Banned since 2018 in European fields, neonicotinoids nevertheless remain at the heart of debates on the future of agriculture and biodiversity. These synthetic insecticides, widely used since the 1990s, are recognized for their toxic effects on bees, but their consequences on other species remained less documented. For the first time, a study conducted by Thomas Perrot, researcher at the Foundation for Biodiversity Research (FRB), and published in the journal Environmental Pollution, shows the beginnings of recovery in certain species of insectivorous birds in France.
These results, from data collected on more than 1,900 sites by the Temporal Monitoring of Common Birds (STOC) of the National Museum of Natural History, suggest a direct link between the ban on these pesticides and the increase in populations of birds dependent on insects for food.
Imidacloprid implicated in documented decline of insectivorous birds
Imidacloprid, the main neonicotinoid used in France until 2018, is now identified as a major factor in the decline of insectivorous birds. This pesticide was found massively in surface waters, agricultural soils, earthworms, and even in the tissues of rodents and birds. It affects both the availability of food (especially insects) and the direct health of birds through acute or chronic toxicity. Insectivorous species, which are closely dependent on invertebrates, remain the most vulnerable to these effects.
The study analyzed data from French Breeding Bird Survey (FBBS) on nearly 2,000 plots between 2013 and 2022. Result: the presence of imidacloprid was associated with a 12.7% drop in the abundance of insectivorous birds before the ban, and another 9% after. This shows a persistence of impact, despite the official cessation of use.
Granivores and generalist species, on the other hand, showed no significant links. Or only non-linear responses to pesticides. This distinction reinforces the idea that neonicotinoids act primarily through the insect food chain. It confirms the hypotheses of previous work carried out in the United States and the Netherlands.
The researchers also introduced an innovative indicator, the Total Applied Toxicity (TAT). It measures the cumulative toxicity of pesticides on different biological groups. This tool confirms that the environmental impact goes well beyond imidacloprid alone. He calls for a global review of the management of agricultural inputs.
A timid but measurable recovery after the European ban
The European Union's decision to ban neonicotinoids in 2018 aimed to stem their dramatic impact on pollinators. But its effects on bird populations remained little studied. Four years later, researchers note a slight but real recovery in insectivorous species. The data show a reduction in the gap in abundance between sites exposed to imidacloprid and those that were not.
This limited recovery remains hampered by the high persistence of imidacloprid in soils and aquatic environments. Several recent studies demonstrate that this molecule can remain active several years after its application. In France, although its use has been prohibited since 2018, exemptions have been granted for the cultivation of sugar beets in 2021 and 2022. Which thus prolongs the presence of the pesticide in the environment.
Furthermore, other environmental pressures persist, such as habitat fragmentation, climate change or agricultural intensification. This complicates the interpretation of the data and makes it difficult to exclusively attribute the changes observed to the cessation of the pesticide.
For Thomas Perrot, these results demonstrate that a strict regulatory framework can generate measurable effects on biodiversity. However, the slowness of the process is a challenge. “
It will probably take several decades to see a real restoration of populations », he explains to Guardian. An observation based on the historical precedents of DDT.
Unequal response dynamics depending on species and ecological contexts
One of the key results of Perrot and colleagues' study was the clear difference in response between groups of birds. Insectivores react noticeably to imidacloprid. While granivores and generalist species show greater resilience. This variability highlights the importance of considering diets in conservation policies.
The study analyzed the abundances of 57 species on 1,983 plots distributed throughout France. Insectivores showed linear sensitivity to imidacloprid. In other words, the greater the exposure, the more populations fall. On the other hand, granivores sometimes experienced a peak in abundance at an intermediate level of exposure. This suggests complex mechanisms or interactions with other variables.
These results also reveal spatial heterogeneity. Insectivorous birds are more numerous in the center, northwest and east of France. While granivores dominate in the south. This distribution reflects both ecological conditions and the differentiated uses of pesticides, linked to local crops.
Another determining factor is the configuration of the landscapes. Intensive agricultural areas, with few hedges or meadows, promote the concentration of chemicals and deplete food resources. Conversely, plots of extensive or organic agriculture, better equipped with semi-natural habitats, offer a refuge for biodiversity.
A turning point to be confirmed for agricultural biodiversity
If the ban on imidacloprid marks a regulatory break, the results of the study show that the ecological transition remains to be consolidated. The slowness of the biological response highlights the limits of a purely regulatory approach. The persistence of neonicotinoids, their accumulation in soils, and occasional exemptions undermine restoration efforts.
For Thomas Perrot, the challenge now is to go beyond the ban. “ We must strengthen actions to restore habitats, limit all pesticides, and integrate biodiversity into agricultural models. “. The TAT indicator, introduced in the study, offers a new method to assess the combined impact of chemicals on wildlife. Because, indeed, it takes into account direct and indirect effects. This type of tool could guide more global and better targeted policies.
The study also highlights the role of European policies, notably the “Farm to Fork” strategy of the Green Deal. But their application remains uneven. In addition, the objectives of reducing pesticides by 50% by 2030 still seem distant. The simplification of substance authorization procedures, pressure from agrochemical lobbies and the heterogeneity of practices between countries are slowing down progress.
To accelerate the movement, the authors call for strengthening funding for agroecological agriculture, generalizing ecological infrastructure (hedges, grassy strips), and supporting independent research on the cumulative effects of chemicals. We must promote the ecological diversity of landscapes. It is not only about preserving birds, but more broadly about guaranteeing resilient ecosystems and ecosystem services essential to agriculture itself.
Source: Thomas Perrot et al., “Weak recovery of insectivorous bird populations after ban of neonicotinoids in France, hinting at lasting impacts“. Environmental Pollution, Volume 385, 15, November 2025, 127132
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