Abstract
The abundance of insects has decreased for the last decades in many parts of the world although so far few studies have quantified this reduction because there have only been few baseline studies dating back decades that have allowed comparison of ancient and recent population estimates. Such a paired design is particularly powerful because it reduces or eliminates bias caused by differences in identity and experience of observers, identity of study sites, years, time of season, and time of day, and it ensures identity of sampling procedures. Here, I compiled information on the reduction in abundance of insects in Europe and Algeria by the same persons compiling the abundance of insects from the same 21 study sites during 1951–1997 and again a second time in 1998–2018. There was a reduction by 47% in the abundance of insects. The difference in abundance in old compared to new samples declined with latitude, with a significant variance among taxa. This reduction in abundance of insects was of such a magnitude that it must have consequences for insectivores and the role that insects play in ecosystems.
Highlights
IntroductionExtensive surveys of insects have shown dramatic reductions in abundance by as much as 80%, even in nature reserves (Hallmann et al, 2017; Møller, 2019; Morrissey et al, 2015; Sánchez-Bayo & Wyckhuys, 2019)
Extensive surveys of insects have shown dramatic reductions in abundance by as much as 80%, even in nature reserves (Hallmann et al, 2017; Møller, 2019; Morrissey et al, 2015; Sánchez-Bayo & Wyckhuys, 2019). These changes have been attributed to a diversity of drivers including farming practice, land-use, and the associated factors such as use of pesticides, biological interactions, and climate change (Sánchez-Bayo & Wyckhuys, 2019; Vogel, 2017)
The objectives of this study were to (a) test whether the abundance of insects has decreased during the recent three decades relying on studies where closely matched samples allowed for comparison across long temporal scales, (b) whether this decline differed among habitats, and (c) whether the decline differed among latitudes
Summary
Extensive surveys of insects have shown dramatic reductions in abundance by as much as 80%, even in nature reserves (Hallmann et al, 2017; Møller, 2019; Morrissey et al, 2015; Sánchez-Bayo & Wyckhuys, 2019). While some studies have documented such reductions in insect abundance over time (Hallmann et al, 2017; Sánchez-Bayo & Wyckhuys, 2019), others have shown little or no change in abundance of insects (Conrad, Warren, Fox, Parsons, & Woiwod, 2006; Conrad, Woiwod, & Perry, 2002; Shortall et al, 2009). This raises questions about generality, and the underlying mechanisms accounting for heterogeneity in such effects. Climate change has caused a strong decline in abundance of many taxa including
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
