The paleoecological and paleoenvironmental record of the late Quaternary is rich in examples of past regime shifts in both climate and ecosystem dynamics.  These cannot be used as direct analogues for future regime shifts under natural or human-driven environmental change.  Every past regime shift has comprised a unique realization of environment and ecology, as will those of the future.  However, the past can play two important roles in forecasting, understanding and responding to regime shifts.

Results/Conclusions

First, the paleoecological record provides a large and diverse array of case studies in which the causes, rates, and consequences of regime shifts can be assessed.  Climatic and ecological regime shifts are frequently linked, with climatic changes driving changes in ecosystem properties, including vegetation dominants and disturbance regimes. This is not always the case, and examples may also be found of ecosystems that have resisted environmental variations or where ecological regime shifts have occurred in the absence of major climate change.  Taken together, these case studies can help assess sensitivity and resistance to climate-driven and other regime shifts.

Second, the antiquity of existing ecosystems, and the range of climate variability they have experienced, can be assessed using paleoecological and paleoenvironmental records.  In some cases it is possible to identify the specific combination of climate means and variability that led to development of extant ecosystems, and the range of conditions under which they were maintained.  This may provide information on the climate thresholds beyond which the ecosystems will degrade or collapse.