Pesticides are among the central drivers of global species extinction. They are used in modern agriculture to secure yields, but they deeply interfere with ecological processes. It has long been known that these chemical plant protection products have effects far beyond their actual target organisms. Recent research increasingly shows the true extent of these effects.
As early as 2025, a meta-analysis in the journal Nature Communications showed that pesticides have negative impacts worldwide on hundreds of non-target species. The evaluation of more than 1,700 studies documented impairments in growth, reproduction, behavior, and survival in over 800 species. It also became clear that modern pesticides are by no means more environmentally friendly than older active ingredients.
However, this comprehensive analysis left open the question of whether the described biological damage also translates into measurable population declines of wild animal species in the open landscape. A new pesticide study from France, published in 2026 in the Proceedings of the Royal Society B, now addresses this.
What is the study about?
The study investigates how strongly pesticide use is linked to the abundance of common bird species in agricultural landscapes. This is analyzed for all of France, with the aim of making the influence of pesticides visible under real-world conditions.
The focus is on common breeding bird species, i.e., species that were long considered comparatively robust and inhabit large parts of agricultural landscapes. The analysis is based on extensive bird counts from a citizen science program, which were linked with regional data on pesticide use.
The aim of the study was to answer the following question: Is there a measurable correlation between pesticides in the landscape and the abundance of birds, and can this effect be separated from other aspects of intensive agriculture?
(© Maasaak, CC BY-SA 4.0, via Wikimedia Commons)
How did the researchers proceed?
The analysis was conducted at a national level. 242 different pesticide active ingredients were considered – almost all substances sold in 2017 – in relation to the agricultural area of the respective region.
To verify the validity of the data, the researchers compared sales figures with measurements of pesticide residues in water bodies. A correlation emerged: Regions with high pesticide sales also showed higher residues. The sales data thus serve as a reliable indicator of regional environmental pollution.
The bird population data comes from the French Breeding Bird Monitoring (STOC), a long-standing citizen science program with standardized counts. 64 common bird species at over 2,000 counting points in agricultural landscapes were analyzed. It is also crucial that the influence of pesticides was separated from other factors of intensive agriculture, such as landscape structure, fertilization, or climate.
More Pesticides, Higher Bird Decline
Long-term data had already shown a significant decline in common bird species in France for years. An evaluation published in 2021, based on the same bird monitoring system as the current study, documented a population loss of approximately 29% within three decades (1989–2019). Agricultural landscapes and urban areas were particularly affected, while losses in forest habitats were significantly lower or populations remained largely stable there.
The new pesticide study now provides an explanation for these long-term trends. Its central finding is: With increasing pesticide use, the abundance of most bird species decreases. This pattern is evident in 84.4% of the species studied, with 25 of them showing statistically significant results. The results thus point to a widespread negative impact of pesticides on bird populations in agricultural landscapes.
Not Only Typical Farmland Birds Are Affected
The researchers also show that the link between pesticide use and bird abundance extends far beyond a few sensitive specialists. In regions with high pesticide use, not only classic farmland birds are less common, but also numerous widespread species that regularly use agricultural areas for foraging. Pesticides thus affect the entire spectrum of species in agricultural landscapes.
The study does not provide specific decline figures for individual species. Instead, it analyzes how the abundance of bird species changes spatially with regional pesticide use. For many typical agricultural species, a clear negative correlation emerges – as well as for several species actually considered adaptable.
Classic Agricultural Species
Expected affected species include birds of the open agricultural landscape whose way of life is closely tied to fields, arable land, and meadows.
(© Kostikidis Georgios, CC BY-SA 4.0, via Wikimedia Commons)
- Skylark (Alauda arvensis)
The skylark is significantly less common in regions with high pesticide use. A key reason is likely the decline in insects, which are indispensable for raising young birds. Regardless of this study, the skylark has been considered a species of concern throughout Europe for years, with documented strong long-term declines (see, among others, in the Biodiversity Fact Check of 2024). - Corn Bunting (Emberiza calandra)
The corn bunting also reacts significantly negatively to high pesticide use. It relies on structurally rich agricultural landscapes with fallow land, field margins, and a diverse food supply – structures that are increasingly lacking in intensively managed regions. Accordingly, it has long been among the losers of modern agriculture. - Grey Partridge (Perdix perdix)
The grey partridge is particularly sensitive to insect losses. Chicks feed almost exclusively on insects in their first weeks of life. If these are decimated by pesticides, survival and reproduction rates decrease significantly. The partridge is therefore considered a classic example of indirect pesticide effects, where the birds themselves are not poisoned, but their food source disappears.
In addition to skylarks, corn buntings, and partridges, the study includes numerous other common bird species of agricultural landscapes. These include, among others, Yellowhammer, Lapwing, Starling, Chaffinch, Great and Blue Tit, as well as various warbler and wagtail species. For these species too, a predominantly negative correlation between pesticide use and abundance is observed.
