Old forest ecosystems are forests that dominated by large, old trees and have structurally complex vegetation layers. Old forests were mapped where polygons included old structural stage ecosystems (except for old riparian forests, which were included in the Riparian category).

Old forest ecosystems are dominated by large, old trees, which includes old Coniferous Woodlands and Old Broadleaved Woodlands. Old Forest Ecosystems are dominated by large old trees usually greater than 150 years of age. Most of these forests have been lost to selective logging of larger trees and have in-growth of dense young trees resulting from fire exclusion.

On wetter sites, forest development occurs more quickly than on drier sites. Historically, these wetter sites did not burn as frequently and multi-layered forests were able to develop. Moist forests are also at increased risk of loss to catastrophic wildlife relative to historical levels. Increased forest densities places stress on older trees and makes the more susceptible to attack by insects such as spruce budworm. Moist forests are, by nature, denser, more multi-layered and less affected by forest ingrowth.

Some of the Species At Risk found within Old Forest Ecosystems are: Rubber Boa, Wolverine, White-headed Woodpecker, Lewis’ Woodpecker, Common Nighthawk, Flammulated Owl.