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

Indicators

Land degradation indicators contain simplified, synthetic information on the state and tendency of complex processes such as desertification. They can be easily communicated to the public or policy-makers, they can be used as easy synthetic information in GIS systems to determine spatial extension and geographic distribution of degraded areas and to relate human actions (causes) to environmental conditions (effects) (Rubio and Bochet, 1998).

Land degradation indicators have the capacity to engage a wide range of stakeholders, from policy-makers to land managers, to provide interdisciplinary information about the nature of environmental change. Until now, scientists have not reached consensus about a standard set of indicators to use in monitoring desertification (Pinet et al., 2006). Such consensus is probably not possible or even desirable as conditions and processes leading to desertification show such (spatial) variability that it is impossible to monitor desertification in any place without a set of site-specific indicators.

Adaptive land management depends on effective monitoring to detect change as early as possible. However, it is increasingly claimed that existing indicators provide few benefits to users who as a consequence rarely apply them (Carruthers and Tinning, 2003; Innes and Booher, 1999). Partly, this is because indicators are usually developed by experts and applied without engaging local communities (Riley, 2001). Sustainable development literature and the United Nations Convention to Combat Desertification (UNCCD) stress the need for local communities to participate in all stages of project planning and implementation, including the selection, collection and monitoring of indicators (WCED, 1987; UNCCD, 1994; Corbiere-Nicollier et al., 2003). To do this, the methods used to collect, apply and interpret indicators must be in a form that can easily be used by non-specialists. To achieve widespread uptake, land degradation indicators must also be clearly linked to community needs, priorities and goals.

This is an enormous methodological challenge, but one that could bring many rewards. In the hands of local communities, degradation indicators have the potential to go beyond simply measuring progress. They can enhance the overall understanding of environmental and social problems and empower communities to respond appropriately to environmental change without having to rely on external experts. If the monitoring process can open a dialogue about land degradation with neighbours and policy-makers, indicators may be able to help relocalise and enrich land degradation policy decisions, and enhance the sustainability of local livelihoods.

Many indices have been proposed to describe the susceptibility of drylands to desertification (Pinet et al., 2006; and e.g. Tongway and Hindley, 2000). One of the most important issues is the identification of land degradation indicators which have a general applicability to the Mediterranean Basin as a whole and which can be observed with operational remote sensing systems (Hill et al., 1995, Lacaze et al., 1996). Indicators and approaches to develop and subsequently monitor them differ from expert-led, top-down to community-based, bottom-up (Reed et al., 2006). In their paper on the selection procedure of desertification indicators in Europe, Rubio and Bochet (1998) give a list of criteria to which indicators can be allocated.

As it is not the objective of this review to enumerate all possible desertification indicators, three projects are discussed here, that worked on indicator systems.

DESERTLINKS: DIS4ME

The major aim of the DESERTLINKS project (see Appendix II) was to contribute to the work of the UNCCD by developing a desertification indicator system for Mediterranean Europe. In their list of candidate indicators, a division is made between ecological, economic and social indicators. The indicator system (DIS4ME; Desertification Indicator System for Mediterranean Europe) contains about 150 desertification indicators of relevance to the Mediterranean. It has been designed to provide a tool to enable users from a wide range of backgrounds (including scientists, policymakers and farmers) to identify where desertification is a problem; to assess how critical the problem is and to better understand the processes of desertification. Each indicator is fully described and is available in a database allowing the user to select indicators according to various logical frameworks, temporal and spatial scales. An Environmental Sensitivity Index can be calculated by selecting values for 13 different indicators associated with vegetation, soil, climate and management. Details are available at the DESERTLINKS website (see Appendix II)

MedAction

MedAction (see Appendix II) aims at assessing the main issues underlying the causes and effects of land degradation; and at developing integrated policy options and mitigation strategies to combat desertification in the Northern Mediterranean region. They use a list of 65 indicators, subdivided into ecological (precipitation, soil, slope, vegetation, soil degradation), economic (income, prices, unemployment, equity, infrastructure, tourism, agricultural land use, consumption, trade), social (population, public perception) and institutional (subsidies, agricultural organisations, laws, European Union). The final key indicators that were selected by MedAction are given in Table 5.1. This table serves here as an example of potential indicators for use in DESIRE.

Table 5.1. List of key indicators, based on the hierarchy of the Factor and Sector tables. (From: Greeuw et al., 2001)

INDEX

The prime goal of INDEX (Indicators and Thresholds for Desertification, Soil Quality and Remediation, see Appendix II) is to apply knowledge to develop modern, rapid, sensitive, universal, multivariate indicators with which the dynamic state of land degradation as well as its remediation can be assessed. The assessed indicators are subdivided into biological (bulk and molecular microbiological and enzymatic activities), humus (in terms of bulk, humo-enzymes and available humus) and physical (mineralogy and structure, soil hydraulics, particle size stability, pore size distribution and rheology) indicators.