation cover vanishes due to human activity.

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Desertification, explained

Humans are driving the transformation of drylands into desert on an unprecedented scale around the world, with serious consequences. But there are solutions.

As global temperatures rise and the human population expands, more of the planet is vulnerable to desertification, the permanent degradation of land that was once arable.

While interpretations of the term desertification vary, the concern centers on human-caused land degradation in areas with low or variable rainfall known as drylands: arid, semi-arid, and sub-humid lands . These drylands account for more than 40 percent of the world's terrestrial surface area.

While land degradation has occurred throughout history, the pace has accelerated, reaching 30 to 35 times the historical rate, according to the United Nations . This degradation tends to be driven by a number of factors, including urbanization , mining, farming, and ranching. In the course of these activities, trees and other vegetation are cleared away , animal hooves pound the dirt, and crops deplete nutrients in the soil. Climate change also plays a significant role, increasing the risk of drought .

All of this contributes to soil erosion and an inability for the land to retain water or regrow plants. About 2 billion people live on the drylands that are vulnerable to desertification, which could displace an estimated 50 million people by 2030.

Where is desertification happening, and why?

The risk of desertification is widespread and spans more than 100 countries , hitting some of the poorest and most vulnerable populations the hardest, since subsistence farming is common across many of the affected regions.

More than 75 percent of Earth's land area is already degraded, according to the European Commission's World Atlas of Desertification , and more than 90 percent could become degraded by 2050. The commission's Joint Research Centre found that a total area half of the size of the European Union (1.61 million square miles, or 4.18 million square kilometers) is degraded annually, with Africa and Asia being the most affected.

The drivers of land degradation vary with different locations, and causes often overlap with each other. In the regions of Uzbekistan and Kazakhstan surrounding the Aral Sea , excessive use of water for agricultural irrigation has been a primary culprit in causing the sea to shrink , leaving behind a saline desert. And in Africa's Sahel region , bordered by the Sahara Desert to the north and savannas to the south, population growth has caused an increase in wood harvesting, illegal farming, and land-clearing for housing, among other changes.

The prospect of climate change and warmer average temperatures could amplify these effects. The Mediterranean region would experience a drastic transformation with warming of 2 degrees Celsius, according to one study , with all of southern Spain becoming desert. Another recent study found that the same level of warming would result in "aridification," or drying out, of up to 30 percent of Earth's land surface.

A herder family tends pastures beside a growing desert.

When land becomes desert, its ability to support surrounding populations of people and animals declines sharply. Food often doesn't grow, water can't be collected, and habitats shift. This often produces several human health problems that range from malnutrition, respiratory disease caused by dusty air, and other diseases stemming from a lack of clean water.

Desertification solutions

In 1994, the United Nations established the Convention to Combat Desertification (UNCCD), through which 122 countries have committed to Land Degradation Neutrality targets, similar to the way countries in the climate Paris Agreement have agreed to targets for reducing carbon pollution. These efforts involve working with farmers to safeguard arable land, repairing degraded land, and managing water supplies more effectively.

The UNCCD has also promoted the Great Green Wall Initiative , an effort to restore 386,000 square miles (100 million hectares) across 20 countries in Africa by 2030. A similar effort is underway in northern China , with the government planting trees along the border of the Gobi desert to prevent it from expanding as farming, livestock grazing , and urbanization , along with climate change, removed buffering vegetation.

However, the results for these types of restoration efforts so far have been mixed. One type of mesquite tree planted in East Africa to buffer against desertification has proved to be invasive and problematic . The Great Green Wall initiative in Africa has evolved away from the idea of simply planting trees and toward the idea of " re-greening ," or supporting small farmers in managing land to maximize water harvesting (via stone barriers that decrease water runoff, for example) and nurture natural regrowth of trees and vegetation.

"The absolute number of farmers in these [at-risk rural] regions is so large that even simple and inexpensive interventions can have regional impacts," write the authors of the World Atlas of Desertification, noting that more than 80 percent of the world's farms are managed by individual households, primarily in Africa and Asia. "Smallholders are now seen as part of the solution of land degradation rather than a main problem, which was a prevailing view of the past."

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Desertification: Causes, Effects, And Solutions

Soaring temperatures and improper disaster management have resulted in increased desertification rates across the globe. Coupled with droughts and a drop in agricultural productivity, the effects of desertification cannot be ignored. To curb such high rates of land degradation that many regions of the world are experiencing, effective risk management is needed. What is desertification and what are the main causes and solutions?

What Is Desertification?

Desertification has a few varying definitions, but mostly centres around semi-arid, sub-humid lands; in simple terms, it can be described as areas with low or variable rainfall. In addition, there is also the added element of human-induced land degradation owing to an expanding population and rampant deforestation.

Land degradation is a systematic global issue. The scale of the problem has been questioned for decades, with estimates of degraded areas ranging between 15 to 60 million kilometres. Currently, an estimated 2 billion people live on drylands vulnerable to this phenomenon and scientists predict that the effects of desertification could lead to the displacement of around 50 million people by 2030 as a result of the soaring temperatures, large-scale deforestation, and ecosystem damage in many parts of the world. Alone in Asia, more than 2 billion people will be living in dryland conditions, while Africa sees at least 1 billion in the same (Figure 1) .

What Are the Causes of Desertification?

Land degradation has been ongoing for several decades. Droughts –  increasingly frequent extreme weather events caused by global warming – also amplify this situation and can lead to the depletion of nutrients from the soil and the inability of land to regrow plants, resulting in drylands that currently cover about 40% of the globe, from the Mediterranean regions and the south-western parts of the US to Asia and the Middle East. Droughts, coupled with land degradation, give rise to desertification.

But this phenomenon is also caused by activities such as urbanisation, ranching, mining, and clearing of land and emission generation. By further contributing to a rise in temperatures and a reduction in precipitation, human interventions create a vicious cycle that only exacerbates the issue.

The degradation of land leads to a reduction in soil productivity, which can lead to a variety of complexities such as environmental hazards, food insecurity as well as loss of biodiversity and ecosystem services. 

Where Does Desertification Occur the Most?

More than 60% of Central Asia is vulnerable to desertification processes. Soaring temperatures in parts of China, Uzbekistan, Kyrgyzstan, and many other countries have been a cause of concern. Scientists have concluded that, since the 1980s, much of the Central Asian region was classified as having a desert climate . However, the issue has now spread toward northern Uzbekistan and Kyrgyzstan, southern Kazakhstan, and around the areas of the Junggar Basin in north-western China. Mountains across the continental region have become hotter and wetter, resulting in the retreat of glaciers. An example of this is the Tian Shan region in north-western China . Here, an increase in temperature and precipitation in the form of rain instead of snow has contributed to the melting of ice at mountain tops . Thereby, glaciers in Central Asia are unable to replenish ice and as a consequence, less meltwater will flow to nearby regions, causing water shortages that affect people as well as the agricultural sector.

You Might Also Like: Glaciers in China Melting at ‘Shocking’ Pace, Scientists Say

Desertification is a huge issue also in Africa. For example, poor harvesting and a surge in barren lands continue to plague the inhabitants of Engaruka, Tanzania . In Mauritania, a drop in rainfall has worsened agricultural production and has left many farmers struggling to grow enough food to eat or sell. 

What Are the Main Effects of Desertification?

Desertification is attributed to soaring temperatures and/or drop in precipitation; this is likely to result in the modification and replacement of plant communities by species that are adapted to hotter and drier conditions. The most common change induced by desertification is the conversion of native vegetation by woody plants and invasive shrub species (for example Bufflegrass and Onion-weed in southwest America, and the Tamarisk plant in the Sahara). 

In this regard, Jeffrey Dukes, an ecologist from Carnegie Institution for Science’s Department of Global Ecology at Stanford said : “[Desertification] is going to have consequences for things like the grazing animals that are dependent on the steppe or the grasslands”. In some regions, he adds, extended periods of drought will reduce the land’s productivity until it becomes ‘dead’ soil. 

Desertification can also cause loss of biodiversity and loss of aquifers. In Africa, with nearly 45% of the landmass experiencing desertification, many people face even greater risks. In Mauritania, the dire situation has caused food insecurity, housing problems and population health declines . Villagers are trying to migrate as their houses become buried under the sand in addition to a lack of water sources and income. 

Desertification has also led to an increase in the frequency of dust storms. Particulate matter, pathogens, and allergens are detrimental to human health. The health effects caused by dust storms are greatest in the areas in the immediate vicinity of their origin and regions like the Sahara Desert, Central, and eastern Asia, the Middle East, and Australia are largely affected. In places such as the Sahara region, the Middle East, and South as well as East Asia, dust storms have been attributed to causing approximately 15–50% of all cardiopulmonary deaths .

