Will Extreme Climatic Events Facilitate Biological Invasions?

© The Ecological Society of America www.frontiersinecology.org E are experiencing not only gradual shifts in mean climate conditions but also dramatic changes in climate variability and prevalence of extreme climatic events (ECEs). ECEs such as droughts, floods, severe storms, and heat waves are changing in frequency, magnitude, timing, and duration, depending on the region and the specific climate event (WebPanel 1; Easterling et al. 2000; Karl et al. 2008). These extreme events can strongly influence terrestrial and aquatic ecosystems (Parmesan et al. 2000; Thibault and Brown 2008) and may combine synergistically with other agents of environmental change, such as species invasions, to dramatically change ecosystems. Previous studies have shown that changes in broad climatic conditions may influence the probability of species invasions, while highlighting that the effects of changing climate are likely to be diverse and context-dependent (Rahel and Olden 2008; Walther et al. 2009; Bradley et al. 2010). However, the potential for ECEs in particular to promote species invasions has not been systematically assessed. Here, we use theory from community ecology and invasion biology to identify mechanisms and pathways by which ECEs may affect the establishment and spread of introduced species in recipient ecosystems. We then review current evidence for ECE impacts on invasions and assess the potential for changes in the frequency and magnitude of ECEs to affect species introductions in the future. By focusing on mechanisms of invasion following an ECE, we assess whether generalizations about invasion risk are possible across species, ecosystems, and ECE type. Finally, we highlight critical areas of research necessary for a better understanding of these processes, and suggest strategies for anticipating and subsequently managing invasions associated with ECEs.