The Ecological Importance of Sound
Soundscape Ecology, The Acoustic Niche Hypothesis, and understanding how sound contributes to conservation.
What is an ecological niche?
The ecological niche of a species is defined by the specific position or role in an ecosystem and the particular resources it requires to function (1). “Ecological niche” can be considered a multidimensional “biospace” occupied by a species within a given ecosystem within varying environmental components or factors that may benefit a given organism (1). The concept of a niche focuses on the biological activity space in which a species exists within a given habitat (1). This space is controlled by a species’ physiological and behavioral limits required for survival and reproduction and influenced by environmental factors, such as temperature and predation, acting upon the system (1). Any given habitat can consist of multiple interacting environmental factors, both abiotic and biotic, which can consistently change at different rates (1). These definitions are prevalent in the scientific community as it helps ecologists understand how interactions of other species influence a given system and how specific interactions benefit or impact the environment. In the last few decades, a new field of ecology has emerged to understand how sound contributes to the ecological characteristics of a given environment and how sound influences a species’ multidimensional-use requirements.
Soundscape Ecology
Soundscape ecology aims at understanding three major components to sound (2):
Anthrophony - human-derived sounds from activities and built environments (i.e. urban landscapes)
Biophony - sounds produced by biotic organisms
Geophony - natural geophysical sounds (i.e. rain, wind, etc.)
Sounds produced in various landscapes are influenced by all three sound inputs across space and time reflecting ecosystem processes and human activities (2,3). A “soundscape” is the combination of all sound inputs integrated across a given landscape (3). Soundscape ecology shares similar research interests with landscape ecology and biogeography, in understanding interactions and landscape relationships centered with spatial patterns and connecting ecological processes (3). Such processes and patterns of interaction can be studied at multiple spatial scales that are applicable to natural resource management or effective decision-making (3).
Soundscape ecology applies comprehensive approaches to studying linkages in human and environmental interactions and outcomes (3). This study style is best suited for identifying and understanding threats to soundscapes and the possible benefits that more diverse and complex soundscapes produce (3). Ecologists understand that animals will navigate through various landscapes using a variety of senses (i.e., visual, acoustic, smell); soundscape ecology can be best used as an information-based tool to understand how organisms may adapt or function within their surroundings to locate resources (3). Such study methods could provide an “organismal perspective” on land-use change impacted by climate change (3).
Pijanowski et al. (2011).
The Morphological Adaptation & Acoustic Niche Hypotheses
The morphological adaptation hypothesis describes how ecological feedbacks influence changes in animal signals, focusing on the sender and the organism’s physical characteristics (i.e., body size, trachea length, beak structure, etc.), which influence what types of sound signals and organism can produce (4).
Pijanowski et al. (2011).
Mature ecosystems have more diverse species, creating a rich soundscape (3). The acoustic niche hypothesis proposes that a species occupies a unique frequency bandwidth (3). Each species’ sound varies in time to avoid competition and is likely acquired via evolution (3). This hypothesis expands on ecological niches by including acoustic-based aspects of ecosystems to classical environmental indicators (3).
The acoustic niche hypothesis focuses on the interactions between the sender and its surroundings. It proposes that certain groups of organisms will adjust their sounds to maximize distance and contact with another individual of the same species. A perfect species example is the White Bellbird (Procnias albus), which has one of the most powerful songs documented, averaging 125 decibels, which is the equivalent of hearing a jet take off approximately 50 meters away (5).
Climate Change and Other Impacts on Soundscapes
Human activity in undisturbed areas increases anthropogenic sound’s spatial and temporal patterns (anthrophony). Our built environments, composed of artificial structures and surfaces for shelter or transportation, shape these human activity patterns (3). These built environments change natural ecosystems and habitat structures, which is considered the greatest threat to biodiversity (3). Human encroachment and our built environments within these undisturbed areas result in habitat fragmented or contraction in species’ range.
Climate patterns can also influence plant community structure, affecting the diversity of animals within a given ecosystem (3). Climate change may also alter geophony patterns by increasing the frequency of extreme events (i.e., thunder, long rain periods, etc.), which have the potential to interfere with animal communication (3). Noise pollution in the ocean is a typical example of anthropogenic activity disrupting natural sound systems (3).
Because urban landscapes are dominated by human-produced sounds that radiate from various sources like machines, sirens, or the friction of tires on pavement, natural systems can be drastically affected by our day-to-day lifestyle (4). Rachel Carson’s book Silent Spring (1962) shows how the sound of nature is interconnected and links directly to environmental quality, since sound is a fundamental property of nature and can quickly be impacted even by the smallest of factors (4).
Soundscape Conservation - Why is this important to study?
Soundscape ecologists collect sound recordings of different areas to illustrate the complexity and composition of various ecosystems, similar to an ecologist who collects data over time to identify changes or shifts within the ecosystem (2). These recordings can provide important insight into shifts within a given soundscape, such as significant landscape changes from extreme weather events like droughts throughout the west coast of the United States or anthropomorphic changes like logging operations in the Amazon Rainforest (2). Researchers are uncovering changes in soundscapes over time: the lower the amount of sound produced by wildlife results in a less vibrant soundscape and an ecosystem with less biodiversity than was previously documented (2).
Soundscapes provide ecosystem services to humans in multiple forms and are essential to developing intimate attachments with humans and influencing one’s values about the natural world (3). Many soundscapes contribute to cultural, historical, recreational, aesthetic, and therapeutic values making them a powerful tool to connect humans to their environment (3). Soundscape conservation also can be more beneficial than noise mitigation, and certain forms of technology can be applied to protect various ecosystems from anthropogenic activity (3).
Sounds can also aid in ecosystem health recovery; a recent study showed that playing recordings of healthy coral reefs within a dead coral reef led to twice as many fish species interacting in the area than without a healthy coral sound influencing ecological diversity (6).
Soundscapes have often been referred to as an endangered resource due to the increasing loss of natural sounds could indicate human activity weakening connection with nature (3). By improving our relationship with sound and actively listening to the natural world, we can only truly appreciate the world we live in (3).
References
“Ecological Niche.” Ecological Niche - an Overview | ScienceDirect Topics, https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ecological-niche.
Dunham, Christopher. “Soundscape Ecology.” ArcGIS StoryMaps, Esri, 26 Jan. 2022, https://storymaps.arcgis.com/stories/0662e88fb58a419f88375658ccfb37fe.
Pijanowski, Bryan C., et al. “What Is Soundscape Ecology? an Introduction and Overview of an Emerging New Science.” Landscape Ecology, vol. 26, no. 9, 2011, pp. 1213–1232., https://doi.org/10.1007/s10980-011-9600-8.
Pijanowski, Bryan C., et al. “Soundscape Ecology: The Science of Sound in the Landscape.” BioScience, vol. 61, no. 3, 2011, pp. 203–216., https://doi.org/10.1525/bio.2011.61.3.6.
“The White Bellbird - the Bird with the Most Powerful Song in the World.” Avibirds.com, 8 Feb. 2021, https://avibirds.com/white-bellbird/.
Masumori, Atsushi, et al. “Evolving Acoustic Niche Differentiation and Soundscape Complexity Based on Intraspecific Sound Communication.” The 2020 Conference on Artificial Life, 2020, https://doi.org/10.1162/isal_a_00296.