CEA presented 16 posters at SETAC Dublin in April/May 2023. We will be showcasing each of these presentations in a series of ‘SETAC Spotlight’ articles. This week it is:
Occurrence of common frog and common toad in agricultural fields in Germany: potential for exposure to plant protection products
Authors: Arnd Weyers1, Nadine S. Taylor2, Hanna S. Schuster2, Jan Sadowski3 and Lennart Weltje4
1Bayer AG, Crop Science Division, Environmental Safety, Monheim, Germany; 2Cambridge Environmental Assessments (RSK ADAS Ltd.), Cambridge, UK; 3University of Münster, Institute of Landscape Ecology, Heisenbergstraße 2, 48149 Münster, Germany; 4BASF SE, Agricultural Solutions – Ecotoxicology, Speyerer Strasse 2, 67117 Limburgerhof, Germany.
The appropriate and effective assessment of the ecological risk of chemicals to amphibians is a current topic of debate. Amphibians are a highly endangered class of vertebrates and while the major causes for population declines are habitat loss and diseases, other factors like introduced predatory species and exposure to chemicals, including plant protection products (PPPs), are also implied. For risk assessment of PPPs, a consideration of exposure and toxicity is required. Here, we present results of a project that studied occurrence and habitat use of adult and metamorph common frogs (Rana temporaria) and common toads (Bufo bufo) in an agricultural landscape, and the implications for potential exposure to PPPs.
The 4 sites (ponds) selected for the study had > 85% agricultural land (mainly cereal fields) surrounding the ponds and were suitable to study amphibian occurrence in agricultural land. Adults were monitored with radio tracking devices for 2 years and juveniles were caught in pitfall traps using drift fences and then released.
Adult frogs and toads were rarely observed in arable fields, i.e. only 0.5% and 4% of the sightings, respectively. Abundance of metamorphs in arable land around two sites was 0% and 16% of the catches. For a third site, completely surrounded by arable fields, the number was higher at 39% (frogs) and 26% (toads) of sightings. The fourth site had no interpretable metamorph data, because of an accidental manure contamination of the water body killing most tadpoles. Metamorphs of both species tended to remain close to their natal ponds and their in-field occurrence decreased with distance from the water body.
Thus, the presence of amphibians in arable fields was limited and primarily occurred later in the summer, when metamorphs had left the breeding pond and when crops were denser and hence crop interception of sprayed PPPs is higher. This, together with the hiding behaviour during the day would limit the risk of dermal exposure.
The use of buffer zones around water bodies in agricultural areas would thus be highly effective as a risk mitigation strategy in protecting the metamorph life stages and will also reduce spray drift entry into water bodies following PPP applications. We hope that the results will contribute to data-driven environmental decision-making and to the discussion on effective risk assessment and mitigation options for this taxonomic group.
If you would like to discuss any of the topics raised in this article, feel free to contact us.
The poster is available for free download.
You can find all of the other posters that CEA presented at SETAC Dublin here. You can also find all of our publications from previous conferences and links to journal articles we have authored on our library page.
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