Road Ecology Center

Here I report the ecological impact assessment of a section of European Highway E18 east in Helsinki, Finland. This two-lane section of highway was constructed through the shore pastures of the Pernajanlahti Bay, which is one of the most important nature conservation areas on the southern coast of Finland. It is a wetland area characterized by extensive shore meadows and reed swamps offering habitats to a diverse and abundant birdlife. Wetland bird populations in the target area as well as in a control area were monitored before, during, and after the road construction. The results indicated that after the highway had been opened for traffic, the mean conservation value of the wetland bird community in the target area had decreased by 25 % as compared with the control area. The decline in conservation value was mainly due to the loss of several habitat specialist species, such as European bittern (Botaurus stellaris), ruff (Philomagnus pugnax) and little gull (Larus minutus). Abundance of breeding wader birds also declined in areas near the highway, where the traffic noise level exceeded 56 dB, but did not change much in areas with lower noise load. In contrast to wader birds, population abundance of passerine birds did not show any directional response to disturbance by the highway, regardless of noise level. Despite the negative effects of the highway on conservation value and on many bird populations in the Pernajanlahti Bay, the highway is currently being expanded with another two-lane roadway. The effects of traffic noise could be to some extent mitigated by noise barriers.