The impacts of desertification in conjunction with climate change on socio-economic systems were also exemplified in an IPCC Report on climate change and land degradation. The report suggests that the interplay between desertification and climate change greatly affects the achievement of the targets of SDGs 13 (climate action) and 15 (life on land) , thereby highlighting the need for efficient policy actions on land degradation neutrality and climate change mitigation (Figure 2) .

How Can We Solve Desertification?

A new global approach of proactive action and risk management efforts is warranted in today’s changing landscape and climate. Droughts seem to be concurrent with desertification in many parts of the Earth. 

In Niger, local bodies have rehabilitated land to restore soil fertility, which has positively affected the country whose economy is largely dependent on agriculture. Here, the smallholder farmers have taken the initiative into their own hands by developing the principle of farmer-managed natural regeneration (FMNR) . This technique involves the regeneration and multiplication of valuable trees whose roots already lay underneath their land, encouraging significant tree growth. Felled tree stumps, sprouting root systems, and seeds are regrown; this has boosted soil productivity, improved agricultural income and the lands are greener than before.

Village communities in Kenya and Tanzanian are fighting droughts and desertification by digging semi-circular trenches that store water when it rains, thereby retaining moisture for plants and trees. 

Some World Bank-funded projects have helped carry out ecological restoration and fixing of sand dunes in north-western China. One of the major problems of desertification is the migration or shifting of sands threatening infrastructure, villages, and irrigated farmland. Stabilisation of dunes (synonymously dune-fixing) is based on the straw-checkerboard technique. This technique involves planting straws of wheat, rice, reeds, and other plants in a checkerboard shape where half is buried and the other half is exposed. Desertification control efforts have also benefited several communities living in these areas by creating jobs and increasing incomes through the growing of sand-fixing shrub species and greenhouses .

Several other countries have already taken charge of curbing land degradation through tree-planting efforts. A nationwide ongoing effort is the “Great Green Wall of China” which has aimed to plant 88 million acres of forests in a 3000-mile network with a goal to tackle deforestation. A similar anti-desertification tree planting ambition, “Great Green Wall” of Africa has also been moving steadily since its inception in 2007. The plan to restore the degraded lands of the Sahel Region has had its fair share of progress and setbacks, but last year’s major boost announced at the One Planet Summit has planned to accelerate its completion in order to support the local farmers and support the agriculture business.

Every year, the United Nations observes the World Day to Combat Desertification and Drought, an occasion to promote public awareness of the presence of desertification and drought. This day is considered a unique moment to remind people of the ways in which land degradation can be solved through efficient problem-solving techniques and the cooperation between local, governmental, and environmental bodies. 

You might also like: The Great Green Wall Receives an Economic Boost, But Is It Enough to Save It?

In May 2022, the 15th Conference of Parties (COP15) of the United Nations Convention to Combat Desertification (UNCCD) brought together ministers, high-level officials, the private sector, NGOs, and stakeholders to adopt resolutions that aim to drive progress in the protection and restoration of land . Among the resolutions adopted to curb desertification were the development of land restoration projects as well as increasing efforts to involve women in land management and collect gender-disaggregated data on the impacts of desertification and droughts. Promoting land-based jobs for youth and land-based youth entrepreneurship to strengthen youth participation and robust data monitoring of land restoration processes was also highlighted. Another key moment from this event was the launch of the Abidjan Legacy Programme; a US$2.5 billion project to strengthen supply chains while tackling the issues of deforestation and climate change. 

The takeaways from this are straightforward: A call to action and risk management efforts should be at the forefront of every planned proposal to curb environmental degradation. Be it land, soil, or water, efficient cooperation, and community efforts will certainly go a long way in mitigating the consequences of climate change and environmental degradation. 

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Desertification poses a serious challenge to sustainable development and humanity’s ability to survive in many areas of the world. The UNCCD’s goal is a future that avoids, reduces, and reverses desertification. Our work paves the way for a land degradation neutral world, one that fosters sustainable development to achieve the goals set in the UN’s 2030 Agenda for Sustainable Development.​

Humanity needs productive land. Yet the desertification and the mounting losses of productive land driven by human action and climate change have the potential to change the way billions of people will live, both now and later in this century.​ The warming global climate means desertification poses a challenge across the world, especially in existing drylands. As the global population increases, ever-larger areas are devoted to intensive agriculture. Widely, excessive irrigation erodes precious soil and depletes aquifers, especially in arid areas. ​

Currently, about 500 million people live within areas that have experienced desertification since the 1980s. People living in already degraded or desertified areas are increasingly negatively affected by climate change.​ Desertification aggravates existing economic, social, and environmental problems like poverty, poor health, lack of food security, biodiversity loss, water scarcity, forced migration, and lowered resilience to climate change or natural disasters.​

Addressing desertification requires long-term integrated strategies that focus on:​

• improving already degraded land​
• ongoing rehabilitation and conservation​
• managing sustainable land and water resources. ​

We work with scientists and governments to monitor land changes worldwide and drive efforts to slow land degradation. We do so by focusing on incentives that motivate and drive producers and consumers to change their behavior. ​

We advise and support the development, adoption, monitoring, and evaluation of policies designed to ensure all the world’s land-based ecosystems not only survive, but thrive, supporting the wellbeing of present and future generations.​

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Desertification: what is it and why is it one of the greatest threats of our time?

Deep trouble. Image:  REUTERS/ Mohamed Nureldin Abdallah

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Desertification has been described as the “ the greatest environmental challenge of our time ” and climate change is making it worse.

While the term may bring to mind the windswept sand dunes of the Sahara or the vast salt pans of the Kalahari, it’s an issue that reaches far beyond those living in and around the world’s deserts, threatening the food security and livelihoods of more than two billion people.

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.

This week, 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.

Ahead of the report, Carbon Brief looks at what desertification is, the role that climate change plays and what impact it is having around the world.

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”.

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 productivity 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”.

In simple terms, this means the amount of rainfall the area receives is between 5-65% of how much it loses through evaporation and transpiration from the land surface and vegetation, respectively. Any area that receives more than this is referred to as “humid”.

You can see this more clearly in the map below, 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 (pdf) – 90% of whom live in developing countries.

Drylands are particularly susceptible to land degradation because of scarce and variable rainfall as well as poor soil fertility. But what does this degradation look like?

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.

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 groundwater.

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Mix of causes

According to a recent report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), “land degradation is almost always the result of multiple interacting causes”.

The direct causes of desertification can be broadly divided between those relating to how the land is – or isn’t – managed and those relating to the climate. The former includes factors 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”.

Looking first at the role of the climate, a significant factor is that the land surface is warming more quickly than the Earth’s surface as a whole. (This is because the land has a lower “ heat capacity ” than the water in the oceans, which means it needs less heat to raise its temperature.) So, while global average temperatures are around 1.1C warmer now than in pre-industrial times , the land surface has warmed by approximately 1.7C. The chart below compares changes in land temperatures in four different records with a global average temperature since 1970 (blue line).

Global average land temperatures from four datasets: CRUTEM4 (purple), NASA (red), NOAA (yellow) and Berkeley (grey) for 1970 to the present day, relative to a 1961-90 baseline. Also shown is global temperature from the HadCRUT4 record (blue). Chart by Carbon Brief using Highcharts .

While this sustained, human-caused warming can by itself add to heat stress faced by vegetation, it is also linked to worsening extreme weather events , explains Prof Lindsay Stringer , a professor in environment and development at the University of Leeds and a lead author on the land degradation chapter of the forthcoming IPCC land report. She tells Carbon Brief:

“Climate change affects the frequency and magnitude of extreme events like droughts and floods. In areas that are naturally dry for example, a drought can have a huge impact on vegetation cover and productivity, particularly if that land is being used by high numbers of livestock. As plants die off due to lack of water, the soil becomes bare and is more easily eroded by wind, and by water when the rains do eventually come.”

(Stringer is commenting here in her role at her home institution and not in her capacity as an IPCC author. This is the case with all the scientists quoted in this article.)

Both natural variability in climate and global warming can also affect rainfall patterns around the world, which can contribute to desertification. Rainfall has a cooling effect on the land surface, so a decline in rainfall can allow soils to dry out in the heat and become more prone to erosion. On the other hand, heavy rainfall can erode soil itself and cause waterlogging and subsidence.

For example, widespread drought – and associated desertification – in the Sahel region of Africa in the second half of the 20th century has been linked to natural fluctuations in the Atlantic, Pacific and Indian Oceans , while research also suggests a partial recovery in rains was driven by warming sea surface temperatures in the Mediterranean .

