Page 32 - Summer 2021

FEATURED ARTICLE
Inaudible Noise Pollution of the Invertebrate World
Maggie Raboin
Introduction
Anthropogenic sound is widely recognized as an issue of environmental concern (Shannon et al., 2016). Produced by human activities like those associated with urbaniza- tion, economic development, transportation networks, and recreation, anthropogenic sound now penetrates some of the quietest places on Earth (Buxton et al., 2017). In fact, over 60% of US protected lands experience noise levels double those of background noise, despite their distance from major metropolitan areas (Buxton et al., 2017). For vertebrates, the consequences of noise in natural landscapes have been found to be multifaceted, impacting mating, movement, predator-prey dynamics, and physiology (Shannon et al., 2016). However, research has mostly focused on the impacts of pressure waves on vertebrates, with the impact of anthropogenic sound on invertebrates and the acoustic modalities they rely on (mainly particle motion and substrate-borne sound) remaining largely unstudied.
Indeed, when evaluated in 2016, only 4% of the work on the impact of anthropogenic sound on animals had been on invertebrates, despite their comprising 97% of species on Earth (Shannon et al., 2016). However, recent research investigating anthropogenic sound and invertebrates sug- gests that the impact of noise on invertebrate behavior, physiology, and communities is likely diverse and com- plicated. The goal of this article is to introduce readers to invertebrates, their bioacoustics, and the potential effects of anthropogenic sound on invertebrates.
Invertebrate Decline
In natural history museums, you can find millions of individual invertebrates, from ants and anemones to stoneflies and shrimp. All are collected with care, metic- ulously analyzed by morphology, labeled, and stored on a shelf. These animals were once so abundant that their swarms darkened skies, fields, and intertidal zones.
Perhaps most telling, invertebrates were once so numerous that their services to ecosystems were once incalculable and their disappearance inconceivable. However, in the last decade, the scientists that collect and identify inver- tebrates began to notice a concerning trend, a precipitate drop-off in the number of invertebrates visiting their traps. In fact, in parts of the world such as Germany, Puerto Rico, and the United States mainland, scientists have reported up to a 90% loss in the abundance of some invertebrate populations (Goulson, 2019).
To talk about invertebrates as a single group (defined as organisms lacking a backbone) in many ways obscures the diversity of organisms within. Invertebrates range from insects, spiders, and worms in terrestrial ecosystems to corals, clams, and squid in marine ecosystems. They are often considered valuable because of their propensity to be eaten by more charismatic fauna. Although they make up a substantial portion of the diets of many vertebrates, like amphibians, reptiles, birds, and mammals, they also per- form other vital roles in ecosystems. From nutrient cycling in soils and marine environments to pollination and con- trolling pest populations, invertebrates are the little engines that make ecosystems go. Dramatic declines in their abun- dances are predicted to result in major consequences for the world’s ecosystems and economies (Cardoso et al., 2020).
We are still in the early days of understanding the magni- tude and consequences of historic invertebrate declines. Recent changes in their populations have been attrib- uted to several factors, including climate change, habitat loss, and pesticide use (Goulson, 2019). However, most models of invertebrate decline fail to account for the extent of loss. Traditional strategies for the conservation of species, stopping decline and restoring populations, often hinge on understanding an animal’s habitat and population structure, with less attention paid to the ani- mal’s “habit,” their way of being in and sensing the world.
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32 Acoustics Today • Summer 2021 | Volume 17, issue 2
https://doi.org/10.1121/AT.2021.17.2.32