Humans can leave the trees standing and still destroy the forest. In Malaysia, researchers have been listening to white-handed gibbons. Or, increasingly, listening for them.
Gibbons are famous for their extraordinary morning songs. Their calls can travel more than half a mile through dense forest and play a role in maintaining territories, communicating between groups and maintaining social relationships. But one group living beside a highway appears to be going quiet. Research reported by The Guardian found that white-handed gibbons living near heavy traffic called during just 36% of recordings. At a secluded beachfront site, gibbons called in 71.4%. At a hiking trail, they called in 84.6%. The research has not yet been peer reviewed, and there are important limitations. Researchers cannot yet say for certain that traffic is causing the difference. The highway gibbons may sometimes have started singing before recording began at 6am, for example. But within individual sites, the estimated odds of calling also fell as background sound increased. And when traffic became significant at the hiking site, the gibbons appeared to change how they sang. Humans are changing the soundtrack of the forest.
This is not just singing
It would be easy to treat this as a sad story about humans making the countryside a little less pleasant. It is much bigger than that. Gibbon songs have functions. They communicate with partners. They communicate with neighbouring groups. They help establish territory. Their calls may warn of predators. Other animals, including birds and squirrels, apparently recognise and respond to those warnings too. If traffic makes communication harder, the consequences do not necessarily stop with the animal making the call. The researchers even found that 93.3% of the phrases recorded from the highway group occurred during solo songs.
Why?
Nobody knows yet.
One possibility is that traffic makes it harder for paired gibbons to hear one another well enough to coordinate. Imagine trying to maintain a conversation while somebody permanently runs a motorway through the room.
Except this is their home.
We built the motorway.
A forest is more than trees
We have a habit of measuring destruction by what we can see. Cut the forest down and everyone understands that habitat has been destroyed. Leave the trees standing and apparently everything is fine. But what if those trees are surrounded by roads, houses and industry? What if the air is filled with traffic throughout the day? What if animals have to sing earlier, louder or differently simply to communicate?
What if some stop calling?
A patch of forest can still contain trees, food and sleeping sites while becoming fundamentally different for the individuals trying to live there. We have written before about this absurd human relationship with nature. We fill land, sea and air with plastic, chemicals, artificial light, concrete, traffic and noise, fragment habitats and destabilise ecosystems, then discuss how to “manage” the animals attempting to survive what we created.
Noise belongs on that list.
Humans are drowning animals out
The gibbons are not alone. Research has found human-generated noise interfering with animals across species. Background noise can make it harder for bats to detect prey. Traffic noise can mask communication between parent birds and their young. Other research has linked noise pollution with reduced bird diversity in urban parks.
This should not be surprising.
Humans rely enormously on sound. Imagine trying to raise children, find food, warn somebody of danger, locate a partner or defend your home while machinery roars beside you all day.
Then imagine having no walls.
White-handed gibbons are already endangered. Their population is believed to have fallen by more than 50% over the past 45 years, with habitat destruction, hunting and capture among the threats they face. Now even some of the forest left behind may not provide the refuge it appears to. This is why counting hectares is not enough. An animal does not experience habitat as a green shape on a conservation map.
They experience light. Smell. Temperature. Food. Other animals. Freedom of movement. And sound.
Protecting a forest while surrounding it with the constant roar of human development is not the same as leaving those who live there alone. Sometimes destruction looks like a chainsaw.
Sometimes the trees remain standing.
You just cannot hear the gibbons anymore.
This kinda reminds me of the disruption the honey industry causes due to people basing their idea of destruction to what they see instead of the facts.
Several people I have had conversations about specifically honey would say "honey makes sure pollinators don't go extinct" and they truly didn't understand how misinformed they were. There are thousands of breeds of pollinators and they think that continuing to breed honey bees well out of proportion to other pollinators that it's not going to affect anything.
If honey bees outnumber certain breeds of butterfly in an area honey bees wouldn't normally be because someone decided to open a honey business for example, they may encroach on "their land," beating them out on pollen collection potentially leading to the erasure of those butterflies in that area or causing that breed to go extinct.
Like learning that every breed of fig has a specific breed of wasp that eats it, to specific breeds of cordyceps fungi only infecting specific breeds of ants, or certain breeds of larger insects only eat specific breeds of smaller or lesser insects, certain pollinators only pollinate/collect pollen from specific plants.
This all means that if we cause specific breeds of pollinators to go extinct their absence may cause specific plants to go extinct because they aren't breeding through pollination and if that were to happen, whatever may eat those pollinated plants might die, and then the predator to that may die, etc... all the way up the food chain causing a whole set of breeds of flora and fauna to go extinct.
Nature is very "intelligent" and resilient but it can very easily be disrupted by one domino being removed from the cycle.