Fred Heimbach

Ecological models in support of regulatory risk assessments of pesticides: developing a strategy for the future.

Abstract This brief communication reports on the main findings of the LEMTOX workshop, held from 9 to 12 September 2007, at the Helmholtz Centre for Environmental Research (UFZ) in Leipzig, Germany. The workshop brought together a diverse group of stakeholders from academia, regulatory authorities, contract research organizations, and industry, representing Europe, the United States, and Asia, to discuss the role of ecological modeling in risk assessments of pesticides, particularly under the European regulatory framework. The following questions were addressed: What are the potential benefits of using ecological models in pesticide registration and risk assessment? What obstacles prevent ecological modeling from being used routinely in regulatory submissions? What actions are needed to overcome the identified obstacles? What recommendations should be made to ensure good modeling practice in this context? The workshop focused exclusively on population models, and discussion was focused on those categories of population models that link effects on individuals (e.g., survival, growth, reproduction, behavior) to effects on population dynamics. The workshop participants concluded that the overall benefits of ecological modeling are that it could bring more ecology into ecological risk assessment, and it could provide an excellent tool for exploring the importance of, and interactions among, ecological complexities. However, there are a number of challenges that need to be overcome before such models will receive wide acceptance for pesticide risk assessment, despite having been used extensively in other contexts (e.g., conservation biology). The need for guidance on Good Modeling Practice (on model development, analysis, interpretation, evaluation, documentation, and communication), as well as the need for case studies that can be used to explore the added value of ecological models for risk assessment, were identified as top priorities. Assessing recovery potential of exposed nontarget species and clarifying the ecological relevance of standard laboratory test results are two areas for which ecological modeling may be able to provide considerable benefits.

An individual‐based approach to model spatial population dynamics of invertebrates in aquatic ecosystems after pesticide contamination

In the present study we present a population model (Metapopulation model for Assessing Spatial and Temporal Effects of Pesticides [MASTEP]) describing the effects on and recovery of the waterlouse Asellus aquaticus after exposure to a fast-acting, nonpersistent insecticide as a result of spray drift in pond, ditch, and stream scenarios. The model used the spatial and temporal distribution of the exposure in different treatment conditions as an input parameter. A dose-response relation derived from a hypothetical mesocosm study was used to link the exposure with the effects. The modeled landscape was represented as a lattice of 1- by 1-m cells. The model included processes of mortality of A. aquaticus, life history, random walk between cells, density dependence of population regulation, and, in the case of the stream scenario, medium-distance drift of A. aquaticus due to flow. All parameter estimates were based on expert judgment and the results of a thorough review of published information on the ecology of A. aquaticus. In the treated part of the water body, the ditch scenario proved to be the worst-case situation, due to the absence of drift of A. aquaticus. Effects in the pond scenario were smaller because the pond was exposed from one side, allowing migration from the other, less contaminated side. The results of the stream scenario showed the importance of including drift for the population recovery in the 100-m stretch of the stream that was treated. It should be noted, however, that the inclusion of drift had a negligible impact on numbers in the stream as a whole (600 m).

Correlation between data from laboratory and field tests for investigating the toxicity of pesticides to earthworms

Abstract A laboratory procedure using an artificial soil (“Artificial Soil Test”) and Eisenia fetida as test species is widely used to investigate the toxicity of pesticides to earthworms. In order to validate the results of this test in respect to natural earthworm populations, and to allow the ecological significance of the laboratory data to be interpreted and extrapolated to the field, a field test was developed. Pesticides were sprayed on perennial grassland plots which had high abundances and species diversities of earthworms. In the field tests, the biomass of the earthworms and their abundance were determined shortly (4–6 weeks) after pesticide application in spring, in autumn of the same year, and in spring of the following year. To date, 21 field tests using 12 different products have been conducted. The pesticides were sprayed at the highest recommended application rate and at four times this rate. An exposure calculation was used which allowed comparison of laboratory LC 50 -values to “estimated environmental concentrations” (EEC) in soils derived from field application rates. A good correlation was found between laboratory results and effects on earthworm populations in the field. Relatively pronounced field effects were observed with pesticides of high intrinsic toxicity and high application rates; short-term effects were found with the less toxic compounds. No, or negligible, effects were found on earthworm populations in the field with pesticides that showed low toxicity to earthworms in laboratory tests, or that were applied at low rates.

