Conserving Natural Soundscapes

The natural soundscape is the result of vocal activity of many organisms (vertebrates and invertebrate, terrestrial and aquatic) that use this mechanism to communicate and to adapt themselves to an unpredictable world. The soundscape is the result of the overlap of biophonies, geophonies, and anthrophonies (Fig. 8.17).

Anthrophony
Fig. 8.17 The potential trend of biophony, geophony, and anthrophony along a gradient of disturbance (after Napoletano 2008)

The conservation of the natural soundscape allows one to conserve and to preserve habitat and biodiversity. Bernie Krause, an American bioacoustician that coined the term, "biophony" (Krause 1987), warns about the risk that sounds from many habitats "are forever silenced" (Krause 2002) and that the increasing human clamor produces dangerous consequences on community equilibria. He reported evidences that the frog chorus when interrupted by strong sounds like the passage of an aircraft, allow predators to intercept easily the singing frogs. We have a suspicion that the poverty of beech forest along the Apennines (Italy) is related to the continuous noise of airplanes crossing the region (Fig. 8.18). The symphony of Nature is the result of the vocalization of creatures in relationship to one another and this symphony has several consequences on the vital habits of many species. Krause wrote: "This biophony, or creature choir, serves as a vital gauge of a habitat's health. But it also conveys data about its age, its level of stress, and can provide us with an abundance of other valuable new information."

Soundscapes have to be considered not only as an important aesthetic component of our living system but also as a true resource (spiritual and symbolic for humans, and as adaptative mechanisms for many other species). In our genotype probably persist the ancestral mechanisms that allow us to distinguish signals of dangerous-ness, signals of a safe place, and signals of changes of a specific situation. The sudden silence that follows when a predator appears in a natural scenario is immediately considered a sign of danger also by inexperienced people. On the contrary the rhythmic biophony of a quiet forest immediately evokes a feeling of safety.

The soundscape is not a separate component but a vital part of our fragile biological surroundings. Human intrusion into natural systems and the use of fossil fuels for energy have reduced biophony and geophony and advanced anthrophony. This trend can be observed moving from natural systems toward urbanized systems. Animal communication remains strongly affected by the increase of anthrophony that can

Bird Soundscape Recorder
Fig. 8.18 A soundscape of a bird community living in a beech forest of the Northern Apennines, during the breeding season. Peaks represent the area with a maximum of acoustic activity recorded by using 20 digital recorders 100 m apart from each other

reduce such traits with dramatic influences on population survival and community coalescence.

The soundscape represents a new and challenging argument shared by ecological, bioacoustic and eco-semiotic approaches. The soundscape is an energy dimension in space, time, and energy well presented by FFT (Fourier Fast Transforms) that enable one to move from a temporal domain of sound to the frequency domain and allow sound to be "visible." Spectrograms are the representation of frequencies in time and intensity. A fourth dimension is represented by the location of each sound source. Following the Farina methods (Farina and Morri 2008), Morri (2008) it is possible to quantify sound in terms of frequency (Hz)xy and intensity (dB)xy at the different locations (xy) and to interpolate the data on a geographical map by using interpolation procedures from geostatistic and GIS algorithms (Fig. 8.18).

The distribution of sounds across a landscape (the soundscape) represents a source of information that can be used by organisms to localize resources, to avoid predators, to reduce competition.

The soundscape contributes to the functioning of several eco-fields such as the mating eco-field, foraging eco-field, safety eco-field, etc. The acoustic cues and their spatiality probably guide information in a very efficient and fast way. The short memory of the physical acoustic phenomena obliges organisms to repeat messages

Fig. 8.19 Spectrogram from a Congo forest clearing soundscape. The acoustic (semiotic) niche is shared by at least by six types of organisms. Sound record by acoustic globe at 18.15 in a forest clearing (Bai Hokou, WWF research station in a primeval forest in the Dzanga Sangha Reserve -Central African Republic. 2°51'10.97" N 16°27'52.43" E, courtesy of David Monacchi, University of Macerata, Italy)

Fig. 8.19 Spectrogram from a Congo forest clearing soundscape. The acoustic (semiotic) niche is shared by at least by six types of organisms. Sound record by acoustic globe at 18.15 in a forest clearing (Bai Hokou, WWF research station in a primeval forest in the Dzanga Sangha Reserve -Central African Republic. 2°51'10.97" N 16°27'52.43" E, courtesy of David Monacchi, University of Macerata, Italy)

several times a day according to the presence of other overlapping and degrading sounds (Fig. 8.19).

The well-known Lombard effect produces an increase of loudness in many song birds living in landscapes dominated by anthrophonies.

The regularities of insect, amphibian, and bird sounds are very informative processes that act as key-stone elements in a sea of silence.

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