In this new post, Sam Ross—a Postdoc at the Okinawa Institute of Science and Technology Graduate University, Japan—presents his review paper ‘Passive acoustic monitoring provides a fresh perspective on fundamental ecological questions’. He discusses how acoustic monitoring isn’t just for applied ecology and conservation, and some of developments on the horizon.

About the paper

From a bleary-eyed dawn chorus, to magnificent symphonies of whale song, to deafening choruses of tropical insects, the natural world is awash with the sounds of life. For years, people have been taking detailed records of these soundscapes using microphones. More recently, ecologists are making use of the digital age to leave autonomous recording devices outside in forests, mountains, rivers, the deep sea, and beyond, to capture the rhythm of natural ecosystems. Such work has been transformative for the way we survey biodiversity in challenging locations and has informed conservation management of species and habitats the world over. However, acoustic monitoring is no longer only an applied tool; ecologists now often use acoustic data to explore fundamental questions concerning the natural world.

In this review, we focused on the use of passive acoustic monitoring to answer some of the longstanding basic questions that have intrigued ecologists for decades, as well as emerging questions where soundscapes are opening up new research directions. Our main message is a simple one: acoustic monitoring isn’t only for applied ecologists; it can be used to answer fundamental ecological questions too.

We reviewed the use of acoustic monitoring for basic research, focusing on both the advantages of acoustic monitoring data for answering ecological questions and the challenges of setting up acoustic monitoring projects and using the resulting data for research. Acoustic data can contribute to so many interesting questions that we couldn’t cover everything here, so we focused on a few example cases. Firstly, we discussed species discoveries and the foundational question: how much life is there on earth? Secondly, we focused on population dynamics and change (both in time and space). Next, we considered the role of climate change in shaping phenology and distribution for many species—research questions gaining more and more attention. Then we explored ecological responses to, and recovery from, disturbances such as land-use change, pollution, or extreme weather events. These examples are not exhaustive, but were intended to provide a glimpse into the kinds of research questions that can be addressed using acoustic data.

Our aim was for this paper to increase accessibility for non-specialists who haven’t worked with acoustic data before, and hopefully encourage the broader use of acoustic monitoring for basic research. We also hope the paper is useful for ecoacousticians to reflect on the growing use of acoustic monitoring in fundamental research, remaining challenges, and near-future developments to which these experts can directly contribute.

Though acoustic recording technology has been around for a long time—and humans have been listening to ecosystems for even longer—there is still much to learn by listening to nature. We hope this review motivates the use of passive acoustic monitoring approaches to think about blue-skies research and the grand challenges affecting our planet—much of what we can learn by recording and experiencing natural soundscapes is fundamental to our knowledge of life on earth.

About the research

Our paper arose after Darren O’Connell and I organised a Thematic Session on soundscape disturbance and recovery at the 2020 BES Annual Meeting. After the session, we approached a few others, and everyone we spoke to was interested in contributing. The team we put together was really a who’s who of ecoacoustics (all people whose work I’ve admired but whom I hadn’t met), so working together was really a dream. I felt like I was assembling the Avengers of soundscape ecology! The process of writing this paper was really inspiring—everyone contributed a lot to the paper, and our online discussions were full of great ideas. Because of time zones, I was up late whenever we met, but I always left feeling freshly invigorated and excited about our ideas and the field more broadly.

Several of the team noted that this is the kind of paper we wished we could cite when doing our own research and writing grant proposals, but there wasn’t quite anything like it out there. So it’s a great feeling to know that now there is a reference that very explicitly says acoustic monitoring is also useful for fundamental research, not just applied ecology.

In the paper, we also charted the near future of ecoacoustic research, looking at the applications of acoustic monitoring on the horizon. These include the ability to precisely pinpoint the location of individual animals, and global efforts to build soundscape databases which will act as important baselines under continuing global environmental change. I’m really interested to see whether our hopes and predictions hold true in the coming years.

About the author

I’m currently a postdoc working in Okinawa, Japan, and the paper discussed here was one of the main outputs from a one-year Canon Foundation in Europe research fellowship to conduct research in Japan. The other part of that fellowship was a project—started during my PhD at Trinity College Dublin, Ireland—where I investigated the impact of two large typhoons on vocalising animal communities across the island of Okinawa using acoustic monitoring data. That project joined my two main research interests: ecological stability and soundscape ecology.

I am probably proudest of my 2022 Global Change Biology article on the combined impacts of predator extinctions and heatwaves on freshwater community stability. As someone who mostly works at a computer, this was my first real foray into experimental ecology, and it was rough; we had lots of mesocosms to monitor, and there was a 10-day period where I had to stay up all night carefully adjusting water temperatures. In the end the project was a success, and the experience gave me such incredible respect for experimental ecologists everywhere. Now, I’m starting to plan my next experiment and wondering how I’ve convinced myself that doing another one is a good idea…

In my spare time, I scoot around Okinawa on a 50cc moped (scoot scoot!), occasionally stopping at a little restaurant or izakaya to eat. My advice to budding ecologists would be to pursue your academic interests even if they’re a little disjointed. There’s nothing wrong with being a generalist; my projects and publications are a bit all over the place, but it’s kept things interesting, and, for me, academic freedom is one of the best things about being an early career ecologist.

Enjoyed the blogpost? Read the research here!