Drones help solve the forest carbon capture riddle in Thailand

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This aerial photograph taken on November 22, 2023 shows a drone doing a forest restoration survey over a reforested area in Chiang Mai.

A patch of woodland is being surveyed as part of a decades-long project led by Stephen Elliott and his team that has reforested about 100 hectares (247 acres) by planting a handful of key species. [Manan Vatsyayana/AFP]

Published On 20 Dec 2023

On a hillside overlooking cabbage fields outside the northern Thai city of Chiang Mai, a drone’s rotors begin to whir, lifting it over a patch of forest.

It moves back and forth atop the rich canopy, transmitting photos to be knitted into a 3D model that reveals the woodland’s health and helps estimate how much carbon it can absorb.

Drones are part of an increasingly sophisticated arsenal used by scientists to understand forests and their role in the battle against climate change.

The basic premise is simple: woodlands suck in and store carbon dioxide, the greenhouse gas that is the largest contributor to climate change.

But how much they absorb is a complicated question.

A forest’s size is a key part of the answer – and deforestation has caused tree cover to fall 12 percent globally since 2000, according to Global Forest Watch.

But composition is also important: different species sequester carbon differently, and trees’ age and size matter, too.

Knowing how much carbon forests store is crucial to understanding how quickly the world needs to cut emissions, and most current estimates mix high-level imagery from satellites with small, labour-intensive ground surveys.

“Normally, we would go into this forest, we would put in the pole, we would have our piece of string, 5 metres [16.4 feet] long. We would walk around in a circle, we would measure all the trees in a circle,” explained Stephen Elliott, research director at Chiang Mai University’s Forest Restoration Research Unit (FORRU).

“[But] if you’ve got 20 students stomping around with tape measures and poles … you’re going to trash the understory,” he said, referring to the layer of vegetation between the forest floor and the canopy.

That is where the drone comes in, he said, gesturing to the Phantom model hovering overhead.

“With this, you don’t set foot in the forest.”

This picture taken on November 22, 2023 shows a drone to be used by Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew for a mapping survey of reforested land on a hillside near Chiang Mai.

The team's goal is not large-scale reforestation but developing best practices: planting native species, encouraging the return of animals that bring in seeds from other species and working with local communities. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew creating a 3D model of overlapping images taken from his drone at his lab in Chiang Mai.

At his lab, Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew creates a 3D model of overlapping images taken from his drone. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew pointing to a computer screen while creating a 3D model of overlapping images taken from his drone at his lab in Chiang Mai.

'We collect data or capture (images) every three seconds,' explained Worayut Takaew. 'The overlapping images are then rendered into a 3D model that can be viewed from different angles.' [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew showing on display the path of a drone to assist in forest mapping of a reforested land on a hillside near Chiang Mai.

The drone's 3D model is a potent visual representation of the project's success, particularly compared with straggly untouched control plots nearby. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows Stephen Elliott, research director at Chiang Mai University's Forest Restoration Research Unit (FORRU)

'Once you've got the model, you can measure the height of every tree in the model. Not samples, every tree,' said Stephen Elliott, explaining that the project is also being developed as a way to avoid labour-intensive ground surveys. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows Stephen Elliott, research director at Chiang Mai University's Forest Restoration Research Unit (FORRU), holding a picture of barren land before it was reforested on a hillside near Chiang Mai.

Elliott holds a picture of barren land before it was reforested on a hillside near Chiang Mai. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew packing his drone after a forest mapping session of a reforested area on a hillside near Chiang Mai.

For all its bird's-eye insights, the drone has one major limitation: it cannot see below the canopy. For that, researchers need technology like LiDAR - high-resolution, remote-sensing equipment that effectively scans the whole forest. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows a decades-old metal strip with details of the native species, year and zone of plantation, protruding from a full grown tree at the Chiang Mai University's Forest Restoration Research Unit (FORRU) reforested land on a hillside near Chiang Mai.

'You can go inside the forest ... and really reconstruct the shape and the size of each tree,' explained Emmanuel Paradis, a researcher at France's National Research Institute for Sustainable Development. He is leading a multiyear project to build the most accurate analysis yet of how much carbon Thailand's forests can store. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew demonstrating how a soil sample is collected for research in a reforested area on a hillside near Chiang Mai.

The project will survey five different types of forests, including some of FORRU's plots, using drone-mounted LiDAR and advanced analysis of the microbes and fungi in the soil that sustain trees. 'The aim is to estimate at the country level ... how much carbon can be stored by 1 hectare anywhere in Thailand,' Paradis said. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows plants of native species used by Chiang Mai University's Forest Restoration Research Unit (FORRU) for forest restoration projects in Chiang Mai.

The stakes are high at a time of fierce debate about whether existing estimates of the world's forest carbon capacity are right. 'Many people, and I'm a bit of this opinion, think that these estimates are not accurate enough,' Paradis said. 'Estimations which are too optimistic can give too much hope and too much optimism on the possibilities of forests to store carbon.' [Manan Vatsyayana/AFP]

This aerial photograph taken on November 22, 2023 shows a reforested area atop a hill in Chiang Mai.

The urgency of the question is driving fast developments, including the launch next year of the European Space Agency's Biomass satellite, designed to monitor forest carbon stocks. [Manan Vatsyayana/AFP]

This picture taken on November 22, 2023 shows a drone being flown by Chiang Mai University's Forest Restoration Research Unit (FORRU) field research officer Worayut Takaew during a mapping survey of a reforested area on a hillside near Chiang Mai.

'The technology is evolving, the satellites are more and more precise... and the statistical technologies are more and more precise,' said Paradis. [Manan Vatsyayana/AFP]

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