From soils to oceans, pesticides found “in all environments”

Soil, atmosphere, aquatic environments to the bottom of the oceans: contamination of the environment by pesticides “is proven for all walks of life”. The conclusion comes from a study coordinated by Inrae (the National Research Institute for Agriculture and Food) and Ifremer (French Research Institute for the Exploitation of the Sea), published on Thursday May 5. About forty researchers sifted through 4,000 scientific studies. They draw up an inventory of the effects of phytosanitary products on the biodiversity of French territory. Such an inventory had not been carried out since 2008.

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Phytosanitary products correspond to pesticides used in the agricultural sector, green spaces, gardens, or infrastructure (weeding railway tracks, for example), but also so-called biocontrol products, such as natural oils used as repellent in crops. Agricultural uses are responsible for 95 to 98% of the contamination noted by the study.

“Contamination peaks” near crops

Unsurprisingly, it is therefore next to cultivation areas that “contamination peaks” are raised. But not only: high concentrations of glyphosates have thus been found on the French coasts. And some chemical compounds have been found even in marine sediments, more than 3,000 meters deep or in regions near the poles. These substances found in the oceans have often been banned for several years, the study says.

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This presence is not neutral. “Phytosanitary products are one of the major causes of the decline of certain species”, emphasizes Wilfried Sanchez, Deputy Scientific Director of Ifremer. The first victims are terrestrial invertebrates: pollinators, such as bees, but also beetles, usually predators of certain crop pests. On a European scale, it is estimated that the contamination “would induce losses of up to 40% within these populations”.

“Sublethal” effects

Birds are also concerned, whether they are granivores (and therefore feed on contaminated seeds) or insectivores, through the consumption of contaminated prey. In this regard, “the preponderant role of neonicotinoids on the decline of certain populations has been highlighted”, notes the study. These insecticides are best known to the general public for their negative impact on pollinators. They had also been banned in France in 2018, before being temporarily authorized again for the cultivation of beets.

“Phytos” do not always lead to the death of certain living species, but can have deleterious effects: modification of behavior, reduction in reproduction, disruption of flight. At the level of marine organisms, the consequences are less clear: a link has been noted between pesticides and increased sensitivity of oysters or dolphins to certain viruses, but the impacts have only been observed at the level of certain individuals, without to be able to establish to what extent the species as a whole could be endangered.

Proposed solutions

Agricultural production itself could ultimately suffer from the use of products intended to protect it. Pollinators and predators of pests are indeed threatened. “The disappearance of these two essential services for cultivated agricultural production suggests a degradation that will ultimately affect human well-being”warns Wilfried Sanchez.

The authors nevertheless propose solutions to reduce the dispersion of these products in the environment, apart from the pure and simple reduction of their use. According to Laure Mamy, director of soil science research at Inrae, setting up buffer zones, such as hedges, grass strips or wetlands, can also help trap pesticides, “with an efficiency of up to 60%”.


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