Holocene, and probably occurred during the glacial periods when dust levels were significantly higher around the world (Overpeck et al., 1996). Ecosystems may be dominated by early successional species. Given that the economy depends on many late-successional species, losses of existing trees would dig into inventories of standing timber and raise timber prices, perhaps for long periods of time. Wildlife dependent on mature systems may be especially stressed; landscape appearances may dramatically change; and runoff may change completely from historic ranges. These changes suggest the potential for large damages.

The impact of climate change on forest systems is currently an area of intensive research (e.g., Hansen et al., 2001a; Shafer et al., 2001), although the focus is on gradual climate change. These studies suggest that there may be some immediate damages associated with dieback in forests and that long-term productivity may increase in some species if CO2 fertilization occurs, but not in others. Some paradoxes lurk here, however. In a study of how forests in the United States might adjust to future climate change, Sohngen and Mendelsohn (1998) were surprised to find that a scenario with significant dieback of existing stands did almost as well as a scenario where natural change occurred more slowly (Sohngen and Mendelsohn, 1998). Their study illustrates the important point that adaptation (or well-designed management) can help ecosystems to adjust more rapidly and with lower overall economic costs.

Little is known about how climate-change impacts on forests would affect nonmarket services. Little is known about what would happen to wildlife because of complex interactions, and how much people would value the changes. Forest products such as fruits, nuts, medicine, and mushrooms are highly valued, but it is not clear how the flow or value of these products might change with abrupt climate change. Although ecologists predict that biomes will shift with warming, there has been little accompanying social science research to evaluate such shifts. There has been scant research on how forests might change in appearance or how much people would care about the changes. Thus, many of the quality-of-life effects on forests have not been evaluated.

Water Resources

There is a growing awareness of the scarcity of freshwater at the earth’s surface compared with the total amount of water on the planet, and concern about how climate change might affect water resources (Gleick, 2000;



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