Summary

Evaluering af pesticidindikatoren PestNaB

Background

According to the Danish parliamentary majority of November 2007, the consumption of pesticides by Danish agriculture must be reduced and, in 2008, the Danish government initiated an advanced evaluation of the Pesticide Action Plan 2004-2009. In this context, a new and truer indicator should be developed, which rather than considering the treatment frequencies measures the harmful effects of the pesticides to allow more applied and effective actions against this impact.

The report ”Indikator for pesticiders belastning af naturen (PestNaB) [Indicator of the pressures of pesticides on nature (PestNaB)]” recommends a new indicator, PestNaB, which was developed as an indicator for monitoring and calculating the pressures of pesticides (Kjær et al. 2008).

PestNaB is based on various calculations including databases on pesticide sales, use of agricultural areas for different crops, pesticide application in relation to these crops and the geographic placing of the landscape elements such as hedges, streams, lakes and ponds in relation to the cultivated fields (Kjær et al. 2008) [PestNaB also uses the tern “nature elements” as a synonym of “landscape elements”]. The results of the indicator calculations are meant to form part of the basis for decisions and as a target for the future Danish environmental policy regarding pesticide application. The results must be applicable for assessing effects of various initiatives for reduction of the pressures on nature of the pesticides, e.g. reduced consumption of pesticides and application of less toxic pesticides.

In order to assess its reliability and suitability as an indicator of the environmental pressures of pesticides, this project has carried out an evaluation of the assumptions and calculation methods, sensitivity and uncertainty and data foundation of PestNaB.

Preconditions and methods of calculation

Pesticides may put pressures on nature in many ways, which cannot all be reflected in a set of indicators, partly due to lack of knowledge on a number of conditions and partly due to lack of data. Naturally, PestNaB can only include conditions, on which knowledge and data exist.

In its present form, PestNaB is composed of 18 subindicators. Each subindicator produces a value for the pressures of the pesticides on a given landscape element (a protection category), e.g. pressures on organisms in surface waters because of wind drift or pressures on bees on the field surface. The individual subindicators are expressed either as an environmental pressure figure or as a treatment index. The environmental pressure figure is calculated as a ratio of the exposure of a given nature element to an effect concentration for the same element. PestNaB comprises very simple measures for exposure.

The below table gives an overview of the protection categories and pressures included (+) or not included (-) in PestNaB.

Protection category	Direct effects	Indirect effects	Secondary effects	Other effects⁴⁾
Field surface	+¹⁾	+²⁾	+³⁾	-
Edge biotopes	+	-	-	-
Surface waters	+	-	-	-
Sediment	-	-	-	-
Ground water	-	-	-	-
Air	-	-	-	-

1) Lacking microorganisms
2) Lacking contribution from fungicides
3) Lacking account of bioaccumulation
4) Other effects include e.g. long-term effects, endocrine disrupters, accumulation

Omission of ground water contamination is due to the fact that the protection of ground water is primarily motivated by health considerations using maximum allowable concentration level. It may also be argued that in order to obtain a permit, it must be proven that leaching to ground water is below a certain level. That PestNaB does not include potential effects in the air falls in line with the fact that in Denmark, no specific requirements have previously been made for investigations or accounts of evaporation of pesticides from soil and treated crops or for investigations of the degradation of pesticides or their metabolites in the air.

At present, PestNaB only includes pesticides applied in agriculture although in principle, the indicator might be extended to comprise other uses of pesticides in outdoor cultivation.

In the calculations, the individual subindicators are weighted equally, i.e. PestNaB does not make any prioritization of which landscape elements are most important. It should be noted that no timescale is incorporated in PestNaB. Therefore, the load on surface water caused by drainage will not really take place until a certain time after the pesticide spraying while the load on surface water caused by spray drift will take place shortly after the pesticide spraying.

Sensitivity and uncertainties

The analysis included the following topics:

Aggregation. In the aggregated indicator, the individual subindicators rate equally. At the aggregation in PestNaB, the cases, in which at least one subindicator is inconsistent with the other subindicators, are omitted. On the face of it, this seems to be a substantial simplification and this procedure involves a risk of valuable information being lost. The influence on the calculation results of this simplification was assessed and analysed.

Weighting. At the calculation of the aggregated indicator, a small improvement is weighted as much as a large improvement and a small aggravation is weighted as much as a large aggravation. It was analysed whether a change of the acceptance criterion for when a subindicator indicates higher (or lower) pressures in one scenario compared to another, will influence PestNaB.

Effects of various initiatives. This includes e.g. presentation of effects of reduced pesticide consumption and prohibition of certain pesticides.

Effects of changes of land use. This includes e.g. withdrawal of fallows for agricultural use, conversion to organic farming and establishment of natural areas.

Sensitivity to critical data. Critical data are e.g. the toxicity of the pesticides, distance to natural areas and amount of nature. The analysis included the pointing out of the most critical parameters that must be determined with utmost precision. At the same time, it was assessed whether these parameters may be determined with the necessary precision.

Correlation between the individual subindicators. This included an analysis of whether, in certain cases, indicators are negatively correlated and whether there are “dominant” subindicators.

The analysis showed that introduction of changes to the applied aggregation principle gave the same conclusions as the present aggregation principle and that the conclusions were only affected to a lesser extent by minor changes to the acceptance level. Furthermore, the analysis showed that all in all, PestNaB may be characterized as a robust indicator that can reflect the consequence of the pressures on nature as a result of realistic changes of the Danish pesticide consumption, removal of the most critical pesticides and introduction of pesticide-free zones.

