Beech trees are currently found throughout much of the eastern United States (left panel). This distribution is determined largely by the climate. Changes in climate as a result of the increasing concentrations of carbon dioxide and other greenhouse gases are expected to change the optimum growing range for beech trees, thereby changing their distribution. Predictions of future climate conditions from the climate models of the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) and the NASA Goddard Institute for Space Studies (GISS) have been used to estimate the types of shifts in optimum growing range that could occur a century hence as a result of changes in the concentrations of greenhouse gases alone (thus representing an extreme condition). While this warming will likely be delayed somewhat as a result of sulfate aerosol injections, the results suggest that the optimum growing ranges may shift roughly 300 miles to the north, changing the character of forests. The figure is adapted from M.B. Davis and C. Zabinsky, Changes in geographical range resulting from greenhouse warming: Effects on biodiversity in forests. In: Global Warming and Biological Diversity [R.L. Peters and T.E. Lovejoy (eds.)]. Yale University Press, New Haven, CT (1992).