Understory vegetation can promote bird sounds and reduce traffic noise in urban park soundscapes

Natural soundscapes commonly experienced in parks are increasingly valued as an important cultural ecosystem service with the potential to promote greater mental well-being for people. Yet the quality of urban park soundscapes can differ, containing varying proportions of natural sounds, such as bird calls, and anthropogenic noise, such as vehicle traffic. These soundscapes are linked to underlying landscape features yet their role in shaping both beneficial natural sounds and unwanted anthropogenic noise remains unclear. We address this gap by analysing the influence of park and surrounding landscape characteristics on a range of urban park soundscapes in Brisbane, Australia, with respect to bird sounds and traffic noise. We recorded audio in 67 parks in Brisbane, Australia and quantified bird call volume, bird call diversity and traffic noise volume for each recording. We then used multiple linear regression analyses to determine the influence of land cover classes, vertical vegetation density and distance to a main road on each of these dimensions. We show that greater vegetation density in the understory has a positive influence on the loudness and diversity of bird calls within park soundscapes and a negative influence on traffic noise. Traffic noise was also associated with greater proximity to a main road and higher canopy height, whilst greater impervious surface appeared to increase the dominant sound type (i.e. either bird sounds or traffic noise) within the soundscape. These findings highlight the importance of managing the landscape features of urban parks to promote higher quality soundscapes. Results suggest that greater vegetation density and complexity, particularly in the understory, has potential as a nature-based solution to enhance the diversity of bird calls within park soundscapes whilst also mitigating traffic noise.