Climate-induced forest dieback drives compositional changes in insect communities that are more pronounced for rare species

Lucas Sire,Paul Schmidt Yáñez,Diego Fontaneto,Jörg Müller,Cai Wang,Michael T Monaghan,Annie Bézier,Carlos Lopez-Vaamonde,Jérémy Cours,Simon Thorn,Laurent Larrieu,Elisabeth A Herniou,Christophe Bouget,Béatrice Courtial,Douglas W Yu

doi:10.1038/s42003-021-02968-4

Abstract

Species richness, abundance and biomass of insects have recently undergone marked declines in Europe. We metabarcoded 211 Malaise-trap samples to investigate whether drought-induced forest dieback and subsequent salvage logging had an impact on ca. 3000 species of flying insects in silver fir Pyrenean forests. While forest dieback had no measurable impact on species richness, there were significant changes in community composition that were consistent with those observed during natural forest succession. Importantly, most observed changes were driven by rare species. Variation was explained primarily by canopy openness at the local scale, and the tree-related microhabitat diversity and deadwood amount at landscape scales. The levels of salvage logging in our study did not explain compositional changes. We conclude that forest dieback drives changes in species assemblages that mimic natural forest succession, and markedly increases the risk of catastrophic loss of rare species through homogenization of environmental conditions.

Highlights

IntroductionAbundance and biomass of insects have recently undergone marked declines in Europe
Species richness, abundance and biomass of insects have recently undergone marked declines in Europe
Marked declines in insect abundance, biomass and species richness have recently been quantified in Europe[2]

Summary

Introduction

Abundance and biomass of insects have recently undergone marked declines in Europe. 1234567890():,; Insects are vital components of biodiversity, providing important ecosystem services such as pollination and pest regulation, while performing disservices as disease vectors and plant pests[1] Global changes, including those of climate, land use and land cover, can lead to degradation and habitat loss, chemical and light pollution or invasive species. These changes have caused major decreases in biomass, abundance and species richness of insects[2], and this accelerating decline has become a major cause for concern. Drought-induced forest diebacks can cause major structural changes such as an increase in canopy openness and reduction in foliage density, which in turn increases light availability, potentially changing the community structure of understory plants and their associated herbivorous insects[9]. While insect decline is independent of forest protection status, it has been presented as lower in terms of species richness for plots undergoing dieback[2]

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