Moth species richness and diversity decline in a 30-year time series in Norway, irrespective of species\u2019 latitudinal range extent and habitat

Ryan C Burner,Anne Sverdrup-Thygeson,Vidar Selås,Sverre Kobro,Rannveig M Jacobsen

doi:10.1007/s10841-021-00353-4

Abstract

IntroductionInsects are reported to be in decline around the globe, but long-term datasets are rare. The causes of these trends are elusive, with changes in land use and climate among the top candidates. Yet if species traits can predict rates of population change, this can help identify underlying mechanisms. If climate change is important, for example, high-latitude species may decline as temperate species expand. Land use changes, however, may impact species that rely on certain habitats.Aims and methodsWe present 30 years of moth captures (comprising 97,032 individuals of 808 species) from a site in southeast Norway to test for population trends that are correlated with species traits. We use time series analyses and joint species distribution models combined with local climate and habitat data.Results and discussionSpecies richness declined by 8.2% per decade and total abundance appeared to decline as well (−9.4%, p = 0.14) but inter-annual variability was high. One-fifth of species declined, although 6% increased. Winter and summer weather were correlated with annual rates of abundance change for many species. Opposite to general expectation, many species responded negatively to higher summer and winter temperatures. Surprisingly, species’ northern range limits and the habitat in which their food plants grew were not strong predictors of their time trends or their responses to climatic variation. Complex and indirect effects of both land use and climate change may play a role in these declines.Implications for insect conservationOur results provide additional evidence for long-term declines in insect abundance. The multifaceted causes of population changes may limit the ability of species traits to reveal which species are most at risk.

Highlights

Insects are reported to be in decline around the globe, but long-term datasets are rare
These declines may be due to a host of factors, including land use changes, pesticides and pollution, introduced species, and climate change (Habel et al 2019a, Seibold et al 2019, Raven and Wagner 2021, Wagner et al 2021)
Continuous long-term datasets, rather than comparisons between several time points (Seibold et al 2019), are especially important for taxa that exhibit population cycles and high inter-annual variability (Welti et al 2020). There are few such datasets from Fennoscandia, even though high-latitude systems are experiencing some of the strongest effects of climate change (Hunter et al 2014, Loboda et al 2017)

Summary

Introduction

Insects are reported to be in decline around the globe, but long-term datasets are rare. The causes of these trends are elusive, with changes in land use and climate among the top candidates. If climate change is important, for example, high-latitude species may decline as temperate species expand. Winter and summer weather were correlated with annual rates of abundance change for many species. Continuous long-term datasets, rather than comparisons between several time points (Seibold et al 2019), are especially important for taxa (like many insects) that exhibit population cycles and high inter-annual variability (Welti et al 2020). There are few such datasets from Fennoscandia, even though high-latitude systems are experiencing some of the strongest effects of climate change (Hunter et al 2014, Loboda et al 2017)

Methods

Results

Conclusion