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between one-third and one-half of terrestrial biological production is used or dominated by human action (Vitousek et al., 1997), and human-induced land-use changes are difficult to anticipate, the prediction of future vegetation distributions is a difficult undertaking. However, even in the absence of local-scale ecosystem forecasting skill, there is value in assessing the large-scale response of modeled ecosystems to uninitialized climate-model forecasts. Such models can be used to assess the future, large-scale response of terrestrial carbon sinks to altered climate or to anthropogenic inputs, for instance, or the effects of large-scale, vegetation-related albedo or surface roughness changes on climate. As longer time series of the relevant vegetation data become available for testing ecosystem-climate models, and these models are more rigorously validated and improved, the value of their forecasts will increase, particularly to the societies and institutions that depend most directly on ecosystems.