Much of the forest in Canada consists of even-aged stands, due to such cyclical and widespread disturbances as fire and insect infestation. Healthy ecosystems can tolerate periodic disturbances. Indeed the renewal of some forest types depends on natural disturbance, more particularly fire, which is often necessary to give an ecosystem a fresh start. In eastern Canada, insects are the major type of disturbance. Fire is the most important disturbance in the western boreal forest.
Harvesting is the predominant disturbance in British Columbia's coastal forest.
Fire, insects and disease affected an average of 1.14 million ha annually between 1978 and 1992, while harvesting was carried out on an average of 887,000 ha annually during the same years. Competing vegetation and other natural factors can prevent the natural regeneration of some forest stands. Planting and seeding programs are carried out on sites that have not regenerated several years after harvesting or natural disturbances. These programs have been successful in eliminating most of the backlog of understocked sites. An increase in planting and seeding activity was recorded in 1994, for the first time since 1990.