A dry landscape and a dire season: we explain the current bushfire environment

By Andrew SullivanDecember 18th, 2019

Sydney and New South Wales (NSW) north coast residents continue to battle poor air quality as a result of fires burning through the state. Our bushfire expert Andrew Sullivan delves beyond the smoke haze to explain the current crisis and the tough conditions ahead.
orange-tinged smoke haze from bushfire across Sydney harbour

A suburb in a smoke haze. Sydney, Australia. 2019-12-04. Source: Shutterstock.

 

Why have bushfires started much earlier this year and why have they been so severe?

While it seems the fires recently experienced in southern Queensland and northern NSW started well before the onset of the summer bushfire season, the fire season in these regions generally ranges from August to December. So, the fires have been during the traditional fire season and not ‘early’ at all.

map of australia showing bushfire season times across the country ranging from Summer to Autumn towards the bottom of Australia and Winter to Spring further north

Bushfire seasons in Australia. Source: ‘Bushfires in Australia’ by RH Luke and AG McArthur (1978)

These fires have been particularly severe because much of the east coast of Australia has been suffering from drought. For the last 18 months, large sections of NSW and south-east Queensland have received the lowest rainfall totals on record, as shown in the rainfall deficit map below.

Extended drought means vegetation across large parts of the countryside is  available to burn as fuel. Therefore, areas usually moist and green at this time of year are more easily ignited, burning more and not impeding the progress of bushfires. Combined with many sources of ignitions and several days of hot strong winds, this has led to the large and numerous bushfires we’ve seen.

Map of Australia showing lots of areas across the country experiencing rainfall deficiencies with many showing lowest rainfall on record

Map of rainfall deficit for the period June 2018 to November 2019. Source: Bureau of Meteorology

What effect has climate change had on bushfires over the recent years?

It’s difficult to attribute any single weather event such as a drought to climate change. Australia has always experienced extended periods of rainfall deficit. But the increasing frequency of the combination of synoptic weather patterns bringing hot, dry winds from the centre of continent and the extensive dryness of the fuels may be considered indicators that climate change is having an impact on traditional fire weather patterns.

Many parts of Australia have historically experienced extensive and severe bushfire seasons (for example 1994 and 1968 in NSW) so in that sense it isn’t unusual. However, we expect the impacts of climate change will mean we will have more of this type of weather and that may result in an increase in the number and severity of bushfire events.

What do you predict will happen by the end of this bushfire season?

At this point it is difficult to predict what the rest of the bushfire season will bring. We are seeing indications the season will continue as it started. These indicators include continued lack of rain and frequent hot dry windy conditions. There is high potential for extensive fires as the fire season moves south.

Until extensive rain falls across much of the countryside, any day of hot dry windy conditions will result in elevated fire danger and the potential for any ignition source to develop into a large and destructive fire.

trees and a dry environment burning and a sun showing through the smoke haze

The North Black range fire west of Braidwood, east of Canberra. Source: CSIRO

How much of the bush and grassland will survive?

Much of the Australia’s native landscape has adapted to regular bushfires. Indeed, many native species need fire to regenerate and without it will not thrive. In many of the areas burnt by the recent fires, the vegetation will recover. Within a few years it will be difficult to see a fire has occurred at all.

Is there anything we can do to minimize the damage, or it is too late?

Lots of factors influence the behaviour and spread of bushfires and the damage they may do. There are a number of actions we can take to minimize the potential damage done by a bushfire. This includes fuel management before the fire season, ignition restrictions (e.g. total fire bans) before the onset of a bad fire day, and fire suppression when a bushfire breaks out.

Fuel management over large tracts of land primarily consists of the lighting of controlled burns under conditions that result in relatively mild fire behaviour that consumes fuel without the risk of the fire escaping. Once the fire season begins it’s often too late to conduct controlled burning because the risk of fires escaping is too great.

Forecasts of elevated fire danger may prompt declarations of total fire bans. This is to reduce the potential for bushfires to break out by restricting activities known to start bushfires.

arial photo of mountainous landscape showing smoke from bushfire

A photo taken during a flight from Brisbane to Canberra last week shows the extensive burning and residual smoke from fires on the NSW north coast. Source: Andrew Sullivan, CSIRO.

