Nathanael Melia, director and principal scientist at Climate Prescience, authored a paper last year which revealed new climate change-driven wildfire conditions emerging for twenty-first century Aotearoa, with formerly unaffected regions now facing the possibility of “very-extreme” wildfire weather that led to Australia’s 2019/2020 Black Summer bushfires.

Melia says that last week’s fires in Twizel and Lake Tekapo/Takapō, and flooding that led to a state of emergency in Queenstown as well as road closures to the West Coast of the South Island, could be just the start of a season of extreme events.

“As we saw in the European summer, you’ve got this situation where they were oscillating between ‘this region has flooding, this region has fires’,” he says. 

“You’ve got this fire event that occurred in quite cool temperatures, which is not uncommon in New Zealand. But then with flooding in Queenstown and on the coast – it’s not a great start if we want to avoid what has happened in the Northern Hemisphere over this summer.”

Last week NIWA recorded the North Island’s hottest ever September temperature, with the mercury hitting 29.6˚C in Wairoa on Thursday, beating the previous record of 27.7˚C in Hastings in September 1955.

Meanwhile, an atmospheric river was forecast for Bay of Plenty and Gisborne

“Climate scientists and meteorologists have spent 2023 gawping at the record ocean temperatures, extreme weather events, and the rapid switch from La Niña to El Niño in the Pacific,” Melia says.

No two El Niño events are the same, and depend on what else is happening in the climate system. “Wildfire weather conditions depend on variables like temperature, rain, wind, and humidity. With El Niño’s influence, we expect all of these variables to lean in the direction of increased wildfire weather risk, especially for areas on the eastern and northeastern sides of our islands.”

He clarifies that predicting the weather on seasonal timescales is notoriously difficult – if not impossible. “Having said that, if you only had September conditions to go on for the last 25 years, betting that 2023/2024 would see the worst wildfire weather might get you about even odds.”

The last time New Zealand faced these kinds of El Niño conditions was 1997/98. “But climate change has escalated the risk in the past 20 years. The background warming level does mean that things are jumping off a higher platform. It’s really worrying.”

He says it’s “50/50” that we’re going to see the worst wildfire conditions that we’ve seen in 25 years.

“This El Niño is looking strong, and we’ve had a lot of wet weather, so there’s a high potential for vegetation to grow big and then dry out and become fuel,” Melia says. “To put it simply, it’s looking bad.”

Carbon forestry adding to wildfire risk?

Rather than sequestering carbon as intended, carbon forestry could add to the risk of wildfires and ultimately lead to increased carbon emissions, particularly if planted in inappropriate areas.

Last week the Guardian reported that Canada’s out-of-control forest fires released 2 billion tonnes of CO2 – probably triple the country’s annual carbon footprint.

“In our wildfire research we published last year, one of the implications I was keen to communicate is the risk of planting pines in regions capable of extreme and very extreme wildfire weather,” Melia says. “For example, those semi-arid areas along State Highway 8 between Lake Tekapo and Cromwell.”

Pinus radiata grows successfully in this dry terrain but planting there is risky. “It’s remarkably drought resistant, but that doesn’t mean it won’t dry out in our driest regions.”

While advising the Ministry of Primary Industries regarding Pinus radiata plantations in Central Otago and McKenzie country, Melia has told the government agency that they shouldn’t depend on them, as they could all be lost to fire.

“Going through some of these semi-arid landscapes, there is pine forest there, and winds accelerated down through the mountains and valleys can create really dangerous conditions.”

Somewhere like Tairāwhiti/Gisborne could get the biggest drought kick from El Niño. “However there’s been so much rain there it may take a while for those trees to become drought-stressed.”

Pine plantations at the top of the South Island are also at risk. “Marlborough is another area likely to get a drought kick from El Niño and is a top area of concern.”

Carbon forestry could have a higher risk of fire if it is not maintained to the same level as forestry for timber. “If you’re planting for timber you do interventions with spacing, pruning, and thinning to encourage tall, straight growth. And you might not necessarily do that for carbon farming,” Melia says.

“If it’s planted and just left rather than actively thinned, then there could be a lot of fuel there, plus the risk of the scrub underneath drying out. But it’s a big unknown.”

And rather than encouraging carbon sequestration, some aspects of the ETS could be making the fire risk worse. “Under the ETS you can get more credits if you plant at a higher density.” But denser vegetation can dry out to become a tinder box of explosive resins.

But in terms of fire risk, it’s not a simple case of native planting: good, pine: bad, Melia says. “Old growth natives are very fire resistant. But if you go and plant natives it’s often things like manuka that dries out and is highly flammable.”

There are also grass, scrub and bush ecosystems in Aotearoa that are far more flammable than pine plantations. “Grass fires can be really flashy and very dangerous, burning very hot and very fast.”

Sometimes the way local authorities deal with wilding pines can also add to fire risk.

“Dealing with wilding pines, you could be making the fire risk worse by just poisoning them. Poisoning a pine tree is potentially a huge fire risk. All the moisture is gone but flammable stuff is left behind. It’s like kindling.”

Ultimately, humans represent the biggest fire risk of all. “Wildfires need ignition. In Aotearoa, ignition means people. This means that wildfire can occur essentially anywhere around us, not just those regions that may have the most extreme risks.”

Melia says that Fire and Emergency New Zealand “has heaps” on how to mitigate the risks of wildfire to rural properties.

“Keeping a defensible space and keeping on top of that vegetation on your perimeters now in the growing season is a key one”