Evaluating mitigation measures to reduce negative impacts of infrastructure construction on vegetation and wildlife

Abstract

Evaluating mitigation measures to reduce negative impacts of infrastructure construction on vegetation and wildlife

The human footprint is large and growing worldwide. Land-use related to technical infrastructure development, such as road construction or power grid systems, leads to degradation of natural habitat and contributes to 23% of anthropogenic GHG emissions globally. Combined, this causes major declines in biodiversity and, in extension, ecosystem function. Nevertheless, human mobility will further increase and so will technical infrastructure development. In both road construction and power grid system projects large areas are influenced by construction work and accordingly, large areas of habitat are fragmentated and lost. An approach to combat biodiversity loss due to infrastructure development, is to apply the principles and ideas of ecological restoration within the planning and implementation of mitigation measures. There is a general lack of assessment on the effectiveness of mitigation measures in the construction sector, internationally and in Norway. In order to truly minimise impacts on and restore and protect biodiversity, it is therefore of highest importance to thoroughly assess and evaluate the effectiveness of mitigation measures.

The aims of this thesis are threefold; to give an impression of the negative impacts of large infrastructure projects on biodiversity in Norway, to study the mitigation measures conducted to reduce these negative impacts and to evaluate the effectiveness of the mitigation measures. This was addressed by using forest inventory data to investigate impacts of distance to roads and houses on moose browsing, and a possible cascading effect on tree recruitment. Further, landscape fragmentation and its mitigation for moose and deer, in form of effective use and placement of wildlife crossing structures, was investigated by the use of a novel method (Equivalent Connected Habitat). Lastly, the effectiveness of revegetation measures in large infrastructure constructions was evaluated with vegetation analysis, comparing different revegetation treatments and levels of survey detail.

Jointly considering the results show, that there is a high pressure from large infrastructure on ecosystems and biodiversity in Norway. Long-term landscape scale planning is important, for the effectiveness of both wildlife crossing structures and revegetation measures. Wildlife crossing structures might have little mitigation effect, if the landscape around is degraded. Time is most important for a successful vegetation recovery, while choice of revegetation treatment is of lesser importance. However, when considering species composition, natural recovery (with or without added topsoil) will in most situations give better or equally good results in terms of vegetation development. It is further necessary to have rather detailed vegetation data to evaluate revegetation measures. This thesis demonstrates the lack of

successful monitoring of mitigation measures. To truly protect and restore biodiversity we need to know the outcome of mitigation measures an hence, a well-planned, thought-through, repeatable and targeted monitoring of mitigation measures is needed, preferably over a longer time period. Where possible, i.e. in projects with a pre-construction period, a BACI (Before-after-control-impact) approach is recommended.