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Highlight 11--The Effects of Climate Change on Ecosystems

GD scientists with experience in relating past climates to vegetation cover have produced maps showing potential changes in the distribution of Douglas fir (Pseudotsuga menziesii). Figure 11 shows the distribution of this tree in the present climate and in a modeled future climate having carbon dioxide levels twice those of pre-industrial times (a 2 x CO2 climate). Under such future climate conditions, temperatures in the Western United States may be as much as 3°-5° C warmer than present. The left panel illustrates where this tree is found today. On the right panel, green represents sites where the species is found today and where it could continue to live under the simulated 2 x CO2 climate. Red indicates sites where it occurs today but would not survive under the simulated 2 x CO2 climate. Blue represents sites where it does not exist today but could be found under the simulated future conditions. Although the changes illustrated by this figure are specific to the particular climate simulations used here, they are probably representative of the changes that may occur.

Figure 11. Present distribution of the Douglas fir in western North America and predicted changes in its distribution in a 2 x CO2 climate. A 2 x CO2 climate has twice as much carbon dioxide as pre- industrial times. Map from Thompson and others (in press).

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