Dr Katerina Michaelides , a senior lecturer in the Drylands Research Group at the University of Bristol and contributing author on the desertification chapter of the IPCC land report, describes a shift to drier conditions as the main impact of a warming climate on desertification. She tells Carbon Brief:

“The main effect of climate change is through aridification, a progressive change of the climate towards a more arid state – whereby rainfall decreases in relation to the evaporative demand – as this directly affects water supply to vegetation and soils.”

Climate change is also a contributing factor to wildfires , causing warmer – and sometimes drier – seasons that provide ideal conditions for fires to take hold. And a warmer climate can speed up the decomposition of organic carbon in soils, leaving them depleted and less able to retain water and nutrients .

As well as physical impacts on the landscape, climate change can impact on humans “because it reduces options for adaptation and livelihoods, and can drive people to overexploit the land”, notes Stringer.

That overexploitation refers to the way that humans can mismanage land and cause it to degrade. Perhaps the most obvious way is through deforestation. Removing trees can upset the balance of nutrients in the soil and takes away the roots that helps bind the soil together, leaving it at risk of being eroded and washed or blown away.

Forests also play a significant role in the water cycle – particularly in the tropics. For example, research published in the 1970s showed that the Amazon rainforest generates around half of its own rainfall. This means that clearing the forests runs the risk of causing the local climate to dry, adding to the risk of desertification.

Food production is also a major driver of desertification. Growing demand for food can see cropland expand into forests and grasslands , and use of intensive farming methods to maximise yields. Overgrazing of livestock can strip rangelands of vegetation and nutrients.

This demand can often have wider political and socioeconomic drivers, notes Stringer:

“For example, demand for meat in Europe can drive the clearance of forest land in South America. So, while desertification is experienced in particular locations, its drivers are global and coming largely from the prevailing global political and economic system.”

Local and global impacts

Of course, none of these drivers acts in isolation. 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”, says 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. He tells Carbon Brief:

“The [result is] declines in crop and livestock 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.”

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, tells Carbon Brief:

“Wildlife, especially large mammals, have limited capacities for timely adaptation to the coupled effects of climate change and desertification.”

For example, a study (pdf) of the Cholistan Desert region of Pakistan found that the “flora and fauna have been thinning out gradually with the increasing severity of desertization”. And a 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. Practically speaking, the consequences of this are less available land for grazing, and less productive soils. Ecosystems start to look different as more drought tolerant shrubs invade what used to be grasslands and more bare soil is exposed.”

This has “devastating consequences for food security, livelihoods and biodiversity”, she explains:

“Where food security and livelihoods are intimately tied to the land, the consequences of desertification are particularly immediate. 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 to desertification and drought each year. This is an area that could produce 20m tonnes of grain annually.

This has a considerable financial impact. 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 croplands” is equivalent to about 16% of its GDP .

Loss of livestock, reduced crop yields and declining food security are very visible human impacts of desertification, says Stringer:

“People cope with these kinds of challenges in various ways – by skipping meals to save food; buying what they can – which is difficult for those living in poverty with few other livelihood options – collecting wild foods, and in extreme conditions, often combined with other drivers, people move away from affected areas, abandoning the land.”

People are particularly vulnerable to the impacts of desertification where they have “insecure property rights, where there are few economic supports for farmers, where there are high levels of poverty and inequality, and where governance is weak”, Stringer adds.

Another impact of desertification is an increase in sand and dust storms. These natural phenomena – known variously as “sirocco”, “haboob”, “yellow dust”, “white storms”, and the “harmattan” – occur when strong winds blow loose sand and dirt from bare, dry soils. Research suggests that global annual dust emissions have increased by 25% between the late nineteenth century and today, with climate change and land use change the key drivers.

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 promot[ing] 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 .

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.

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.

Soil respiration indicates the soil’s ability to sustain plant growth . And typically, respiration declines with decreasing soil moisture to a point where microbial activity effectively stops . While this reduces the CO2 the microbes release, it also inhibits plant growth, which means the vegetation is taking up less CO2 from the atmosphere through photosynthesis. Overall, dry soils are more likely to be net emitters of CO2.

So as soils become more arid, they will tend to be less able to sequester carbon from the atmosphere, and thus will contribute to climate change. Other forms of degradation also generally release CO2 into the atmosphere, such as deforestation , overgrazing – by stripping the land of vegetation – and wildfires .

Mapping troubles

“Most dryland environments around the world are being affected by desertification to some extent,” says Michaelides.

But coming up with a robust global estimate for desertification is not straightforward, explains Kimutai:

“Current estimates of the extent and severity of desertification vary greatly due to missing and/or unreliable information. The multiplicity and complexity of the processes of desertification make its quantification even more difficult. Studies have used different methods based on different definitions.”

And identifying desertification is made harder because it tends to emerge relatively slowly, adds Michaelides:

“At the start of the process, desertification may be hard to detect, and because it’s slow it may take decades to realise that a place is changing. By the time it is detected, it may be hard to halt or reverse.”

Desertification across the Earth’s land surface was first mapped in a study published in the journal Economic Geography in 1977. It noted that: “For much of the world, there is little good information on the extent of desertification in individual countries”. The map – shown below – graded areas of desertification as “slight”, “moderate”, “severe” or “very severe” based on a combination of “published information, personal experience, and consultation with colleagues”.

In 1992, the United Nations Environment Programme (UNEP) published its first “ World Atlas of Desertification ” (WAD). It mapped global human-caused land degradation, drawing heavily on the UNEP-funded “ Global Assessment of Human-induced Soil Degradation ” (GLASOD). The GLASOD project was itself based on expert judgement, with more than 250 soil and environmental scientists contributing to regional assessments that fed into its global map, which it published in 1991.

The GLASOD map, shown below, details the extent and degree of land degradation across the world. It categorised the degradation into chemical (red shading), wind (yellow), physical (purple) or water (blue).

While GLASOD was also used for the second WAD , published in 1997, the map came under criticism for a lack of consistency and reproducibility. Subsequent datasets, such as the “ Global Assessment of Land Degradation and Improvement ” (GLADA), have benefitted from the addition of satellite data .

Nevertheless, by the time the third WAD – produced by the Joint Research Centre of the European Commission – came around two decades later, the authors “decided to take a different path”. As the report puts it:

“Land degradation cannot be globally mapped by a single indicator or through any arithmetic or modelled combination of variables. A single global map of land degradation cannot satisfy all views or needs.”

Instead of a single metric, the atlas considers a set of “14 variables often associated with land degradation”, such as aridity, livestock density, tree loss and decreasing land productivity.

As such, the map below – taken from the Atlas – does not show land degradation itself, but the “convergence of evidence” of where these variables coincide. The parts of the world with the most potential issues (shown by orange and red shading) – such as India, Pakistan, Zimbabwe and Mexico – are thus identified as particularly at risk from degradation.

As desertification cannot be characterised by a single metric, it is also tricky to make projections for how rates of degradation could change in the future.

In addition, there are numerous socio-economic drivers that will contribute. For example, the number of people directly affected by desertification is likely to increase purely because of population growth. The population living in drylands across the world is projected to increase by 43% to four billion by 2050.

The impact of climate change on aridity is also complicated. A warmer climate is generally more able to evaporate moisture from the land surface – potentially increasing dryness in combination with hotter temperatures.

However, climate change will also affect rainfall patterns, and a warmer atmosphere can hold more water vapour, potentially increasing both average and heavy rainfall in some areas.

There is also a conceptual question of distinguishing long-term changes in the dryness of an area with the relatively short-term nature of droughts.

In general, the global area of drylands is expected to expand as the climate warms. Projections under the RCP4.5 and RCP8.5 emissions scenarios suggest drylands will increase by 11% and 23% , respectively, compared to 1961-90. This would mean drylands could make up either 50% or 56%, respectively, of the Earth’s land surface by the end of this century, up from around 38% today.

This expansion of arid regions will occur principally “over southwest North America, the northern fringe of Africa, southern Africa, and Australia”, another study says, while “major expansions of semiarid regions will occur over the north side of the Mediterranean, southern Africa, and North and South America”.

Research also shows that climate change is already increasing both the likelihood and severity of droughts around the world . This trend is likely to continue. For example, one study , using the intermediate emissions scenario “RCP4.5”, projects “large increases (up to 50%–200% in a relative sense) in frequency for future moderate and severe drought over most of the Americas, Europe, southern Africa, and Australia”.

Another study notes that climate model simulations “suggest severe and widespread droughts in the next 30–90 years over many land areas resulting from either decreased precipitation and/or increased evaporation”.

However, it should be noted that not all drylands are expected to get more arid with climate change. The map below, for example, shows the projected change for a measure of aridity (defined as the ratio of rainfall to potential evapotranspiration , PET) by 2100 under climate model simulations for RCP8.5. The areas shaded red are those expected to become drier – because PET will increase more than rainfall – while those in green are expected to become wetter. The latter includes much of the Sahel and East Africa, as well as India and parts of northern and western China.

