Identifying agricultural pesticides that may pose a risk for birds

Abstract

In this study, we analyze changing patterns of pesticide use in agriculture in Great Britain over the 1990–2016 period, with respect to the risk they pose to birds. The weight of pesticides applied decreased by 51% between 1990 and 2016, but the area treated increased by 63% over the same period. Over this period, there has been considerable turnover in the pesticides used. The European Union (including Great Britain until 2020) has restricted or banned many pesticides for agricultural use, including organophosphates and carbamates. However, new generations of active substances have been introduced, such as the neonicotinoids, some of which have since been banned. In this analysis, we estimate the annual ‘toxic load’ of agricultural pesticide use in Great Britain for birds, measured as the total number of LD50 doses for corn buntings, Emberiza calandra. We have previously performed similar analyses for bees, for which the total toxic load increased six-fold during this period. In contrast, for birds the total toxic load fell by 80.5%, although still correspond to 8.3e+11 corn bunting LD50 doses in 2016. The decrease in toxicity is largely due to declining use of highly toxic organophosphates in recent years. We identify the pesticides in current use that may pose the highest risk to birds, which include a mix of insecticides, herbicides, fungicides, molluscicides, acaricides and plant growth regulators. The insecticide ethoprop was ranked highest in 2016, with a toxic load of 71 billion potential corn bunting kills. Some of the other chemicals presenting a high toxic load, such as the herbicide chlormequat, are not highly toxic to birds (in terms of LD50) but are used in very large quantities. However, it is important to stress that, in reality, only a tiny proportion of pesticides applied will be ingested by birds, and this will vary according to timing and method of application, persistence of the active substance and many other factors. We further note that impacts of pesticides on birds might often be indirect, for example via depleting their food supply, and that sublethal impacts may occur at much lower doses than the LD50, neither of which do we investigate here. Nonetheless, we suggest that this is a useful approach to highlight pesticides that might be worth closer study with regard to possible impacts.

Noninvasively Collected Fecal Samples as Indicators of Multiple Pesticide Exposure in Wild Birds

“…Finding sources of pesticide residues is a complex undertaking because many factors influence if and when a pesticide comes into contact with birds (Tassin de Montaigu & Goulson, 2020). Gross et al (2020) analyzed fecal samples in the 24‐h period following dosing and found residues of the parent active substance.…”

“…Over the past few decades, research has found a range of lethal and sublethal effects on birds caused by pesticides (Tassin de Montaigu & Goulson, 2020). Reduced survival and fertility, poisoning, abnormalities, and reduced mobility and navigation ability were found (Tassin de Montaigu & Goulson, 2020). We found no significant differences in relative weight, fat, or muscle score between exposed and unexposed Eurasian skylarks, but we did observe a possible decrease in the probability of a sample containing pesticide residues in individuals with better body condition (Figure 2).…”

Field evidence of UK wild bird exposure to fludioxonil and extrapolation to other pesticides used as seed treatments

“…While there has been much research on the effects of insecticides on birds, other pesticides have received little or no attention. Fungicides and herbicides tend to be less acutely toxic to non-target species than insecticides, but are applied in higher quantities than insecticides (Lopez-Antia et al 2016;Tassin de Montaigu and Goulson 2020). A handful of studies have investigated the effects of seed treatment with fungicides on bird species (McGary et al 2001;Grote et al 2008;Satre et al 2009;Köhler and Triebskorn 2013;Lopez-Antia et al 2013Pandey and Mohanty 2015;Gross et al 2020;Ortiz-Santaliestra et al 2020;Mateo et al 2016).…”

“…Firstly, we estimated the LD50 (mg/bird) (the dose of substance that gives a 50% probability of death), for each species observed feeding on treated seeds using scaling factors based on weight (Mineau et al 1996(Mineau et al , 2001Tassin de Montaigu and Goulson 2020). For the five insecticides and 15 fungicides that are frequently used as seed treatment (in Europe, North America, and/or Asia), the LD50 (mg/kg of body weight) was obtained from the Pesticides Properties DataBase (PPDB University of Hertfordshire).…”

“…The dose ingested by birds in a single feeding bout on treated seeds can be sufficient to cause lethal and sublethal effects (Prosser and Hart 2005). Even if less acutely toxic to avian species, fungicides are applied in greater quantities than insecticides (Tassin de Montaigu and Goulson 2020) and could represent a risk to birds. Mateo et al (2016) estimated, using daily food intake, that the fungicides thiram and tebuconazole could represent a risk to red-breasted geese (Branta ruficollis).…”