of private timberland owners to plant and harvest timber. Other concerns, such as endangered species requirements, could result in additional and possibly quite large withdrawals from the timber base. On a large scale, such actions could significantly reduce the domestic timber base and hence the supply potential. However, the aggregate effect of such actions on U.S. domestic consumption of forest products is problematic. The worldwide industrial wood market has become truly integrated. A reduction in domestic production is likely to be offset by both decreased exports and increased imports. Additional supplies could be forthcoming initially from Canada, and from a variety of other sources. Although some analysts ( Darr, 1988) have suggested that the ability to increase Canadian harvests is limited, others ( Williams, 1986) have suggested that the potential supply from Canada is indeed massive and would require only strong economic incentives to be released.
Another concern relates to the future effects of a possible global warming on the U.S. forest estate. Although the long-term effects of warming on the nation's forests are unclear, some analyses indicate that they are likely to reduce modestly the area and volume of forest both worldwide and in the United States ( Sedjo and Solomon, 1989). Another unknown is the nature of the transition of the forest from its present configuration to one consistent with the climate conditions associated with a warming. Such a transition could provide abundant timber supplies in the short run in the form of salvage logging. In the longer term, however, timber supplies could be affected adversely if productivity were affected negatively.
In the absence of a global catastrophe, the physical potential of the United States to produce the vast majority of society's wood needs appears certain. The economic potential also exists. Timber can be harvested from existing forests and delivered to mills at economically acceptable costs. If timber supply problems arise in the United States, they would almost surely result from decisions to withdraw massive amounts of public timberland from the timber base, or from federal or state policies that discourage the private sector from continuing to make large investments in timber growing.
This draft has benefited from the suggestions and comments of Perry Hagenstein, John Fedkiw, Robert Nelson, John McMahon, R. N. Pierson, Lester Holley, Pierre Crosson, Ken Frederick, Marion Clawson, Robert Wolf, John Zivnuska, and a number of anonymous reviewers at the U.S. Department of Agriculture. In addition to his detailed comments, Fedkiw's own work was a valuable source of some of the historical information used in this chapter.