Demography-environment relationships improve mechanistic understanding of range dynamics under climate change
Abstract
Species respond to climate change with range and abundance dynamics. To better explain and predict them, we need a mechanistic understanding of how the underlying demographic processes are shaped by climatic conditions. Here, we aim to infer demography-climate relationships from distribution and abundance data. For this, we developed spatially explicit, process-based models for eight Swiss breeding bird populations, which jointly consider dispersal, population dynamics and the climate-dependence of three demographic processes – juvenile survival, adult survival and fecundity. The models were calibrated to 267 nationwide abundance time series in a Bayesian framework and showed moderate to excellent goodness-of-fit and discriminatory power. The most influential climatic predictors for population performance were the mean breeding-season temperature and the total winter precipitation. Contemporary climate change benefitted the population trends of typical mountain birds, leading to lower population losses or even slight increases, whereas lowland birds were adversely affected. Our results emphasize that generic process-based models embedded in a robust statistical framework can improve our predictions of range dynamics and may allow disentangling of the underlying processes. For future research, we advocate a stronger integration of experimental and empirical studies in order to gain more precise insights into the mechanisms by which climate affects populations.
What the paper shows and why it matters (AI-generated)
Building spatially explicit, climate-sensitive demographic models for eight Swiss breeding bird populations and fitting them to 267 abundance time series, the authors get something a purely correlative model can't offer: which specific demographic rate — juvenile survival, adult survival, fecundity — is actually responding to a given climate variable. The finding that mountain and lowland populations are already trending in opposite directions under the same warming climate is a concrete, checkable prediction, not just a proof of method, and the approach has since fed directly into the authors' own further work linking climate and demography.