Rare events and their role in ecological dynamics.

Rare events are low-frequency environmental events whose magnitude and ecological consequences can vary across ecosystems. In this review, we clarify the terminology used to describe these anomalies and propose a statistical definition that disentangles environmental rarity and magnitude from ecological impact. Rare events generate a wide range of responses, from population declines and ecosystem reorganisation to neutral or even positive demographic outcomes. Exceptionally intense perturbations potentially dominate ecological outcomes regardless of their rarity. More commonly, however, their influence on long-term dynamics emerges from the joint effects of magnitude and return interval, such that less extreme but more frequent perturbations could contribute more consistently to population trajectories than rarer events. Long-term demographic studies are essential to identify how rare events shape ecological dynamics.