This relationship is especially important in the poorer soils of northern forests, precisely the areas where the mycorrhizae are most rapidly being lost. Until 1950, virtually all timber was harvested from virgin forests. The industry would no longer be able to economically contribute to local economies. It would require the harvest of more trees to produce the same tonnage of wood pulp, or board feet of lumber. Thus, the worker would work longer to make the same income.
Paper is the largest use of trees harvested in North America.