PESERA-DESMICE: Land management evaluation model

Table of Contents

1. Authors
2. Summary
3. Acronyms
4. Introduction
5. Coarse-scale model description
   1. The PESERA model: summary
   2. Alternative approaches to assessing soil erosion
   3. Process representation in PESERA
   4. Extensions of PESERA
   5. Adapting PESERA
   6. Assessment at catchment scales
6. Cost-effectiveness modelling
   1. Step 1
   2. Step 2
   3. Step 3
   4. Step 4
   5. Step 5
   6. Step 6
   7. Step 7
   8. Step 8
   9. Step 9
   10. Step 10
   11. Step 11
   12. Step 12
7. Agent-Based modelling in Spain
   1. Phase 1
   2. Phase 2
   3. Phase 3
   4. Phase 4
   5. Phase 5
   6. Phase 6
8. Input-Output modelling in Spain
   1. Model construction
   2. Scenario analyses
9. References

Model construction

The starting point of the input-output model is the construction of an inter-industry I/O matrix (see Figure 4.4 above). No such table is available for the region, so the first step will be to construct this from a recently published national I/O table for Spain for 2005, which distinguishes 73 sectors (Instituto Nacional de Estadística, April 2009). Regional economic data from the Centro Regional de Estadística de Murcia will be used to adapt the national table to the regional economy. The first step herein is to multiply the national data with regional sector employment coefficients, based on the assumption that the labour productivity in Murcia is comparable to that of Spain as a whole (following Miller and Blair, 1985). As regional employment statistics are available for 26 sectors, the original 73 x 73 I/O table will first be aggregated to a 26 x 26 I/O table.

When the size of the 26 regional industries has been established, the output from each sector can be distributed across industries as intermediate consumption using the technical coefficients from the national table, and to final consumption and export. In the case that the regional production does not suffice to fulfil intermediate consumption by other regional industries, we will assume that the deficit will be imported. In order to validate these calculations, we will use the regional statistics on import and export. In doing so, we take stock of Boomsma and Oosterhaven's (1992) warning that failure to take into account regional trade data tends to overestimate a regions inter-industry relations (and any subsequent multiplier effects when performing scenario analyses based on erroneously constructed tables).

A next step in model construction is to split the agricultural sector, currently in its entirety considered as one of the 26 sectors in regional statistics, to account for the major land use categories (tree crops, annual crops and (irrigated) horticulture and livestock production). Regional agricultural economic statistics will be used to inform this step.

Once the inter-industry I/O table is complete, the model can be extended with environmental matrices. An important source of information is the Integrated Environmental and Economic Accounting System (IEEA) maintained by INE. Its water use budgets have been used successfully in I/O studies at the national level (Duarte et al., 2002) and regional level (for Andalucía, Dietzenbacher and Velázquez, 2007). Water use is important to consider in our model both because water resources depletion is a serious environmental issue in Murcia, and because the agricultural sector is by far the largest regarding water consumption.

In considering the effect of soil erosion (mitigation) on agricultural land on the wider economy, it should be noted that soil is usually not a natural resource of economic importance. Rather, the effect of soil erosion (mitigation) should be accounted for by incorporating matrices for carbon and nitrogen cycles, being the most important elements contained in soil for inclusion in economic accounting. Regarding the carbon cycle, soil conservation helps build up organic matter in the soil and e.g. replacement of fertilizers by organic mulches reduces fossil carbon dependency. Regarding the nitrogen cycle; the better organic matter content due to soil conservation increases yields without the need of chemical fertilizers, while ongoing land degradation on the other hand increases dependency on chemical fertilizers. Application of locally produced organic matter on agricultural fields adds value for these residual products otherwise lost (even leading to eutrophication of surface water resources). The (important) effect of soil erosion (and technologies to remediate it) on green water - water stored in the soil and used by plants - will be indirectly considered through changed water budgets and crop productivity in scenarios with as opposed to without mitigation strategies (Section 4.2.3).

The I/O model will finally also include accounting rows for agri-environmental subsidies and capital input.