Transport infrastructure has a wide array of effects on terrestrial and aquatic ecosystems, and road and railway networks are increasingly being associated with a loss of biodiversity worldwide. Environmental Impact Assessment (EIA) and Strategic Environmental Assessment (SEA) are two legal frameworks that concern physical planning, with the potential to identify, predict, mitigate and/or compensate transport infrastructure effects with negative impacts on biodiversity. The aim of this study was to review the treatment of ecological impacts in environmental assessment of transport infrastructure plans and projects. A literature review on the topic of EIA, SEA, biodiversity and transport infrastructure was conducted, and 17 problem categories on the treatment of biodiversity were formulated by means of a content analysis. A review of environmental impact statements and environmental reports (EIS/ER) produced between 2005 and 2013 in Sweden and the UK was then conducted using the list of problems as a checklist The results show that the treatment of ecological impacts has improved substantially over the years, but that some impacts remain problematic; the treatment of fragmentation, the absence of quantitative analysis and that the impact assessment study area was in general delimited without consideration for the scales of ecological processes. Actions to improve the treatment of ecological impacts could include improved guidelines for spatial and temporal delimitation, and the establishment of a quantitative framework including tools, methods and threshold values. Additionally, capacity building and further method development of EIA and SEA friendly spatial ecological models can aid in clarifying the costs as well as the benefits in development/biodiversity tradeoffs.

Transportation infrastructure has a wide range of effects on ecological processes, which result in both positive and negative impacts for biodiversity. However, the treatment of biodiversity in planning and environmental assessment have been criticized, especially regarding habitat loss and fragmentation effects, the low use of quantitative methods and that of assessments being descriptive rather than analytical and predictive. The aim of this study was to assess the impacts of the Swedish road network by spatial modelling of road effects, to explore potential impacts of fragmentation and disturbance effects of roads on habitat networks for selected ecological profiles, and to discuss the utility of applying quantitative methods for environmental assessment purposes. Habitat and landcover data was used for creating habitat networks for six ecological profiles. Fragmentation and disturbance effects were modelled in GIS and FRAGSTATS was used to quantify ecologically important landscape metrics on habitat amount and connectivity. The results showed that natural grasslands and southern broadleaved forest were substantially more exposed to road effects in Sweden, compared to old coniferous and trivial broadleaved forest. Furthermore, habitat loss was a main consequence of road effects, and forest species with high area demands were most prone to be adversely impacted. Suggestions on method development in order to increase the quality of the analysis methods for environmental assessment are discussed. The potential is seen as high for use of quantitative ecological methods to generate baseline environmental information as well as coarse predictions on likely consequences of development options, useful for environmental assessment.