Technical Bulletins & Special Reports

Technical Bulletin No. 0909: Defining Old-Growth in Canada and Identifying Wildlife Habitat in Old-Growth Boreal Forest Stands

In Canada, as elsewhere, there is concern about the impact of forestry operations on species that may depend on old-growth forest. However, during debates on old forest, a distinction is not always made between wildlife that require “mature and older” forest and those that need only true “old-growth.” This is challenging for the forest industry, in terms of providing appropriate amounts of “mature and older” forest on the landscape versus providing strictly “old-growth.” This technical bulletin provides a literature review of old-growth forest definitions used in all the forest regions of Canada as well as a review of the relationship between wildlife species and old-growth stands in the Boreal Forest Region. Over 300 papers and books were reviewed and approximately 170 are cited in this report. Fundamentally, there are two approaches to defining old-growth forest stands. The first approach uses age-specific definitions. In this approach, stands, trees, or ecological sites are designated old-growth when they reach a specific age. This type of definition is common across Canada and is useful in preparing forest management plans because it is clear and the information is available in forest inventories. However, the diversity and complexity of forests in Canada means that old-growth conditions may occur at different ages, even for the same tree species, depending on the local conditions. This has led some to define old-growth to be when physical characteristics or the ecological function of the stand reaches a certain point. These process-based definitions can be vague, or can be more complex and require more sophisticated measurements than age-specific definitions.