The impact of climate change on Bushfire Risk

Posted on 21 March 21 2018 by Daniela Antonia

Not long ago Australia had a leading research centre for the scientific study of bushfire hazards and the impact of climate change on such hazards. The Bushfire Cooperative Research Centre (CRC) was set-up in the aftermath of the catastrophic Canberra and Australian Alps that occurred during the summer of 2002-2003. It was jointly funded by the Commonwealth and state governments and other research partners, for eleven years, from 2003 until 2014, when the federal government pulled out. The Bushfire CRC did a huge amount of incredibly useful work in helping us better understand bushfire behaviour, risk and integrating this knowledge into government agency policies and procedures. The Bushfire and Natural Hazards CRC, which replaced it, has limped along since, for the most part carefully avoiding any mention of ‘climate change impacts’.

One of the Bushfire CRC’s papers, “Bushfire weather in southeast Australia: recent trends and projected climate change impacts” (Lucas, Hennessy, Mills and Bathols, 2007) helpfully quantifies the projected impacts of climate change on bushfire risk. Consistent with most Australian state fire agency practices, it focuses on using the Forest Fire Danger Index (FFDI) to quantify bushfire weather risk. FFDI is based on measurements of the soil dryness (“drought factor”), air temperature, wind speed and atmospheric humidity (pp. 7-8). Bushfire hazard is a function of these climatic factors, which vary over the course of the day-night, as well as a number of other factors including:

• Fuel – this is anything that can burn but in the bush, mostly its vegetation. Considerations include how much is there, what type (fine/coarse, easily ignitable), continuity of fuel (how easily can a fire move through it or jump from one concentration of it to another).
• Topography and air-flow effects – these can have complicating effects on how fast a fire moves and in what direction. Because the heat of a fire creates a column of upward-moving air this sucks in more air towards it, creating its own weather systems, which are further influenced by the topography it is moving through. Generally, for example, a fire will move more rapidly up-slope than down, because that upward moving air is preceding it, pre-heating everything in its path and sucking more air in behind it.
• Infrastructure – how well are buildings or other assets protected? For example, is flammable or explosive material located nearby, is is protected from ember penetration, is it built to withstand radiant heat from the fire front or direct flame contact, can emergency services easily access the site, is reliable water for fire fighting available?

Climate is, therefore, not the only factor affecting bushfire risk, but it is nonetheless significant, and it is important to understand how a changing climate might affect the risk from bushfires that communities will face in the future. Lucas et al., in the above report, predicted how ‘high’ and ‘low’ climate change scenarios were likely to affect the incidence of fire danger days in Australia, for 2020 and 2050. In short, they predicted that:

“The number of ‘very high’ fire danger days generally increases 2-13% by 2020 for
the low scenarios and 10-30% for the high scenarios [Table reference omitted]. By 2050, the range is much broader, generally 5-23% for the low scenarios and 20-100% for the high scenarios.

“The number of ‘extreme’ fire danger days generally increases 5-25% by 2020 for
the low scenarios and 15-65% for the high scenarios [Table reference omitted]. By 2050, the increases are generally 10-50% for the low scenarios and 100-300% for the high scenarios.”

(p. 2)

Lucas et al.’s report includes analysis of climate change fire impacts for a range of populations across Australia. The closest and most comparable centre to Tathra is that given for Nowra. This shows a clearly increasing FFDI trend over the period from 1973 to 2007 (p. 73, top figure, below table). In the table at the top of page 73 the report notes that, in 2007, Nowra was experiencing 8.8 days per year of ‘high’, ‘extreme’ or ‘catastrophic’ fire weather. It predicted that, under a ‘low’ climate change scenario Nowra would experience 8.7 to 9.1 of those days by 2020, or, under a ‘high’ climate change scenario, it would experience 9.2 to 10.3 such days. By 2050, days of ‘high’ and greater fire danger would increase to 8.9 to 9.6 days using ‘low’ climate change modelling, or 10.8 to 14.7 days in a high change scenario.

