P.Esticide use in the US has declined more than 40 percent over the past three decades, and some organisms, including mammals and birds, have benefited from declines in pesticide use and improvements in product design, according to a study published April 2 science. However, increasing the pesticide effect is at the expense of the health of other species.
“Compounds that are particularly toxic to vertebrates have been replaced by compounds with lower vertebrate toxicity, and that is indeed a success,” explains co-author Ralf Schulz, ecotoxicologist at the Universities of Koblenz and Landau in Germany The guard. “At the same time, pesticides became more specific and therefore unfortunately more toxic to ‘non-target organisms’ such as pollinators and aquatic invertebrates.”
Schulz and his team combined self-reported data from the US Geological Survey on the use of 381 pesticides by farmers between 1992 and 2016 with data from the Environmental Protection Agency (EPA) on the toxic dosage effects of these chemicals on eight species of animals and plants: fish, mammals, Birds, pollinators, terrestrial and aquatic invertebrates, and land and aquatic plants. Using the two data streams, the authors calculated an overall use toxicity score for each group to assess changes in pesticide use and their effects over time.
Taken together, the results show that despite the decline in their use, pesticides continue to adversely affect many different life forms. The toxicity of pesticides doubled in aquatic invertebrates such as plankton and insect larvae, and so did important pollinators such as bees. Mammals and birds were the only groups to benefit over the course of the study – their toxicity levels dropped more than 95 percent – but even these groups can be negatively affected by changes in the food web.
“The bottom line is that these pesticides, once thought to be relatively harmless and so short-lived that they wouldn’t harm ecosystems, are anything but,” says Lynn Goldman, a former EPA scientist who was not involved in the study. opposite Associated Press.
The results largely reflect how technology has changed the landscape of pesticide design. Pesticides have gotten stronger, sometimes requiring as little as 6 grams per acre compared to several kilograms of older chemicals like organophosphates and carbamate pesticides. science Reports. Companies have also gotten better at tailoring their products to specific agricultural pest species while minimizing inadvertent damage to other organisms, although they are not specific enough to distinguish between pests and potentially beneficial insects.
This vertebrate / invertebrate compromise could have unintended consequences for the health and functioning of ecosystems, says Schulz. Aside from their importance as pollinators, many insect species are food for other animals, and the current study does not measure the accumulation of toxins in the food web, as Schulz tells the AP, which he would like to pursue in future research.
In the current study, plants also registered increasing toxicity, even in species that have been genetically engineered to reduce their need for pesticides. For example, a stem of corn has been modified to make an insecticidal chemical. However, as the insects developed a tolerance to the chemical, farmers responded with more frequent uses of other pesticides. Wild plants are also susceptible to pesticide toxicity, particularly from commonly used weed killers, and their use risks reducing overall plant diversity in uncultivated areas around agricultural fields.
To avoid this future, countries around the world need to think more critically about pesticide use, says John Tooker, an entomologist at Penn State who was not involved in the research science. “The patterns in US pesticide use and toxicity data should be a cautionary story to the rest of the world, much of which appears to rely on pesticide use rather than ecological pest control interactions.”