Hypothesizing if responses to climate change affect herbicide exposure risk for amphibians

Abstract

Pesticide use is well known to be detrimental for maintaining biodiversity in the agricultural landscape. Amphibians are especially affected by these agrochemicals. In particular, these animals' high sensitivity was demonstrated for glyphosate-based herbicides which are dominating the world market today. Pesticide impacts are influenced by several co-stressors, and we for the first time link the exposure risk of amphibians to these commonly used pesticides to observed recent effects from ongoing climate change. In a simple verbal model, based on present-day data from Germany, we show that amphibian populations which have undergone phenological shift towards earlier reproduction potentially suffer less from applications of glyphosate-based herbicides compared to those which (yet) show no such reproductive shift. Although, apparently observed recent climate change effects lower the exposure risk, we advocate that amphibians are not necessarily safer now, mainly because farmers most likely will adapt their cultivation practices in the future if climate change becomes more obvious. Rather, we conclude that combining pesticide applications, climate change and phenological responses need an increased consideration in amphibian conservation. The results from our verbal model should be seen as a hypothesis that needs to be tested with specific field studies and (based on these data which are widely lacking today) more complex modelling of future exposure risk of pesticides to amphibians.

Rodeo™ Herbicide Negatively Affects Blanchard's Cricket Frogs (Acris blanchardi) Survival and Alters the Skin-Associated Bacterial Community

“…The increased mortality in our highest Rodeo concentration was consistent with other studies, however, demonstrating reduced survival in several amphibian species at environmentally relevant concentrations of glyphosate-based herbicides (Relyea, 2005;Relyea and Hoverman, 2006). Furthermore, environmental factors such as competitors, predators, and temperature, may exacerbate negative effects of glyphosate on amphibian survival across life stages (Relyea et al, 2005;Wagner et al, 2013;Lö tters et al, 2014). Acris blanchardi have a central North American distribution (Gamble et al, 2008) and habitats vary in numerous biotic and abiotic ways, so some populations may be more sensitive to glyphosate exposure than others.…”

Temperature-Dependence of Glyphosate-Based Herbicide's Effects on Egg and Tadpole Growth of Common Toads

“…Asian amphibian species have shown temperature-dependent toxicity patterns with the pesticide methomyl (Lau et al, 2015). However, Lötters et al (2014) state that a phenological shift of certain amphibian species toward earlier reproduction due to climate change might expose them less to glyphosate-based herbicides compared to those which do not show a shift in reproduction time. In Europe, the Common toad (B. bufo) is the most widespread amphibian species, living in habitats from lowland up to mountainous areas over 2000 m above sea-level (Cabela et al, 2001;Arnold and Ovenden, 2002).…”

How Does Changing Pesticide Usage Over Time Affect Migrating Amphibians: A Case Study on the Use of Glyphosate-Based Herbicides in German Agriculture Over 20 Years

“…This is because both the migration modes of the species (i.e., early or late migrating species) and the crop cultivation systems with respect to GLY applications are widely similar. Additionally, both the timing of agricultural cultivation and the timing of amphibian activity are driven by climate and weather conditions and may lead to a uniform time shift (Lötters et al, 2014). Thus, we are confident the observed trends are valid for arable regions in the northern lowlands of Germany where glyphosate is applied and amphibians are present.…”