Improved process descriptions in the PESERA model

Table of Contents

1. Authors
2. Abstract
3. Introduction
4. General extensions to PESERA
   1. Grazing
   2. Fire
   3. Wind Erosion
5. Particular extensions to PESERA
   1. Mulching and/or maintaining ground cover vegetation within tree crops
   2. Retention of crop residues as litter layer at harvesting of arable and other crops
   3. Irrigation and water harvesting for croplands
   4. Invasion and clearance of unpalatable species
   5. Terracing and strip cropping
   6. Nitrogen budgeting and rotations
6. Other extensions to PESERA
   1. Mass movements
   2. Data collection calibration of PESERA against reservoir data
7. Conclusions
8. References

Introduction

The principal objective of WB5 is to "develop a model for the main bio-physical and socio-economic processes interacting within an agro-ecosystem, building on existing experience in combination with results generated within WBs 1-4". Deliverable 5.1.1 described the principles of a model that is designed to evaluate the likely biophysical and socio-economic effects of applying remediation strategies selected by stakeholders in WB3 at a regional scale, by scaling up results from field trials and secondary data. This model will be applied in all study areas for which there is sufficient data. A more complex additional socio-economic model is also being developed for application in a single study site (the Guadalentin catchment in SE Spain) to further explore factors influencing the adoption of remediation strategies by land managers and the wider effects of adoption on the regional economy.

Increasingly sophisticated models are being used to represent both biophysical and socio-economic processes in relation to land degradation, usually within disciplinary boundaries. More recently there have been an increasing number of attempts to connect these models in mutually relevant ways, and in ways that are increasingly informed by inputs from stakeholders. The importance of participatory modelling, especially in land degradation and rehabilitation, derives from the awareness of the inadequacy of traditional, engineering approaches to dealing with these "complex and ill-structured problems(Giordano et al., 2007). It has become increasingly obvious that traditional modelling approaches have to be combined with inputs from stakeholders, influencing both model design and interpretation of results if the use of models is to feed effectively into policy design and implementation (Prell et al., 2007). However, although there are now approaches that can incorporate inputs from stakeholders into model development, many limitations remain. For example, stakeholder knowledge tends to be restricted to local contexts, so input to models with regional or global coverage is difficult; and there are generally competing stakeholder interests. In the DESIRE project we are making one significantly innovative attempt to incorporate stakeholder inputs into an integrated model combining social, economic and environmental systems, with the following features, which are more fully explored in deliverable 5.1.1:

• The DESIRE project collaborates with stakeholders to define the most important land degradation processes (WB1) and potential solutions to model in WB5. Stakeholder analysis is used to ensure a cross-section of stakeholders with different knowledge are represented and decision support tools are used to negotiate differing stakeholder priorities (WB3);
• Information collected from stakeholders in WB3 provides the basis for assessing the cost-effectiveness of remediation options across environmental and socio-economic gradients;
• Environmental effects of selected remediation options are evaluated using the PESERA model;
• The resulting linked models have the potential to be applied around the world through the case study approach of the DESIRE project, whilst retaining and building on inputs based on local knowledge;
• In one study site, this is expanded by incorporating stakeholder inputs into (Agent Based) models of human behaviour using data from structured questionnaires and combining this with a (Input-Output) regional economic model.

Linking environmental and socio-economic models not only facilitates a spatially explicit evaluation of mitigation strategies, but also gives spatial expression to the pattern of adoption of mitigation strategies by individual land users, based on economic analysis of available alternative options within each model cell. The coupled models can also be used to model the likely impact of both environmental (e.g. climate change) and socio-economic (e.g. policy) scenarios, providing estimates of global impact of land degradation mitigation, built on local realities.

Figure 1.1: Schematic overview of model interrelations within WB5

Figure 1.1 gives an overview of the inter-relationships within WB5. Deliverable 5.1.1 has described how the biophysical model proposed for the DESIRE project builds on and extends the PESERA model (Kirkby et al., 2008), originally developed for Pan-European Soil Erosion Risk Assessment within a dedicated EU (FP5) project. The original PESERA model is being extended to capture the role of grazing, fire and wind erosion more effectively, and enhance pedotransfer functions on the basis of dialogue and data within each study area. Current work on these components is reported in Section 2 below. The model is being adapted to each study area to reflect indicators and land degradation drivers identified in WBs 1 & 2 as closely as possible. The modified model will look at the biophysical effects of different remediation options that we have trialled in study areas at a regional or perhaps national scale. These results will be integrated with field trial results in all study areas, and will form the basis of a final stakeholder workshop, in which we will discuss recommendations for policy-makers and extension services. Locally calibrated application of the PESERA model will then be used to expand the results of pilot area studies to a larger hinterland, in order to evaluate the impact of recommended conservation measures for the surrounding area. The extent of this wider hinterland will be constrained by broad similarities of environment (guided by WB 2) and the availability of coarse (1km) resolution data, although reference data is already available at this scale for much of Europe.

In this report we expand the developments in the PESERA model, first describing general developments that have been shared between the DeSurvey and DESIRE projects, second taking each of the mitigation strategies that have been proposed by our study area partners and showing how these are incorporated into the model code, and third discussing the incorporation of coarse and fine modelling approaches developed by other partners and how far these can be effectively incorporated into the PESERA framework. This third component is still ongoing, awaiting full details from partners that are also due in month 36.

The mitigation strategies that have been proposed for application have already been listed in D5.1.1 and are summarised in Table 1 below (Table 2.2 from D 5.1.1).

Table 1: Parameters and methods from PESERA that can be adapted to represent the impact of different SLM technologies proposed in DESIRE (Table 2.2 from D 5.1.1)

To meet the needs of the integrated models that are being developed, the PESERA model needs first to be run to equilibrium, in order to establish average values of runoff, erosion and productivity under current conditions and to establish initial conditions for runs with explicit time series drawn as realisations of future climatic conditions. Using the same time series for climate in each site, the model can then be run again, applying alternative proposed technologies either as a step-change or through gradual adoption over time. These runs are then used to assess the expected responses of land managers to the changing performance and its economic consequences. In order to do this, PESERA has been developed to ensure that model output responds appropriately to the remedial SLM technologies that are being proposed within the project through WB3. The impacts of relevant SLM approaches will then be incorporated in the cost-effectiveness modelling and agent-based modelling. In the sections below we expand on the approach followed for each relevant activity or treatment. As can be seen below, we have been developing methods that represent all but the last technique listed in Table 1 (plastic sheeting/ greenhouses).