Drones, AI helping Tongariro National Park regeneration efforts after destructive fires

Drone and AI technology is helping regeneration efforts in the central North Island's Tongariro National Park after two fires tore through.

The first, most damaging, blaze flared a year ago this Sunday and closed the popular Tongariro Crossing track for more than a week.

A smaller blaze a month later caused further damage to the same area.

Keeping out invasive weeds and animals

Look closely into the dull grey colouring of the charred Mangatepopo Valley and some green shoots are visible.

Department of Conservation (DOC) principal ranger Dan Van Der Lubbe is leading the recovery efforts there.

"It took out 3000 hectares of tussock grassland and regenerating alpine scrub. What we can see now is the natural regrowth after one year," he said.

Red tussock and flax were coming back, while larger celery pines were dead, their black outlines slowly rotting.

A 10-year restorative rāhui introduced by Ngāti Hikairo ki Tongariro is in place on the damaged land, with the hope it will prevent people from unwittingly bringing in invasive weeds. DOC also asks Tongariro Crossing trampers to check their gear so they're not bringing any seeds in.

Stopping the likes of gorse and heather from spreading, as well as keeping out animals such as rabbits, hares, deer and even wallabies, would allow the land to recover naturally, Van Der Lubbe said.

There are all sorts of programmes to help achieve this, including managing mites that eat heather and broom in the wider area.

"These fires have happened here repeatedly over the last thousands of years. In the last 150 years there have been about three fires in this area, so it's just natural regeneration that occurs."

RNZ had a look around the fire damage at the Mangatepopo end of the Tongariro Crossing. The colour of the untouched vegetation is in contrast to the fire-damaged land, which leaped over the access road.

It's closed the Mangatepopo Track, which Van Der Lubbe said was under repair.

He was part of the firefighting efforts last year and helped bulldoze fire breaks.

Up at the car park, where tourists are dropped of to begin their walk, firefighters put in a huge shift to protect newly opened facilities and a newly installed pou.

"This was put in a within a month or so of the first fire. It signified the protection that Ngāti Hikairo and Tūwharetoa have over the national park.

"We are very lucky it didn't get destroyed in the fire. He got a little bit charred down by his feet," Van Der Lubbe said.

Tech at the forefront of recovery

After the fire the government announced $3.5 million of funding for the recovery.

The work that came out of that was at least a silver lining, Van Der Lubbe said.

For this, DOC used iwi contractors where possible, and brought in specialists when needed.

"Funding from this project has allowed us to investigate new technologies to make our work more effective and more efficient.

"We've started using drones to monitor gorse and broom and wilding conifers. The drone comes in, takes photographs and then they use their AI platform to find all the plants.

"Rather than me sending a helicopter into a block and saying, 'Just search the whole area', I can give them a pinpoint of where the weeds are and they just go and hit those."

The company behind that is Rotorua-based company Interpine. Its chief technology officer Dave Herries, who has worked there for 27 years, also volunteers for firefighting efforts and was on the ground last year.

He led an intelligence team, which used drones to identify hot spots. Firefighters use an app through their phones to see where these are, so they can put them out.

It's similar for the weed identification efforts.

"After the fire had settled we came in to take imagery of the fire ground for the recovery process and subsequently have been back on a regular basis, capturing snapshots over time."

The company had undertaken three large aerial surveys of the fire zone, and would do another one in December, Herries said.

These provided a visual record of changes to the site.

The AI tech made for efficient use of time.

"[It lets] the Department of Conservation, their contractors and their rangers to be able to identify those weed invasions and target them specifically.

"When we're talking about a fire ground which reached over 3000ha we do need to optimise the use of those ground resources."

Nervousness remains

In nearby Waimarino tourist-reliant businesses initially lost bookings.

Tongariro Crossing Lodge owner Louis van Wyk said last summer quickly returned to normality, although he fielded calls from overseas for a while asking if the crossing was closed.

This year lodge guests who walked the track didn't even mention the fire damage.

Van Wyk is a volunteer firefighter, who helped with last year's efforts to contain the blazes. He's still relieved that a change in weather helped avert a bigger disaster last November.

"I'm grateful, but at the same time quite apprehensive that something like that could happen again.

"It just showed with the dry spring we had - and that's in the forecast again for a dry summer - that with a little bit of human error and carelessness those kinds of things can happen again, and that makes me a little bit nervous."

Ruapehu mayor Weston Kirton said the fire took a toll.

"The figures are always difficult to work through, but any disruption with people coming into the area is quite significant in terms of accommodation and cancellations of activities and the like," he said.

"So, people are scared off by just the image of fires, for example. There was certainly an impact on the economy, there's no doubt about that."

Kirton said various agencies learnt a lot from their responses to the fires, which would help for future events.

Last year's fires started through sparks flying - from a vehicle losing its rear wheel in November and a broken axle in December.