Today, 17th June, is the World Day to Combat Desertification, with an event being held by the United Nations Convention to Combat Desertification (UNCCD), and hosted at the World Bank in partnership with the Global Environment Facility (GEF)TerrAfrica and Connect4Climate. The UNCCD have recently published a comprehensive report on the impacts of desertification.

Here we look at what desertification is, how it is affected by climate change, and what this means for global populations.

What is desertification?

Desertification is a form of land degradation by which land becomes more arid.  It’s definition is debated, but it generally refers to “the process of fertile land transforming into desert typically as a result of deforestation, drought, or improper/inappropriate agriculture” (Princeton University Dictionary).  This process usually results in the desertified land losing its vegetation, water bodies (lakes, streams), and wildlife.

“Desertification is a silent, invisible crisis that is destabilizing communities on a global scale.”

From the United Nations Convention to Combat Desertification (UNCCD), 2014

The primary cause of desertification is the removal of vegetation. This causes removal of nutrients from the soil, making land infertile and unusable for arable farming.  The reason for the initial removal of vegetation varies, but the two dominant reasons are:

  • Human activity – cutting down trees to allow more grazing, or over-grazing of land by farmed animals.
  • Climate change – warming of air temperatures and decreases in precipitation can cause drought conditions and prevent the sustained growth of vegetation.

With these processes combined, around 12 million hectares of productive land become barren every year due to desertification and drought alone (UNCCD, 2014).

 

Which regions are affected?

Desertification is a major problem across the world, most notably in dryland areas (including large areas in Africa, such as the Sahel. About 40% of Earth’s land is covered by drylands, and these areas are home to over 2 billion people.

Drylands are highly vulnerable to natural and human destruction, due to the low water content of the soil (UNCCD, 2014). However, it is important to remember that land degradation can affect all regions – drought and desertification is not always synonymous with dryland areas. About one third of all global agricultural land is either highly or moderately degraded. Australia was the first country to establish a national drought policy, and though other countries (Kiribati and Morocco) have made the first steps toward this, it remains one of the only countries to have a comprehensive drought management strategy.

 

This map from the Natural Resource Conservation Service shows global desertification vulnerability. This map is based on a reclassification of the global soil climate map and global soil map (soil type is closely linked to climate, and so varies across the globe in response to the local environmental conditions).

This map from the Natural Resource Conservation Service shows global desertification vulnerability. This map is based on a reclassification of the global soil climate map and global soil map (soil type is closely linked to climate, and so varies across the globe in response to the local environmental conditions).

How will climate change impact desertification? And populations?

As the climate changes, many areas begin to experience different weather and climate patterns. In many dryland areas (INSERT SOME EXAMPLES), the climate is become even more arid and rivers, lakes and underground water sources are drying up. With climate change, terrestrial biomes also adjust – through changes in their range and species composition. This can have major impacts not only on physical processes (such as the water cycle), but also on ecosystem functions. In terms of global populations, these changes also mean that food-production zones are shifting, and in many regions crops and livestock are failing.

 

Number  of drought  disasters (1974–2004).  From: EMDAT - www.emdat.net

Number
of drought
disasters (1974–2004). From: EMDAT – www.emdat.net

In the last few decades…

From 1900-2005, precipitation declined in the Sahel, the Mediterranean region, southern Africa and parts of southern Asia. Over the last 40 years or so, the global area affected by drought has increased markedly, and more intense, longer droughts have been observed over much wider areas – particularly in the tropics and sub-tropics. Over the same time period, temperatures in the Sahel have risen by 1.5-2.0 °C, and the incidences of drought and erratic rainfall have increased. From 1950-1980 10-14% of the land mass was classified as dry. From 2000-2010 this figure had risen to 25-30%.

This increase in droughts, as well as flash floods that are stronger, more frequent and widespread is destroying the land. This is because, under drought conditions the land becomes extremely dry (or desiccated) meaning that its surface layers often become fragmented (unconsolidated or friable) and susceptible to erosion. When the rain falls, and flash flood events occur, much of this material prepared under drought conditions is very quickly swept away, further degrading the land surface. It important to remember that, even when it does rain in highly arid regions, this is not necessarily enough to fully recharge the water that was once stored in the land. It can take a many decades to reverse the impacts of drought and desertification.

 

Over the next few decades…

With continued climate change, and the projected increase in global temperatures coupled with reduced rainfall in many dryland regions, there may be considerable impacts for land cover and desertification.

Over the next few decades, the average river run-off and water availability in some dry regions (including dry parts of the tropics) is projected to decrease by 10-30%.

 

By 2020, an estimated 60 million people could move from the desertified areas of sub-Saharan Africa towards North Africa and Europe.

By 2025, up to 2.4 billion people across the world may be living in areas subject to periods of intense water scarcity. This may displace as many as 700 million people. People

By 2050, 200 million people worldwide may be permanently displaced environmental migrants.  

 From the United Nations Convention to Combat Desertification (UNCCD), 2014

Climate change and its impacts on desertification are large scale issues which require regional and global scale measures. The UNCCD have recently indicated that: “The climatic effects on land occur at ecosystem and landscape levels. Therefore, individual and community efforts to rehabilitate the land are at their most effective when they are part of a country-wide or regional-level effort to preserve and rehabilitate landscapes.” (UNCCD, 2014).