New Zealand 'needs to be prepared' for increased extreme fire risk

Because of climate change the extreme conditions that preceded last year's Tasman fires are expected to more than double in frequency by the end of the century. Photo / File

As devastating fires grip Australia experts here are warning New Zealanders need to be better prepared as the "extreme fire" risk increases with climate change.

So far 24 people have died, more than 1600 homes have been lost and more than half a billion animals thought to have been killed during the horrific Australian bushfires where almost six million hectares have burnt.

Researchers have warned that in parts of New Zealand the number of days of "extreme fire risk" could greatly increase by 2040, and more than double by the end of the century.

Already 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.

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 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.

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

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.

Projections of the annual frequency of Very High and Extreme forest fire danger over the fire season months from baseline (a) to 2040 (b) and 2090 (c). Image / Scion

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.

Scion fire scientist Grant Pearce previously told the Herald fire seasons would also start earlier in spring and drag on later through autumn.

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.

Fire and Emergency New Zealand national manager for rural fire Tim Mitchell said they were already seeing changes in terms of the length of the season and complexity of fires, such as the Port Hills fire in 2017, and last year's Pigeon Valley blaze.

Mitchell said he was "confident" they had the resources available to deal with the current risk.

The combined structure of Fenz, which brought rural and urban firefighters under the same organisation - unlike their Australian counterparts, allowed them to utilise all available services when needed.

The sky turns red from the fires in Omeo, Australia. Photo / Getty Images

They also worked alongside other government agencies in firefighting, such as the Department of Conservation and the Defence Force, and forestry workers were also being trained in fire suppression.

But, as the intensities of the fires increased with climate change, there was greater importance on preventing them occurring in the first place, Mitchell said.

"Some of the intensities of the fires now are at a point where no matter how much ability you have, dealing with those fires is limited. So it is important we are managing the risk better."

For those living in rural communities, especially in lifestyle blocks surrounded by vegetation, fire prevention measures included keeping grass short - especially over summer, planting low-flammability species around their properties, and ensuring access ways were open.

There was a prevailing attitude in New Zealand that it "won't happen to us", which needed to change, Mitchell said.

"These prevention measures are happening, but unfortunately some people think 'it won't happen here', or for them the work is too costly or time-consuming. It is frustrating.

"Wildfires can happen any time, it only takes one spark. We all own the risk."

Where and how properties were developed also needed to factor in the increasing fire risk.

"When new developments go into rural areas we would like see more thought put into how they are developed, so there is separation between forested areas, good access to water and multiple ways in and out.

"Also in terms of how buildings are constructed, if in high risk areas we need to think more about using materials with greater ability to withstand fire."

A bushfire rages near Sydney. Photo / Getty Images

While the risk was increasing as the climate in certain areas became drier and windier, the type of fire would be unlikely to ever match those occurring in Australia, Mitchell said.

"The Australian environment is very different. They have a lot of eucalyptus, which is highly flammable, continental temperatures that can get extremely high and winds that often blow the same direction for long periods.

"Our climate is much different, and it is rare for winds to blow the same way day after day. The risk is low, but when you look at the Tasman and Port Hills fires, it can happen."

There have been concerns about the growth in forestry increasing the fire risk, but Mitchell said it all depended on how well those forests were managed.

"If there are appropriate fire breaks and mitigation measures in place they are generally fine, but often commercial pressures come in and it can be compromised. So it is more about how the forest is established, rather than forestry on its own."