Such numbers may not seem huge. One gets lost in numbers, but think about it this way – every year days of high fire danger literally “blow up” and we all feel the stress of wondering if, where and when a catastrophic fire might start. If those days increase by even one more day per year, let alone five more such days, that equals a 4 to 18 percent increase in the days when catastrophic bushfires become a real risk to our communities.

Even if Tathra has seen days like last Sunday before, every extra day like that, which happens because of the longer fire danger seasons we are seeing, is a proportional increase in the risk that a devastating fire will happen.

As Lucas et al. point out, changes to the length of the fire danger season and incidence of ‘high’ and above fire danger weather are also likely to have a range of other impacts including:

• A smaller window of opportunity for hazard reduction burning to be carried out in the non-fire season.
• A greater demand for resources for fire fighting and emergency response activities.
• Significant impacts on ecosystems resulting from shorter intervals between fires, including threats to biodiversity and, possibly, species extinctions.

Lucas et al. considered their predictions in the light of observed trends in bushfire behavior and found that climate data indicates that there has been an increase already in the incidence of fire danger weather (p. 3). They question the causes of this; whether “interdecadal variability may have been exacerbated by climate change” (p.4), but are inconclusive about the underlying cause. They asserted that ongoing monitoring is needed to determine whether this has been the case. While they note that, if an increase in fire danger is simply the result of natural climatic variation from one decade to another, then “it might be expected that fire-weather conditions will return to levels something more along the lines of those suggested in the 2020 scenarios” (p.4). If fire danger conditions remain high, however, “then the conclusion must be that the models used to make these projections are too conservative. Whatever the case, continued observation, as well as improved modelling are required to resolve this question” (p. 5). Clearly the Federal Government has been intent on ignoring well thought-out scientific advice once again. Ongoing monitoring is absolutely necessary if we are to understand and adequately respond to a changing global climate. Climate change denial like that heard from Prime Minister Malcolm Turnbull when he toured Tathra on Monday is blatantly obfuscating and unhelpful to our communities, which need action. (For more info, see this report on Turnbull’s comments in Tathra).

Whether or not anthropogenic (caused by humans) climate change is proven, we are fools to continue to ignore signs that the climate is changing. Changes in fire frequency and behaviour are one of the clearest indicators of it. To fail to adopt the precautionary principle and act to protect human and nonhuman communities in every way we can is pure negligence. We must addressing the problems caused by our activities, including greenhouse gas emissions and alteration of soils, water cycles, surface character and other factors that affect local micro-climates as well as global climatic drivers. Grass roots action can go a long way, but political support is also required. Politics cannot be left out of events like that just witnessed by Tathra.

Reference

Lucas, C., Hennessy, K., Mills, G. and Bathols, J., 2007 (September), “Bushfire weather in southeast Australia: recent trends and projected climate change impacts”, Bushfire CRC and Australian Bureau of Meteorology (CSIRO Marine and Atmospheric Research), Consultancy Report prepared for The Climate Institute of Australia

Notes

The Bushfire CRC’s papers can still be found online at http://www.bushfirecrc.com/

The Bushfire and Natural Hazards CRC is also a valuable resource. More can be found on their website: https://www.bnhcrc.com.au/

Search Google Scholar and you will find a host of other valuable work on Climate Change and Bushfire Risk. For example, here are some quick searchs to get you going:

• Google Scholar Climate change impact on bushfire risk.
• Results for post 2014 reports, to update you.

The author

Daniela Brozek Cordier, BSc, GradDipEnvSt(Hons), was a Senior Environmental Consultant with the firm nghenvironmental, in Bega NSW, from 2003 to 2014. During that period she wrote numerous bushfire assessment and hazard reports for proposed developments and management activities across south eastern NSW. She was, during that period, a member of Fire Planning Australia and completed much bushfire hazard assessment and other training through that and other organisations, including the NSW Rural Fire Service. Arriving in NSW soon after the 2003 Alpine fires, she saw first hand the impact of these. She also went to primary school in Dunalley, a small town affected by a catastrophic fire in 2013, during which her parents’ home was seriously threatened. She visited soon after the fire and again witnessed the impact of these fires. She now lives in Tasmania.