Advances in our understanding of the direct and indirect effects of anthropogenic noise on ecological systems

Background/Question/Methods

Human activities that support the growing human population have altered landscapes around the world, including a near-ubiquitous transformation of the acoustic environment due to anthropogenic noise. Estimates suggest sound levels in marine environments have increased by 12 decibels (dB) worldwide due to shipping noise and that 88% of the contiguous U.S. are exposed to anthropogenic noise. Recent work has documented severe responses by animal populations and communities to this stimulus, suggesting that the acoustic environment is a critical, yet largely under recognized, ecological dimension for many species. Critical gaps in our understanding span a mechanistic understanding of why some species appear more sensitive than others and what the broader-scale impacts are for ecological communities. Here, using my long-term research in the gas fields of NW New Mexico as a case study, plus evidence from a large synthetic study, I provide an overview of new insights on the mechanisms driving sensitivities to anthropogenic noise and the ecological ramifications of altered acoustic conditions.

Results/Conclusions

Evidence from New Mexico and other recent studies suggest that noise reduces avian diversity by approximately one-third and that many species that remain in noisy environments are present in lower densities. These responses have several indirect ecological consequences. Loss and density reductions of key species drastically alter ecological processes ranging from predator-prey relationships to patterns of seed dispersal and pollination. Importantly, direct effects of noise on species sensitivities are nonrandom. A synthesis of 308 populations of 183 bird species reveals that density reductions and species loss in noisy environments is influenced by vocal traits and foraging guild. Specifically, birds with low frequency vocalizations that experience more masking from noise are more sensitive and birds with animal-based diets are more sensitive than those with plant-based diets. Taken together, these findings suggest that alterations in the acoustic environment can have profound consequences for ecological communities through direct and indirect effects. Importantly, direct impacts at the species level appear to be nonrandom and are driven by how organisms use the acoustic environment to obtain, interpret and respond to acoustic cues used in a variety of capacities.