January 2000: Policy direction for biodiversity is now represented by the Landscape Unit Planning Guide. This Extension Note should be regarded as technical background only.
In the depths of many mature and old-growth forests in British Columbia, a specialized range of plant and animal life exists. Some of these species depend on the more stable climatic environment of the forested interior, while others require the snags and decaying woody debris often found there. Some of the animals require large unbroken tracts of such habitat to hunt and breed. However, the amount and quality of this habitat have gradually decreased as human settlement, roads, logging, and agriculture have fragmented the province's forested landscape.
As forests are cut, edges are created. The environmental conditions produced along these edges may modify habitat values that are important to interior forest dwellers. Many landscape ecologists have voiced concern about this habitat disruption and about the potential loss of landscape-level biodiversity that may ensue if interior habitat ecosystems and processes are not sustained. Preserving sufficient interior habitat is therefore important to protect these species and maintain biodiversity.
The Forest Practices Code acknowledges the importance of landscape ecology concepts by enabling district managers to designate planning areas called "landscape units," each with specific landscape unit objectives. The Biodiversity Guidebook (B.C. Ministry of Forests and B.C. Ministry of Environment, Lands and Parks 1995), a component of the Code, recommends procedures to maintain biodiversity at both landscape and stand levels. These procedures, which use principles of ecosystem management tempered by social considerations, recognize that the habitat needs of most interior forest organisms can be maintained if excessive edge habitat is avoided and if forested areas are of adequate size to preserve interior habitat conditions.
This extension note is the sixth in a series designed to raise awareness of landscape ecology concepts and to provide background for the ecologically based forest management approach recommended in the Biodiversity Guidebook. The focus here is on the related topics of forest interior habitat and edge effects. We first define and differentiate between edge environments and forest interior habitats. Then we discuss several general ecological principles concerning edge environments and their effects on interior habitat and the plant and animal life that depends on it. We conclude by examining how excessive edge habitat might be prevented and forest interior habitat quality maintained at the landscape level.
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Updated April 17, 2007