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Pesticides likely affect over 800 species of microbes, fungi, plants, insects, fish, birds and mammals, according to a new study. These species are non-target organisms that are not intended for harm by pesticides like insecticide, fungicide and herbicide, showed the report published in Nature Communication.
The pesticides negatively affect growth, reproduction and behaviour, such as their ability to catch prey, find plants to forage upon, move or attract mates, damage cells and metabolism and survival within terrestrial and aquatic systems. “It is often assumed that pesticides are toxic primarily to the target pest and closely related organisms, but this is clearly not true. Concerningly, we found pervasive negative impacts across plants, animals, fungi and microbes, threatening the integrity of ecosystems,” Dave Goulson of the University of Sussex and author of the study said in a statement.
Previous studies have shown that fungicides may affect arbuscular mycorrhizal fungi (natural root symbionts that provide essential plant inorganic nutrients to host plants), affecting their symbioses with higher plants. Herbicides may reduce plant pollen viability and carbohydrate metabolism, while insecticides that target pest herbivores could drive long-term declines in non-target insect pollinators.
Individual studies have reported on negative impacts on microorganisms, plants, invertebrates, amphibians, birds and mammals. Regulatory risk assessments of pesticides, however, have focused on a limited number of species like rats, zebrafish, algae, honeybees and earthworm, the study noted.
It added that the agricultural industry, governmental bodies and conservation organisations debate on the real-world hazards posed by pesticides. This is majorly due to a lack of understanding pesticide effects across different species.
So, the researchers from China and Europe set out to analyse how different types of pesticides affect the diversity of multiple non-target eukaryotic and prokaryotic organisms across all trophic levels, and across climatic zones, for major mechanisms of exposure, such as those acting in aquatic or terrestrial environments.
The team integrated 20,212 estimates of pesticide effects reported from 1,705 experimental studies, which have looked at the effects of insecticides, fungicides and herbicides on animals (invertebrates and vertebrates), plants (dicotyledonous, monocotyledonous and spore-producing) and microorganisms (bacteria and fungi studies).
Studies analysed also included laboratory and field experiments from temperate and tropical climatic zones, both in aquatic and terrestrial systems.
The analysis showed that insecticides, fungicides and herbicides broadly affect non-target organisms tested by consistently decreasing growth and reproduction, while also eliciting behavioural responses in animals and disturbing metabolic or physiological status. These harmful effects were more pronounced in temperate regions than the tropics.
The researchers called for policy changes to reduce pesticide use and increase adoption of green pesticides. They also recommended post-licensing biodiversity monitoring to understand and predict hazards such as long-term low-level exposure and cumulative effects at the landscape level.
“Pesticides are a necessary evil, without which global food production and farmers’ livelihoods would likely collapse. However, our findings highlight the need for policies and practices to reduce their use. This could include bottom-up initiatives led by farmers such as regenerative agriculture, as well as government policies such as Defra’s Sustainable Farming Incentive, which pays farmers to reduce insecticide use on crops,” Ben Woodcock, an ecologist at the United Kingdom Centre for Ecology & Hydrology, said in a statement.
