Rapid plant growth increases fire risk
Any Canterbury fire this summer has ‘‘the potential to get big’’ with the fastest plant growth in the region for 30 years heightening risks, emergency services warn.
Fire and Emergency NZ (Fenz) is warning people across the region to take precautions because last year’s dry and warm winter, followed by considerable rain, means a significant fire risk during January.
The warning comes as scientists and academics caution that the 2017 Port Hills fires ‘‘could become the norm that New Zealand fire agencies have to deal with’’, and criticise agencies for paying ‘‘lip service to lessons learned’’.
MetService is expecting high pressure to dominate the country’s weather during January. On Saturday Wakanui, near Ashburton, recorded the highest temperature of summer so far, at 33.8 degrees Celsius.
Fenz integrated risk manager Darrin Woods said last year’s warmer winter made for ‘‘fairly high soil moisture content’’ across the region. That allowed for better growth in spring.
‘‘The big difference is that we’re still green. Ordinarily, we’d expect the grass fuels to be cured off, they’d already be quite brown,’’ he said.
‘‘When you look at the Port Hills and around the place at the moment, it has got a brown tinge but that’s the seed heads, basically the grass heads, so if you bore down into that it’s still very green.’’
Grass and shrub fires were already happening, but were ‘‘just not as aggressive as they could be’’. Places like Banks Peninsula were experiencing growth which had not been seen for three decades.
‘‘But as we get a continuation of summer conditions – warmer weather and, in particular, the wind – those grasses are going to dry out and get brown, and get to the point where any fire has the potential to get big.’’
The impending season was significantly different to that of February 2017, where fires burned 1645 hectares on the Port Hills, destroying nine homes and claiming the life of helicopter pilot Steve Askin.
Woods said it was ‘‘unusual’’ to be this far into summer without fire restrictions in Canterbury, but pastures had so far been greener. The system used to assess restrictions had not changed from what the Christchurch City Council used before Fenz took over in 2017.
He said there had already been restrictions in place by this time in 2017, before the Port Hills fires.
‘‘The amount of grass out there is higher, but from a Port Hills perspective the bulk of the fuel has been burnt, it’s been salvage logged and it’s gone. But people shouldn’t underestimate the speed with which a grass fire can develop and grow.
‘‘They’re extremely fast and they’ve been responsible for a number of fatalities around the world. They’re often underestimated because it’s just seen as a low fuel, but they can grown very quickly.’’
People could help reduce the risk by keeping lawns short, away from structures and clearing guttering. Mowing lawns at a cooler time of day and avoiding nor-west winds helped to reduce the risk of ‘‘stone strike’’, where a spark is caused by a lawn mower hitting a rock.
The warning comes as a special issue of the Australasian Journal of Disaster and Trauma Studies highlighted the lessons learned and failings in the management of the Port Hills fires.
One paper, written by Lincoln University environmental management senior lecturer Roy
Montgomery, criticised the many separate formal reviews about the fires as paying ‘‘lip service to the concept of lessons learned’’.
Fenz, the Prime Minister’s office and the Christchurch and Selwyn councils all conducted reviews. Montgomery was critical of all except the Christchurch City Council’ review.
‘‘No integrated, sharedresponsibility-focussed review, free from any pre-emptive terms of reference, has been conducted to date,’’ he said.
Of the two 2017 fires which eventually merged, one was almost certainly deliberate and the other considered suspicious, Montgomery said, calling the fire ‘‘in effect a $30 million crime’’.
Grant Pearce, a senior fire scientist at Scion and a leading specialist in wildfire behaviour, said New Zealanders ‘‘increasingly need to learn to live with wildfire events’’. ‘‘The Port Hills wildfire could become the norm that New Zealand fire agencies have to deal with,’’ he said. ‘‘Now is the time to re-think the use of planning controls and homeowner education to mitigate future fire losses at the ruralurban interface’’.
Recent fires, including the Port Hills blazes, should serve as a ‘‘major prompt’’ for fire agencies and local councils to raise awareness of the threats and ways to manage the danger.
‘‘Perhaps more importantly, they should also prompt a significant review of the treatment of wildfire risk in local planning processes across the country,’’ he said.
‘‘This should include the need to better identify wildfire prone areas, and to include stronger controls on development and construction, alongside the provision of defensible space in these high fire risk areas.’’