A global synthesis of phenological responses to climate change

Abstract

Phenology, or the timing of seasonal activities, is shifting with climate change, resulting in disruptions to the timing of migration and breeding and in emerging asynchronies between interacting species1-5. Recent syntheses have concluded that trophic level1, latitude6, and how phenological responses are measured7 are key to determining the strength of phenological responses to climate change. However, despite these insights, researchers still lack a comprehensive framework that can predict responses to climate change globally and across diverse taxa. For example, little is known about whether phenological shifts are driven by different climatic factors across regions or which ecologically important species characteristics (e.g., body size) predict the strength of phenological responses. Here, we address these questions by synthesizing hundreds of published time series of animal phenology from across the planet. We find that temperature drives phenological responses at mid-latitudes, but precipitation is more important at lower latitudes, likely because these climate factors often drive seasonality in each of these regions. Body size is also negatively associated with the strength of phenological shift, suggesting emerging asynchronies between interacting species that differ in size, such as hosts and ectoparasites and predators and prey. Finally, although there are many compelling biological explanations for spring phenological delays, some examples of delays are associated with short annual records prone to sampling error. As climate change intensifies, our findings arm biologists with predictions concerning which climatic variables and organismal traits drive phenological shifts.