Climate model simulations also suggest that rainfall, when it does occur, will be more intense for almost the entire world , potentially increasing the risks of soil erosion. Projections indicate that most of the world will see a 16-24% increase in heavy precipitation intensity by 2100.

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”.

Stopping desertification before it starts requires measures to “protect against soil erosion, to prevent vegetation loss, to prevent overgrazing or land mismanagement”, she explains:

“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.”

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 in the video below, is a hierarchy of responses: first 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.

“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. She tells Carbon Brief:

“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.

But these measures can’t just be applied anywhere, notes Akhtar-Schuster:

“Because SLM has to be adapted to local circumstances there is no such thing as a one size fits all toolkit to avoid or reduce desertification. However, all these locally adapted tools will have the best effects if they are embedded in an integrated national land use planning system.”

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:

“Solutions therefore need to identify who ‘wins’ and who ‘loses out’ and should incorporate strategies that compensate or minimise inequities.”

“Everyone forgets that last part about equity and fairness,” she adds. The other aspect that has also been overlooked historically is getting community buy-in on proposed solutions, says Stringer.

Research shows that using traditional knowledge can be particularly beneficial for tackling land degradation. Not least because communities living in drylands have done so successfully for generations, despite the tricky environmental conditions.

This idea is increasingly being taken on board, says Stringer – a response to “top-down interventions” that have proved “ineffective” because of a lack of community involvement.

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20.2: Desertification

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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. [2] It is caused by a variety of factors, such as climate change and human activities. Desertification is a significant global ecological and environmental problem. [3]

Global Desertification Vulnerability Map

Lake Chad in a 2001 satellite image, with the actual lake in blue. The lake has shrunk by 94% since the 1960s. [1]

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 [2] of these is that of the Princeton University Dictionary which defines it as “the process of fertile land transforming into desert typically as a result of deforestation, drought or improper/inappropriate agriculture” [4]

The earliest known discussion of the topic arose soon after the French colonization of West Africa, when the Comité d’Etudes commissioned a study on desséchement progressif to explore the prehistoric expansion of the Sahara Desert. [5]

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. [6]

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. [7] [3] [8] [9] [10] 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. [11] [12]

Areas affected

Sun, Moon and Telescopes above the Desert. [13]

Drylands occupy approximately 40–41% of Earth’s land area [14] [15] and are home to more than 2 billion people. [15] 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. [16] [17]

As of 1998, the then-current degree of southward expansion of the Sahara was not well known, due to a lack of recent, measurable expansion of the desert into the Sahel at the time. [18]

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. [19] One outcome of this observation suggests an optimal planting strategy for agriculture in arid environments. [20]

A herd of goats in Norte Chico, Chile. Overgrazing of drylands is one of the primary causes of desertification.

A shepherd guiding his sheep through the high desert outside of Marrakech, Morocco.

The immediate cause is the removal 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. [21] 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. Alternatively, recent research has suggested that the movement and migration of large herds of livestock and wildlife has an integral role in the preservation of vegetation and soil fertilization, and that the removal of livestock and wildlife (largely by human influence) has been the main driver of increasing desertification. [22] [23] [24] [25] [26]

At least 90% of the inhabitants of drylands live in developing nations, where they also suffer from poor economic and social conditions. [16] 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. [27]

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 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. [28]

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. [29] [30]

Countermeasures and prevention

Anti-sand shields in north Sahara, Tunisia.

Jojoba plantations, such as those shown, have played a role in combating edge effects of desertification in the Thar Desert, India. [ citation needed ]

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. [ citation needed ] Another issue is a lack of political will, and lack of funding to support land reclamation and anti-desertification programs. [31]

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. [32] [33]

Reforestation gets at one of the root causes of desertification and isn’t just a treatment of the symptoms. Environmental organizations [34] 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. [35]

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. [36]

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 of flowing within the trenches and causing erosion. Stone walls are placed around the trenches to prevent the trenches of closing up again. The method was invented by Peter Westerveld. [37]

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. [38]

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. [39]

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. [40]

Managed grazing methods are argued to be able to restore grasslands, thereby decreasing atmospheric CO 2 levels. [41]

Managed grazing

Restoring grasslands store CO 2 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. [42] A method proposed to restore grasslands uses fences with many small paddocks and moving herds from one paddock to another after a day a two in order to mimick natural grazers and allowing the grass to grow optimally. [42] [43] [44] It is estimated that increasing the carbon content of the soils in the world’s 3.5 billion hectares of agricultural grassland would offset nearly 12 years of CO 2 emissions. [42] Allan Savory, as part of holistic management, claims that 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. [41]

Visible soil erosion outside of Leuchars.

Mitigation:

• Arid Lands Information Network—Kenya
• Biochar Fertilisation using carbon
• United Nations Convention to Combat Desertification
• Desert greening
• Ecological engineering
• Green Wall of China
• Holistic management
• ^ Mayell, Hillary (April 26, 2001). “Shrinking African Lake Offers Lesson on Finite Resources” . National Geographic News . Retrieved 20 June 2011.
• ^ a b Geist (2005), p. 2
• ^ a b Geist (2005), p. 4
• ^ Google Dictionary (2012)
• ^ Mortimore, Michael (1989). Adapting to drought: farmers, famines, and desertification in west Africa . Cambridge University Press. p. 12. ISBN 978-0-521-32312-3.
• ^ United States Geological Survey, “Desertification” , 1997
• ^ LOWDERMILK, W C. “CONQUEST OF THE LAND THROUGH SEVEN THOUSAND YEARS” . Soil Conservation Service . United States Department of Agriculture. Retrieved 9 April 2014.
• ^ Whitford, Walter G. (2002). Ecology of desert systems . Academic Press. p. 277. ISBN 978-0-12-747261-4.
• ^ Bogumil Terminski (2011), Towards Recognition and Protection of Forced Environmental Migrants in the Public International Law: Refugee or IDPs Umbrella, Policy Studies Organization (PSO), Washington.
• ^ Geist, Helmut. “The causes and progression of desertification” . Antony Rowe Ltd . Ashgate publishing limited. Retrieved 6 July 2013.
• ^ Dregne, H.E. “Desertification of Arid Lands” . Columbia University. Retrieved 3 December 2013.
• ^ “Sun, Moon and Telescopes above the Desert” . ESO Picture of the Week . Retrieved 30 April 2012.
• ^ Bauer (2007), p. 78
• ^ a b Johnson et al (2006), p. 1
• ^ a b Holtz (2007)
• ^ World Bank (2009). Gender in agriculture sourcebook . World Bank Publications. p. 454. ISBN 978-0-8213-7587-7.
• ^ Klausmeier, Christopher (1999). “Regular and irregular patterns in semiarid vegetation”. Science 284 (5421): 1826–1828. doi: 10.1126/science.284.5421.1826 .
• ^ Straw squares method: planting with empty spaces in between plants to combat desertification
• ^ Geeson, Nichola et al (2002). Mediterranean desertification: a mosaic of processes and responses . John Wiley & Sons. p. 58. ISBN 978-0-470-84448-9.
• ^ Savory, Allan. “Allan Savory: How to green the world’s deserts and reverse climate change” .
• ^ Savory, Allan. “Holistic resource management: a conceptual framework for ecologically sound economic modelling” . Ecological Economics . Elsevier Science Publishers. Retrieved 10 March 2013.
• ^ Butterfield, Jody (2006). Holistic Management Handbook: Healthy Land, Healthy Profits, Second Edition . Island Press. ISBN 1559638850.
• ^ Savory, Allan. “Response to request for information on the “science” and “methodology” underpinning Holistic Management and holistic planned grazing” . Savory Institute . Retrieved 10 March 2013.
• ^ Drury, Steve. “Large-animal extinction in Australia linked to human hunters” . Earth-Pages. Retrieved 9 June 2014.
• ^ Dobie, Ph. 2001. “Poverty and the drylands”, in Global Drylands Imperative, Challenge paper, Undp, Nairobi (Kenya) 16 p.
• ^ Cornet A., 2002. Desertification and its relationship to the environment and development: a problem that affects us all. In: Ministère des Affaires étrangères/adpf, Johannesburg. World Summit on Sustainable Development. 2002. What is at stake? The contribution of scientists to the debate: 91-125..
• ^ Pasternak, Dov & Schlissel, Arnold (2001). Combating desertification with plants . Springer. p. 20. ISBN 978-0-306-46632-8.
• ^ Briassoulis, Helen (2005). Policy integration for complex environmental problems: the example of Mediterranean desertification . Ashgate Publishing. p. 161. ISBN 978-0-7546-4243-5.
• ^ Briassoulis, Helen (2005). Policy integration for complex environmental problems: the example of Mediterranean desertification . Ashgate Publishing. p. 237. ISBN 978-0-7546-4243-5.
• ^ Techniques for Desert Reclamation by Andrew S. Goudie
• ^ Desert reclamation projects
• ^ For example, Eden Reforestation Projects .
• ^ Arid sandy soils becoming consolidated; zai-system
• ^ Westerveld’s Naga Foundation
• ^ List of plants to halt desertification; some of which may be soil-fixating
• ^ Rethinking landscapes, Nicol-André Berdellé July 2011 H2O magazine
• ^ “Sprouting Trees From the Underground Forest — A Simple Way to Fight Desertification and Climate Change – Water Matters – State of the Planet” . Blogs.ei.columbia.edu. 2011-10-18. Retrieved 2012-08-11.
• ^ a b “How cows could repair the world” . nationalgeographic.com. March 6, 2013. Retrieved May 5, 2013.
• ^ a b c “How fences could save the planet” . newstatesman.com. January 13, 2011. Retrieved May 5, 2013.
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• Provided by : Wikipedia. Located at : http://en.Wikipedia.org/wiki/Desertification . License : CC BY-SA: Attribution-ShareAlike

