Vulnerabilities

World-wide

The global area of dryland is increasing rapidly. This was shown from data over the period 1948–2005, and seems to proceed towards the end of this century, according to projections of a large number of climate models (4).

The aridity of a region is generally measured by the aridity index (AI), which is the ratio of total annual precipitation to potential evapotranspiration. Drylands are defined as regions with AI < 0.65 (4). 

Dryland expansion rate will increase in future decades: according to projections of 20 global climate models, global dryland area may increase by 11% and 23% by the end of the twenty-first century under a moderate and high-end scenario of climate change  (the so-called RCP4.5 and RCP8.5 scenario), respectively, relative to the reference period of 1961–1990. As a result dryland will cover the global land surface by 50% - 56% in 2100. Under the high-end scenario of climate change, 78% of dryland expansion may occur in developing countries. The increasing aridity, enhanced warming and rapidly growing human population will exacerbate the risk of land degradation and desertification in these countries in the near future (4).

Drylands are divided into subtypes of hyper-arid (AI < 0.05), arid (0.05 ≤ AI < 0.2), semiarid (0.2 ≤ AI < 0.5) and dry subhumid (0.5 ≤ AI < 0.65) regions (Middleton and Thomas, 1997). During the period 1948–2005 the observed global land areal increases in hyper-arid, arid, semiarid and subhumid land types are 0.62%, 1.16%, 2.32% and 3.32%. Under the moderate scenario of climate change the dryland subtypes of dry subhumid, semiarid, arid and hyper-arid comprise 8.9%, 19.0%, 14.4% and 8.4% of the global land area in 2100. Under the high-end scenario of climate change these subtypes of dry subhumid, semiarid, arid and hyper-arid comprise 8.3%, 20.3%, 14.9% and 12.6% of the global land area (4).

Strict management and rational utilization of water resources, along with the restoration of soils and vegetation to reduce ecosystem vulnerability on a global scale, are urgently needed to develop a global action plan to prevent future desertification and eradicate the present global desertification problems (4). 

Mediterranean area

Over the last decades, the Mediterranean area has been identified as an areas with a significant increase of drylands extent (2). 

The current cost of soil erosion, organic matter decline, salinisation, landslides and contamination is estimated to be EUR 38 billion annually for the EU, in the form of damage to infrastructures, treatment of water contaminated through the soil, disposal of sediments, depreciation of land and costs related to the ecosystem functions of soil (1).

The larger Mediterranean Basin will have warmer and dryer climate conditions at the end of this century. Desertification in the Mediterranean region is largely due to poor land-use practices and land degradation. Hotter and drier conditions at the end of this century, however, will likely extend the desertification-prone areas northwards in the Mediterranean Basin to encompass areas currently not at risk. In addition, the rate of desertification would increase due to increases in erosion, salinization and forest fire hazard and reductions in soil quality (3). 

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Europe.

1. JRC-EEA (2010), in: IPCC (2014)
2. Spinoni et al. (2015)
3. Ozturk et al. (2015)
4. Huang et al. (2016)