Effectiveness of Boundary Structures in Limiting Residential Encroachment into Urban Forests

Urban forests provide essential functions in support of human communities; however, studies indicate adjacent residential land uses degrade urban forests following development. The resulting impacts are known as encroachment. Local Ontario governments rely primarily on passive management, such as boundary structures (e.g. fences) to limit this degradation but do not know whether they are effective for limiting the area of the forest floor covered by these impacts. Transect and quadrat sampling of 40 forest edges adjacent to 186 residential properties were sampled in six Southern Ontario municipalities to determine impact frequency and area cover of encroachment. The results indicated some structures are effective in reducing the frequency and area cover of some encroachment behaviours. Other behaviours were not significantly reduced by any structural treatment. Furthermore, some behaviours were increased by structures. Substantial areas of encroachment continued to occur under even the most effective boundary treatments. The treatment most successful in reducing frequency and area was ungated fencing in combination with a mown grass strip. It was found to reduce the incidence of yard extensions and concentrate encroachments closest to forest edges.