Elicitation of Expert Judgments of Climate Change Impacts on Forest Ecosystems

Detailed interviews were conducted with 11 leading ecologists to obtainindividualqualitative and quantitative estimates of the likely impact of a2 × CO₂] climate change onminimally disturbed forest ecosystems. Results display a much richer diversityof opinion thanis apparent in qualitative consensus summaries, such as those of the IPCC.Experts attachdifferent relative importance to key factors and processes such as soilnutrients, fire, CO₂fertilization, competition, and plant-pest-predator interactions. Assumptionsand uncertaintiesabout future fire regimes are particularly crucial. Despite these differences,most of the expertsbelieve that standing biomass in minimally disturbed Northern forests wouldincrease and soilcarbon would decrease. There is less agreement about impacts on carbon storagein tropicalforests. Estimates of migration rates in northern forests displayed a rangeof more than fourorders of magnitude. Estimates of extinction rates and dynamic response showsignificantvariation between experts. A series of questions about research needs foundconsensus on theimportance of expanding observational and experimental work on ecosystemprocesses and ofexpanding regional and larger-scale observational, monitoring and modelingstudies. Results ofthe type reported here can be helpful in performing sensitivity analysis inintegrated assessmentmodels, as the basis for focused discussions of the state of currentunderstanding and researchneeds, and, if repeated over time, as a quantitative measure of progress inthis and other fieldsof global change research.