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Desertification and its effects

Desertification is a phenomenon that ranks among the greatest environmental challenges of our time.

Although desertification can include the encroachment of sand dunes on land, it doesn’t refer to the advance of deserts. Rather, it is the persistent degradation of dryland ecosystems by climate change and mainly human activities: unsustainable farming that depletes the nutrients in the soil, mining, overgrazing (animals eat away grasses and erode topsoil with their hooves) and clear-cutting of land, when the tree and plant cover that binds the soil is removed. It occurs when trees and bushes are stripped away for fuelwood and timber, or to clear land for cultivation.

Wind and water erosion aggravate the damage, carrying away topsoil and leaving behind a highly infertile mix of dust and sand. It is the combination of these factors that transforms degraded land into desert. 

Impact of desertification in nature and population

Desertification is a global issue, with serious implications worldwide for biodiversity, eco-safety, poverty eradication, socio-economic stability and sustainable development.

Drylands are already fragile. As they become degraded, the impact on people, livestock and environment can be devastating. Some 50 million people may be displaced within the next 10 years as a result of desertification.

The issue of desertification is not new though — it played a significant role in human history, contributing to the collapse of several large empires, and the displacement of local populations. But today, the pace of arable land degradation is estimated at 30 to 35 times the historical rate.

Some two billion people depend on ecosystems in dry land areas, 90% of whom live in developing countries. A downward spiral is created in many underdeveloped countries, where overpopulation causes pressure to exploit drylands for farming. These marginally productive regions are overgrazed, the land is exhausted and groundwater is overdrafted.

Some actions could help to reduce desertification:

• Reforestation and tree regeneration.
• Water management — saving, reuse of treated water, rainwater harvesting, desalination, or direct use of seawater for salt-loving plants.
• Buttressing the soil through the use of sand fences, shelter belts, woodlots and windbreaks.
• Enrichment and hyper-fertilizing of soil through planting.
• Farmer Managed Natural Regeneration (FMNR), enabling native sprouting tree growth through selective pruning of shrub shoots. The residue from pruned tress can be used to provide mulching for fields thus increasing soil water retention and reducing evaporation.

Towards sustainable development thanks to UNCCD

Desertification, along with climate change and the loss of biodiversity, were identified as the greatest challenges to sustainable development during the 1992 Rio Earth Summit.

Two years later, in 1994, the General Assembly established the United Nations Convention to Combat Desertification (UNCCD) , the sole legally binding international agreement linking environment and development to sustainable land management, and declared 17 June "World Day to Combat Desertification and Drought" by its resolution A/RES/49/115 .

Later on, in 2007, the UN General Assembly declared 2010-2020 the United Nations Decade for Deserts and the fight against Desertification to mobilize global action to fight land degradation, led again by the UNCCD Secretariat.

UNCCD's 197 parties (169 affected by desertification) work together to maintain and restore land and soil productivity, and to mitigate the effects of drought in drylands — the arid, semi-arid and dry sub-humid areas, where some of the most vulnerable ecosystems and peoples can be found.

Since 2017, the UNCCD and its partners supported about 70 drought-prone countries to develop national action plans to reduce drought disasters.

UNCCD Official website

Other links related to UNCCD

• About the Convention  
• UNCCD 2018-2030 Strategic Framework  
• Drought Toolbox

Desertification

• Reference work entry
• Cite this reference work entry

• Monique M. Mainguet  

Part of the book series: Encyclopedia of Earth Science ((EESS))

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Evolution of the definition

The word desertification has a Latin origin: - fication , which means the action of doing (or creating) comes from fieri , the passive form of the verb facere , to do, while desert is derived from both the adjective desertus , meaning uninhabited, and the noun desertum , a desert area. Quoting Budge, El-Baz (1988) wrote:

The word desert originated as an ancient Egyptian hieroglyph pronounced tesert , meaning a place that was forsaken or left behind... From this came the Latin verb desere , to abandon. From the latter came desertum , a waste place or wilderness, and desertus , meaning abandoned or relinquished. This in itself implies that the desert had [once] been a better place. In it, there was life - in some places teeming life. There was much vegetation, grasses and trees, many animals and human beings. Then something happened, and the place became a wasteland; it was deserted. In a wider sense, desertification can signify an environmental crisis which produces...

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Cross-references

Arid Zone Management and Problems ; Carrying Capacity ; Ecological Stress ; Off-the-Road Vehicles (ORVs) ; Salinization, Salt Seepage ; Soil Erosion ; Wadis (Arroyos)

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1972, in the meaning defined above

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• Published: 22 June 2020

Desertifying deserts

• Jaime Martínez-Valderrama   ORCID: orcid.org/0000-0001-5859-5674 1 ,
• Emilio Guirado   ORCID: orcid.org/0000-0001-5348-7391 1 &
• Fernando T. Maestre   ORCID: orcid.org/0000-0002-7434-4856 1 , 2  

Nature Sustainability volume  3 ,  pages 572–575 ( 2020 ) Cite this article

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The current definition of desertification excludes hyper-arid zones given their lack of economic activity. However, the 101 million people living there, ongoing land degradation associated with the use of groundwater for intensive agriculture and climate-change-induced aridity call for a revision of this definition.

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Acknowledgements

This work was funded by the European Research Council grant agreement no. 647038 (BIODESERT). F.T.M. acknowledges support from Generalitat Valenciana (CIDEGENT/2018/041). The authors would like to thank D. J. Eldridge for his valuable comments and revisions of the text.

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Martínez-Valderrama, J., Guirado, E. & Maestre, F.T. Desertifying deserts. Nat Sustain 3 , 572–575 (2020). https://doi.org/10.1038/s41893-020-0561-2

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ENCYCLOPEDIC ENTRY

Deserts are areas that receive very little precipitation.

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Deserts are areas that receive very little precipitation . People often use the adjectives “hot,” “dry,” and “empty” to describe deserts , but these words do not tell the whole story. Although some deserts are very hot, with daytime temperatures as high as 54°C (130°F), other deserts have cold winters or are cold year-round. And most deserts , far from being empty and lifeless, are home to a variety of plants, animals, and other organisms . People have adapted to life in the desert for thou sands of years. One thing all deserts have in common is that they are arid , or dry. Most experts agree that a desert is an area of land that receives no more than 25 centimeters (10 inches) of precipitation a year. The amount of evaporation in a desert often greatly exceeds the annual rainfall. In all deserts , there is little water available for plants and other organisms . Deserts are found on every continent and cover about one-fifth of Earth’s land area. They are home to around 1 billion people—one-sixth of the Earth’s population. Although the word “ desert ” may bring to mind a sea of shifting sand , dunes cover only about 10 percent of the world’s deserts . Some deserts are mountainous. Others are dry expanses of rock, sand , or salt flats . Kinds of Deserts The world’s deserts can be divided into five types—subtropical, coastal, rain shadow , interior, and polar. Deserts are divided into these types according to the causes of their dryness. Subtropical Deserts Subtropical deserts are caused by the circulation patterns of air masses . They are found along the Tropic of Cancer , between 15 and 30 degrees north of the Equator , or along the Tropic of Capricorn , between 15 and 30 degrees south of the Equator . Hot, moist air rises into the atmosphere near the Equator . As the air rises, it cools and drops its moisture as heavy tropical rains. The resulting cooler, drier air mass moves away from the Equator . As it approaches the tropics, the air descends and warms up again. The descending air hinders the formation of clouds , so very little rain falls on the land below. The world’s largest hot desert , the Sahara, is a subtropical desert in northern Africa. The Sahara Desert is almost the size of the entire continental United States. Other subtropical deserts include the Kalahari Desert in southern Africa and the Tanami Desert in northern Australia. Coastal Deserts Cold ocean currents contribute to the formation of coastal deserts . Air blowing toward shore , chilled by contact with cold water, produces a layer of fog . This heavy fog drifts onto land. Although humidity is high, the atmospheric changes that normally cause rainfall are not present. A coastal desert may be almost totally rainless, yet damp with fog . The Atacama Desert , on the Pacific shores of Chile, is a coastal desert . Some areas of the Atacama are often covered by fog . But the region can go decades without rainfall. In fact, the Atacama Desert is the driest place on Earth. Some weather stations in the Atacama have never recorded a drop of rain. Rain Shadow Deserts Rain shadow deserts exist near the leeward slopes of some mountain ranges . Leeward slopes face away from prevailing winds . When moisture-laden air hits a mountain range , it is forced to rise. The air then cools and forms clouds that drop moisture on the windward ( wind -facing) slopes. When the air moves over the mountaintop and begins to descend the leeward slopes, there is little moisture left. The descending air warms up, making it difficult for clouds to form. Death Valley , in the U.S. states of California and Nevada, is a rain shadow desert . Death Valley , the lowest and driest place in North America, is in the rain shadow of the Sierra Nevada mountains.

