Soundscapes: An indicator of Ecosystem health and restoration

Many of our ecosystems are depleted and are not functioning as they should – as conservationists this makes our lives much harder, as we try to protect and restore habitats and species and look to reverse the widespread declines in biodiversity that we have seen over recent years. There is a changing mindset in how we should view and restore nature – not as individual habitats or species, but as a larger system that is dynamic and that requires keystone species and diversity to function and be resilient. Large scale initiatives, such as species reintroductions and rewilding, aim to restore this ecosystem function. With a change in approach to restoration, we must also review how we monitor the health of these ecosystems. Can measuring individual species groups provide an accurate representation of the whole ecosystem function? No – it is far to complex to be measured in this way.

I have been involved in designing many monitoring strategies aimed at improving the way that we monitor species reintroductions, such as beavers, but also management techniques and rewilding. This aims to review the best indicators of change within a system to monitor the impact the restoration or species reintroduction is having. Often, the monitoring I undertake includes indicators such as bats, moths, invertebrates, bryophytes and fungi. These are important indicators of change, as they tell us a lot about how the environment is changing. We also monitor multiple indicator taxa to gain a better perspective of change, rather than relying on one species alone. But, is this enough to provide us with information on how an ecosystem is functioning? It certainly tells us a lot of robust data, especially when interpreted with the correct analytical tools (in these cases, the Biodiversity Quality Calculator which provides information on species richness, species turnover, rarity and biomass). But can it be useful for the large scale habitat restoration and rewilding schemes that we aspired to achieve in the UK? This is likely to require a slightly different approach.

Have you ever stepped out your front door or your car, and stopped to listen to the sound of bird song, the buzz of bees, or the sound of a trickling stream? Most of us notice when an environment has a lot of different natural sounds compared to one that is quiet or silent. By listening to the sound of wildlife and nature, we can start to identify how diverse that system is. This is referred to as a soundscape, as is a way of measuring how diverse a habitat or landscape is. I believe that soundscapes can provide us with even more data about what is happening within a system as a whole and on a larger scale than some of the more intensive monitoring.

Soundscapes use bioacoustics monitors to record all sound within a system - animals that emit sound, abiotic sounds such as running water, and human sounds. The monitors can be set to record sound for a specific period, such as dawn and dusk choruses, or throughout the day and night. This approach is often used to measure the impact of a development or operational site on biodiversity, but we can also apply it to understanding our ecosystems and landscapes as a whole. As with any other resource, species compete to be heard within a landscape. This means that that different species occupy a different frequency. The higher the diversity of frequencies and the more bandwidth that is occupied indicates how diverse an ecosystem is. Lower sound diversity is likely to indicate a depleted ecosystem.

Soundscape analysis doesn’t always look to identify species within the recording, it just analysis sound in the form of graphs and pictures to show diversity. It can be used to isolate human and abiotic sounds from animal sounds, although often abiotic sound is just as important within our most treasured landscapes (the sound of waves hitting the shore is just as important as the seabirds that are present). This sound recording can be taken to assess the diversity of species, as well as the importance of abiotic sounds to the user (especially within tourist hotspots).

Returning to an earlier point – how does this apply to monitoring ecosystem restoration and recovery? Well, if we can use bioacoustics sensors to record soundscapes, and analyse the diversity, we use this to indicate the health of the ecosystem. For example, studies have shown that species richness recorded little different between continuous forest and fragmented forest. When comparing soundscapes, however, the sound diversity was greater within larger parcels of forest compared to fragmented forests. This more detailed information can help to monitor the impact of large scale and experimental restoration approaches, like rewilding. It can also be used to monitor the success of nature recovery networks in connecting our landscapes for biodiversity, and can also monitor the impact of the return of keystone species to large areas. In addition, when this is compared to satellite images of change in habitat composition over time following restoration, we can build an accurate picture of landscapes and ecosystems restoration success at a fraction of the cost. Soundscapes will be crucial in understanding how our ecosystems are coping with climate change and other pressures, as well as large scale restoration in the future, and will be more cost effective than more intensive monitoring techniques.