Abundance of insects and aerial insectivorous birds in relation to pesticide and fertilizer use

Wei Liang,Wiesław Walankiewicz,Johannes Erritzøe,Dorota Czeszczewik,Anders Pape Møller,Indrikis Krams,Einar Flensted-Jensen,Karsten Laursen

doi:10.1186/s40657-021-00278-1

Abstract

BackgroundThe abundance of insects has decreased considerably during recent decades, resulting in current abundance showing 70–80% reductions in more than 15 studies across temperate climate zones. Dramatic reductions in the abundance of insects are likely to have consequences for other taxa at higher trophic levels such as predators and parasites. Pesticides, fertilizers and agricultural land use are likely candidates accounting for such reductions in the abundance of insects.MethodsHere we surveyed the abundance of flying insects, and the reduction in the abundance of insects as a consequence of intensive reduction in agricultural practice linked to fertilizer use and pesticide use. Finally we demonstrated consistency in abundance of birds among study sites.ResultsWe demonstrated that the use of fertilizers and pesticides had reduced the abundance of insects, with consequences for the abundance of insectivorous bird species such as Barn Swallows (Hirundo rustica), House Martins (Delichon urbicum) and Swifts (Apus apus). Juvenile Barn Swallows were negatively affected by the reduced abundance of insects and hence the reproductive success of insectivorous bird species. These effects imply that the abundance of insects could be reduced by the availability of insect food.ConclusionsThese effects of intensive agriculture on insect food abundance are likely to have negative impacts on populations of insects and their avian predators. This hypothesis was validated by a reduction in the abundance of insects, linked to an increase in the abundance of fertilizers and a general change in farming practice.

Highlights

The abundance of insects has decreased considerably during recent decades, resulting in current abundance showing 70–80% reductions in more than 15 studies across temperate climate zones
Traditional agriculture has affected land-use (Tucker and Heath 1994; Donald et al 2001; Schimmelfenning and Sedelmeier 2005; Raven and Wagner 2021), and such effects combined with change in land-use and agricultural practice have affected insects and other taxa
Declines in abundance of avian predators have often been attributed to the negative impacts of such predators on insects, and the negative effects of agriculture on the abundance of insects (Nyffeler and Bonte 2020; Møller 2013)

Summary

Introduction

The abundance of insects has decreased considerably during recent decades, resulting in current abundance showing 70–80% reductions in more than 15 studies across temperate climate zones. Declines in abundance of insects have been documented across large parts of Europe, and even nature reserves contain many fewer insects than just 50 years ago, with reductions in the Møller et al Avian Res (2021) 12:43 abundance of insects as large as 80% (Hallmann et al 2012; Møller 2019) Attempts to attribute these changes in farming practice to specific factors have been unsuccessful, mainly because some of these strongly negative effects had been observed in well studied taxa that have been strongly negatively affected (Hallmann et al 2017; Nocera et al 2012). Declines in abundance of avian predators have often been attributed to the negative impacts of such predators on insects, and the negative effects of agriculture on the abundance of insects (Nyffeler and Bonte 2020; Møller 2013)

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