Ecologists ask burning questions of New Zealand bush
Lincoln University student Jenny Dent measures temperatures of burning gorse on the 'plant BBQ'; temperatures are measured using an infrared thermometer (Photo: Tim Curran)
It sounds like every science student’s dream – burning things to see, well, just how well they burn. But Lincoln University ecologist Tim Curran hopes his flammability research will have a very serious application in assisting with the prevention and understanding of bushfires.
Dr Curran is using a so-called “plant BBQ” to assess the flammability of different kinds of New Zealand flora.
“It’s quite literally a 44-gallon drum, cut in half with a grill on top of it,” he says. “You put the sample on there, pre-heat the sample, and ignite it – and it just seemed to me to be, obviously a novel way, but also a really effective way of measuring shoot flammability.”
Previous New Zealand research in this area has either relied on anecdotal reports from firefighters, or on studies focusing on just the leaves of plants, and Dr Curran is hoping to bridge that gap through rigorous study of whole shoots.
The research could one day be used to help limit the spread of fires.
“There’s an increasing amount of effort being spent around the world to try and work out what we can do with our own plantings and the different species that we plant – how that might be able to influence or create fire breaks,” he says. “And what we can do here is start to give some guidelines”.
In the shelterbelts of Canterbury farms, Dr Curran finds a tangible example of how the data could come in useful.
“Instead of having shelterbelts of gorse and other more flammable species – if you think you’re at risk of fires, by planting some other species that are lower in flammability then that’s going to potentially decrease your fire risk.”
A pressing concern
Recent weeks have seen a period of intense bushfires in Australia, as well as sporadic wildfires in New Zealand.
The risk of fire in New Zealand’s rural areas is well established; a study conducted by the National Institute of Water and Atmospheric Research (NIWA) concluded that on average around 3000 vegetation fires burn around 7000 hectares of rural land each year.
Dr Curran says the risk of fire danger is only expected to increase in coming years as climate change leaves many parts of the country hotter and drier.
“We really need to know the flammability of different plants so we can start to think about what’s going to happen in the future.”
However he warns that planting less flammable plants in fire-prone areas can only go some way to preventing the start and spread of fires.
“It only works up to a certain point. If you get really good fire conditions, like what Australia’s been experiencing in the last couple of weeks, it’s not going to matter too much exactly which species you have planted. But below those really extreme thresholds – that’s where it can make a difference.”
Just the beginning
Dr Curran constructed his plant BBQ after seeing it described in a research paper produced by scientists in Argentina. He says he and his team are still working towards fine-tuning its use.
“At the moment, mainly we’ve just been focusing on a fairly small amount of species, so we’ve done quite a bit of work with gorse, also some work on macrocarpa and on pines. And that’s mainly been looking at trying to sort of calibrate the device but also work out how moisture content and how the amount of dry matter – those sort of things – influences flammability.”
Already though, the experiments have shown promise in helping to throw new light on a well-documented fiery culprit.
“With gorse, one of the things that we have been able to demonstrate is that – while people have already known this – gorse retains a lot of dead material, increasing its flammability. One of my students has been actually quantifying that and showing how that relationship works.”
And Dr Curran says the team now hopes to expand the scope of their research.
“So [we’ve had] some fairly small questions to start with – making sure we’ve got the technique down pat before we start looking at broad-scale comparisons across species.”