Every pyromaniacs dream… the science plant BBQ

In recent decades, climate change has been a cause for social and environmental transformation. For example, the inclusion of words such as ‘eco-anxiety’ to the Oxford English Dictionary shows the growing apprehension we have about the future of our climate. Next time you are feeling overwhelmed as a result of the environment, you’ll have the perfect word to describe it! The reasoning behind part of this social shift is due to ecological impacts caused by events such as rising sea levels, ocean acidification and wildfire. 

When I was growing up, we lived on the outskirts of Rangiora. I was 7 years old when I experienced uncontrolled fire for the first time; the boundary trees of a farm I could see from my bedroom window went up in flames. After a couple of hours, and a team of fire fighters, the blaze was put out. This event was minuscule compared to the damage caused by the Port Hills fire in 2017, which burnt 1,660 hectares of land, or 1,646 rugby fields, over a worryingly 66 days.

The Sugarloaf transmission tower is threatened by multiple fires burning out-of-control in the Port Hills south of Christchurch, New Zealand (Left), Image by Ross Younger from Flicker.
Orroral Valley Fire viewed from Tuggeranong, Australia (Right), Image by Nick D from Wikimedia Commons.

More recently, our neighbours across the ditch experienced one of the worst fire events in history. The Australian Bushfires of 2019/20 burnt a whopping 18.626 million hectares of land; equivalent to too many rugby fields to count!

The impacts of wildfire go beyond immediate destruction. Long term effects include challenges for biodiversity and human health. Additionally, the economic toll of wildfires can be extremely pressing. The Port Hills fire alone cost $7.9 million NZD to suppress; I would hate to think of the cost imposed by the Australian Bushfires. Throughout these events, astounding acts of courage were witnessed, whilst land, infrastructure and, regrettably, lives were lost; but could these events have been prevented or the severity of damage lessened? 

Though recent fires in New Zealand may not be as severe as those witnessed overseas, further destructive fire events are looming. Future conditions likely to be more common in much of New Zealand are hotter temperatures, lower rainfall and windier conditions: a recipe for a fiery landscape. One of the key factors that impacts the scale and intensity of fires is vegetation and their corresponding fuel loads. For example, a plant with a low moisture content and high dead material percentage will, in theory, pose a higher risk if fire were present. However, little research in New Zealand, or worldwide, has put this to the test empirically. 

Sarah Wyse from the University of Canterbury and her team of scientists acknowledged this knowledge gap and took it as an opportunity. “A quantitative assessment of shoot flammability for 60 tree and shrub species supports rankings based on expert opinion” was published in the Journal of Wildland Fire in 2016. The aim of this paper was to quantify the shoot-level flammability of 60 native and exotic plant species found in New Zealand and compare these results with rankings derived from previous studies. 

Plant barbeque in action! Image by Georgina Woods

One of the key pieces of equipment required for this study was a plant barbeque; yes you heard me right. Built out of a 44-gallon drum, the plant barbeque is every pyromaniacs dream. Rather than just burning components of a plant, this study burnt whole shoots (maximum 70 cm long) which preserved much of the plant’s structure. Each sample was left on the grill for 2 minutes to create the same environment as if an approaching wildfire. Once the sample had heated, it received direct flame from a blow torch for 10 seconds. Following this, measurements, such as ignition time, burning time and maximum temperature, were recorded. Overall, this approach creates more realistic wildfire conditions and much more ecologically significant data.

The study found species such as gorse, manna gum and kūmarahou to be high in flammability whereas species such as whauwhaupaku, hangehange and kotukutuku were low in flammability. These findings have contributed to paving the way for the development of mitigation tools, such as green firebreaks. Green firebreaks are strips of vegetation comprised of plant species that are low in flammability. This reduces the spread of fire, making our landscapes more resilient. As well as this, they contribute to encouraging native biodiversity to flourish.  

This is only the beginning for plant flammability, which has scope for future research. One of the co-authors of this project, Tim Curran from Lincoln University, has a goal to make this data set and future research known worldwide. Further investigation is going to continually contribute to the existing valuable pool of knowledge, tackling the challenges that continue to threaten humankind.

As we experience the consequences of climate change, it is normal to feel that creeping sense of eco-anxiety, but this research may help you ease those nerves. Knowing more about a problem is always helpful. So, whilst Sarah, Tim and other keen researchers help expand what we know about plant flammability, I’d save your marshmallows for another day; perhaps we won’t end up as a ball of flames after all. 

This article was prepared by Bachelor of Science (Honours) student Georgina Woods as part of the ECOL608 Research Methods in Ecology course.

Citation: Wyse, S. V., Perry, G. L. W., O’Connell, D. M., Holland, P. S., Wright, M. J., Hosted, C. L., Whitelock, S. L., Geary, I. J., Maurin, K. J. L., & Curran, T. J. (2016). A quantitative assessment of shoot flammability for 60 tree and shrub species supports rankings based on expert opinion. International Journal of Wildland Fire, 25(4), 466–477. https://doi.org/10.1071/WF15047

Leave a Reply