Interior Deserts Interior deserts , which are found in the heart of continents , exist because no moisture-laden winds reach them. By the time air masses from coastal areas reach the interior, they have lost all their moisture. Interior deserts are sometimes called inland deserts . The Gobi Desert , in China and Mongolia, lies hundreds of kilometers from the ocean. Winds that reach the Gobi have long since lost their moisture. The Gobi is also in the rain shadow of the Himalaya mountains to the south. Polar Deserts Parts of the Arctic and the Antarctic are classified as deserts . These polar deserts contain great quantities of water, but most of it is locked in glaciers and ice sheets year-round. So, despite the presence of millions of liters of water, there is actually little available for plants and animals. The largest desert in the world is also the coldest. Almost the entire continent of Ant arctica is a polar desert , experiencing little precipitation . Few organisms can withstand the freezing, dry climate of Ant arctica . Changing Deserts The regions that are deserts today were not always so dry. Between 8000 and 3000 BCE, for example, the Sahara had a much milder, moister climate . Climatologists identify this period as the “ Green Sahara .” Archaeological evidence of past settlements is abundant in the middle of what are arid , unproductive areas of the Sahara today. This evidence includes rock paintings, graves , and tools. Fossils and artifacts show that lime and olive trees, oaks, and oleanders once bloomed in the Sahara. Elephants, gazelles, rhinos, giraffes, and people used stream-fed pools and lakes. There were three or four other moist periods in the Sahara. Similar lush conditions existed as recently as 25,000 years ago. Between the moist periods came periods of dryness much like today’s. The Sahara is not the only desert to have dramatic climate change . The Ghaggar River , in what is now India and Pakistan, was a major water source for Mohenjo-daro , an urban area of the ancient Indus Valley Civilization . Over time, the Ghaggar changed course and now only flows during the rainy monsoon season. Mohenjo-daro is now a part of the vast Thar and Cholistan deserts . Most of Earth’s deserts will continue to undergo periods of climate change . Desert Characteristics Humidity —water vapor in the air—is near zero in most deserts . Light rains often e vaporate in the dry air, never reaching the ground. Rainstorms sometimes come as violent cloudbursts . A cloudburst may bring as much as 25 centimeters (10 inches) of rain in a single hour—the only rain the desert gets all year. Desert humidity is usually so low that not enough water vapor exists to form clouds . The sun’s rays beat down through cloudless skies and bake the land. The ground heats the air so much that air rises in waves you can actually see. These shimmering waves confuse the eye, causing travelers to see distorted images called mirages . Temperature extremes are a characteristic of most deserts . In some deserts , temperatures rise so high that people are at risk of dehydration and even death. At night, these areas cool quickly because they lack the insulation provided by humidity and clouds . Temperatures can drop to 4°C (40°F) or lower. In the Chihuahuan Desert , in the United States and Mexico, temperatures can vary by dozens of degrees in one day. Daytime temperatures in the Chihuahua can climb beyond 37°C (100°F), while nighttime temperatures can dip below freezing (0°C or 32°F).

Winds at speeds of about 100 kilometers per hour (60 miles per hour) sweep through some deserts . With little vegetation to block it, the wind can carry sand and dust across entire continents and even oceans. Windstorms in the Sahara hurl so much material into the air that African dust sometimes crosses the Atlantic Ocean. Sunsets on the Atlantic coast of the U.S. state of Florida, for example, can be tinted yellow. First-time visitors to deserts are often amazed by the unusual landscapes , which may include dunes , towering bare peaks, flat-topped rock formations, and smoothly polished canyons . These features differ from those of wetter regions, which are often gently rounded by regular rainfall and softened by lush vegetation . Water helps carve desert lands. During a sudden storm, water scours the dry, hard-baked land, gathering sand , rocks, and other loose material as it flows. As the muddy water roars downhill, it cuts deep channels, called arroyos or wadis . A thunderstorm can send a fast-moving torrent of water—a flash flood —down a dry arroyo . A flash flood like this can sweep away anything and anyone in its path. Many desert regions di scourage visitors from hiking or camping in arroyos for this reason. Even urban areas in deserts can be vulnerable to flash floods . The city of Jeddah, Saudi Arabia, sits in the Arabian Desert . In 2011, Jeddah was struck by a sudden thunderstorm and flash flood . Roads and buildings were washed away, and more than 100 people died. Even in a desert , water and wind eventually wear away softer rock. Sometimes, rock is carved into tablelike formations such as mesas and buttes . At the foot of these formations, water drops its burden of gravel , sand , and other sediment, forming deposits called alluvial fans . Many deserts have no drainage to a river , lake, or ocean. Rainwater, including water from flash floods , collects in large depressions called basins . The shallow lakes that form in basins eventually e vaporate , leaving playas , or salt-surfaced lake beds. Playas , also called sinks, pans, or salt flats , can be hundreds of kilometers wide. The Black Rock Desert in the U.S. state of Nevada, for instance, is all that remains of the prehistoric Lake Lahontan. The hard, flat surface of desert salt flats are often ideal for car racing. In 1997, British pilot Andy Green set the land speed record in Black Rock Desert —1,228 kilometers per hour (763 miles per hour). Green’s vehicle, the ThrustSSC, was the first car to break the sound barrier . Wind is the primary sculptor of a desert ’s hills of sand , called dunes . Wind builds dunes that rise as high as 180 meters (590 feet). Dunes migrate constantly with the wind . They usually shift a few meters a year, but a particularly violent sandstorm can move a dune 20 meters (65 feet) in a single day. Sandstorms may bury everything in their path—rocks, fields, and even towns. One legend holds that the Persian Emperor Cambyses II sent an army of 50,000 men to the Siwa Oasis in western Egypt around 530 BCE. Halfway there, an enormous sandstorm swallowed the entire group. Archaeologists in the Sahara have been unsuccessfully looking for the “Lost Army of Cambyses” ever since. Water in the Desert Rain is usually the main source of water in a desert , but it falls very rarely. Many desert dwellers rely on groundwater , stored in aquifers below the surface. Groundwater comes from rain or other precipitation , like snow or hail. It seeps into the ground, where it can remain for thou sands of years. Underground water sometimes rises to the surface, forming springs or seeps. A fertile green area called an oasis , or cienega , may exist near such a water source. About 90 major, inhabited oases dot the Sahara. These oases are supported by some of the world’s largest supplies of underground water. People, animals, and plants all surround these oases, which provide stable access to water, food, and shelter. When groundwater doesn’t seep to the surface, people often drill into the ground to get to it. Many desert cities, from the American Southwest to the Middle East , rely heavily on such aquifers to fill their water needs. Rural Israeli communities called kibbutzim rely on aquifers to furnish water for crops and even fish farming in the dry Negev Desert .

