Desertification and land degradation: origins, processes and solutions

Table of Contents

1. Authors and acknowledgements
2. Introduction
   1. Aims
   2. Definitions and key concepts
   3. Synthesis of previous and ongoing projects
   4. Key issues and outline
3. Evolution of desertification in the Mediterranean
   1. Climatic fluctuation
   2. Human influence
4. Primary drivers of desertification
   1. Biophysical and socio-economic causes
   2. Pathways of desertification
   3. Driving forces in the Mediterranean
   4. Synthesis of causes for DESIRE hotspots
   5. Conclusions
5. Processes and consequences of desertification in the Mediterranean
   1. Socio-economic and political factors
   2. Biophysical processes
   3. Conclusions
6. Indicators: monitoring desertification
   1. History of monitoring
   2. Indicators
   3. Monitoring and mapping techniques
   4. Concluding remarks
7. Modelling desertification
   1. Definition of modelling
   2. Model types
   3. Biophysical modelling
   4. Socio-economic and participatory modelling
   5. Gaps and progression in modelling
8. Solutions
   1. Biophysical solutions
   2. Political and socio-economic solutions
9. References

Socio-economic and political factors

Although there are socio-economic and political causes and consequences of desertification, this chapter focuses on how these factors influence desertification processes.

Urbanization

The consequences of increased urbanization in Mediterranean countries may lead to degradation or even trigger desertification. There is a number of problems due to urbanization. First, an increase in the consumption of (often prime) land that is poorly planned and regulated so that settlement may occur in increasingly marginal locations, for example, on steep slopes which may be vulnerable to landsliding (Wainwright and Thornes, 2004). Also, due to urbanization agricultural use of areas is pushed to marginal land, raising problems there. Second, water supply comes under increasing pressure and drainage and removal of waste water and sewage become increasingly difficult. Third, issues of the production of solid waste are important and air pollution increases. Also, an increase in impervious surfaces leads to an increased risk of flooding, especially when expansion of the urban area includes mountainous terrain and aquifers may become depleted as a result of overexploitation (Conacher and Sala, 1998).

Competition for scarce water and unsustainable water management

Drought and shortage of water are an inherent part of the Mediterranean type of climate and of the desertification problem. The areas that experience this type of climate have a dry season in which soils and vegetation become water-stressed. Subsequently, most of the available precipitation typically falls in torrential storms, leading to problems such as water erosion and flooding, which may be exacerbated by drought-enhanced soil water repellency. All problems related to desertification as described in this chapter (e.g. wind erosion, salinization etc) can eventually be traced back to water related problems, so they could all be categorized under this heading. These problems, however, are experienced as such by the local people. Under the heading 'water related problems', problems directly related to water are discussed including flooding and the competition for scarce water sources. Overexploitation of the scarce water resources by e.g. bad management or agricultural practices is often a problem. Increasing tourism and urbanization also add to this competition.

Competition for scarce water resources is a problem in many areas susceptible to desertification that is likely to be compounded by climate change in many drylands. According to Stern (2006), over 1 billion people will suffer water shortages as a consequence of climate change by 2100. In addition to increased demand for irrigation under future climate change, water shortages may be further compounded by increasing tourism, urbanization or industrialisation. Changes in agricultural practices, such as transitions from nomadic to settled agriculture and technological advances that facilitate year-round irrigation, aggravate the problem. Increased water demand from the agricultural, industrial and domestic sectors in many dryland countries has led to ground-water extraction far in excess of recharge rates, leading to fears about the long-term viabililty of these systems. In areas adjacent to salt-water aquifers, over-extraction of ground water can lead to aquifer and soil salinization (this is often a particular problem in coastal areas). Where aquifers cover wide areas, and particularly where water is supplied by rivers that cross international boundaries, competition for water becomes an international political issue. For example, there is predicted to be a 75% drop in Nile waters that supply water to ten countries by 2100 (Stern, 2006). At a local level, there are numerous examples of grassroots institutions that successfully manage access to water between groups of farmers, but such co-operation will increasingly need to take place at a national and international scale.

Abandonment

In contrast to the trend of cultivating more marginal lands in some countries, there is a distinct trend of the abandonment of formerly cultivated marginal lands in the EU Mediterranean countries. The effects of this process are difficult to predict, as the abandoned fields show different evolutions depending on various environmental and land-use features (Kosmas et al., 2002). On the one hand, degradation may decrease when cultivation techniques (e.g. ploughing, leading to erosion) have ceased and natural vegetation takes over. On the other hand there is a risk of further degradation when cultivation structures (e.g. terraces) collapse and when (over)grazing is allowed on the abandoned lands. However, land abandonment is not a recent or new phenomenon (Thornes, 2002); it occurred throughout (early) history in the Mediterranean basin.

Policies

Many land use changes are the direct or indirect effect of local, regional, national or EU policies. An example of the latter is the subsidy farmers get for cultivation of certain crops, e.g. almonds or olives in SE Spain. Without these subsidies, land use would probably be different. Processes such as urban migration and consequent rural depopulation and irrigated agriculture expansion form the social dynamics of desertification and have more often than not been supported, if not initiated, by governmental intervention (Oñate et al., 2005). Wilson and Juntti (2005) explore the policy-related factors and processes that have contributed to desertification.