Abrupt climate changes in the past offer a natural experiment for study the rates and types of ecological response under times of rapid change - a critical issue given that anthropogenic modifications of atmospheric chemistry are increasing the risk of future rapid climate change. Multiproxy lake-sediment records are ideal for examining vegetational responses to abrupt climate change, because indices of past climate change (e.g. oxygen and hydrogen isotopes, chironomids and ostracodes) and past vegetational change (pollen and larger plant fossils) can be extracted from the same sediments. High-resolution paleoecological and paleoclimatological records in North America and Europe consistently show that vegetation response times to late-glacial climate change were less than 200 years, and may have been on the order of decades or less.
At the same time, there is growing evidence that many ecological systems can experience non-linear abrupt responses to progressive forcing, when some threshold of resilience is passed. Given the widespread observations of abrupt changes in the paleoecological record, a major research question is whether these abrupt changes represent linear responses of ecological systems to abrupt climate forcing, or non-linear responses caused by coupled biosphere-atmosphere feedbacks and/or the passing of tipping points governed by localized and site-specific factors.
Williams J. W., Blois, J.L. and Shuman, B.N. (2011) Extrinsic and intrinsic forcing of abrupt ecological change: Case studies from the late Quaternary. Journal of Ecology 99: 664-677.
Williams, J.W., Shuman, B., Bartlein, P.J., Diffenbaugh, N.S. and Webb, T., III (2010) Rapid, time-transgressive, and variable responses to early-Holocene midcontinental drying in North America. Geology 38:135-138.
Williams, J.W, Shuman, B., and Bartlein, P.J. (2009) Rapid responses of the prairie-forest ecotone to early Holocene aridity in mid-continental North America. Global and Planetary Change 66: 195-207
Williams, J. W., Post, D. M., Cwynar, L. C., Lotter, A. F., Levesque, A. J. (2002) Rapid vegetation responses to past climate change. Geology 30: 971-974.
Shuman, B. N., Webb III, T., Bartlein, P. J., Williams, J. W. (2002) The anatomy of a climatic oscillation: Vegetation change in eastern North America during the Younger Dryas chronozone. Quaternary Science Reviews 21: 1777-1791
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