Modelling pesticide risk: A marginal cost-benefit analysis of environmental buffer-zone programme
A newly developed indicator of the pesticide risk for aquatic biocenosis in surface water bodies is applied within an economic sector model, and is used to evaluate alternative designs for an environmental policy programme. For rural districts (‘Landkreise’) across Germany, different widths of riparian buffer zones adjacent to surface water bodies are evaluated in terms of efficient cost/risk ratios. The indicator is defined as acute risk under worst-case input conditions and is based on combining a sectoral model, a national survey on pesticide use and a toxicological risk assessment model. The nation-wide survey provides data on pesticide use by agricultural crop. On this basis, crop-specific risk indices for aquatic biocenosis are calculated by means of eco-toxic criteria for indicator organisms and aggregated through crop patterns to the rural-district level. GIS is used to calculate the influences of natural site factors (e.g. soil types, land use distance to water bodies, etc.) on pesticide input in surface water and to calculate the regional risk potentials at regional level. An economic cost–impact analysis is conducted based on the new indicator. Opportunity costs of converting agricultural land to riparian buffer strips are estimated using the agricultural sector model RAUMIS, for buffer strip widths of 3, 30 and 50 m, as per the European the environmental programme EC 99/1257/EEC. These costs are then compared with estimated risk reduction potentials at the regional level of administrative districts. Results show that cost–impact ratios are most efficient for 3 m buffer strips and in those regions with the lowest costs from changing agricultural land use (e.g. through reduced livestock production). A major future research need in this area is a higher spatial resolution at the grid-level.