PestNaB is little sensitive to minor changes of the toxicity values (within the same order of magnitude) for the most critical pesticides, which makes PestNaB robust to minor uncertainties in the determination of the toxicity of the pesticides. The analysis also proved that PestNaB concludes higher pressures on nature if more nature is introduced in Denmark and the pesticide consumption is kept constant (or is increased).

In its fully aggregated form, PestNaB is a conservative indicator, meaning that potentially reduced pressures on e.g. the aquatic environment will not necessarily be reflected in the aggregated indicator value.

Basic data

As for many other ecotoxicological assessments, the basic data in PestNaB for assessing the pressures of the pesticides on the environment are based on standardized laboratory tests with single species. The extrapolation of results from laboratory tests with single species to assessment of effects on the environment at ecosystem level involves considerable uncertainty. Naturally, PestNaB is limited by the availability of ecotoxicity data on pesticides and is thus dependent on the data requirements made in connection with the authorisation of pesticides. Only test data on acute toxicity are included in PestNaB. Other factors such as persistence and accumulation of pesticides in organisms and the environment, potential endocrine disrupting effects of pesticides on fish, birds and mammals, combination effects with other chemical substances, pressures on microorganisms in soil and water, and pressures and effects of fungicides on the food basis of the field surface are not included in PestNaB. Such factors are essential for a risk assessment of the effects of pesticides on the environment, which is, however, not the aim of PestNaB.

In PestNaB, the location of the landscape elements is categorized on the basis of maps from the National Survey and Cadastre in Denmark (named Map 10), which is based on aerial photos. As the landscape elements (banks, hedgerows, groups of trees, forests, moors, wetlands, lakes and ponds and ancient monuments) are very important for PestNaB, it may be critical if the basic maps are not updated. It should be noted that the present basic maps date back to 2002-2006.

In its present version, PestNaB calculates area application of pesticides on the basis of data on the total sales of the individual pesticides in Denmark, the distribution of crop types in Denmark and knowledge on which pesticides are used for the various crops. The present version of PestNaB is thus directly related to the main crops of the pesticides statistics (10 different crops) (Danish EPA 2009). The basic data on the geographical distribution of the crop types in the individual fields are updated annually. Information on the amounts of pesticides applied to each crop at farm level is available in sprayer’s journals. However, at present, these sprayer’s journals are not available in electronic form.

Conclusion

PestNaB uses ranking as the primary method, i.e. PestNaB consequently compares two scenarios and indicates whether one of the scenarios results in higher pressures on nature than the other one. This means that PestNaB may be applied to indicate changes in the pressures on nature. However, PestNaB does not give any answers to whether the application of pesticides results in adverse effects on nature as the basic data are based on data from laboratory tests with single species, which are often far from representative of the many different organisms in the natural environments and only with considerable uncertainty, these data can be extrapolated in connection with a risk assessment of effects at ecosystem level.

In most areas, PestNaB is based on acceptable principles of environmental risk assessment of chemical substances. Environmental risk assessments are based on an extrapolation of results from laboratory tests into the real conditions of nature. The extrapolation of results from laboratory tests with single species to assessment of effects on the environment at ecosystem level involves considerable uncertainty as it is extremely difficult to fully investigate these effects. PestNaB makes not attempt to explain the total pressures on nature. PestNaB assesses the pressures on nature in relation to selected organisms that are especially relevant in a characterization of the pressures of the pesticides on nature with respect to both direct and indirect effects. Furthermore, the analysis proved that PestNaB is little sensitive to minor changes in the data used for the calculations.

The analyses indicate that the calculation principles of PestNaB result in estimations of the influence of changes in pesticide consumption and land use consistent with expectations. Furthermore, the magnitude of fluctuations in the calculated ranking potency reflects the degree of changes incorporated in the scenarios. However, it must be emphasized that at present, it is not possible to verify PestNaB by comparing calculation results with actual measurements. The exposure assessment of PestNaB is based on the location of the different landscape elements in Map 10 from the National Survey and Cadastre in Denmark, which was elaborated in 2002-2006 (landscape elements are e.g. banks, hedgerows, groups of trees, forests, moors, wetlands, lakes and ponds and ancient monuments). As land use and landscape elements change from one year to the next, it may be critical that information on the location of landscape elements is not updated. The area application of pesticides is estimated on the basis of data on the total sales of the individual pesticides in Denmark, the distribution of crop types in Denmark and knowledge on which pesticides are typically used for the various crops. However, information on the amounts of pesticides applied to the individual fields is available in sprayer’s journals. Access to these sprayer’s journals would thus heavily improve the knowledge on the actual pesticides and amounts applied in the fields. Thereby, a more precise knowledge on the exposure of the landscape elements to pesticides could be achieved.

The results obtained by using PestNaB may be difficult to understand and thus to interpret for non-experts. E.g., all subindicators of PestNaB may not necessarily point in the same direction and reduced pressures may be the result of lesser amounts applied of pesticides, of application of less toxic pesticides and/or of less nature or a combination of these parameters.

The use of PestNaB in connection with the establishing of pesticide policy objectives and action plans and monitoring of the development of the pesticide consumption and pressures on nature cannot stand alone but should form part of a broader assessment of pesticide consumption and pressures on nature.

PestNaB can be applied directly as a tool for analysis of the influence of potential initiatives for the reduction of the acute pressures of the pesticides on nature as the parameters can be changed individually.