NET GROWTH of wood (total growth minus mortality) in the United States was 11.2 percent higher in 1977 than in 1970 from essentially the same acreage of commercial forestland. This is one of the more dramatic and important relationships revealed by the Forest Service's report, Forest Statistics of the United States, 1977, which was circulated in draft for comment in the summer of 1978.
The increase in wood growth in the 1970-77 period was part of a much longer upward trend that has largely gone unrecognized in public discussions. Annual net growth has risen by 56 percent since detailed inventories first began in 1952—and has risen by almost four times over the estimated net growth in 1920. Recent increases were shared by almost all regions and by almost all ownership groups within each region. During the 1970-77 period, net growth of wood exceeded harvests by 53 percent, thus leading to a substantial increase in inventory of standing timber. The increase in inventory was particularly large for hardwoods but was also evident for the softwoods.
These statistics on growth and on the increased timber inventory are in direct opposition to a widely held view that this country is denuding its forests. At an earlier period in American history, the extensive natural stands of timber were indeed being cut faster than they were growing, and much previously forested land was denuded or rendered unproductive. While much that happened during that period of earlier exploitation was highly undesirable from a conservation viewpoint, the harvest of the old growth stands did open up the areas to much more rapid growth of healthy new stands of timber. Today, as a nation we are growing more and more wood and are building up our forests at a fairly rapid rate.
The productive capacity of American forests has been persistently underestimated. In the early 1900s Gifford Pinchot, the first head of the Forest Service, and President Theodore Roosevelt made statements about impending "timber famine" which implicitly assumed no future growth of timber. Detailed projections of future timber supply have been made by the Forest Service in 1933, 1946, 1952, 1962, and 1970, every one of which has proved to be far lower than the actual growth in later years. In 1970, for instance, the projection was for a growth of 19.5 billion cubic feet of wood in 1980, whereas in 1977 the actual growth was 21.9 billion cubic feet. Actually, the discrepancy between estimate and reality was much wider than this, because the projection was for essentially no increase in growth, whereas in fact there was an increase over the 1970-77 period of more than 2 billion cubic feet of net growth.
In 1933 the Forest Service estimated the "ultimate biological capacity" of American forests—including the biological possibilities of intensive forest management—at only 80 percent of the growth actually achieved in 1977. Thus it appears that trees are not only America's renewable resource, as many foresters argue, but their growth is increasing significantly from year to year—without any indication yet that the forests are nearing a "biological capacity."
A version of this article appeared in print in the January 1979 issue of Resources magazine.
