04.09.2019 |

US agriculture 48 times more toxic to insects than 25 years ago

Neonics pose a threat to insects (Photo: CC0)

US agriculture is 48 times more toxic to bees and other insects than it was 25 years ago, new research shows. According to a study published in the journal PLOS One, neonicotinoid pesticides are to blame for most of the increase in toxicity. “It is alarming that U.S. agriculture has become so much more toxic to insect life in the past two decades,” said study co-author Kendra Klein, who is also a senior staff scientist at Friends of the Earth. “We need to phase out neonicotinoid pesticides to protect bees and other insects that are critical to biodiversity and the farms that feed us.” The peer-reviewed study, published on August 6, quantifies how hazardous US agricultural lands and surrounding areas have become for insect by calculating the Acute Insecticide Toxicity Loading (AITL). This new method accounts for the total mass of insecticides used in the US, acute toxicity to insects (bees) and the environmental persistence of the pesticides. It provides a way to compare changes in the toxicity of U.S. agriculture for insects on a yearly basis from 1992 through 2014.

The study reveals that the toxicity load has increased dramatically since neonicotinoids, a class of insecticides which affect the central nervous system of insects, were introduced in the 1990s. The authors found a 48-fold increase in toxic load from 1992 to 2014. Neonicotinoids are primarily responsible for this increase, representing between 61 to nearly 99% of the total toxicity loading in 2014. The study also shows a dramatic increase in the toxicity load beginning in the mid-2000s, which is when the practice of using neonicotinoids to coat the seeds of commodity crops like corn and soy started. Seed coatings now account for approximately 80-90% of total neonicotinoid use in the US. The three neonicotinoids that contributed most to the increasing toxic load were imidacloprid and clothianidin, manufactured by Bayer, and thiamethoxam, a product of Syngenta-ChemChina. In their press release, Friends of the Earth point to research, including an Environmental Protection Agency assessment, which shows that neonicotinoid seed coatings provide little to no economic benefits to farmers but come at a high cost to the environment. Only about 5% of the neonicotinoid coating is absorbed by the plant, the remainder is left in the soil where it can harm wildlife and run off to contaminate rivers, lakes and drinking water sources.

According to the study, the persistence of neonicotinoids creates a cumulative toxic burden in the environment that is much higher than that experienced by insects 25 or more years ago. While other commonly used insecticides break down within hours or days, neonicotinoids can be effective at killing insects for months to years after application. The authors state that the increase in toxic load measured by the study is consistent with recent reports of dramatic declines in beneficial insects and bird populations. “Our screening analysis demonstrates an increase in pesticide toxicity loading over the past 26 years, which potentially threatens the health of honey bees and other pollinators and may contribute to declines in beneficial insect populations as well as insectivorous birds and other insect consumers,” the authors warn. They assert that existing regulations for the registration of pesticides in the US are not adequate to prevent the introduction of chemicals that can cause harm in the environment. “Congress must pass the Saving America’s Pollinators Act to ban neonicotinoids,” said Klein. “In addition, we need to rapidly shift our food system away from dependence on harmful pesticides and toward organic farming methods that work with nature rather than against it.” (ab)

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