Widespread Species Also Affected
The French study also shows that even supposedly robust “commonplace species” are less common in pesticide-rich regions, including:
(© Francesco Veronesi from Italy, CC BY-SA 2.0, via Wikimedia Commons)
- Nightingale (Luscinia megarhynchos)
Although not a typical agricultural bird, the nightingale shows a negative correlation with pesticide use. It often searches for insect food in adjacent agricultural areas – if the supply there decreases, this directly affects breeding success. - Chiffchaff (Phylloscopus collybita)
The chiffchaff, actually tied to forests and woodlands, regularly uses agricultural areas for insect hunting. It is also less common in regions with high pesticide use, which underscores the reach of indirect effects. - Blackbird (Turdus merula)
The blackbird is considered an adaptable generalist. It is all the more remarkable that it is less common in intensively managed agricultural landscapes with high pesticide use. This indicates that even robust species reach ecological stress limits. - House Sparrow (Passer domesticus)
The house sparrow is also less common in pesticide-rich regions. While adult birds sometimes eat seeds, young birds depend on protein-rich insects. The decline of this food source directly affects breeding success – another example of indirect pesticide effects.
The fact that both specialized farmland birds and widespread species react negatively makes it clear: Pesticides weaken not only individual species, but the ecological basis of entire agricultural landscapes. If even adaptable species become rarer, this is a strong warning sign for the state of agriculturally shaped ecosystems.
Pesticides as an Independent Driver of Bird Decline
(© Monnet et al. (2026), Proceedings of the Royal Society B, modified, CC BY 4.0)
One result of the study is that the negative influence of pesticides cannot be explained solely by other characteristics of intensive agriculture. Even when factors such as large field structures, a low proportion of hedges and fallow land, high mineral fertilization, or intensive tillage are statistically considered, the correlation between pesticide use and declining bird abundance persists. Pesticides are therefore not just an accompanying phenomenon of intensive agriculture, but an independent driver of bird decline.
This is an important point because public debate often argues that the loss of biodiversity is primarily due to landscape homogenization or over-fertilization. The current study from France suggests that in comparable landscapes, differences in pesticide use have measurable effects on bird populations. Pesticides primarily act indirectly – for example, through the decline of insects as a food source or through changes in plant diversity relevant for foraging and breeding.
Quantity or Toxicity – What is Decisive?
The researchers wanted to know not only whether pesticides affect bird populations, but also exactly how. For this, they compared two approaches: On the one hand, the total quantity of pesticides used, and on the other hand, a hazard index that additionally considers toxicity (LD50), environmental persistence, and toxic degradation products – i.e., how toxic and long-lasting the individual active ingredients are.
The result was clear: Even the total quantity of pesticides used explains well where bird species are less common. The more complex hazard index provided hardly any additional insights. So, what was decisive was not which specific agent was used, but how much was sprayed overall.
However, this does not mean that the toxicity of individual active ingredients plays no role. Anne-Christine Monnet and her team explain the finding as follows: In regions with high pesticide use, many different agents are usually used simultaneously – including very problematic substances. The total quantity therefore already reflects this combined burden well.
In short: Where a lot of pesticide is applied, the overall ecological burden is high.
Consequences for Species Protection
For practical species protection, this means: It is not enough to replace individual active ingredients or make minor adjustments. A fundamental reduction in pesticide use in agricultural landscapes is crucial.
The study also shows that pesticides make an independent contribution to the decline of bird populations – regardless of landscape structure, fertilization, or climate. Not only rare or highly specialized species are affected, but a large proportion of common bird species.
This makes it clear: The decline in bird diversity is not a marginal problem of individual species, but a structural result of intensive agriculture. A noticeable reduction in pesticide use is therefore a central prerequisite for the long-term preservation of biodiversity in agricultural landscapes.
Sources
- Muséum national d’Histoire naturelle (MNHN), Office français de la biodiversité (OFB), & Ligue pour la Protection des Oiseaux (LPO). (2021). Suivi temporel des oiseaux communs : bilan 1989–2019. Paris.
- Monnet, A.-C., Cairo, M., Deguines, N., et al. (2026). Common birds have higher abundances in croplands with lower pesticide purchases. Proceedings of the Royal Society B, 293, 20252370. https://doi.org/10.1098/rspb.2025.2370
About the author: Doreen Fräßdorf
Doreen Fräßdorf is the author and publisher of artensterben.de. She researches and writes about extinct and endangered species in the modern era, with a focus on red lists, scientific studies, historical sources, and current conservation efforts. The goal is a clear, evidence-based overview of biodiversity loss and species protection.
She is also the author of a non-fiction book about extinct modern-era mammals.
Support this blog
If you enjoyed this post, I would appreciate a small donation. This keeps artensterben.de ad-free and without paywalls, so all readers have free access to the content.
Alternatively, you can support my work by buying my book or via my Amazon wishlist.
Thank you!
