Wilderness Overflight Soundscape Index (OSI): Mapping, measuring and describing overflight soundscape impacts at nested scales

Wilderness is both a conservation and recreational resource. These competing demands and uses can present challenges for managers. In Australia, wilderness areas are measured and mapped with the National Wilderness Inventory (NWI) approach, however, the NWI does not account for the experiential impacts of aircraft overflights on park users. Here, we adapt a reserve-scale mensuration method developed in the U.S.A. for incorporation into the Australian NWI framework. We innovate within our approach by using a decision tree and raster mapping processes to assess soundscape impacts at nested scales of individual pixels, flight path, and reserve-scale. We apply our technique to the Tasmanian Wilderness World Heritage Area (TWWHA), to first evaluate overflight soundscape impacts at the flight-path scale, then at the overall cumulative reserve-scale. The results indicate overflight soundscape noise impacts to ∼506,814 ha (32%) of the TWWHA. Cumulative overflight soundscape impacts were detected in the south-west of the reserve, an area comparatively free of complex private or public built infrastructure, other than a public landing strip, adjacent infrastructure node (Melaleuca), and low-volume walking tracks. Conversely, negligible cumulative overflight soundscape impacts were detected in the north of the reserve, where the majority of built public and private tourism infrastructure, use, and major formed tracks are located. These results are counter-intuitive and reveal spatiotemporal patterns that may be modified through management interventions, while maintaining existing air access provisions. While we apply our method to the TWWHA, it is widely relevant to managers who must manage recreation uses, and air access, within protected areas.