# Contrasting 50‐Year Trends of Moth Communities Depending on Elevation and Species Traits

## TL;DR

Moth populations in Switzerland have declined at low elevations but increased at high elevations over 50 years, likely due to climate change, land use, and light pollution.

## Contribution

The study reveals elevation-dependent moth trends and identifies drivers like climate change and land use affecting insect communities.

## Key findings

- Moth abundance, richness, and biomass decreased at low elevations but increased at high elevations over 50 years.
- Cold-adapted, food-specialized, and pupal overwintering species shifted their ranges upward with elevation.
- Climate change, land use, and light pollution are key drivers of these moth community changes.

## Abstract

Following alarming studies on insect declines, evidence for contrasting patterns in temporal insect trends is growing. Differences in environmental conditions (e.g., climate), anthropogenic pressures (e.g., land‐use and climate change), and insect community composition may drive contrasting trends. With increasing elevation, these factors change quickly, which makes elevational gradients an ideal study case to disentangle their roles for differences in temporal trends. We thus analysed 2.8 million moth records collected in Switzerland. Fifty‐year trends (1972–2021) depended on local conditions and insect community composition: moth abundance, richness and biomass at low elevation decreased but increased at high elevation. These changes mainly concerned cold‐adapted, mono‐ and oligophagous, and pupal overwintering species, which shifted their ranges upwards. Our results point to climate change but also intensive land use and light pollution as drivers of moth community changes and suggest that high‐elevation habitats as refugia could be key to sustain moth diversity.

This study, based on 2.8 million moth records in Switzerland from 1972 to 2021, shows that moth numbers decreased at low elevations but increased at high elevations. These changes mainly affected cold‐adapted, food‐specialised and pupal overwintering species. The findings point to climate change, but also land use and light pollution as drivers and demonstrate how temporal trends are affected by environmental conditions, anthropogenic pressures and insect community composition.