Preparing for severe weather seasons is a key focus for researchers who need to consider the affects of climate change. PHOTO: Carl Coleman, NSW Rural Fire Service
By David Bruce. This article first appeared in Issue Four 2018 of Fire Australia.
Bushfires along the east coast was the topic of discussion when Bushfire and Natural Hazards CRC CEO Dr Richard Thornton was asked to comment to the media in August.
“Heat, drought, flood and fire are not new phenomena for Australia; we have seen these before and we will see them again,” said Dr Thornton. “Although it is not common to have bushfires in northern NSW in August, it’s certainly not unprecedented. It was the severity of the August fires that was exceptional.
“What is different now is that there is an underlying one degree Celsius increase in average temperatures, which means that the variability of ‘normal’ events sits on top of that. We are seeing weather records routinely being broken across the continent and indeed the world, and all indications are that we are on a trajectory that will see temperatures continue to increase.
“What this means for extreme hazards, we cannot be sure. This is an area in critical need of further research into weather prediction, land planning, infrastructure development, population trends and community awareness.
Climate change is causing more severe weather, but demographic changes are having an equal impact and deserve just as much of our attention.
“Here in Australia, it has been unusually dry and warm over the last few months. When preceding conditions have been like this, and the bush and grass is so dry, it does not take much for a fire to get going once the wind is up— regardless of the season.”
Dr Thornton said Australia was familiar with year-round bushfires, which feature across the north of the continent in the middle of the year and move southwards at the end of the year and into the new year. However, these seasons are now getting longer—as are the fire seasons in the northern hemisphere.
“With fire seasons lengthening and overlapping across the globe, we need to think of new ways of dealing with bushfires, floods, cyclones and heatwaves,” Dr Thornton explained. “The old ways of sharing resources around Australia and with the northern hemisphere may not always be possible, so we need to discover better ways to manage all our resources.”
Dr Thornton said this was not only a matter of managing resources, such as water-bombing aircraft and firefighting vehicles.
“Firefighting is still very much done by people, despite advances in technology— and a great many of these are volunteers from the community. Our research shows that those human resources are now being stretched with the bushfire seasons getting longer, while our emergency services still regularly deal with floods, cyclones and severe storms, plus other demands such as motor vehicle accidents and search and rescue.”
The Southern Australia Seasonal Bushfire Outlook—released by the Bushfire and Natural Hazards CRC in September—is used by fire authorities to make strategic decisions on resource planning and prescribed fire management for the fire season. The map shows the bushfire outlook for southern Australia through to the end of 2018. This map has been combined with the outlook for the northern Australia bushfire season, which was released in July, to show the areas of fire potential for all of Australia.
A summary of the outlook for those areas covered is provided below.
Queensland
Dry conditions have led to areas in south-west Queensland enduring one of the most severe droughts in decades. As a result, almost all of inland southern Queensland has very sparse vegetation and fuel loads. While this reduces the potential for high-intensity grass fires, note that fully cured grass—even with low fuel loads—can carry fast-moving fires in hot, dry and windy conditions. Vegetation along the Coral Coast has experienced below-average rainfall over the past 12 months, with above-normal fire potential expected. Further south, forest and grassy vegetation has soil moisture much below the long-term average. Fuel loads in these areas are above the long-term average, with these areas likely to have above-normal fire potential for the 2018 fire season.
New South Wales
Weather conditions have been exceptionally dry over NSW during 2018, with the Murray–Darling Basin recording its driest January–July since 1965 (more than 50 years). This has allowed severe rainfall deficiencies to accumulate in many areas west of the Great Dividing Range, but also through the Greater Sydney region. At the end of August, the Department of Primary Industries mapped nearly all of NSW as being in some state of drought, with 21% classified as in intense drought, 49% experiencing drought conditions, and a further 30% as drought affected.
Windy conditions in August resulted in many significant bushfires in forested areas up and down the east coast, and there is significant concern for the potential of an above-normal fire season in forested areas on and east of the Divide. Reports of grassland fuel conditions west of the Divide have indicated that while grassy vegetation is cured, it is below average in quantity or load, resulting in an assessment of normal fire season potential for grassland areas west of the Divide. Note that while grass load is reduced and therefore the potential intensity of grass fires may be reduced, highly cured grass creates the potential for grass fires to spread rapidly.
