BANGKOK — Deep in the tropical forests of Indonesia or Peru, illegal loggers may fell just one valuable tree per acre, transporting it along a hauling trail or shipping it down a nearby waterway. Though these losses contribute to forest degradation and impact greenhouse gas emissions, both might be difficult to detect via satellite imagery. A hole created by one tree can be camouflaged by the dense foliage of its neighbors, and until now, groups relied on often flawed data to surmise emissions.
To tackle these limitations, a team of scientists has employed tools to remotely measure how much timber is removed from forests, and the resulting greenhouse gas emissions. Tim Pearson, Winrock International Ecosystem Services director, and his team have developed a new method that combines specialized aerial imagery with mapping and algorithms to automate the detection of extracted trees and the emissions impact of selective — often illegal — logging.
It’s a method that can provide a snapshot of tens of thousands acres of forest to discover whether logging has happened and how many logs have been taken, Pearson explained.
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Timber harvested from tropical regions is responsible for more than 1 billion tons of carbon dioxide emissions annually, according to a 2017 report co-authored by Pearson. Yet there is currently no means to independently estimate extracted trees and associated greenhouse gas emissions, he said. Winrock previously devised a way to estimate emissions from logging, but the method relied on reports from governments or timber companies, which are often unreliable and don’t account for illegal activity.
“That certainly creates a weakness because you're assuming that those numbers are absolutely correct,” Pearson said. “And sometimes, governments don't even know very well what timber volumes are coming out of the forest because the systems in place are not adequate to do that … or even the government may not entirely be forthright with its numbers.”
Timber companies could also be dishonest by taking more timber than they’re supposed to without reporting it.
“There were no systems in place to know what these numbers are,” Pearson said. “This is the start of an approach to be able to do that, so that we can start to know what logging is happening legally and illegally. And we can start to capture what the greenhouse gases are.”
The NASA-funded research used a remote sensing method called LiDAR, short for “light detection and ranging,” combined with on-the-ground surveys to create equations that estimate legal and illegal logging and their carbon emissions. LiDAR allows the viewer to peer through gaps in trees, and the Winrock equations use those gaps in forest cover and the dimensions of logging roads and paths created by dragging downed trees through the woods to explain variations in data.
Remote sensing is already used to detect logging and forest health around the world, World Resources Institute Indonesia Climate and Forests Senior Manager Arief Wijaya told Devex. It’s often the scale of the area that determines what sort of satellite data to employ to make forest management choices, he said.
In Indonesia, where Winrock conducted its latest research and where Wijaya is based, the national space agency relies on three ground stations to gain access to various forms of satellite data. The human resource capacity to analyze the information is readily available in both the space agency and the country’s Ministry of Environment, Wijaya said. Still, he’d like to see the government shift to using available technology more effectively.
Indonesia’s land cover maps, for example, are based on interpretation of satellite data, but “it’s still manually digitized,” Wijaya said. “There is another technique using a more automatic way of satellite data interpretation that could actually have more objective results. It would be even less labor intensive and also hopefully more modern, more reliable.”
LiDAR, he said, is another example of a promising, modern approach to forest management that’s already been used for various projects in Peru and Central Africa — and one that can be successfully combined with other sources of information to create a much more accurate understanding of forests. But the sophisticated method, which currently requires flying the technology in a plane over forested areas, also comes at a cost that could prevent wide-scale application.
“In the future, we may have more options,” Wijaya said, referencing the European Space Agency’s Biomass forest carbon-monitoring satellite, scheduled to launch in 2021. The United States are also “expecting a space-borne LiDAR, which would simplify things and remove some of those costs, as well as accelerate the ability to create relationships that could be extrapolated across the world,” Pearson said.
Depending on the scale of forest a government or company is aiming to cover, “the cost does start to become pretty reasonable,” Pearson said. “There are massive costs to sending out teams of individuals, particularly to really hard-to-access areas, and those numbers can mount up really quickly. This approach allows you to just sidestep that.”
Next, Pearson would like to see LiDAR used to determine forest loss and resulting greenhouse gas emissions in the Congo Basin and the Amazon.