Anthropogenic noise in US national parks – sources and spatial extent

In an era of unprecedented environmental change, US national parks are refuges of natural ecosystems and facilitate connections between humans and nature. However, anthropogenic noise is an increasingly pervasive threat in these parks. To diagnose noise levels and sources, we analyzed thousands of hours of acoustic recordings collected across park units and summarized results from continental-scale sound models. We found that anthropogenic noise was audible in 37% of park recordings, and that parks with high road density and those in close proximity to large airports experienced a greater number of noise events. The most common noise sources were aircraft and road vehicles, but, when present, trains and watercraft generated the loudest noise levels. Sound models show that anthropogenic noise caused a tenfold increase in median sound levels in 36% of parks, and loud areas were often localized. Our analysis identifies situations where noise management would yield the greatest benefits to park visitors and wildlife.