When a bushfire does break out, firefighting strategies include direct attack of the flames (usually with water, either from the ground or the air) and indirect attack where control lines are constructed (often by physically removing the fuel on the ground or applying flame retardant from the air) to restrict fire spread. Sometimes new fires are intentionally lit to consume the fuel between a control line and the advancing fire.

How can you protect your own property from bushfires?

Residents can also help reduce the risk of fires impacting their properties. These include:

  • reducing bushfire fuel like removing leaves from gutters
  • ensuring a safe path of exit in the event of a fire impacting your property
  • appropriate design, construction and maintenance of your property
  • enacting your bushfire plans when the arrival of a fire is imminent
  • being alert and responding appropriately to fire authority warnings.

To learn more about bushfire prevention and response in your area, contact your local fire authority. If you are in an emergency situation, please call 000.

CSIRO is an Australian authority on fire management, behaviour and prediction. We provide training to all state fire agencies to better understand and manage bushfires.

4 comments

  1. Could Andrew comment on whether fuel loads are significantly higher than they have been historically. Conversely, what impact has agricultural clearing had on reducing the risk and occurrence of dangerous fires?

  2. This article overlooks the web of life in forests and bushland. A forest is so much more than trees – it is habitat beginning with microfauna in the leaf litter. Remove too much of the leaf litter, too frequently, and all fauna that rely on the food chain will decline. Bird life, and animals at the top of the food chain will be seriously diminished. So while I am coming to accept that widespread fuel reduction is becoming necessary, it is not without a major cost to biodiversity and to public health. It would be helpful were an integrated risk analysis undertaken: risk of loss of life (residents and firefighters), of domestic animals and property, of public health through pollution and of biodiversity. Only then can public policy reflect the needs of all and political decisions be made in the light of evidence.

  3. I recently heard an idea, meant as a joke about rainfall in (on?) Australia. It was suggested that ‘we’ build some mountains using unprocessed plastic rubbish in areas of Australia that would affect air flow, cooling the air and resulting in a likely increase in precipitation. It sounds silly, but would it be possible? How extensive in height and area would such a ‘mountain’ be? It would surely help in removing plastic without burning it.

  4. The article says: “In many of the areas burnt by the recent fires, the vegetation will recover. Within a few years it will be difficult to see a fire has occurred at all”.
    This prompts me to ask: is the CSIRO or anyone else in Australia monitoring both the extent of burnt forests in Australia, and recovery rates of those burnt areas?
    According to my Australia’s Forests at a Glance 2015, Qld, NSW, and VIC (Eastern seaboard of Australia) has 81.9 million hectares of forest, representing 66% of Australia’s national forest area of 124.7m hectares. But how much of this forest area has been burnt, say since 2000? And how does this compare with forest burnt in the previous 20 years? And is the biomass recovery rate (the pace at which trees and ground vegetation recover to pre-burnt biomass levels) the same in 2019 as it was in 1980? I very much doubt it, and also doubt that anyone is doing this research.
    I have my doubts because Robert Glasser, former UN staffer working on Disaster Risk Reduction, has warned that the ‘cascading impacts’ of a warming planet are not being researched sufficiently, largely because it is such an immensely difficult field to get a handle on, even with the best computer modelling tools available these days.
    Surely one ‘cascading impact’ of more frequent bushfires happening in an increasingly drier country is that the dryness means biomass does not recover nearly as quickly. This in turn gives rise to a negative feedback loop of less rainfall because we know that de-forestation effects weather patterns over deforested areas – namely less rainfall.
    When, therefore, I contemplate the huge number of fires down the length of the eastern seaboard of Australia this bushfire season, I have my doubts about the wisdom of the sentence “Within a few years it will be difficult to see a fire has occurred at all”. The sentiment is reassuring, much like when Scott Morrison tells us Australia is meeting its green-house gas emission reduction commitments. Yeah, sure!

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