Drilling into aquifers provides water for drinking, agriculture , industry , and hygiene . However, it comes at a cost to the environment. Aquifers take a long time to refill. If desert communities use groundwater faster than it is replenished, water shortages can occur. The Mojave Desert , in southern California and Nevada, for instance, is sinking due to aquifer depletion . The booming desert communities of Las Vegas, Nevada, and California’s “ Inland Empire ” are using water faster than the aquifer is being refilled. The water level in the aquifer has sunk as much as 30 meters (100 feet) since the 1950s, while the land above the aquifer has sunk as much as 10 centimeters (4 inches). Rivers sometimes provide water in a desert . The Colorado River , for instance, flows through three deserts in the American Southwest: the Great Basin , the Sonoran, and the Mojave. Seven states—Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona, and California—rely on the river for some of their water supply. People often modify rivers to help distribute and store water in a desert . The Nile River ecosystem dominates the eastern part of the Sahara Desert , for instance. The Nile provides the most reliable, plentiful source of freshwater in the region. Between 1958 and 1971, the government of Egypt constructed a massive dam on the Upper Nile (the southern part of the river , near Egypt’s border with Sudan). The Aswan Dam harnesses the power of the Nile for hydroelectricity used in in dustry . It also stores water in a manmade lake, Lake Nasser, to protect the country’s communities and agriculture against drought . Construction of the Aswan High Dam was a huge engineering project. Local desert communities can divert rivers on a smaller scale. Throughout the Middle East , communities have dug artificial wadis , where freshwater can flow during rainy seasons. In countries like Yemen, artificial wadis can carry enough water for whitewater rafting trips during certain times of the year. When deserts and water supplies cross state and national borders, people often fight over water rights . This has happened among the states in the Colorado River Basin , which have negotiated for many years over the division of the river ’s water. Rapidly expanding populations in California, Nevada, and Arizona have compounded the problem. Agreements that were made in the early 20th century failed to account for Native American water rights . Mexican access to the Colorado, which has its delta in the Mexican state of Baja California, was ignored. Desert agriculture , including cotton production, demanded a large portion of the Colorado. The environmental impact of dams was not considered when the structures were built. States of the Colorado River Basin continue to negotiate today to prepare for population growth, agricultural development , and the possibility of future droughts . Life in the Desert Plants and animals adapt to desert habitats in many ways. Desert plants grow far apart, allowing them to obtain as much water around them as possible. This spacing gives some desert regions a desolate appearance. In some deserts , plants have unique leaves to capture sunlight for photosynthesis , the process plants use to make food. Small pores in the leaves, called stomata , take in carbon dioxide . When they open, they also release water vapor . In the desert , all these stomata would quickly dry out a plant. So desert plants typically have tiny, waxy leaves. Cactuses have no leaves at all. They produce food in their green stems. Some desert plants, such as cactuses , have shallow, wide-spreading root systems . The plants soak up water quickly and store it in their cells . Saguaro cactuses , which live in the Sonoran Desert of Arizona and northern Mexico, expand like accordions to store water in the cells of their trunks and branches. A large saguaro is a living storage tower that can hold hundreds of liters of water. Other desert plants have very deep roots. The roots of a mesquite tree, for example, can reach water more than 30 meters (100 feet) underground. Mesquites , saguaros, and many other desert plants also have thorns to protect them from grazing animals . Many desert plants are annuals , which means they only live for one season. Their seeds may lie dormant for years during long dry spells. When rain finally comes, the seeds sprout rapidly. Plants grow, bloom, produce new seeds, and die, often in a short span of time. A soaking rain can change a desert into a wonderland of flowers almost overnight.

Animals that have adapted to a desert environment are called xerocoles . Xerocoles include species of insects, reptiles, birds, and mammals. Some xerocoles avoid the sun by resting in scarce shade. Many escape the heat in cool burrows they dig in the ground. The fennec fox, for example, is native to the Sahara Desert . Fennec fox communities work together to dig large burrows , some as large as 93 square meters (1,000 square feet). Dew can collect in these burrows , providing the foxes with fresh water. However, fennec foxes have adapted so they do not have to drink water at all: Their kidneys retain enough water from the food they eat. Most xerocoles are nocturnal . They sleep through the hot days and do their hunting and foraging at night. Deserts that seem desolate during the day are very active in the cool nighttime air. Foxes, coyotes, rats, and rabbits are all nocturnal desert mammals. Snakes and lizards are familiar desert reptiles. Insects such as moths and flies are abundant in the desert . Most desert birds are restricted to areas near water, such as river banks. However, some birds, such as the roadrunner, have adapted to life in the desert . The roadrunner, native to the deserts of North America, obtains water from its food. Some xerocoles have bodies that help them handle the heat. A desert tortoise’s thick shell insulates the animal and reduces water loss. Sand lizards, native to the deserts of Europe and Asia, are nicknamed “dancing lizards” because of the way they quickly lift one leg at a time off the hot desert sand . A jackrabbit’s long ears contain blood vessels that release heat. Some desert vultures urinate on their own legs, cooling them by e vaporation . Many desert animals have developed ingenious ways of getting the water they need. The thorny devil, a lizard that lives in the Australian Outback , has a system of tiny grooves and channels on its body that lead to its mouth. The lizard catches rain and dew in these grooves and sucks them into its mouth by gulping. Camels are very efficient water users. The animals do not store water in their humps, as people once believed. The humps store fat. Hydrogen molecules in the fat combine with inhaled oxygen to form water. During a shortage of food or water, camels draw upon this fat for nutrition and moisture. Dromedary camels, native to the Arabian and Sahara deserts , can lose up to 30 percent of their body weight without harm. Camels, nicknamed “ships of the desert ,” are widely used for transportation, meat, and milk in the Maghreb (a region in Northwest Africa), the Middle East , and the Indian Sub continent . People and the Desert About 1 billion people live in deserts . Many of these people rely on centuries-old customs to make their lives as comfortable as possible Civilizations throughout the Middle East and Maghreb have adapted their clothing to the hot, dry conditions of the Sahara and Arabian deserts . Clothing is versatile and based on robes made of rectangles of fabric. Long-sleeved, full-length, and often white, these robes shield all but the head and hands from the wind , sand , heat, and cold. White reflects sunlight, and the loose fit allows cooling air to flow across the skin. These robes of loose cloth can be adjusted (folded) for length, sleeves, and pockets, depending on the wearer and the climate . A thobe is a full-length, long-sleeved white robe. An abaya is a sleeveless cloak that protects the wearer from dust and heat. A djebba is a short, square pullover shirt worn by men. A kaffiyeh is a rectangular piece of cloth folded loosely around the head to protect the wearer from sun exposure, dust , and sand . It can be folded and unfolded to cover the mouth, nose, and eyes. Kaffiyehs are secured around the head with a cord called an agal . A turban is similar to a kaffiyeh , but wrapped around the head instead of being secured with an agal . Turbans are also much longer—up to six meters (20 feet)! Desert dwellers have also adapted their shelters for the unique climate . The ancient Anasazi peoples of the southwestern United States and northern Mexico constructed huge apartment complexes in the rocky cliffs of the Sonoran Desert . These cliff dwellings, sometimes dozens of meters off the ground, were constructed with thick, earthen walls that provided insulation . Although temperatures outside varied greatly from day to night, temperatures inside did not. Tiny, high windows let in only a little light and helped keep out dust and sand .

The need to find food and water has led many desert civilizations to become nomadic . Nomadic cultures are those that do not have permanent settlements. In the deserts of the Middle East and Asia, nomadic tent communities continue to flourish . Tent walls are made of thick, sturdy cloth that can keep out sand and dust , but also allow cool breezes to blow through. Tents can be rolled up and transported on pack animals (usually horses, donkeys, or camels). Nomads move frequently so their flocks of sheep and goats will have water and grazing land. Besides animals like camels and goats, a variety of desert vegetation is found in oases and along the shores of rivers and lakes. Figs, olives, and oranges thrive in desert oases and have been harvested for centuries. Some desert areas rely on resources brought from more fertile areas—food trucked in from distant farmlands or, more frequently, water piped from wetter regions. Large areas of desert soil are irrigated by water pumped from underground sources or brought by canal from distant rivers or lakes. The booming Inland Empire of southeastern California is made up of deserts (the Mojave and the Sonoran) that rely on water for agriculture , in dustry , and residential development. Canals and aqueducts supply the Inland Empire with water from the Colorado River , to the east, and the Sierra Nevada snowmelt to the north. A variety of crops can thrive in these irrigated oases. Sugar cane is a very water-intensive crop mostly harvested in tropical regions. However, sugar cane is also harvested in the deserts of Pakistan and Australia. Water for irrigation is transported from hundreds of kilometers away, or drilled from hundreds of meters underground. Oases in desert climates have been popular spots for tourists for centuries. Spas ring the Dead Sea, a saline lake in the Judean Desert of Israel and Jordan. The Dead Sea has had flourishing spas since the time of King David . Air transportation and the development of air conditioning have made the sunny climate of deserts even more accessible and attractive to people from colder regions. Populations at resorts like Palm Springs , California, and Las Vegas, Nevada, have boomed. Desert parks, such as Death Valley National Park, California, attract thou sands of visitors every year. People who migrate to the warm, dry desert for the winter and return to more temperate climates in the spring are sometimes called “ snowbirds .” In rural areas, hot days turn into cool nights, providing welcome relief from the scorching sun. But in cities, structures like buildings, roads, and parking lots hold on to daytime heat long after the sun sets. The temperature stays high even at night, making the city an “island” of heat in the middle of the desert . This is called the urban heat island effect. It is less pronounced in desert cities than cities built in heavily forested areas. Cities like New York City, New York, and Atlanta, Georgia, can be 5 degrees warmer than the surrounding area. New York was built on wetland habitat , and Atlanta was built in a wooded area. Cities like Phoenix, Arizona, or Kuwait City, Kuwait, have a much smaller urban heat island effect. They may be only slightly warmer than the surrounding desert . Deserts can hold economically valuable resources that drive civilizations and economies. The most notable desert resource in the world is the massive oil reserves in the Arabian Desert of the Middle East . More than half of the proven oil reserves in the world lie beneath the sands of the Arabian Desert , mostly in Saudi Arabia. The oil in dustry draws companies, migrant workers, engineers, geologists , and biologists to the Middle East . Desertification Desertification is the process of productive cropland turning into non-productive, desert -like environments. Desertification usually happens in semi- arid areas that border deserts . Human activities are a primary cause of desertification . These activities include overgrazing of livestock , deforestation , overcultivation of farmland, and poor irrigation practices. Overgrazing and de forestation remove plants that anchor the soil. As a result, wind and water erode the nutrient -rich topsoil . Hooves from grazing livestock compact the soil, preventing it from absorbing water and fertilizers . Agricultural production is devastated , and the economy of a region suffers.

