Sabah's SAFE soundcheck
Researchers are using a unique method to measure the health of Sabah’s rainforests: recording its sounds in the Stability of Altered Forest Environment (SAFE) Acoustics Project.
WHEN Robert Ewers wants to know how unhealthy an ecosystem is, he listens for the “sound of silence”.
If a rainforest is noisy, it’s healthy. If it’s quiet or only has a few sounds, something is probably wrong with it – usually because humans have interfered with it.
The Imperial College of London professor of ecology and his team of researchers have been collecting sounds from rainforests in Sabah; he answered questions about the project in an online interview.
“We are listening to the aggregation of animals making noises. It’s like a black box of that part of the forest,” says Prof Ewers, the project’s principal investigator.
“A healthy forest has more or different ‘variables’, like species. We’ve measured 128 variables from the audio we’ve collected.
“Some of the recordings in a virgin forest reserve have a background of constant noise,” he says. A rainforest that has been logged, however, does not.
“Different species, different variables in an unhealthy forest,” he explains.
Researchers working in the SAFE (Stability of Altered
Forest Environment) Acoustics Project have placed solarpowered microphones (one is pictured above attached to the tree trunk) and recorders in strategic parts of the rainforests in Sabah and used them to determine the health of the ecosystem.
SAFE works locally with Universiti Malaysia Sabah, the Sabah Forestry Department and the South-east Asia Rainforest Research Partnership.
Mega-diverse island
Touted as one of the largest ecological experiments in the world, SAFE was devised to study how biodiversity and ecosystem functions change when forests are modified by human activities. According to its website, there are 223 projects in 18 research areas, involving 474 researchers from 16 countries.
In Sabah, the audio is recorded and collected from a 8,000ha area within the Kalabakan forest in Tawau district in the south-eastern part of the state.
Sabah lies on the northern part of the Island of Borneo, which has often been described by scientists and naturalists as a treasure trove of biodiversity.
Besides being home to 221 species of mammals and 420 species of birds, the island’s lush virgin rainforest – where it has not fallen to logging and clearing for plantations, of course – harbours 15,000 species of flowering plants and 3,000 species of trees, including the tallest tropical tree, the 100.8m yellow meranti recently discovered in the pristine Danum Valley conservation area not far from Kalabakan.
The SAFE project location in Kalabakan includes part of the forest that was originally meant to be converted into an oil palm plantation. Thankfully for Prof Ewers and his team, the plantation never kicked off.
Recordings are taken from various types of forest sites: riparian forest reserves, old growth, cleared forests, logged fragments and on an oil palm plantation.
To make the recordings, researchers have had to resort to developing their own equipment to install on trees. Most commercially available electronics aren’t designed to work outdoors, particularly in tropical forests where rain, temperatures of over 30°C, and high humidity are a daily occurrence; those that might withstand the conditions tend to be too expensive and require regular maintenance.
Prof Ewers explains that what the team eventually developed is, basically, microphones connected to the Internet to stream the sounds out to a website for analysis.
Between two extremes
While the project has been ongoing at the Kalabakan site for 10 years, it’s only been three years since the team started collecting the audio recordings.
The site in Kalabakan was chosen because the researchers want to track the conservation of the forest.
“Where there is virgin forest, the (audio) conditions are excellent. Where the forest has been salvage logged, it has been trashed,” says Prof Ewers.
“We have taken audio of the rainforest in Maliau Basin before and that was spectacular,” he says, adding that the health of the forests they monitor is often “between these two extremes” (salvage logged and conserved).
Unlike the Kalabakan forest, the Maliau Basin Conservation Area – also known as Sabah’s “Lost World” – in the interior Tongod district, has been gazetted as Protection Forest Reserve (Class I).
Audio recordings are analysed with artificial intelligence: using machine learning, the audio is analysed both by identifying and tracking the population of the individual species making the calls as well as assigning a number to the general activity in the clip.
At its campsite alone in Kalabakan, the team has identified and found over 120 species of birds and over 40 species of frogs and reptiles.
Health check
Forests, especially rainforests, play a crucial role in mitigating climate change by acting as carbon sinks; rainforests are also an arbour for the world’s flora and fauna. But monitoring all that biodiversity the conventional way is actually really expensive, says Prof Ewers.
According to SAFE’S website, biodiversity monitoring is traditionaldone ly manually by highly skilled specialists or scientists trained to recognise animals within a forest by sight or sound. While this is a tried and tested method, it is expensive, slow, and susceptible to human biases.
“When you send in people, you end up monitoring only a handful of species at a time, never all at once. What we want is a general measurement of the health of the forest,” points out Prof Ewers.
By recording the sounds of a forand est then measuring those sounds against set parameters, the SAFE project aims to better – and more cost efficiently – capture that general measureof ment ecosystem health.
The team is hoping that the prowill ject eventually be used as a way to measure a forest’s degradacaused tion by human activity or recovery in long-term conservation projects.
Prof Ewers says, for the shortterm, the SAFE project can be utilised as an early warning system for activities that “shouldn’t be there in the forest”, like poaching and illegal logging.
“We did a trial of that before, played the sounds of gunshots and chainsaws and even people talking, we managed to pick up those sounds (on their equipment), and we can do this automatically,” he says, adding that the team has received a grant for this purpose.
“We are planning to push this out, hopefully, in a year or two.”
What would he consider “spectacular” audio from a healthy rainforest?
“The whooping of the gibbons. We often hear it in the morning at our campsite in Sabah.”
The audio is now available for livestream over at the SAFE project website (acoustics.safeproject.net).