Climate change resources-sound and light

By Claire Thirlwall

Claire Thirlwall is a director of Oxfordshire based landscape practice Thirlwall Associates. Her book “From Idea to Site: a project guide to creating better landscapes” for RIBA Books was published in 2020.

Could sound recordings of the landscapes we work in provide insight into the impact of climate change?

As landscape architects the focus of our work is often on the visual elements of a landscape. However, the work of pioneering sound ecologist Bernie Krause shows that the aural elements can provide insight into the health of ecosystems.

Detroit born Krause began his career in the late 1950s as a musician, initially performing with the folk band The Weavers and then becoming an exponent of electronic music. He worked in music and film until the late 1970s, and his work includes the synthesised sound of helicopter rotor blades for the iconic opening sequence of Apocalypse Now. (1) From 1979, Krause concentrated on the recording and archiving of wild, natural soundscapes from landscapes around the world.

In 2001 Krause and his colleague Stuart Gage were commissioned by the US National Park Service to “quantify and assess the diurnal and seasonal character of the park’s soundscape.” The recording sites were selected to represent a combination of elevation and vegetation diversity. (2)

As part of this work the team developed three terms to define the sources of sounds. These are: Biophony: the collective acoustic signal generated by all non-human sound-producing organisms in a given habitat at a given moment, such as insect noise, birdsong or animal calls.

Geophony: naturally occurring nonbiological sounds, such as water, wind or thunder. Anthrophony: human generated sound, either direct, indirect or via electromechanical devices, such as voices, traffic or music.

By recording the biophony at the same location, at the exact same time of day or night and using similar recording equipment, changes in density and diversity can be detected.

One way to show these changes in the ecosystem is to use a spectrogram (fig 1) – a visual representation of the sounds recorded, with the vertical axis representing the sound frequency and the horizontal axis time.

Soundscape of Mount Rainier, showing marmot, bird, insect and aircraft noises

© National Park Service

Sugarloaf State Park – progressive effects of drought. Spectrogram showing 15 second recordings from the same location. The reduction in biophony follows the progress of the California drought which began in 2011. https://youtu.be/ N2z54euleGU

© Bernie Krause

The California Drought – Sonoma Valley

Every spring for decades, Bernie Krause has recorded the dawn sounds of the area close to his California home. Using similar equipment each time, he has captured the sound of Sonoma Creek, which runs through Sugarloaf Ridge State Park. When the habitat is in a healthy condition, the recordings include the sound of amphibians and birds as well as the sound of the river.

However, December 2011 saw the start of a severe drought that lasted 340 weeks, ending in March 2016. An estimated 102 million trees died and low water levels had a devastating impact on the ecosystem. Despite the drought ending, additional weakened trees are expected to die in future years.

Krause’s work visualises this decline – in 2004 and 2009 the recordings are full of natural sounds, including the sound of running water shown in the low-frequency section of the spectrogram (fig 2). In 2014 the soundscape is dramatically reduced, with the high frequency rhythmic clusters of birdsong much fainter. By 2015 the landscape is almost silent.

The recordings for Sonoma Creek are just one part of the Wild Sanctuary Audio Archive, created over 50 years by Krause and his wife Katherine, that holds over 50 years of field recordings from many different habitats. Scan the QR code to listen to the recording.

In 1989 Krause used a decade of recordings to show that, despite assurances from logging firms, selective logging was impacting the local wildlife. Visually, the changes were minimal, but the recordings showed the decline in insect and bird noise. (3)

Tragically Krause’s home was destroyed in October 2017 when Nuns Fire, one of 18 wildfires, devastated the region. His recordings were backed up off-site, but all the couple’s belongings, including original recordings, photographs and correspondence, were destroyed. (4)

Whilst not replacing detailed habitat surveys or in person recordings, high quality automated sound recordings can be useful when other sampling techniques are impractical, or when trying to find rare or elusive species. Work by sound ecologists has shown the impact of the anthrophony, the sound we make as a species, on other organisms. When artificial sounds are added to natural habitats, organisms struggle to perceive sounds, locate food, navigate or communicate. Some species have adjusted their vocal calls in an attempt to be heard – for example, male great tits (Parus major) change the sound frequency of their call in noisy environments. It is a difficult situation for the male birds as female tits prefer mates with lower frequency calls, but if they stick to a lower frequency they risk not being heard. (5)

Noise pollution also affects bat, owls, frogs and many marine mammals. (6) By recording the biophony, the intricate relationship between organisms can be shown, along with any decline or improvement in that intricate relationship, and existing recordings have the potential to provide a reference point to monitor change over a long timescale. Recording declines in the sound of insect populations or reductions in the noise of river flows, rather than waiting until there is a visible change to a habitat, provides us with an additional tool to assess the impacts of climate change.

¹ P Aspden, ‘The Great Animal Orchestra – collecting the sounds of endangered lives’, 2019, https:// www.ft.com/ content/64202126- deb5-11e9-b8e0- 026e07cbe5b4 [accessed 18 February 2021].

2 B Krause, S Gage & W Joo, ‘Measuring and interpreting the temporal variability in the soundscape at four places in Sequoia National Park’, in Landscape Ecology, vol. 26, 2011, 1247-1256.

3 ‘Bernie Krause on Preserving the Voices of the Wilderness Before They Disappear Forever’.

4 “This used to be so alive”: Glen Ellen sound artist’s life work lost to wildfire’, in Sonoma Index-Tribune, , 2018, https://www. sonomanews. com/article/news/ sonoma-valleysoundscape-artistbernie-krausesearching-for-refugeafter-nu/ [accessed 17 February 2021].

5 W Halfwerk et al., ‘Low-frequency songs lose their potency in noisy urban conditions’, in Proceedings of the National Academy of Sciences, vol. 108, 2011, 14549-14554.

6 mischa, ‘Noise pollution and the environment’, in Curious, 2016, https://www. science.org.au/ curious/earthenvironment/ noise-pollutionand-environment [accessed 18 February 2021].