Herbicides and plant communities – field studies instead of single plant pot experiments in new risk assessment approaches

In this post, Carsten Brühl informs about their recent paper on the risk posed by herbicides to non-target plants.

Large scale field study assessing effects of pesticides on community composition (photo by C. Brühl)

Large scale field study assessing effects of pesticides on community composition (photo by C. Brühl)

In the EFSA “Scientific Opinion addressing the state of the science on risk assessment of plant protection products for non-target terrestrial plants” published in summer 2014 the risk assessment of pesticides towards plants was addressed. So far the risk assessment is mainly based on single species studies generated in a laboratory that do not take reproductive endpoints or interaction between species resulting in effects on community composition into account. One issue that was therefore mentioned in the scientific opinion is the conduct of higher tier studies that can be used for risk assessment “ When required, higher tier tests should be conducted under more realistic conditions.” In the publication of Juliane Schmitz, Peter Stahlschmidt, and Carsten A. Brühl titled “Assessing the Risk of Herbicides to Terrestrial Non-Target Plants Using Higher-Tier Studies” we evaluated the current literature and identified only sixteen field studies with plant species that were performed so far. The paper was recently published in Human and Ecological Risk Assessment.

Abstract: Risk assessment for non-target plants is based on single species phytotoxicity tests. This approach may not reflect relevant ecological processes in terrestrial ecosystems. The current risk assessment scheme is based on endpoints measured at the species level and the assessment of ecological effects relies on the extrapolation from one species to another or from a single species to a community. This extrapolation contains many uncertainties that may be reduced by adopting more realistic testing approaches. However, currently higher-tier plant studies are not obligatory in herbicide risk assessment. We reviewed the published literature and found that potential higher-tier approaches for terrestrial non-target plants are extremely limited. Sixteen studies were found that assessed the effects of herbicides on non-target plants by performing microcosms, mesocosms, or field studies. These studies showed that microcosms might provide useful data and help to reduce uncertainties associated with single-species tests. However, due to the limited number of available studies, much work is required to develop appropriate testing methods for regulatory processes. In addition, field experiments are necessary to establish baseline knowledge concerning the effects of herbicides on natural plant communities and to compare data generated in tiered testing approaches with data obtained from natural systems.

Related publications:

Juliane Schmitz, Melanie Hahn & Carsten A. Brühl (2014) Agrochemicals in field margins – An experimental field study to assess the impacts of herbicides, insecticides, and fertilizer on the plant community. Agriculture, Ecosystems and Environment 193, 60-69.

Juliane Schmitz, Karoline Schäfer & Carsten A. Brühl (2014) Agrochemicals in field margins – Field evaluation of plant reproduction effects. Agriculture, Ecosystems and Environment 189, 82–91.

Juliane Schmitz, Karoline Schäfer & Carsten A. Brühl (2013) Agrochemicals in field margins – Assessing the impacts of herbicides and fertilizer on the common buttercup Ranunculus acris. Environmental Toxicology and Chemistry, 1124-1131.