Environment

Soundscapes of the natural world can tell us so much

Acoustic ecology can assist traditional biodiversity monitoring methods

Seán Ronayne in the documentary Birdsong, which introduced many people to the practise of acoustic or soundscape ecology. Photograph: Chris Maddaloni
Seán Ronayne in the documentary Birdsong, which introduced many people to the practise of acoustic or soundscape ecology. Photograph: Chris Maddaloni
Yvonne Buckley
Thu Jul 25 2024 - 06:00

Summers in hotter climes are marked by the deafening drone of cicadas in the late afternoon or the unmistakable whine of the mosquito on sultry summer evenings. Birdsong has long been admired and hearing different species can bring us back to certain times or places. These are examples of “soundscapes” and they can tell us much about the natural world and our relationship with it.

The beautiful documentary Birdsong, featuring the ornithologist Seán Ronayne, has introduced many people to the practise of acoustic or soundscape ecology. Acoustic ecologists use recording equipment to capture and study the sounds of nature.

Some organisms are most easily detected using acoustic recorders because they are hard to detect visually or present irregularly at a site. By having passive recorders at a site for long periods, animals can be recorded and identified by their sounds. The use of artificial intelligence models is now widespread for the identification of birds and bats.

AI identification of sounds begins by first converting the sound into an image, a spectrogram, with each sound having a unique pattern – like a fingerprint. Massive libraries of spectrograms with known identities can be used to train a detection algorithm. New spectrograms are identified based on the AI algorithm that has been trained on the known library.

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The targeted approach is perfect for identification and study of particular species. However, there are times when the entire soundscape is of interest. For example, there may be many species all making sound at once, making it difficult to identify individual species. In these cases we can use information about the entire soundscape, like a collage of fingerprints overlaying each other, to give us information about the environment.

[ Birdsong is being lost to noise pollution. We must fight for the few sanctuaries left ]

Using these sonic collages, soundscape ecologists ask questions like “what does a healthy ecosystem sound like?”, “how does the soundscape of an ecosystem change after a hurricane?” or “how can we tell if our restoration actions are working?”

A complex soundscape may indicate a higher diversity ecosystem, or one with a high number of different vocal animals or an ecosystem with individuals that make a high diversity of sounds. There is not a clear link between acoustic diversity and biodiversity in general, which makes acoustic monitoring an addition to, rather than a replacement of, traditional biodiversity monitoring methods.

New monitoring techniques for biodiversity are emerging, including the use of environmental DNA (eDNA). Followers of forensic science shows such as CSI might be familiar with the detection and identification of victims or perpetrators at a murder scene from small amounts of DNA in blood or hair. The use of eDNA is like the CSI television show but for nature. By sampling water from a lake or air the DNA of different species can be detected and compared with libraries of known genetic sequences to determine their identity.

There is great potential for new techniques to assist with the monitoring of biodiversity to assess how our actions positively and negatively affect nature. But we lack consistent wide-scale biodiversity monitoring in Ireland. While there are some high quality monitoring schemes to identify and assess different kinds of animals, plants and their habitats, the monitoring is not comprehensive and does not cover a wide range of different habitats.

The lack of consistent and long-term monitoring of biodiversity limits our ability to detect change. Given that there is a legislative commitment to achieving a “biodiversity rich” state by 2050, how will we know if we have achieved this?

[ Making sound pictures to identify birdsong ]

The use of new advances in monitoring technology can certainly help to get comprehensive spatial and temporal coverage but will need to be combined with the “boots on the ground” knowledge of ecosystems and traditional monitoring systems. There are hundreds of monitoring surveys undertaken as part of environmental impact assessments every year in Ireland but these data are not readily available.

Imagine a network of monitoring stations across the country where new technology, combined with tried and tested methods, are used to track biodiversity. Imagine that every time an environmental consultant completes a survey they submit that data to a national monitoring scheme. Biodiversity is multidimensional and we need many different methods to investigate its complexity.

Prof Yvonne Buckley is chair of Zoology at Trinity College Dublin and codirector of the Co-Centre for Climate+Biodiversity+Water