Thermal imaging drones are locating heat still smouldering beneath the ground three months after a wildfire swept through the Cairngorms National Park, according to the pilot flying the missions.
Pete Short has carried out the dawn patrols for almost 2.5 months, since the fire tore through the landscape in July. On a 06:00 launch in the park, he sent a thermal drone into the early morning sky while an observer kept the aircraft in sight as he studied the images streamed to his screen.
“Every week I hope that I find none,” Short said. “On the last thermal flight I did we found eight.”
On the patrol, a white glow appeared on the thermal image beneath a tree. Soil and a loose rock at the coordinates identified by the drone were warm, and smoke rose once a thin layer of earth was scraped away.
“Without the thermal technology we would be totally blind to this,” Short said.
The wildfire began in mid-July and burned across about 3,300 hectares – 33 sq km – of land, the Cairngorms National Park Authority said. At the height of the emergency, five experienced drone pilots were brought together to provide aerial information to the agencies fighting the fire.
Short described it as one of the most challenging environments he has flown in, citing “multiple walls of flame”, personnel and vehicles moving around the site and helicopters operating overhead.
Each hotspot found by the drones is reported to the land manager, which sends teams to dig into the ground and douse it with water.
For Ben Jones, senior site manager for the RSPB at Abernethy, knowing where to deploy those teams has been crucial.
“We’ve been fighting this fire for over two months now and obviously we’ve got limited resources in terms of the number of people we have and we can’t send everybody out everywhere all the time,” he said. “So we really need to know where these specific hot spots are – where we should be sending people – so that they can be as efficient as possible.”
Jones added that the remaining fires cannot simply be ignored despite colder, wetter weather. “Each of these hot spots has got the potential to reignite a larger fire,” he said.
In the forest, tree trunks are blackened and charred, the acrid smell of fire lingers and large areas of the forest floor are scorched. Green shoots, fungi and a small yellow flower are also emerging from the burnt ground.
Dr Sarah Henshall, head of conservation at the Cairngorms National Park Authority, said it was too early to know the full ecological impact of the fire. “Some of that will be incredibly quick, some of it will take years, decades, or even beyond our lifetime,” she said. “It will recover, but we just don’t know what that’s going to look like yet.”
The drones that aided firefighting operations are being given a further task. Short is programming them to repeatedly fly the same routes over the damaged landscape, using predetermined waypoints to capture photographs and video from identical positions month after month and year after year, allowing conservationists to track how the landscape changes.
“This standard drone route will have exactly the same route flown month by month, year by month and visually it’s going to give us some amazing information about how it’s recovering,” Henshall said.
The technology may also help spot future fires before they spread, according to Short, who said obtaining a view above the tree canopy quickly could prove critical.
“It’s those moments before a wildfire gets out of control that could be critical to stopping it before it gets out of hand,” he said.
The patrol identified another hotspot at a location with almost no visible sign from a distance. Guided by the drone, the team found the precise spot, where the ground beneath a thin layer of earth was hot and smoke became obvious once the soil was stoked.
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