Impact of Extreme and Infrequent Events on Terrestrial Ecosystems and Biodiversity Thomas Kitzberger, INIBIOMA-CONICET and Universidad Nacional del Comahue, Bariloche, Argentina r 2013 Elsevier Inc All rights reserved Glossary Acclimation Reversible physiological or morphological changes an organism experiences in response to changing environmental conditions Such physiological changes enable the organism to tolerate (or acclimatize to) the new environmental conditions Atlantic Multidecadal Oscillation (AMO) A mode of variability occurring in the North Atlantic Ocean and which has its principal expression in the sea surface temperature (SST) field Controversy exists with regard to its amplitude, and in particular, the attribution of sea surface temperature change to natural or anthropogenic causes, especially in tropical Atlantic areas important for hurricane development Bottom up effects Refer to controls on the abundance and/or community structure of organisms that derive from supply of resources (light or nutrients for plants, prey organisms for animals) or from physical factors such as temperature of the environment Ecological sorting The process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition It provides an important mechanism whereby new species can fit into an existing community without adaptation El Nin˜o Southern Oscillation (ENSO) An occasional shift in winds and ocean currents, centered in the South Pacific region, with worldwide consequences for climate and biological systems Extremes: A Growing Concern, an Emerging Discipline The concept that discrete extreme events rather than gradual trends can have disproportionate ecological and societal impacts relative to the temporal scale over which they occur has received increased public and scientific attention in the last few years In particular, extreme climatic events such as hot spells, megadroughts, hurricanes, and floods involving adverse societal impacts or large economic costs, which often receive extensive media coverage, are increasingly being perceived as indicators of climate change (Easterling et al., 2000a) Within the climate change science community, there is also a consensus based on instrumental and modeling evidence that a set of weather or climate events from the extreme tails of their frequency distributions are becoming and will become more frequent or more intense (or both) in the near future (Easterling et al., 2000b; Meehl et al., 2007) These advances in understanding climatic extremes as key components of the variability in the climate system are accompanied by a growing awareness of the Encyclopedia of Biodiversity, Volume Functional redundancy Ecosystem property by which more than one species performs a given role so that when one species disappears, the loss of the ecosystem’s efficiency as a whole is relatively small; however if several species are lost, the system essentially collapses Hysteretic response Phenomenon in which the response of a physical system to an external influence depends not only on the present magnitude of that influence but also on the previous history of the system Hysteretic responses involve different forward and backwards trajectories of change Mast fruiting/seeding The production of many seeds/ fruits by a plant every two or more years in regional synchrony with other plants of the same species (community-wide mast fruiting: with other plants of same and different species) Pacific Decadal Oscillation (PDO) A long-term El Nin˜olike pattern of Pacific climate variability While the two climate oscillations ENSO and PDO have similar spatial climate fingerprints, they have very different behavior in time: 20th century PDO ‘‘events‘‘ persisted for 20–30 years, while typical ENSO events persisted for 6–18 months Semelparous An organism producing offspring (flowers and fruits in plants) only once in its lifetime before dying Tele-connection Causal link between patterns of weather in two locations, or between two atmospheric occurrences, which are very far apart, such the El Nin˜o Southern Oscillation, where unusually high sea surface temperatures off the west coast of South America can be connected with droughts in Indonesia importance of discrete extreme events (whether driven by climate, geology, or biological forces) in influencing ecological systems at all levels of organization from individuals to entire biomes (Gaines and Denny, 1993; Parmesan et al., 2000; Jentsch and Beierkuhnlein, 2008; Smith, 2011) An indicator of this emerging subdiscipline is increasing appearance of the term extreme events within the ecological literature (Figure 1) as well as special issues or special reviews on the topic appearing in mayor ecological journals such as New Phytologist (160, 2003), Comptes Rendus Geosciences (340, 2008), and Journal of Ecology (99, 2011) Dimensions of Driver Extremity: Rarity, Intensity, and Severity Despite this increased interest, a clear definition of extreme event is still elusive In climate science, three criteria are often http://dx.doi.org/10.1016/B978-0-12-384719-5.00352-X 209