NZ’s wildfire future: which regions are most at risk?

17 November 2019

NEW ZEALAND – New Zealand’s fast-rising fire danger has prompted questions about how prepared our communities are for big blazes – and whether development should even be allowed in highest-risk places.

As dozens of fires continue to rage across New South Wales and Queensland, a leading fire researcher also says Kiwis should snap out of a prevailing “won’t happen to me” attitude.

Today, rural fires cost the economy about $67m each year – but that figure would swell as fire seasons lengthen by an average 70 per cent in a mere 20 years.

Projections suggest that, by 2040, fire risk in many regions – even wetter places like Taranaki, Manawatu and the South Island’s West Coast – would shift from one end of the scale to the other.

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Unsurprisingly, those regions with higher risk now were characteristically drier ones.

Canterbury, Hawke’s Bay, Gisborne – but also Waikato, the Central North Island and Northland – each year recorded the highest number of rural fires, while Otago and Nelson and Marlborough saw those fires that burned across larger areas.

These trends came down to basic geography: eastern areas were drier as they sat in the rain-shadow of mountain ranges, with prevailing westerly wind flows.

They also tended to receive strong fohn winds that delivered strong gusts on top of high temperatures and low humidity.

Scion fire scientist Grant Pearce said regions with larger population centres saw more fires, which were almost always started by people.

What became our biggest wildfire in 70 years – this year’s Pigeon Valley fire that ravaged 2300ha of pine forest, razed a home and forced the evacuation of a town of 2500 people near Nelson – was sparked by a tractor’s plough in a stony, tinder-dry paddock, amid 28C heat, low humidity and blustery, warm wind.

Pearce pointed out that, despite its risk, fire was still widely used by farmers for removing woody weeds, improving grazing and burning off rubbish and piled tree trimmings.

“A significant number of these burns get out of control starting wildfires, which contributes to the high burned areas seen in places like Otago and Canterbury.”

Changing danger

There have already been some alarming changes: although regions like Marlborough and Wairarapa have always had relatively high danger, it wasn’t until the last 20 years that big fires had broken out.

Northland, too, was seeing a rising number of fires, although most of these were relatively small, typically burning less than 100ha.

Pearce expected a rapid worsening of fire danger in most regions by 2040, before the risk increased more gradually over the rest of the century.

That was due to a combination of less rainfall, higher temperatures and stronger winds in many areas, driving a higher number of “severe” fire weather days, especially the east and north of both islands.

In already fire-prone places like Canterbury, these danger days would balloon from 30 to 40 days to 40 to 50 days in future.

But the more dramatic shifts would be seen in greener Manawatu, Whanganui and coastal Otago, where severe fire weather could double or even treble, climbing from five to 10 days to 15 to 20 days.

By 2040, the annual average number of fire danger days would jump from around six to more than eight in Kaitaia; eight to 12 in Auckland; nearly 17 to nearly 33 in Wellington; 39 to 45 in Christchurch; six to 14 in Kaikoura; and five to 18 in Dunedin.

Pearce said fire seasons would also start earlier in spring and drag on later through autumn.

“But unlike North America, where snow covers the ground for many months during the winter, New Zealand can experience bad fire weather days at practically any time of year.”

That meant fires could break out anywhere there were flammable fuels like gorse, manuka scrub or frost-cured tussock.

Further, fires of the future could behave more aggressively – and prove tougher to put out.

What firefighters call “extreme fire” has dangerous features like spotting – where embers and other particles are hurled ahead of the fire front; fire tornadoes and whirls; and “blow-up” conditions, where the inferno suddenly escalates in size and intensity.

Up until now, there haven’t been many cases of these volatile characteristics in New Zealand fires – one was a blaze that scorched 90ha of land near Hanmer Springs in 2016, another was this year’s Pigeon Valley blaze.

More homes at risk

As in other parts of the world, New Zealand has been seeing an increasing number of wildfires threatening not just farmland properties, but also lifestyle blocks and homes on city fringes.

“The past few years has seen a dramatic increase in the number of houses being lost and people evacuated in wildfires.”

Pearce singled out the 2017 Port Hills fire in Christchurch, which destroyed nine homes and forced the evacuation of hundreds, and that same summer’s blazes above Whitianga, where more than 30 houses were lost or damaged.

“Population growth will mean more people-caused fires, and expanding urban development will result in the potential for increased losses of homes and lives.”

Added to that were transformative changes in how we used land.

More exotic forestry, planted through programmes like the Government’s billion trees initiative, or the further spread of pest wilding pines, wouldn’t help.

Spraying, and diseases like myrtle rust, could also leave vast tracts of dead forests and shrub lands ready to burn – and devastatingly quickly, as Australia’s catastrophe has proven.

“Many of our scrub vegetation types, like gorse and manuka, are some of our most flammable fuel types,” Pearce added.

“Continued growth of the manuka honey industry would see increased areas of very flammable vegetation that could fuel more and larger fires.”

‘It won’t happen to me’

With rural and urban areas increasingly overlapping, there was an obvious need for more proactive district planning.

That included tougher restrictions on building in fire-prone areas – right down to what materials homes were constructed from – and even stopping development altogether in those highest-risk spots.

“Greater losses could also see insurance companies stop offering wildfire loss cover in identified high risk areas, as is already starting to be seen in some countries around the world and may well come about after these latest Australian bushfires, as it has for other natural hazard types.”

Amid these future threats, Pearce saw a crucial lesson for the public.

“The common view currently in New Zealand is that wildfire risk is somebody else’s problem, ‘it not going to happen to me’ and, ‘if it does, it won’t happen again’,” he said.

“Obviously, under multiple fire situations or during these large wildfire events, fire services simply can’t protect every property, so homeowners in high risk areas need to understand this, and start to take ownership of the risk themselves.”

People could start by removing flammable materials from around their properties, making emergency and evacuation plans, and talking to their neighbours.

“A shift in mindset around wildfire risk ownership is also needed, away from the fire services to property owners themselves.”

17. November 2019/by GFMCadmin