Reacción a "Reactions to an analysis of the causes of insect decline in Europe"

The study is well done and the data obtained from the literature is analysed using an appropriate method - although, in my opinion, a bit complicated. The distinction between causes, pressures, states, impacts and responses does not help to fully understand the global analysis, which, ultimately, could be summed up in two terms: causes and impacts. Alluvial graphs, on the other hand, are a good way to represent the results.

The study is based on our first paper on insect decline and follows the same structure and methodology: a compilation of studies in the scientific literature on insects and analysis of possible causes based on what the authors of the original studies reported.

The biggest novelty is that the authors also analyse population increases of some of these species (we only analysed declines). Those increases are due to habitat improvement in areas with extensive agriculture (as opposed to intensive agriculture that uses fertilisers and pesticides) or conservation zones, and, in other cases, climate change.

The conclusions are otherwise the same as ours: the overall decline for carabids and lepidoptera is estimated at 39% and 48% respectively, with the declines far exceeding the increases for some of those species (24% carabids and 26 % lepidoptera). Ditto for the causes of declines, which are largely due to habitat modification by human activities, agricultural intensification (inevitably involving the use of fertilizers and pesticides), and to climate change.

[We must take into account] the same limitations that we had when doing our study: the causes analysed are those that the authors of the original studies report in their articles and, in most cases, are presumed, not confirmed.

I am surprised that the authors do not cite any of the articles on the subject published two years ago in a special issue of the Proceedings of the National Academy of Sciences of the United States. They also do not cite our latest review on the subject, published in 2021.

It is not clear why these companies [Bayer, BASF and Syngenta] have funded this study. The curious thing is that the authors reach the same conclusions as us, although they avoid blaming pesticides. Instead, they blame intensive agriculture as the second major cause of declines (the first cause [they cite] is anthropogenic activities in general), although they admit in the text that such agriculture is closely linked to the use of fertilisers and pesticides. That is why we point to fertilisers and pesticides as the second cause of insect decline, since they are an integral part of this type of agriculture and impact insect populations both directly (by killing insects) and indirectly, through changes in animal communities and even habitat (through herbicides) in agricultural areas.

The decline of insects is a reality confirmed by most of the studies that exist on the subject, and the increases in some insect species are due to human interventions aimed at restoring affected ecosystems, or to climate change that favours some species.

To remedy the situation, we need to change from the current intensive agricultural system to another system that is compatible with the biodiversity of insects and other organisms. That is what many researchers—myself included—have repeatedly indicated.