A TEAM of Scion researchers is part of a 27-year history of research into New Zealand’s rural fires, a quiet brigade of climate experts and fire analysts whose job is to help make rural firefighters’ jobs more effective and safer.
Lead researcher Dr Tara Strand says NZ is in a unique position internationally thanks to the excellent relationship between researchers, Fire and Emergency NZ, the Conservation Department and other rural fire responders who work together contributing resources and skills to better understand how to manage wildfires.
And the work is starting to prove the traditional understanding of how rural fires behave is not always correct.
“The original theory on fire behaviour was developed in the 1940s. It was based around fire being spread through radiated heat with the fuel in front of a fire igniting once it was heated and spreading on from there.”
However, in recent years this basic theory has proved difficult for capturing extreme fire spread as witnessed in recent wildfires. Improved technology now indicates wildfire behaviour is not as simple as previously thought.
“In the United States our counterparts (US Forest Service) are seeing things in their fire lab that demonstrate fires are moving differently. They are spreading through convection (rather than radiation) where the hot air in a fire rises, cold air sweeps in under that and the fire’s flames effectively are pushed forward into the fuel, causing a rolling pulse effect that spreads the fire through flame contact with the fuel elements.”
Last summer US researchers were excited to come to NZ to prove the new theory with Strand and her colleagues. They initiated the first of several field burn experiments, the first using crop stubble of wheat, barley and triticale.
With carefully placed temperature and wind sensors and high-speed thermal imaging cameras the burn results did much to support the new theory on fire progress.
The stubble burn plots were large areas comprising about two hectares, where the evenly spaced crop rows and uniform stubble height mimicked laboratory fuel conditions as closely as possible.
“What they saw in the lab, we saw in the field.”
Further burn trials will progress to gorse then wilding pine plots to test the new theory in more complex vegetation fuel arrangements.
Strand said NZ cereal crop farmers are generally well versed in good fire control with little evidence over the past 100 years of those farmers injuring or killing themselves from such a practice.
However, burn-offs do escape so improved access to fire weather information and understanding good practices is needed, especially in a changing climate and social-environment.
The research by her team includes a study of the human factors behind wildfires and work is under way on behaviour and attitudes post the Port Hills fire.
“There is also quite a bit of work looking at building community resilience to fire events in Northland, given areas can be isolated and help can be some way off when needed.”
Fire authorities worldwide are also witnessing more urban wildfires, with fires less likely to be remote events on a forested horizon and more in the rural-city fringe. It means understanding how to manage populations caught in them is becoming critical.
Strand said the recent Nelson fire will be regarded as a good case study in the application of sound fire behaviour knowledge to support evacuation decisions and when it is safe to let people back into their homes.
Other research work promises to deliver a prediction tool that will ultimately be available to farmers, foresters and fire agencies to link into via an a web interface or phone application.
The NZ Real-time Fire and Smoke Modelling Framework is under development and will bring in local data sources, including satellite data.
The framework is the engine that sits behind decision support tools, such as real-time fire prediction and smoke modelling. It will allow for early warning, best-guess predictions on a new fire’s likely scale and impacts to be sent to local authorities, allowing them to use resources accordingly.
The Nelson fire provided the researchers an opportunity to run parts of the programme, providing real-time smoke level predictions.
“We also plan to work on a what-if tool that will use the framework for farmers and land managers who do controlled burn-offs.
“They can run what-if fire and smoke scenarios with weather, fuel and burn area data and see what the outcomes are likely to be and if, for example, their burn-off might place smoke over an airport or dilute quickly given the wind conditions.”
As farmers in an increasingly crowded, subdivided hinterland deal with the reverse sensitivities of non-farming neighbours, such a programme will provide proof they have exerted due care and research before igniting their burn-off.
The Government is actively promoting an extra 50,000ha of trees be planted and that will change the fire risk.
“But the fire risk will really depend upon what species and where those trees are planted. If it’s on the West Coast, for example, the risk is not as high.
“A greater concern is the knowledge gap we have in any information about how fire spreads through indigenous plantations, which are also being encouraged.
“Some indigenous trees take a while to start to burn but once going are hard to stop – cabbage trees for example can explode.
“Often these trees will grow above exotic scrub weeds which we do know can burn easily. We also know manuka is a high fire-risk species.”
Work by the researchers in coming months includes developing a training module for those who light fires as part of their living. It will include a practical, field-based component in fire behaviour associated with different light-up patterns.
“The training module will give them a selection of knowledge and tools around igniting and controlling fires and their possible impacts, something that is important given our changing climate and the greater scrutiny they will face.
“Ultimately we are working to better prepare NZ for extreme fire, build resilience, provide authorities with tools that help the decision process and help to keep fire as a land management tool,” Strand said.
