Landscape influence on biophony in an urban environment in the European Alps

Biophony is the acoustic manifestation of biodiversity, and humans interact with biophony in many ways. However, quantifying biophony across urban landscapes has proven difficult in the presence of anthrophony, or sounds generated by humans. Improved assessment methods are required to progress our understanding of the processes influencing biophony across a variety of spatial–temporal scales. We aimed to identify how the landscape influences biophony, as well as the total acoustic environment, along an urban to rural gradient. We designed the study to quantify how soundscape–landscape relationships change across a variety of spatial–temporal scales. We recorded the afternoon acoustic environment during the spring of 2016 at 30 locations in the city of Innsbruck, Austria using a spatially balanced random sampling design. We quantified the total acoustic environment with the sound exposure level (SEL) metric, and developed a new metric, percent biophony (PB), to quantify biophony while avoiding noise bias. We quantified relationships with land cover (LC) classes, as well as a landscape index, distance to nature (D2N), across 10 scales. D2N within 1280 m best predicted PB, while both the LC class trees and D2N within 40 m best predicted SEL. PB increased more throughout the spring at locations with more natural surrounding LC, while PB did not change significantly at locations with more urban surrounding LC. LC and composite indices can serve as reasonable predictors for the acoustic environment; however, the relationships are scale dependent. Mapping soundscapes can help to illustrate possible driving mechanisms and provide a valuable tool for urban management and planning.