Sources of Uncertainty in Modeling Ecosystem Responses to Environmental Change

Abstract:

Multiple sources of uncertainty need to be taken into account in predicting the response of vegetation to projected future climate changes. Differences between climate models are the largest source of uncertainty in climate projections the first part of the 21^st century; differences between scenarios the major source of uncertainty in the last half of the century. While these uncertainties are relatively easy to deal with, the use of ensemble averages is not appropriate because not all models are equally good. Evaluation against palaeoclimate data show that while the large-scale features of projected climates are reliable, estimates of regional climate changes may be seriously underestimated, or even of the wrong sign. Very few efforts have been made to incorporate this uncertainty into projections of future vegetation responses. Further uncertainty results from the failure of current vegetation models to account for adaptive responses of traits and allocation strategies to environment, which can result in arbitrary thresholds in simulated vegetation behavior. While there may be solutions to dealing with these sources of uncertainty, there are irreducible sources of uncertainty related to the chaotic nature of the climate system and its influence on extremes which have a disproportionate influence on vegetation responses to climate change.