Abstract
The ecological impacts of roads and railways extend into the surrounding landscape, leading to habitat degradation and reduced wildlife densities within an area that is considerably larger than the actual road or railway corridor. For birds, an extensive meta-analysis has identified an average of 20% density reduction within 1 km from the infrastructure. I investigated to what extent this density reduction can be expected to compromise the habitat quality and conservation value of Swedish Natura 2000 areas designated for the protection of birds (Special Protection Areas; SPAs). The majority (63%) of Swedish SPAs are, to some extent, found within this 1 km road/railway effect zone (REZ). The total overlap between SPA and REZ is approximately 126,000 ha or 4.2% of the country’s SPA area. There are, however, large differences amongst bio-geographical regions. In the southern (continental) and coastal regions combined, 25.8% of the total SPA area fall within REZ, representing an estimated 4–7% reduction in bird abundance within SPAs. The probability of overlap with REZ is higher for larger SPAs. However, the proportion of overlap is higher for smaller SPAs and, accordingly, smaller sites can be assumed to experience a greater impact from transport infrastructure and traffic. The impacts on Natura 2000 sites are particularly concerning as this network of protected areas is a cornerstone for maintenance and restoration of biodiversity within the EU. I recommend placing a stronger emphasis in the management of Natura 2000 sites on the threats to wildlife conservation caused by transport infrastructure and traffic. Special attention should be paid to sites with a large overlap with the REZ and sites hosting particularly vulnerable taxa or habitats. Infrastructure owners and managers should make their best efforts to minimise and compensate for the negative impacts of roads and railways and associated traffic in SPAs and other protected areas.
Highlights
Ecological impact of transport infrastructureInfrastructure development is recognised as one of the significant drivers of global biodiversity loss and, with increasing traffic and expanding infrastructure networks worldwide, the pressure on biodiversity is expected to increase in coming decades (EEA-FOEN 2011, EEA 2012, OECD 2012)
As most studies in the meta-analysis were conducted in biomes that occur in Sweden, i.e. taiga, temperate broadleaf forest or alpine/tundra (39 of the 49 datasets) and on species that occur in Sweden (105 of the 201 species), I judged the results to be relevant to a Swedish perspective
The results indicate that a significant proportion of Swedish SPAs, both in terms of area and number of sites, lies within a predicted effect zone for birds around present larger transport infrastructure (REZ) and can be expected not to reach their full potential as a bird habitat
Summary
Infrastructure development is recognised as one of the significant drivers of global biodiversity loss and, with increasing traffic and expanding infrastructure networks worldwide, the pressure on biodiversity is expected to increase in coming decades (EEA-FOEN 2011, EEA 2012, OECD 2012). The impacts of transport infrastructure on wildlife are well described (Forman et al 2003, van der Ree et al 2015) and include loss of habitat, traffic casualties, creation of physical barriers, disturbance by noise, light and other visual cues, spread of chemicals, dust and alien species, changes in hydrology and microclimate and accidental spills Most of these impacts extend into the surrounding landscape, leading to degradation and fragmentation of habitats and, for some species, to restricted movements, increased mortality and avoidance of a zone around the infrastructure (Forman et al 2003, EEA-FOEN 2011, van der Ree et al 2015, Tulloch et al 2019). In an assessment of the impact on Natura 2000 sites of major traffic arteries, planned or under construction as part of EU’s TEN-T framework, Byron and Arnold (2008) estimated that 379 SPAs (8% of sites) and 953 SCIs (4% of sites) would be adversely affected by these new traffic arteries, with potential effects on the coherence of the Natura 2000 network
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