Worldwide Soundscapes: a synthesis of passive acoustic monitoring across realms

Abstract

The need for remote, reliable, and scalable monitoring of plummeting biodiversity amidst mounting human pressures on ecosystems and changing climate has sparked enormous interest in Passive Acoustic Monitoring (PAM) over multiple disciplines and ecosystems. Even though PAM could support UN Sustainable Development Goals and the Global Biodiversity Information Facility by facilitating the evaluation of management and conservation actions, global efforts have not yet been synthesised. We collated metadata from 293 soundscape datasets since 2001 describing sampling sites, deployment schedules, focal taxa, and recording parameters. We quantified biological, anthropogenic, and geophysical soundscape components across nine terrestrial and aquatic ecosystems. This is the first global, quantitative analysis of ecoacoustic sampling coverage across spatial, temporal, and ecological scales. Spatial sampling densities are two orders of magnitude higher in terrestrial realms (33 sites/Mkm2) compared to aquatic realms, while substantial data gaps remain in subterranean realms, extreme environments, and tropical waters. Diel and lunar cycles are well-covered, but in temperate regions, a third of freshwater and terrestrial datasets sample only one season while 57% of marine datasets cover all seasons. Opportunities arise for taxonomically broader sampling on land, for increasing spatial coverage in the high seas, and for more spatially-replicated deployments in freshwater. We illustrate the potential of soundscape ecology to address global questions related to macroecology, conservation biology, and phenology using sample soundscapes. PAM-enabled soundscape ecology has come of age to bridge different disciplines and quantify our progress towards Sustainable Development Goals on land and underwater.