Evaluation of environmental impact

Pesticides of similar cost and effectiveness to the farmer may differ strongly with respect to environmental impact(1). How can a farmer take into account the risk for the environment when there are several choices between pesticides? Hayo van der Werf and Christophe Zimmer report of their efforts to provide an environmental yardstick.

A research team at the French National Institute for Agronomic Research (INRA) at Colmar in north eastern France has set up a system to assess the impact of cultivation practices-such as fertiliser and pesticide use, and crop rotation-on the agro-ecosystem. The team has proposed a set of agro-ecological indicators (AEIs) that are calculated from data available on the farm without requiring specific field measurements(2). Fifteen farms in France and Germany are involved in the AEI pilot programme.
    AEIs are generally expressed on a scale from 0 to 10 to make them easy to use. The value seven represents the minimum level of sustainability of the farming system, and is based on scientific knowledge or expert judgement. AEIs are primarily tools to aid the decision-making process and help farmers adapt their cultivation practices and farming systems towards increased sustainability. However, AEIs may also be used by decision makers to monitor or evaluate agro-environmental policies.

Measuring pesticide use with 'Ipest'
The INRA team has established one AEI, known as Ipest, that ranks the environmental impact of pesticide use(3). Ipest is calculated from three variables:

• pesticide characteristics-for example, toxicity to aquatic organisms;

• environmental characteristics-for example, the risk of leaching;

• application characteristics-for example, the site of application: on the crop, on the soil or in the soil.

As it is estimating environmental impact, Ipest does not include acute occupational health toxicity data.
    The effect of the input variables on the risk of environmental impact can be expressed in every-day language. For example, if the runoff risk of the field is great, and the pesticide is applied on the soil and it is toxic to aquatic organisms, then the risk of surface water contamination is also great. For a typical pesticide application, this type of 'rule' is used to calculate four values:  the amount of pesticide applied; risk of groundwater contamination (Rgro); risk of surface water contamination (Rsur); risk of air contamination (Rair). The details of the calculations are not described here (see table).
    These four values are aggregated according to set decision rules to produce a final value for Ipest between 0 (no risk of environmental impact) and 1 (maximum risk of environmental impact) [this figure is used in a separate calculation to produce an AEI between 0-10]. The results are site specific, therefore the Ipest values will alter according to the conditions, such as risk of leaching and run-off of the field. The INRA team hopes the farmer will be able to take into account characteristics of the field that are simple and cheap to measure such as organic matter soil content. 
    The system contains data for about 135 pesticide active ingredients, data on other active ingredients can be simply added. Results (see table) can be used by farmers, according to their conditions, to compare or rank different pesticide applications with respect to one or more of the environmental modules, or of the Ipest indicator.

European comparisons
In 1998 and 1999 the results will be compared with other environmental risk assessment programmes being developed at a number of research institutes across Europe all funded by the European Union (EU). Other EU-funded programmes to compare and evaluate methods and techniques that rank pesticides according to their environmental impact which will be evaluated include: the Pesticide Eco-rating System developed at the University of Hertfordshire UK (see PN37 p14);  the Pesticide Yardstick developed at Centrum voor Landbouw en Milieu in the Netherlands (see PN33 p6); and the PC Plant Protection system developed at the Danish Institute for Plant and Soil Science (see PN34 p7).

Conclusion
New characteristics can be added to the Ipest system if required, and the system is flexible and can be 'fine tuned' by subsequent additional data. This system provides an expert's measure of potential pesticide environmental contamination that can be used by farmers.

1. Van der Werf, HMG, Assessing the impact of pesticides on the environment, Agriculture, Ecosystems and Environment, 1996, 60:81-96.
2. Bockstaller Ch, Ph Girardin and HMG van der Werf, Use of agro-ecological indicators for the evaluation of farming systems, European Journal of Agronomy, 1997 7:261-270.
3. Van der Werf, HMG and Ch Zimmer, An indicator of pesticide environmental impact based on a fuzzy expert system, Chemosphere, March 1998, 36 (10), in press.

Hayo van der Werf and Christophe Zimmer, work for INRA, Station d'Agronomie, BP 507, 68021 Colmar, France, Hayo.vanderWerf@roazhon.inra.fr

[This article first appeared in Pesticides News No. 39, March 1998, page 8]