Carabid beetle and human responses to edge effects in urban forests in Helsinki, Finland

Fennoscandian cities are forested, yet these remnant forest patches are generally small and characterized by sharp edges and high levels of human trampling. Sampling carabid beetles from urban forests in Helsinki revealed that the majority of species neither respond as predicted to distance from the forest edge to the interior, i.e., edge effects, nor to trampling intensity. Yet, habitat type outside these urban forests (e.g., asphalt, grassland, secondary forest) does have an effect on species at the edge and into the forests. It appears that a long history of fragmentation of urban forests in Helsinki has resulted in the loss of forest specialist species, thus resulting in neutral responses to habitat edges in the city. This is in contrast to a similar study performed in Edmonton, Canada, where forest specialists are still present and respond as predicted to edge effects and trampling. Forests in Helsinki also have considerable restorative potential to urban residents. In particular, visitors to forests with thick edges (i.e., with a closed view to the urban matrix) showed the highest restorative potential when compared to visitors in forests with an open or semi-closed view to the urban matrix. Growing ‘thick’ urban forest edges thus have the potential to promote restoration in forest visitors, yet it is still unclear whether these thick edges would benefit forest specialist species, including carabid beetles.