The Finnish forest industry is undergoing a vast expansion, which has raised questions of forest balance. This paper studies the possibilities to increase the amount available timber by means of forest drainage. About third of the Finnish land area is peatlands. The calculations of the investigation are based on Forestry Board districts. Based on earlier studies, there is estimated to be 3,042,000 ha of true drainable swamps, 973,000 ha of poor swamps, 1,381,000 ha of uplands in need of drainage, and 1,205,000 ha of drained peatlands. Therefore, the area of drainable and drained lands totals 6,6 million ha, and requirement of forest drainage 5,4 million ha. The drainage hardly reaches this extent, however. It can be assumed that part of the poor swamps is uneconomical to drain. In addition, a half of the paludified forest land will probably not be drained. Thus, it can be estimated that the area to be drained in the future is about 5 million ha. It seems possible that this area could be drained within about 50 years with the present draining capacity.
Draining of all objects of forests would increase the annual increment of our forests, in time, by about 10.5 million m3. This would signify an increase of 23% compared to the present growth of the forests. The increase in the growth consists mainly of softwood: 16% is birch, and the remaining 84% almost equally of Scots pine and Norway spruce. The increase of growth is relatively slow. Depending on the rate of the drainage program, the mean increase of growth will be reached in about 25–35 years. The increase in removal indicated by the increase in the mean increment will be reached in only 50–60 years.
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