Authors: Ellen A. R. Welti, Anthony Joern, Aaron M. Ellison, David C. Lightfoot, Sydne Record, Nicholas Rodenhouse, Emily H. Stanley & Michael Kaspari
Source: Nature Ecology and Evolution. April, 2021.
Publication type: Article
Abstract: Crossley et al. examine patterns of change in insect abundance and diversity across US Long-Term Ecological Research (LTER) sites, concluding a 鈥渓ack of overall increase or decline鈥. This is notable if true, given mixed conclusions in the literature regarding the nature and ubiquity of insect declines across regions and insect taxonomic groups. The data analysed, downloaded from and collected by US LTER sites, represent unique time series of arthropod abundances. These long-term datasets often provide critical insights, capturing both steady changes and responses to sudden unpredictable events. However, a number of the included datasets are not suitable for estimating long-term observational trends because they come from experiments or have methodological inconsistencies. Additionally, long-term ecological datasets are rarely uniform in sampling effort across their full duration as a result of the changing goals and abilities of a research site to collect data. We suggest that Crossley et al.鈥檚 results rely on a key, but flawed, assumption that sampling was collected 鈥渋n a consistent way over time within each dataset鈥. We document problems with data use prior to statistical analyses from eight LTER sites due to datasets not being suitable for long-term trend estimation and not accounting for sampling variation, using the Konza Prairie (KNZ) grasshopper dataset (CGR022) as an example.