The deserts of Patagonia , the largest in South America, are expanding due to desertification . Patagonia is a major agricultural region where non-native species such as cattle and sheep graze on grassland . Sheep and cattle have reduced the native vegetation in Patagonia , causing loss of valuable topsoil . More than 30 percent of the grasslands of Argentina, Chile, and Bolivia are faced with desertification . People often overuse natural resources to survive and profit in the short term, while neglecting long-term sustainability . Madagascar, for instance, is a tropical island in the Indian Ocean. Seeking greater economic opportunities, farmers in Madagascar engaged in slash-and-burn agriculture . This method relies on cutting and burning forests to create fields for crops . Unfortunately, at the time farmers were investing in slash-and-burn agriculture , Madagascar experienced long-term droughts . With little vegetation to anchor it, the thin topsoil quickly eroded . The island’s central plateau is now a barren desert . Rapid population growth also can lead to overuse of resources , killing plant life and depleting nutrients from the soil. Lake Chad is a source of freshwater for four countries on the edge of the Sahara Desert : Chad, Cameroon, Niger, and Nigeria. These developing countries use Lake Chad’s shallow waters for agriculture , in dustry , and hygiene . Since the 1960s, Lake Chad has shrunk to half its size. Desertification has severely reduced the wetland habitats surrounding the lake, as well as its fishery and grazing lands. Desertification is not new. In the 1930s, parts of the Great Plains of North America became the “ Dust Bowl ” through a combination of drought and poor farming practices. Millions of people had to leave their farms and seek a living in other parts of the country. Desertification is an increasing problem. Every year, about 6 million square kilometers (2.3 million square miles) of land become useless for cultivation due to desertification . The Sahara Desert crept 100 kilometers (39 miles) south between 1950 and 1975. South Africa is losing 300-400 million metric tons (330-441 short tons) of topsoil each year. Many countries are working to reduce the rates of desertification . Trees and other vegetation are being planted to break the force of the wind and to hold the soil. Windbreaks made of trees have been planted throughout the Sahel , the southern border region of the Sahara Desert . These windbreaks anchor the soil and prevent sand from invading populated areas. In China’s Tengger Desert , researchers have developed another way to control wandering dunes . They anchor the drifting sand with a gridlike network of straw fences. Straw is poked partway into the sand , forming a pattern of small squares along the contours of the dunes . The resulting fences break the force of the wind at ground level, stopping dune movement by confining the sand within the squares of the grid. New technologies are also being developed to combat desertification . “ Nanoclay ” is a substance sprayed on desert sands that acts as a binding agent. Nanoclay keeps the sand moist, clumping it together and preventing it from blowing away. Deserts Get Hotter Rising temperatures can have huge effects on fragile desert ecosystems . Global warming is the most current instance of climate change . Human activities such as burning fossil fuels contribute to global warming . In deserts , temperatures are rising even faster than the global average. This warming has effects beyond simply making hot deserts hotter. For example, increasing temperatures lead to the loss of nitrogen , an important nutrient , from the soil. Heat prevents microbes from converting nutrients to nitrates , which are necessary for almost all living things. This can reduce the already limited plant life in deserts . Climate change also affects rainfall patterns. Climate scientists predict that global warming will lead to more rainfall in some regions, but less rainfall in other places. Areas facing reduced precipitation include areas with some of the largest deserts in the world: North Africa (Sahara), the American Southwest (Sonoran and Chihuahuan), the southern Andes ( Patagonia ), and western Australia (Great Victoria). In literature and in legend, deserts are often described as hostile places to avoid. Today, people value desert resources and biodiversity . Communities, governments , and organizations are working to preserve desert habitats and increase desert productivity.

Devil of a Storm Dust devils are common in hot deserts. They look like tiny tornadoes, but they start on the ground rather than in the sky. When patches of ground get very hot, the heated air above them begins to rise and spin. This whirling column of hot air picks up dust and dirt. These spinning columns of dirt can rise hundreds of feet in the air.

Freak Floods Deserts are defined by their dryness. However, flash floods take more lives in deserts than thirst does.

Hot and Cold Deserts The largest hot desert in the world is the Sahara, which is 9 million square kilometers (3.5 million square miles). It isn't the hottest place on Earth, though. That distinction belongs to Death Valley, in California's Mojave Desert. The highest temperature on Earth was recorded there: 56.7 C (134.1 F). The largest polar desert is Antarctica, at 13 million square kilometers (5 million square miles). Antarctica boasts the lowest official temperature recorded on Earth: -89.2 C (-128.6 F), recorded on July 21, 1983.

Rising from the Ashes The desert city of Phoenix, Arizona, is named for the mythical desert bird that burns to death only to be reborn, rising from its own ashes. The city of Phoenix was built on top of the ruins of canals built by the Hohokam people between 500 and 1450 CE. The Hohokam used the canals to irrigate their crops. Modern-day residents also rely on an extensive canal system to provide irrigation.

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Désertification : qu'est-ce que c'est ?

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Dans une première approche un peu simpliste, le terme désertification désigne le phénomène d'avancée du désert du fait d'un manque d'eau. En réalité, le processus s'avère bien plus complexe. Il consiste en la dégradation progressive des terres -- c'est-à-dire d'un sol et de la flore et de la faune qui l'accompagnent -- dans une zone sèche. Le phénomène modifie le cycle de l’eau . Et la région affectée en vient alors peu à peu à présenter les caractéristiques d'aridité d'un vrai  désert .

La Convention de lutte contre la désertification (CLD), mise en place par l'ONU en 1996, définit la désertification comme correspondant à « la dégradation des terres dans les zones arides, semi-arides et subhumides sèches par suite de divers facteurs, parmi lesquels les variations climatiques et les activités humaines. Elle touche plus de 250 millions de personnes dans le monde et ne consiste pas dans l'extension naturelle des déserts. »

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Word history and origins.

Origin of desertification 1

Example Sentences

Efforts to stop desertification—the process by which fertile land becomes desert—have been primarily focused on expensive manual solutions.

At his office, he showed me a series of maps that document China’s elevation, watersheds, flood paths, biodiversity, desertification, ecological security, soil erosion, and cultural heritage.

Impacts of climate change fueled in part by Soviet industrial development are already visible around Russia, from permafrost degradation to desertification in the agriculture-heavy southern reaches of the country.

After the separation of South Sudan, a third of the country is a desert right now, and desertification is moving very fast.

Deeper root systems bolstered soil health, and expanded tree cover cut down on wind and water erosion, halting desertification.

The Sahel has been degraded by human use, not natural desertification; the natural process has been the reverse.

So why do we invariably connect higher temperatures with droughts and desertification?

The presence of a nearby desert has no direct relationship to desertification.

Desertification does not occur in linear, easily mappable patterns.

Desertification may intensify a general climatic trend toward greater aridity, or it may initiate a change in local climate.

This degradation of formerly productive land—desertification—is a complex process.

Unfortunately, an area undergoing desertification is brought to public attention only after the process is well underway.

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