Have you ever thought why people want
to go into the wild or into nature’s lap whenever they have some downtime in
mundane life? If you sum up all the probable explanations behind this, one
common ground is certain, and that is- to hear and feel the lively sound of
nature. Whether it is the sound of leaves touching one another due to a gentle
breeze down the river or lakeside, or perhaps the rhythmic noises of crickets
and cicadas in forested or countryside areas, or the sound of ocean waves
enjoyed from a beach walk, or it can be a compilation of numerous melodies from
frogs to birds and sometimes various mammals or loud primates like gibbons; any
of these can instantly calm one’s mind while filling their heart with peace.
From the surface, a forest might look
silent, but to a listener, it’s a constantly changing acoustic community. In an
orchestra, every instrument has a part to play; their combination creates
something captivating and hypnotic. Nature works much the same way, it’s
countless species and sounds come together to create an intricate melody of a
healthy ecosystem, which we may define as the sound of life.
Every Species Has a Voice
In this urban life, where it’s too
tough to have a good communicative time due to a tight schedule, sometimes one
small ‘meow’ of your house cat or some twittering of your caged birds
gives you valuable company.
In nature, birds communicate in their
intricate ways of singing or calling. Each species has its unique call;
sometimes, within a single species, males and females have different calls. For
example, you may hear the appealing, loud sound of the ‘Asian Koel’, commonly
known as ‘Kokil’ in Bangladesh. In the spring, the male searches for its
mating partner through that call or sometimes uses it to defend its territory.
The melodious song of this bird is so influential that it has been frequently
used in Bangladeshi songs, poetry, and literature.
You may overlook some common amphibians
like frogs or toads in your surroundings. These small creatures, which roam
around from village ponds and urban lakes to diverse types of habitats like
wetlands and forested areas, make some unique calls during the monsoon or
breeding season, known as their breeding calls. These calls are identified by
their partners of the same species. Interestingly, many female frogs tend to
select their male partners based on the loudness, depth and other
characteristics of the male frogs’ calls. So, although these sounds may look
ordinary, they are basically significant for the creatures’ survival on Earth.
Even the tiny insects make loud sounds
that make an ecosystem come alive. If you stay in an area which is adjacent to
the forest or have visited some forested area with sky-touching trees, you must
have heard some hypnotic, rhythmic sounds of cicadas, crickets, or katydids.
These small insects literally give life to a forest or any healthy habitat
through their rhythmic sounds. You may become astonished to know that these
tiny insects can make these loud sounds only by rubbing their wings together or
sometimes using specialized structures called tymbals that buckle rapidly
through muscle action. In fact, sometimes the sound of cicadas can reach over
100 decibels.
If you have ever heard of Gibbon’, a
charismatic tailless primate, you must have been amazed. Their calls
significantly resemble our vocalizations. They are remarkably loud and make
sync with their partner’s call, which is combinedly known as a duet. In hoolock
gibbons, these duet songs are associated with territorial advertisement and
defense, pair bonding, mate defense and social communication. My long-term
research work in a zoo setting with them made me experience one thing: they
even respond to humans who mimic their calls. Though it is very objectionable
to keep these iconic creatures in a small cage and interrupt their natural
behavior through curious visitors, this is not acceptable. Their duet songs
give life to the higher canopy-based forests in Bangladesh’s Sylhet and
Chattogram Hill Tracts.
Also, various mammals, whether they are
domestic or wild, show their presence with their unique mating, territorial, or
alarm calls.
Sound of a Healthy Ecosystem
Species diversity is the main
role-player here. A healthy ecosystem should not necessarily sound “loud”.
Rather, it should have more diverse sound sources, frequencies, rhythms, and
species interacting. A habitat with birds, insects, amphibians, and mammals
produces a much richer acoustic environment than a habitat where only specific
or limited species live.
Different times, different voices. The
soundscape changes throughout the day and night. For example, birds remain
active and dominate the soundscape at dawn. At midday, various insects and
other diurnal animals become prominent. After rain, frogs and some insects may
become particularly active. And at night, nocturnal mammals, owls, amphibians,
and insects take over. Overall, a healthy ecosystem doesn’t have a single
soundtrack; rather, it has a changing composition that is dynamic across
different timeframes.
Abundance of sound is not equivalent to
a healthy ecosystem. For instance, an ecosystem dominated by one extremely
abundant species, or by human-generated noise, may be very loud but not
necessarily healthy.
The Unwanted Instrument and Changing
Soundscape
Nature has its own orchestra, but
humans have introduced an instrument that was never part of the composition:
human-generated noise.
A forest may once have been filled with
the calls of birds, the chorus of frogs, the rhythm of insects and the
occasional call of a mammal. Today, those sounds may have to compete with
traffic, construction, machinery, boats and other sources of anthropogenic
noise. To us, these may seem like ordinary sounds of development and daily
life. To wildlife, however, they can become a form of acoustic disturbance.
When human noise overlaps with the
sounds animals use to communicate, important signals can become harder to hear.
An animal may struggle to find a mate, warn its group of danger, defend its
territory or maintain contact with its offspring. Some species may adjust their
calls or behavior, while others may avoid noisy areas altogether.
When biodiversity declines, the
soundscape changes with it. A species that becomes rare may contribute fewer
calls to the acoustic environment. A species that disappears from a habitat
takes its voice with it. As habitats become fragmented or degraded, the
composition, timing and intensity of biological sounds also shift.
And this is why the metaphor of an
unwanted instrument is so powerful here. The problem is not simply another
sound is being added to the environment, rather the already existing natural
sounds are being lost. Because, when species disappear, their sounds disappear
with them too.
Conserving the Symphony of Life
One beautiful call is not the actual
symphony of life, rather combination of countless voices is. Losing one species will result in decreased
biodiversity and eventually this will result in a poorly sounded ecosystem. So,
protecting forests, wetlands, rivers and other habitats ultimately protect the
conditions that allow the natural soundscape to continue. As musicians
carefully listen
for rhythm, harmony and subtle changes in a composition, conservationists can
learn to listen for changes in nature’s acoustic environment to save the
beautiful sounds of mother nature.
So, the next time we walk through a
forest, stand beside a wetland, or hear the distant call of any wild animal,
perhaps we should pause and listen; not
simply for the beauty of the sound, but for the story it tells about the
ecosystem around us.
The question is not only “How does a
healthy ecosystem sound?”
It is also, “What can we do to make sure we can still hear it?”
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