Forecasted changes in global climate predict not only shifts in average conditions but changes in the frequency and intensity of climate extremes. In the sub-tropics, the passage of extreme cold spells functions as a major structuring force for ecological communities, and can incur substantial losses to biodiversity, agriculture and infrastructure. If these events persist in the future, it is likely that their effects on sub-tropical communities and ecosystems will become more pronounced, as tropical species migrate poleward. Recent extreme cold spells in subtropical China (2008) and U.S. (2010) occurred in ecosystems that are the subject of long-term ecological study, enabling key questions about cold spell affects to be addressed. In this paper, we 1) discuss the meteorological drivers that resulted in these two extreme cold spells, and 2) use findings from case studies published in the Ecosphere special issue ‘Effects of extreme cold spells on the dynamics of sub-tropical communities, and on poleward expansion of tropical species’ and other previously published works to identify consistencies of sub-tropical community resilience and resistance to extreme cold spells.
In this review, we highlight three consistent findings related to this particularly type of extreme climate event. 1) Cold spells drive predictable community change in the subtropics by altering ratios of coexisting tropical and temperate species. 2) Certain landscape features consistently affect sub-tropical resistance and resilience to extreme cold spells, and 3) Native tropical species are more resistant and resilient to extreme cold spells than tropical non-native taxa. Our review should improve forecasts of the response of sub-tropical community dynamics in scenarios where extreme cold spells either increase or decrease in frequency and intensity.