ASSESSMENT OF TRAFFIC NOISE IMPACT IN IMPORTANT BIRD SITES IN SWEDEN -- A PRACTICAL METHOD FOR THE REGIONAL SCALE

Abstract

Previous research has pointed out the negative impact of traffic noise on wildlife adjacent to major roads, but despite the scientific evidence, the impact of traffic noise in natural environments is rarely assessed, and even more rarely mitigated, in road planning, in Sweden as well as in most other countries. It has been argued that the reason to this shortcoming is the lack of a practical method to assess this impact on natural environments. We developed a desktop method for assessing the traffic noise impact on areas of importance for nature conservation, with special emphasis on important bird sites. The method output is a calculation of the effective habitat loss due to traffic noise for each site, based on dose-effect relationships presented in literature, available GIS data on selected habitat types, official road data, and a simplified model for noise distribution. The method has a dual purpose; to estimate the impact of traffic noise on birds at larger geographic scales, and to identify priority sites for mitigation efforts. We applied the method in two Swedish regions with relatively low or moderate road and traffic densities. The results from these case studies pointed out that i) at regional level, the impact zone covers a small part of the land area (0.6 and 3.3% of lower and higher density regions, respectively), ii) for certain important bird habitat types, >10% of sites are within the impact zone, iii) the impact from traffic noise represents an effective loss of 0.02-1.7% of the total area of the selected habitat types. The latter figures can be taken as estimates of the present conservation debt of traffic noise. The results indicate that traffic noise may have a disproportionate impact on some important bird habitats. Because bird sites are often rich also in other taxa, and in addition tend to be important areas for outdoor recreation, we argue that traffic noise may have a broad impact on nature conservation, and that mitigation efforts should be made to minimize this impact. We discuss the general applicability of the method.Keywords: Traffic noise; birds; assessment; method; Sweden.