ecological perspective on extreme climatic events: a synthetic definition and framework to guide future research

1. Growing recognition of the importance of climate extremes as drivers of contemporary and future ecological dynamics has led to increasing interest in studying these locally and globally important phenomena. 2. Many ecological studies examining the impacts of what are deemed climate extremes, such as heat waves and severe drought, do not provide a definition of extremity, either from a statistical context based on the long-term climatic record or from the perspective of the response of the system - are the effects extreme (unusual or profound) in comparison to normal variability? 3. A synthetic definition of an extreme climatic event (ECE) is proposed that includes ‘extremeness' in both the driver and the response: an ECE is as an episode or occurrence in which a statistically rare or unusual climatic period alters ecosystem structure and/or function well outside the bounds of what is considered typical or normal variability. This definition is accompanied by a mechanistic framework based on the concept that extreme response thresholds associated with significant community change and altered ecosystem function must be crossed in order for an ECE to occur. 4. Synthesis. A definition and mechanistic framework for ECEs is used to identify priorities for future research that will enable ecologists to more fully assess the ecological consequences of climate extremes for ecosystem structure and function today and in a future world where their frequency and intensity are expected to increase.