Swamps have the greatest potential for forestry. In Canada, most of the wood harvested from swamps is black spruce. Other commercially important species include tamarack and eastern white cedar. With drainage, or drainage and fer-tilization, the forestry potential of treed wetlands can be improved. However, the costs of forest drainage works can be significant, and the practice has not been, extensive in Canada.
Harvesting is the dominant forestry activity in wetlands.
It is potentially damaging due to the sensi-tivity of wetland sites to damage by machinery and the resulting inhibition of regeneration. Roads that cross wetlands frequently block drainage. The common result is flooding on the upstream side of the road with subsequent killing of woody vegetation and partial drying of the downstream area. Roads on wet sites may require extensive, preparation of the road bed, with a variety of measures to handle drainage. Draining wetlands can have a range of effects depending on the extent and intensity of the drainage works.