How long will Tasmanian fire crisis last?
Director — Fire Centre Research Hub
Professor of Pyrogeography and Fire Science
University of Tasmania
No one could have predicted the current fire crisis. The vast areas burnt and under threat of being burnt by numerous bushfires are the result of a complex mix of climate factors, each on their own quite ordinary, but combined, they have resulted in a historically significant fire crisis. All of the factors stem from weather and climate, and form a pattern that is consistent with climate change. Let’s consider each and reflect on what this means for our community in coming months as we enter the peak of the fire season.
The fires were ignited by lightning in two dry lightning storms. The first storm started a fire in the eastern edge of the Tasmania Wilderness World Heritage Area in late December. There was rightful concern about the threat of the fire to biological, cultural and economic values in the region. The response to stem the fire was prompt, and involved innovative approaches to protect fire-sensitive vegetation. There was sufficient moisture in the landscape for the fire to self-extinguish on moist forest edges, sparing the Florentine Valley and its hugely valuable forest resources. The second storm on January 15 saturated the state in ignitions, and many have established as dangerous fires in eucalypt forests with heavy fuel loads that under the right conditions create enormously intense fires that exceed the control of all known firefighting technologies. Bushfires ignited by dry lightning storms are increasing in Tasmania. We are going to have to learn to live with the inevitable bushfires which are started by lightning in difficult to access areas and that have the capacity to escalate, as in 2016 and this season.
There has been no effective rain in eastern Tasmania since mid-December. Indeed, the month of January may well break a record of the driest month in Tasmania, with essentially no rainfall recorded at many meteorological stations, with Hobart reporting 0.4mm thus far! The abrupt drying is on the back of a longer-term drying trend, which has exhausted groundwater supplies. An obvious sign of this is the drying up of creeks and very low river levels. The parching of the landscape means fires are increasingly able to burn into damp eucalypt forests, and if there isn’t significant rain soon, rainforests and peatland soils will also become combustible.
No substantial rain events are likely in the foreseeable future. The drying trend is being amplified by a steady warming. December and January are now uncharacteristically warm with a straight run of over 30 days in Hobart with maximum temperatures greater than 20C — summer weather more characteristic of the east coast of mainland Australia.
The fires are currently being driven by steady westerly winds, characteristic of the latitude where Tasmania lies. But what is atypical is that these winds are combined with heat and dryness. These winds have been propelling the growth of the fires towards settlements.
The classical dangerous fire weather associated with the passage of cold fronts is still eventuating. This packs a double punch, with strong, hot dry north or northwesterly winds changing to cooler south/southwesterlies, which causes the fire flanks to suddenly become long, dangerous walls of fire, which can catch the unprepared. This is one reason why leaving areas potentially threatened by fire is so critical. We were particularly lucky that a cool change arrived early on January 4, avoiding a serious escalation of the fire on the day when Hobart was intimidated by a blood red sky. Strong northerly winds caused rapid escalation of the many lightning-caused fires already burning on Friday, January 25, and a similar wind change is forecast for today. There are likely to be several more such changes this fire season.
There are significant take-home messages with the current situation.
The fire crisis is likely to continue for at least a month and possibly well into March, and will not end until significant rain falls across the state. The fire danger will oscillate according weather conditions, particularly winds. This means we must think about fire as part of daily life, shift our head space into situational awareness, routinely checking media and looking at weather conditions. We must accept that there will be many false alarms.
Smoke is likely to worsen on days when the fire danger is lower, because the winds will slacken and the pollution will pool in valleys. People vulnerable to smoke pollution need to plan for smoky days, by changing their behaviour, such as finding air-conditioned places to work and rest, and having their medicine available.
We need to be careful in bushland and remote areas, and accept disrupted holiday plans, because bushfire threats could escalate rapidly. We need to consider the incredible workloads the firefighters and emergency services are under. We must be careful with every fire, because any new fire starts will place new demands for firefighting resources.
The fire emergency is ongoing because of uncontrollable climate factors. We need to acknowledge the critical contribution of the Bureau of Meteorology staff, who, like the firefighters, are heroes in this unfolding drama. The meteorologists, with their sophisticated monitoring and modelling of both weather and smoke, are able to predict the future with unprecedented accuracy, and guide our firefighting and emergency responses. They are truly the sages of our time. We must heed their warnings.
This article first appeared in the Mercury on 30 January 2019.