Corridors and connectivity in forest landscape management

Mikko Mönkkönen & Pasi Reunanen

University of Oulu , Department of Biology

Connectivity refers to processes by which the sub-populations of a landscape are interconnected into a demographic unit. Landscape connectivity is not simply a question of physical connectedness of habitat patches. Patches may be physically connected by a corridor, for example, but still perceived unconnected by an organism because of inability to use movement corridors for a reason or another. Ecological forest landscape management procedure has adopted dispersal corridors as one of the main tools in maintaining viable populations. Corridors are established particularly to enhance the dispersal of old-growth forest specialist species. In Finnish system corridors are some 25-100m wide strips of forest along creeks or bordering wetland shores. Timber harvesting is allowed in pine dominated corridors. Corridor surroundings are harvested in two phases. To avoid excessive edge effect in corridors forest on the two sides of the corridor is not cut simultaneously, but the other side is harvested only after the forest on the first harvested side has grown up to one third of the length of the trees in corridors. We surveyed the existing ecological forest landscape management plans to see if they are likely to maintain landscape connectivity for populations of old-growth forest associated species. Using selected cases as examples we conclude that the planned corridor networks are rather aesthetic constructions buffering water courses against negative effects of forestry than dispersal corridors for forest associated species. This is partly because they obviously are too narrow for many forest specialist species, and particularly because they often are not forest at all but wetland habitats along watercourses. The role of corridors varies according to the landscape composition, and they obviously are more important in more heavily fragmented southern Finnish landscapes than in the north where the amount of forest coverage is larger in general. The main implication is that connectivity from the perspective of old-growth forest species will ultimately depend on areas not included into ecological forest management plans. Connectivity becomes a question in the domain of operational forest management: when, where and how to harvest. In the present planning system maintaining landscape connectivity in the long time perspective remains as a challenge for foresters responsible for operational planning.