A Synthesis of the Effects of Noise on Wildlife

Background Global increases in environmental noise – arising from expansion of human populations, transportation networks, and resource extraction – have catalyzed a recent surge of research into the effects of noise on wildlife. Synthesizing a coherent understanding of the consequences of noise from the literature would advance natural resource management and conservation policy, yet is challenging given the multidisciplinary nature of the field. Many types of biological responses have been observed across a wide range of noise sources and for a variety of species and habitats.  Methods We conducted a systematic review of the scientific literature published from 1990 to 2013 on the effects of anthropogenic noise on wildlife, including both terrestrial and aquatic studies. Over 240 papers were reviewed to extract details on the study design, taxonomic group, noise sources, and type of wildlife response. Results The majority of studies documented effects from noise, including altered vocal behaviour to mitigate masking, reduced abundance in noisy habitats, changes in vigilance and foraging behavior, and impacts on individual fitness and the structure of ecological communities. Research effort has concentrated predominantly on European and North American species that rely on vocal communication, with approximately two-thirds of the data set focusing on songbirds and marine mammals. Our synthesis of the literature showed that terrestrial wildlife responses begin at noise levels of approximately 40 dBA, and 20% of papers documented impacts below 50 dBA. It is clear that noise presents diverse threats to species and ecosystems and salient patterns are emerging that can help inform conservation policy. Conclusions Our synthesis highlights the utility of existing scientific information concerning the effects of anthropogenic noise on wildlife for predicting potential outcomes of noise exposure and offers a valuable resource to assist scientists, industry, and natural resource managers working to protect species and habitats. Future research directions that would support more comprehensive predictions regarding the magnitude and severity of noise impacts include: broadening taxonomic scope, exploring interacting stressors, conducting larger-scale studies, standardizing reporting of acoustic metrics, and assessing the biological response to noise-source removal or mitigation.