Towards a modelling framework for integrated assessment in arid and semi-arid regions

Climate variability in combination with socio-economic processes acting on the land may induce a reduction of resource potential and hence cause land degradation. Any forecasting attempt to increase societal early warning capacity has to take the interaction between climate and socio-economics on the land into account. The DeSurvey Integrated Assessment Model (DeSurvey IAM) is a framework to develop policy support systems with the aim to support planners and policy makers that deal with regional development and desertification. Using the DeSurvey IAM, policy makers can carry out an integrated assessment of the impact of different external factors and policy options on a number of relevant indicators. The DeSurvey IAM has been developed with the objective to address a number of policy themes concerning regional development and desertification in arid and semi-arid regions: sustainable agriculture, water resource management and land degradation. By using these themes as a starting point for model integration and by linking the model to policy relevant drivers and indicators we intend to support policy makers at national and regional level by providing assistance in: 1. Understanding the important processes in a region or river basin as well as their mutual interaction; 2. Identification of current or future problems in the region or river basin; 3. Impact assessment of possible policy measures to mitigate identified problems; 4. Evaluation of different alternatives; 5. Improving communication between actors from different sectors and disciplines. The core of the DeSurvey IAM is an integrated modelling framework based on scientific knowledge from previous EU-projects and builds on the MODULUS and MedAction Policy Support Systems. At present, the framework contains some 20 models (e.g. climate, hydrology, water management, erosion, salinisation, vegetation growth, land use, macro-economics, crop choice, irrigation) operating at different spatial and temporal resolutions. Depending on the problem at hand and the data available, a region-specific application can be set up that contains a specific combination of models incorporated. This flexible combination of models allows application for Spain (i.e. an entire country) at national, regional and local (1 km) levels with a temporal resolution varying between monthly (bio-physical components) and yearly (socio-economic components), as well as application for the Guadalentin river basin in Spain at regional to local (1 ha) levels and with a temporal resolution varying between minutes (bio-physical components) and years (socioeconomic components). In the development of the system, focus has been on the scientific and software integration of models with different spatial and temporal scales and resolutions and the applicability of such a system for the envisaged end-users, the policy makers and planners in the region or river basin. The paper provides an overview of the DeSurvey IAM and illustrates how it can help to assess the impact of alternative policies.