Extreme events in lake ecosystem time series

Climate change has generated growing interest in extreme events, and extremes are known to have important consequences for ecosystems. Theoretical mechanisms generating frequent extremes apply to both environmental and biological processes, yet past studies of ecological extremes have focused primarily on the abiotic environment. The rarity or commonness of extremes in biological time series is unknown. We evaluated the statistical tendency to produce extreme events in 595 biological, chemical, physical, and meteorological time series taken from 11 lakes. We found that extreme events were much more likely to occur for biological variables than for other categories. Additional analysis revealed that the tendency to produce extremes was driven primarily by within‐year dynamics, suggesting that processes occurring at short time scales underlie the high frequency of extremes in biological variables. These results should lead us to expect surprises in long‐term observations of biological populations.