The chironomid acute toxicity test: development of a new test system.

This paper describes the basis for a water-only acute chironomid toxicity test guideline using first-instar larvae. The method is based on the OECD test guidelines for the acute Daphnia sp. immobilization test and the long-term tests with Chironomus sp., reflecting the common test procedures currently used by the European agrochemical industry. Development of this guideline proposal is important under the European Plant Protection Products Directive (91/414/EEC), under which an insect species may be required to be tested, particularly for certain insecticides, for which Daphnia sp. may not be representative of the sensitivity of nontarget aquatic invertebrates. Chironomus sp. is a freshwater insect currently used in different international test guidelines. Because their ready availability as a test organism, with culturing conditions and certain test methods already established, Chironomus sp. is regarded as a suitable additional freshwater invertebrate species for regulatory testing.

Field tests on the side effects of pesticides on earthworms: Influence of plot size and cultivation practices

Abstract Standardized field tests, which ran for up to one year, were used to investigate the side effects of pesticides on earthworms under agricultural conditions. The studies were run on 10 × 10 m replicate plots of flat, uniform grassland areas. Benomyl was used as a reference substance. To exclude migration of earthworms from untreated plots to plots where earthworm abundance had been reduced by the test compound, a mechanical barrier was used. The results showed, that an invasion of earthworms from surrounding grassland into benomyl-treated plots without barriers did not occur during a one-year study. In a further study, parathion-methyl was used to investigate the combined effects of cultivation practices and pesticide treatments on earthworms, since laboratory data could not exclude a possible hazard for earthworms under practical conditions. For this study, the pesticide was sprayed on different plots on which either (1) the grass cover was mulched, (2) the grass was cut and removed, or (3) the grass was ploughed and re-seeded just before application on the bare soil. Earthworm samples were collected about two, five and 11 months after application for species identification and enumeration. Earthworms did not seem to be influenced differently by mulching or by cutting and removing the grass. Ploughing, however, reduced earthworm abundance significantly. The results indicated that 0.3 and 1.5 kg a.i. ha −1 of methyl-parathion had no effects on the earthworm abundance. This indicated that earthworm field studies performed on grassland yield the same results as those which are performed in agricultural soils.

Large-scale monitoring of effects of clothianidin-dressed oilseed rape seeds on pollinating insects in Northern Germany: justification of study design and statistical analysis

The commentary by Bailey and Greenwood makes several strong criticisms of the monitoring study of Heimbach et al. (2016), which are not applicable or misleading. These misrepresentations include the claim that the experimental design of this study was inappropriate and that the statistical analysis in the way it was conducted was senseless. Methods have been described in detail by Heimbach et al. (2016); Peters et al. (2016); Rolke et al. (2016a; b); Sterk et al. (2016) and the aspect of “pseudoreplication” has been discussed in Heimbach et al. (2016) and in detail in Rolke et al. (2016a). Therefore the criticism of Bailey and Greenwood does not add new facts to the scientific audience, overall. With this letter, we respond to the points of criticism discussing basic aspects of the study.

Laudation to PD Dr. Wolfgang Ahlf: towards integrated approaches in sediment toxicology and its transfer to sediment quality guidelines

Thanking PD Dr. Wolfgang Ahlf on the occasion of his retirement for his outstanding experimental and conceptual merits in the field of sediment ecotoxicology and his personal 65th anniversary this article will present a laudation. This Editorial furthermore introduces a series of papers on ‘Progress in sediment research and decision making’ which is dedicated to Wolfgang Ahlf, one of the longstanding and leading experts in the field of sediment research. We cordially invite all colleagues who feel they can contribute to the topic to submit a manuscript to ESEU with reference to this series.

Laudation to Prof. Dr. Hans-Toni Ratte--towards conceptual, theory-based ecological science and its transfer to the applied field of ecotoxicology

In order to thank Prof. Dr. Hans-Toni Ratte on the occasion of his retirement for his outstanding experimental and modelling merits in the field of ecotoxicology and ecology and his personal 65th anniversary on November 25th this article will present a laudation.