Bees and other pollinators have been exposed to growing levels of toxicity from pesticides over 25 years, despite the amount used falling in the same period. The toxic exposure is based on US data but probably applies to other countries too.
Countries should consider following with 鈥渢oxicity taxes鈥� on pesticides to encourage farmers to change which products they use, says one of the researchers behind the new findings.
In recent years, pesticides that precisely target crop pests have been linking to falling insect numbers, with the European Union banning outdoor use of several widely used pesticides known as neonicotinoids in 2018. In January, following its exit from the EU, the UK of such 鈥渘eonics鈥� to kill aphids carrying a virus that threatens sugar beet.
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鈥淲e saw people from media, politics and even scientists often talk about how the amount of pesticides changes [over time]. At the same time, we saw, as ecotoxicologists, that the toxicity of pesticides changed. Some insecticides used today are way more toxic to some groups of organism than ones used decades ago,鈥� says Ralf Schulz at the University of Koblenz and Landau, Germany, who led the new research.
He and his team combined US government data on the weight of 381 pesticides used between 1992 and 2016 with their own index of the pesticides鈥� toxicity for different groups of species, from birds and mammals to pollinators and plants, to create a measure dubbed 鈥渢otal applied toxicity鈥�. They found that for pollinators, plants on land and aquatic invertebrates such as dragonflies, this increased by about 80 per cent between 2005 and 2016, even though the weight of pesticides used fell.
鈥淭his data suggests there is more toxic pressure on bees and plants [than thought],鈥� says Schulz. One solution could be a toxicity tax on pesticides, to incentivise farmers away from the most harmful ones, he suggests.
The researchers attributed most of the extra toxicity for insects and plants to the growing use of neonics and another group of insecticides, pyrethroids. While less toxic to birds, mammals and humans than the sort of 鈥渂road-spectrum鈥� pesticides used in the past, both are more harmful to insects that are similar to the pests they closely target.
鈥淥verall, the risk to wild insects 鈥� both pollinators and aquatic insects 鈥� seems to be increasing,鈥� says Dave Goulson at the University of Sussex, who .
The results are based on what species are exposed to in the US, but Schulz says it is fair to assume they are similar in other countries with high pesticide use. One limit to the research is that while it can gives a sense of the toxicity that insects and plants are exposed to, it doesn鈥檛 show how this affects the organisms.
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