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

Gaps and progression in modelling

From the above it is clear that it is impossible to comprehensively model desertification. However, much work has been done to model the various components and processes of desertification, both socio-economic and biophysical aspects. Also, various spatial scales are assessed in various projects, from plot and hillslope scale to European scale (e.g. PESERA).

According to Mulligan (2004), the main progress expected in the next decade concerns the process of modelling itself. In his review, expected progress regarding several topics of desertification modelling is described, which is summarized here:

• improvement in techniques and technologies for downscaling GCM scenarios to the catchment scale;
• deeper understanding of the land surface in determining regional climates and the impacts of land use change on surface fluxes;
• SVATs being able to deal with land surface - atmosphere fluxes over the whole seasonal cycle;
• Hydrological modelling improvements will be in the field of smaller grid sizes, better DEMs, a greater emphasis on physical reality than empiricism and importantly parameterisation and validation;
• Overland flow and erosion research is highly developed and the focus will shift towards nutrient loss or landslides
• Greater emphasis on modelling the ecology of semi-arid vegetation, including interactions between functional types and at the species level, nutrients, species survival and loss of biodiversity due to desertification, the role of genetic variability, etc.;
• Continued integration between physical, biological and socio-economic models, providing decision support against scenarios for environmental change.