The effects of organic farming compared to conventional farming (high pesticide consumer) were compared under natural conditions on behavior and vigor. of several species of birds. The results show, for 6 different species, that the vigor of individuals nesting in hedges surrounded by conventional agriculture is greatly reduced, materializing a significant deterioration in their state of health. This study was published in May 2022 in the journal Agriculture, Ecosystems and Environment by researchers from the Center for Biological Studies in Chizé (CNRS/La Rochelle University) and the Biogeosciences laboratory (CNRS/UBFC/uB).
Exposure to phytosanitary products: effects on bird populations
The intensification of agriculture is causing an unprecedented decline in biodiversity, particularly among birds, and the very high use of phytosanitary products is one of the causes. The impact of pesticides is recognized by the lethal effects following exposure or ingestion of massive doses and/or particularly toxic molecules.
But these negative effects are largely underestimated by studies that are only concerned with acute exposure to higher doses by measuring mortality and often through laboratory experiments that do not mimic the reality on the ground. Few studies are also concerned with behavior.
However, the latter is often the first visible component of intoxication. Thus, the study of the behavior of birds in natural conditions could be a good marker of physiological degradation of organisms due to these chronic and non-lethal exposures.
A deterioration in the vigor of birds nesting in “non-organic” hedges
By capturing 6 species of passerines in hedgerows in the middle of fields in organic farming (without the use of pesticides) or in hedgerows, similar in composition and nature, but bordered by conventional agriculture, the researchers were able to highlight a degradation of the behavioral health status of birds in conventional agriculture during the breeding season.
To do this, the researchers developed a behavioral observation protocol based on the quantification of the movement of birds caught in the net during the simulated approach of a predator, and the number of calls and the number of attempts to escape when the bird was held in hand. The results are final.
Birds captured in conventional agriculture struggled much less when approaching the predator, were much less aggressive, and vocalized less in front of the experimenter. On the other hand, the corpulence of the individuals did not change between the two types of agriculture, tending to show that the difference in behavior observed would be due rather to physiological disturbances in relation to pesticides, than to a drop in available energy ( resulting from a potential difference in resource availability).
An innovative experimental device
Unlike the vast majority of studies that test the effects of pesticides in the laboratory, this study was carried out in natura on a large number of species, allowing the observed effect to be generalized since all the species responded in a similar way. This field study is made possible by the detailed knowledge of the territory: in the Zone Atelier Plaine & Val de Sèvre (south of Niort in the Deux-Sèvres), all the plots in organic farming and conventional farming are known, providing information on the use or not of pesticides at the landscape scale.
To conclude, this study indicates that the behavior of birds could be used to assess the impact of human activities, for example by indicating or even quantitatively measuring the degradation of the quality of life in an ecosystem. Birds, for example in these agricultural landscapes, could thus be qualified as sentinels for human health (and that of ecosystems), reinforcing the nascent approach and concept of environmental health (One Health).
- Vigor: Force, energy developed by an individual for a given action
Jérôme Moreau, Karine Monceau, Gladys Gonnet, Marie Pfister, Vincent Bretagnolle, Organic farming positively affects the vitality of passerine birds in agricultural landscapes, Agriculture, Ecosystems & Environment, Volume 336, 2022, 108034, ISSN 0167-8809
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