Australian Capital Territory
The fire season was declared a month early in the ACT, on 1 September, with fires across NSW during August reinforcing the need to be prepared early. Large fires requiring regional-level bushfire-suppression operations can be expected. In grassland areas, both metropolitan and rural, grass fires could still be a problem due the ongoing drought conditions.
Victoria
Much of East Gippsland has experienced two consecutive years of record low rainfall during autumn and winter. As a result, forests are significantly more flammable than normal, due to an increase in dead material in the near surface and elevated fuels. Unusually early bushfire activity occurred in East Gippsland during July and August, highlighting the severe level of dryness in forests. These dry conditions are likely to be exacerbated during spring and summer with the climate outlook for drier and warmer conditions. These areas can expect above-normal fire potential from August right through summer. Further north, the Great Divide and Alpine regions are experiencing good levels of streamflow and snowfall. As a result, normal bushfire potential is expected across these regions.
In the west, south-west and central regions, normal bushfire potential is also expected, as rain has kept soil moisture at relatively high levels. However, there is some uncertainty around how much dryness may carry over from previous seasons, as well as how quickly warm and dry conditions expected in spring may increase flammability in forests. The timing and severity of grass fires will depend strongly on rainfall patterns during late summer. North and north-western Victoria has experienced below-average rainfall during autumn and winter, resulting in reduced cropping activity and pasture growth. These areas are likely to experience a normal fire season.
Tasmania
For the early part of Tasmania’s fire season, most of the state has normal fire potential. The western half of the state is very wet, and only the strip between Orford and St Helens on the east coast is drier than average. This area has above-normal fire potential, and the area may expand without significant rain. As in recent years, increased fire activity will probably occur in this dry strip before December and will require considerable response efforts. The fire season in the remainder of the state will commence more normally, in late spring or early summer, and provide good conditions for planned burning.
South Australia
Large parts of SA have experienced drier than average conditions since the start of 2018, and with dry conditions forecast to continue, several areas have been identified as having above-normal fire potential. Parts of the Riverlands, Murraylands, and the Flinders Ranges are particularly dry, which means that areas of scrub and woodland have increased fire potential. Populated areas of the Anangu Pitjantjatjara Yankunytjatjara (APY) Lands, particularly those parts infested with buffel grass, also have above-normal fire potential. Despite average winter rainfall, the fuel growth and forecast dry conditions indicate that the potential for bushfire across the populated areas of the Mount Lofty Ranges remains. The dry conditions in agricultural areas have resulted in less cropping activity, with SA forecast to record a decrease in areas planted and in yields from sown crops. This may reduce the risk of fires from agricultural activity in some areas.
Western Australia
As a result of bushfires in previous seasons and mitigation achieved by prescribed burning, higher fuel loads in the forests and shrublands across the Darling Range have been fragmented into smaller parcels. This has resulted in the break-up and reduction of abovenormal fire potential areas within the Swan Coastal Plain, Avon Wheatbelt, Jarrah Forest and Warren regions. Despite good winter rainfall, the underlying and persistent deep rootzone soil moisture deficits along the Darling Range, south-west corner, south coast, Mallee and Esperance Plains have resulted in the forest and shrubland vegetation in these areas being subject to additional water stress. Above-normal fire potential is expected in these areas.
Further north, cooler and wetter wet season conditions were experienced in parts of the Pilbara, Gascoyne and Carnarvon regions, which contributed to the accumulation of higher-than-average grass fuel loads. This has resulted in above-normal fire potential in these regions. The Gascoyne Coast missed the subtropical low rain that travelled further to the east, and is experiencing a rainfall deficit. This has affected grass growth and therefore the region is expected to experience normal fire potential. Parts of south-eastern WA received significant rain in the early part of the year, which is evident in the elevated surface soil moisture in some areas. This has led to increased growth of the shrubs and grasses in these areas. Due to this increased vegetation growth, and therefore expected fuel loads, above-normal fire potential is expected in these parts of the Mallee, Coolgardie, Nullarbor, Hampton and Great Victoria Desert regions.