Editor's Note: (Call to Earth is a CNN initiative in partnership with Rolex. Topher White is a Rolex Associate Laureate.)
(CNN) Visiting a gibbon reserve in Indonesia during the summer of 2011, Topher White was struck by the sounds of the rainforest.
The chirps of birds. The buzzing of insects. The chattering of monkeys.
But what the American engineer couldn't hear was the roar of chainsaws and noise of the illegal loggers he knew were relentlessly tearing down trees and endangering the gibbons' natural habitat.
This prompted an idea: What if he could modify old cell phones and create a device that could listen out for sounds of destruction -- and instantly alert park rangers to the location?
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A year later, White returned to the Indonesian rainforest to test his creation. Not only did his device work, but he says his team found a group of illegal loggers in under 48 hours.
Through his non-profit Rainforest Connection, White repackages old Android smartphones into a recycled plastic box fitted with an extra microphone, battery pack and solar panels. The finished devices look like mechanical flowers and are fastened to trees high up in the canopy, often up to 150 feet.
The upcycled phones use existing cell phone networks which White says are available even deep in the jungle. They record sounds 24 hours a day from up to a mile away.
"They capture all the sounds from the rainforest and stream it up to the cloud where our software runs on it with a few different types of AI to pick out all sorts of things, so chainsaws, logging trucks, people, gun shots," explained White. "And then we can send real time alerts over the cell phone network to locals on the ground."
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Once the rangers receive an alert to their own phones, they can determine whether the activity is suspicious based on its location, White says.
Rainforest Connection now has more than 150 active devices used by local partners to protect areas of rainforest in five countries, including Peru, Cameroon and Brazil.
Detecting illegal logging has typically relied on aerial surveys or satellites -- which can take days or weeks to alert rangers to tree cover loss -- as well as ranger patrols.
Rainforest Connection says its phones are a faster and cheaper alternative. But the technology faces its own challenges -- sometimes from nature itself.
"You never really appreciate how alive the forest is until you see the way that insects can envelop something," said White, giving one example of how nature can bit back. "Everything was fine with the devices and we take it to Peru, and we realize that there is type of termite that loves to take apart every type of plastic."
Forests are home to 80% of the world's land-based species, more than 1 billion people depend on them for their livelihoods and they can help mitigate climate change by absorbing carbon dioxide. But WWF estimates that we are losing 18.7 million acres of forests a year, equivalent to 27 soccer fields every minute.
The UN estimates that deforestation and forest degradation accounts for around 11% of global carbon emissions.
"Every square kilometer that you can avoid being deforested is equivalent to taking 1,000 cars off the road for a year," said White. "Considering the millions of square kilometers that are out there, it's probably the cheapest way to stall climate change."
But illegal timber continues to be lucrative. A report from the UN and Interpol estimates the global illegal timber trade is worth between $30 billion and $100 billion every year.
Deforestation often starts with selling timber, but also includes clearing the forest for farming and houses.
"It's so profitable that they will cut roads through the forest to extract high-priced wood and those roads become the gateway to so much more deforestation," White explained. "If you can stop the roads, you can stop full-scale deforestation."
Instead of partnering with governments, Rainforest Connection says it works with other non-profits, tribes and local communities.
"Every conservation solution is local," said White. "While a lot of what we do involves technology, it's fair to say just as much work goes into the community building and adapting what we do to work in different places."
Indigenous peoples manage at least a fifth of the carbon found in tropical and subtropical forests, according to the Rights and Resources Initiative, a global coalition working for the rights of indigenous peoples.
However, protecting forests can be dangerous. "It is a very scary thing for the people there," said White. "Throughout Africa and Latin America, these are extremely profitable large black-market operations, so violence is not uncommon."
Confronting loggers in the early stages of logging is less risky because they can turn around and leave without a crime having been committed, he says.
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"The faster you can get people to respond, the faster they can get there to stop the logging truck on the way in, or the chainsaw the moment it goes off," he explained. "The stakes are much lower for both the loggers and for the people stopping them."
As illegal logging relies on being able to operate undercover, organizations are reluctant to return to areas they know are under surveillance, White explains.
Alongside preventing illegal logging, the NGO is branching out into what is known as "bioacoustics" -- creating a digital library of raw, acoustic data, which it hopes will be used for conservation.
"To date we have gathered well over 100 years of continuous audio, for all these amazing places where it is very wild, where no one goes," said White. "The same way we use AI and machine learning to pick out chainsaws, we are building ways by which we can look for different animals and species."
"We've never been able to study this en masse," he added. "Bioacoustics is really a revolution as meaningful as the invention of the microscope, when it comes to understanding ecology and nature."