DOI: 10.5061/dryad.5qfttdzh1
title: Data from: The impacts of climate and the extreme drought in 2018 on population growth in Swedish moth species

description: Insects are pivotal to ecosystem diversity and functionality, yet they
 face increasing threats from anthropogenic climate change impacts. A
 growing body of studies reports the effects of changing temperature and
 precipitation patterns, but relatively few studies focus on the
 consequences for insect populations of extreme weather
 events. Here, we examine population growth responses to
 temperature, precipitation, and the extreme summer drought in Sweden in
 2018. For this purpose, we used longitudinal data for 54 moth species
 collected between 2005 and 2023 using light traps at three sites in
 southeastern Sweden. We found a positive relationship between
 temperature and population growth rates across all study sites, while
 precipitation showed a positive relationship at two sites and no effect at
 the third. The results indicated a negative time-lag effect on population
 growth of precipitation the previous year at two of the sites, while there
 were no significant effects of temperature the previous year. Despite the
 extreme drought in 2018, moth populations remained resilient, with no
 dramatic decline in population growth between 2018 and 2019. Our
 results contrast earlier studies reporting severe declines in population
 growth in response to extreme drought events. The discrepancy may reflect
 that selected species in this study predominantly consist of
 range-expanding and migratory species, better able to withstand adverse
 conditions due to a higher climatic tolerance and being habitat and food
 plant generalists. Our findings underscore the importance of an
 increased knowledge of site-specific responses and effects of extreme
 weather events such as droughts when outlining conservation efforts.
description: Statistical Analyses Main
 Analysis: Linear mixed models
 (LMM) Random effects for species
 and year Response variable:
 Population growth rate 
 Predictors: Climate variables, population size, year
 Year Effects Analysis:
 Reference years: 2018 (drought) and 2019
 (post-drought) Random effects
 for site and species Data
 Collection Methods Light trap
 sampling at three sites Daily
 temperature measurements 
 May-August precipitation totals 
 Annual species abundance counts
description: # The impacts of climate and the extreme drought in 2018 on population
 growth in Swedish moth species Authors*: Per-Eric Betzholtz*, Anders
 Forsman & Markus Franzén Contact: Per-Eric Betzholtz **Dataset
 description** \- **Primary data file:** Moths_Raw_Data.csv \- **Period:**
 2005–2023 \- **Geographic location:** Southeast Sweden \- **Study sites:**
 \- Utlangan \- Nedre aleback \- Ossby \- **Key event:** 2018 drought year
 Data files and variables **Moths_Raw_Data.csv** 1\. **Year:** Sampling
 year (2005–2023) 2\. **Site:** Light-trap location name 3\.
 **Species_name_2017:** Moth species identification 4\. **Ln_Ratio:**
 Population growth rate (natural log of Nt+1/Nt) 5\. **Precipitation:**
 May–August precipitation sum (mm) 6\. **Temperature:** Average temperature
 (°C) 7\. **Precipitation_t1:** Previous year May–August precipitation 8\.
 **Temperature_t1:** Previous year temperature 9\. **Individuals:** Number
 of individuals in previous year **Code file description**
 r_script_moths_drought_241120_tot_final.R: This script contains the
 complete R code used to process and analyse the moth dataset. It generates
 publication-quality figures and tables (Figures 1b, 2, 3, S1, and S2) and
 performs statistical analyses using linear mixed models to assess the
 impacts of climate variables and the 2018 drought on moth population
 growth. The script is modularly structured into sections for data setup,
 visualisation, statistical modelling, and reproducibility (session
 information). It utilises key packages including *ggplot2*, *dplyr*,
 *lme4*, and *gridExtra*. Version information \- **Version:** 1.1 \- **Last
 updated:** February 17, 2025