How drones are helping to map Huon pines, Tasmania’s ancient giant trees

If a rare, ancient tree burns in a bushfire but no one has ever marked it on a map, will we ever notice it?

Scientists don’t think we would. And that’s why a new project to “fingerprint” vulnerable trees and select them from aerial images is taking off.

The need for the project was evident after dry lightning struck the rugged terrain of the Gell River region in south-west Tasmania in 2018, marking the start of a devastating bushfire season.

The ensuing fires, which started in the Gell River area, burned 210,000 hectares, destroying several homes and requiring the evacuation of hundreds of people.

But 6% of Tasmania’s Wilderness World Heritage Area also caught fire.

A review later found that the vast majority of threatened vegetation in these areas had developed some ability to cope with the fire, four areas that burned were home to old and vulnerable species and are unlikely to ever recover.

Part of the challenge of protecting these rare and fire-vulnerable species stems from the fact that we don’t know exactly where they all are.

Jayne Balmer is part of the team working to fix this problem.

Dr Jayne Balmer, senior ecologist at Tasmania’s Department of Natural Resources and Environment, says the need for accurate mapping of the state’s Huon Pines was highlighted during the 2019 bushfires.(ABC News: Matthew Growcott)

She is a Senior Ecologist in the Tasmanian Department of Natural Resources and Environment.

“We’re trying to improve the mapping of fire-sensitive communities in the Tasmanian Wilderness World Heritage area…among these are things like the Huon pine,” she said.

The Huon pine is Australia’s longest-lived tree species – with records showing some giants have lived for thousands of years.

Like king billy pine, pencil pine, and fagus, Huon pine species evolved before fire became an important part of the landscape.

Gell river fire
One of the first photos of the River Gell Fire, seen from a helicopter evacuating.(Provided: Teagan Fone-Stephenson)

“These communities trace their ancestry back to Gondwana times – the Huon pine is about 68 million years old in terms of evolutionary history,” Dr Balmer said.

Vegetation mapping for Tasmania’s Wilderness World Heritage areas began in 1990 – and although some information is collected on foot, most mapping is based on interpretations of imagery taken from planes.

Light filters through pine needles
Huon Pine evolved before fire became a major force in its habitat.(Provided: Dr. Emiliano Cimoli)

But it’s hard to spot specific trees and plants from that high.

“They all look green and so it’s kind of like ‘Where’s Wally’ from the air, as well as when you’re looking at aerial photos,” Dr Balmer said.

“Conventional red, green and blue visible spectrum aerial imagery clearly shows no difference between Huon pine and the species with which it coexists.

A man stands in front of a Huon pine with a drone
Professor Arko Lucieer is an expert in high precision aerial surveys.(ABC News: Owain Stia-James)

Dr Balmer contacted Arko Lucieer, a professor at the University of Tasmania who is an expert in high-precision aerial surveying, for help.

Hyperspectral sensors are a special type of camera that can capture 170 bands of light in each frame – rather than just the red, green and blue that humans see – allowing researchers to collect near-infrared images.

Because there are subtle differences in the way each species of tree and plant reflects light, they each have a sort of spectral “fingerprint.”

“So it’s this unique spectral fingerprint of the Huon pine that we’re trying to detect from the air, and with drone technology, find the right combination of sensor parameters to achieve that,” said Professor Lucieer, who is at the head of the School of Geography, Planning and Spatial Sciences.

A drone takes off in the desert
Professor Lucieer’s team is one of the few in the world to use hyperspectral scanners attached to drones.(Provided: Dr. Emiliano Cimoli)

They started by measuring the ‘fingerprint’ of a Huon pine in the Tasmanian Botanic Gardens in Hobart, before taking the technology into the southwestern wilderness and flying over areas where they knew pine trees Huon were.

The team also developed a computer algorithm to analyze each pixel of the mass of collected images.

They found that by using this algorithm, they could successfully make the Huon pines stand out among the other vegetation.

Trees highlighted in red on an aerial map.
The algorithm is able to spot Huon pins on the map.(ABC News)

“There are a handful of teams around the world working with hyperspectral remote sensing on drones, so it’s quite a specialist area,” Prof Lucieer said.

Trees in the forest of South West Tasmania
Vegetation mapping of Tasmanian Wilderness World Heritage areas began in 1990.(Provided: Arko Lucieer)

But there are limits on where and how far drones can fly.

Now they hope to work with state aircraft operators to test the technique on a larger scale.

“Drones have allowed us to fly low and slow and test this technique. The next step is to mount our sensors on an aircraft and fly over much larger areas, so we can map larger remote areas in the south. -west… and produce a map of the Huon pines,” Prof Lucieer said.

In the future, the technique could be applied to map other species, allowing them to monitor a region’s biodiversity and the impacts of climate change, he said.

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