Impact of pesticides on butterflies and bumblebees in the garden

Large-scale impact of pesticides on butterflies and bumblebees in private gardens in France.

Researchers from the Center for Conservation Sciences (Muséum national d'Histoire naturelle / CNRS / UPMC) and the Departmental Observatory of Urban Biodiversity of Seine-Saint-Denis demonstrate for the first time the effects of the use of pesticides by individuals in France.

The scientists drew on data from participatory science to show, on a country-wide scale, the impact of pesticide use by home gardeners on flower insects (which feed on flowers). These effects vary with the environment, can be indirect and affect organisms not initially targeted. These results are published in the journal Biological Conservation.

Pesticides harm butterflies and bumblebees

In urban areas, private gardens represent an important resource in terms of food and shelter for animal species. However, the impact of gardening practices on these species, in particular the use of pesticides, is very difficult to assess on a large scale due, on the one hand, to the absence of standardized measures and, on the other hand, to the lack of standardized measures. difficulty in accessing private property. In an agricultural environment, the methods of growing or using phytosanitary products have proven impacts on biodiversity: it is therefore likely that such effects also exist in private gardens.

The authors of this publication evaluated the large-scale effects of gardening practices on two important groups of flower-growing insects, butterflies and bumblebees, from data collected as part of the Garden Biodiversity Observatory . Their analyzes show that butterflies and bumblebees are less abundant in gardens treated with insecticides, which was expected, but also in those treated with herbicides. Conversely, these insects are more abundant when gardeners use Bordeaux mixture, fungicides and slug granules.

While the impact of insecticides on insects is direct, that of herbicides would be indirect, limiting the resources available to butterflies and bumblebees. The other pesticides studied would have an indirect positive impact, favoring more vigorous plants which then offer more resources to insects. Moreover, the impact of pesticides varies depending on the type of landscape: the negative effects of insecticides are more important in urban areas. This would be due to the difficulty of recolonizing treated gardens in an urban matrix hostile to flower-growing insects.

The use of pesticides has an impact on biodiversity

These results, of national dimension, show for the first time that individual behavior, in a private setting, has an impact on biodiversity, even in a highly anthropized urban landscape. They also prove that the consequences of phytosanitary treatments are complex and have indirect effects on organisms which are not directly targeted. Therefore, while this study shows that butterflies and bumblebees are more abundant in gardens where fungicides or slug killers are used, this obviously does not mean that these pesticides are beneficial for all biodiversity. In particular, the effect on soil fauna should not be underestimated. Other studies, for example, have shown that earthworms are less abundant in agricultural plots treated with herbicides, insecticides or fungicides that did not target them directly.

The Garden Biodiversity Observatory, which provided the data used in this study, is a national observatory co-founded by the National Museum of Natural History, and respectivelyNoé Conservation for the butterflies section and the Groupe Associatif Estuaire for the bumblebee section.It is part of the Museum's participatory science program, Vigie-Nature.

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Reference: Muratet, A., Fontaine, B. (2015). Contrasting impacts of pesticides on butterflies and bumblebees in private gardens in France. Biological Conservation 182: 148–154.

Video: City of Irving Butterfly Gardening (November 2020).