Australia t’s a worrying start to the season. The indefatigable firefighters of New South Wales have been battling scores of firestorms, including at least a dozen that raged uncontained.
Following the warmest September on record, thousands of hectares of the picturesque Blue Mountains, west of Sydney, went up in flames. More than 200 homes were destroyed and at least 100 others were damaged, prompting NSW Premier Barry O’Farrell to declare a state of emergency.
Bushfires always come with Australia’s warmer months. Sometimes extreme events occur, such as in February 2009, when Victorian blazes killed 173 people and destroyed 150 properties.
Are we in for a tough time again? “No one can predict how bad a fire season will be,” says Janet Stanley, the chief research officer and postgraduate research co-ordinator at Monash University’s Sustainability Institute. “With the trend being more days of extreme heat and changes in rainfall patterns, the risk of fire and extreme fires is much higher.”
Mark Adams, dean of Sydney University’s faculty of agriculture, agrees. “Ours has been a land of drought and fire and flood for many millions of years. Each summer presents a risk of bushfire in southern Australia,” he says. “This summer is likely to be risky due to the several years of good rainfall and thus strong growth of understorey grasses and shrubs.”
Might climate change play a part? In 2007 the Intergovernmental Panel on Climate Change had this to say: “An increase in fire danger is likely to be associated with a reduced interval between fires, increased fire intensity, a decrease in fire extinguishments and faster fire spread. In south-east Australia, the frequency of very high and extreme fire danger days is likely to rise by 4 to 25 per cent by 2020 and by 15 to 70 per cent by 2050.”
The growth in greenhouse gases has been tracking at the worst case-scenario, Dr Stanley says, “So the IPCC’s estimate will be conservative”.
This is borne out by a report, published jointly by Australia’s Bushfire Co-operative Research Centre, the CSIRO and the Bureau of Meteorology, warning that days of extreme fire danger each year could soar by 65 per cent by 2020 and by up to 300 per cent by 2050.
Do the projections suggest Australia is doomed? Not necessarily, scientists say. Much can be done to lessen the likelihood of bushfires, even without resorting to new technologies, Dr Stanley suggests.
“In particular, we can do a lot more to prevent arson by working more closely with the community to report suspicions,” she says. “In addition, we need to direct more resources to investigating fires and to planning in other words, preventing houses being built in particularly fire-prone areas.”
Science, Dr Stanley says, has a great deal to offer. “Housing design that reduces the risk of ignition is not commonly enforced in high fire-risk areas,” she says. “More research is also needed into the best ways to prevent bushfires.”
Finally, climate-change scientists need to be listened to, she adds. “And the risks they are talking about should be addressed through adequate government policy to reduce greenhouse gas emissions.”
“The bushfires in NSW are a harsh reminder that Victorians should begin to prepare for the fire season,” says Darrin McKenzie, the acting chief fire officer for Victoria’s Department of Environment and Primary Industry.
Rain over the past few months has made the grass grow, he says. But it has not been enough to reduce the soil’s dryness. “This means the potential for grassfires as well as forest fires is relatively high as we move into summer,” Mr McKenzie warns.
Scientists mostly use computer models to try to predict likely paths of bushfires from their source of ignition.
Victoria, for one, uses specialist software and technology to provide advice during fires and flooding. The software is used to model the likely extent of a bushfire, and also the intensity and time it might take to impact on communities.
Phoenix Rapid Fire, as the software is called, can also predict flame height and how far embers will travel under prevailing weather conditions and the type and density of vegetation involved.
“This information is important for warning communities of fires and telling them what they need to do,” Mr McKenzie says.
Science, Professor Adams says, tells us that fires need a source of ignition, oxygen and fuel.
“We cannot do anything about the weather lightning is the major cause of fire ignition or the oxygen content of the atmosphere, which is about 21 per cent,” he explains.
In other areas much can and should be done. This is reflected in the bushfire survival plans of some increasingly eco-aware Australians whose activities now extend well beyond merely cleaning gutters, mowing lawns and keeping their fingers crossed.
Bushfire-resistant homes are gaining in popularity as the ravages of climate change and progressively drier conditions raise the risk of fire nationwide.
Buildings come under attack in three ways: through flying embers, radiant heat, and/or flame contact. Embers and windborne burning debris enter houses by nipping underneath them, into roof cavities or through windows that break.
Research has shown that most houses destroyed in bushfires survive the passage of the fire front, only to burn down thereafter as fire spreads from ignitions caused by windborne burning debris.
A key factor seems to be maintaining the integrity of a building envelope to resist ignition by embers or radiant heat and penetration of embers into the interior.
Researchers are familiar with the mechanisms, with some adopted in the Building Code of Australia, which refers to Standards Australia’s Construction of buildings in bushfire-prone areas.
Fortunately, many recommended materials also promote energy efficiency and health. In this sense, there is something of a crossover between bushfire-resistant houses and houses that incorporate environmentally sustainable design.
In addition to mud-brick and straw bale, environmentally sustainable materials that are bushfire-resistant and non-toxic include rammed earth, stone, recycled heavy timber and steel. Each material has an associated energy cost, including whether it is locally produced.
Even the use of eco-friendly fittings and furnishings helps, says Hobart-based German building biologist Michael Meyer, an expert on healthy homes.
“After all, once a house is on fire, the fumes will be less toxic if eco-friendly products are used,” Mr Meyer says. “For example, it’s important to install electrical and plumbing systems that contain no polyvinylchloride, or PVC, which can release toxic dioxins.”
In addition, Mr Meyer explains, Melbourne firm Paarhammer has produced double-glazed windows from local ironbark timber that is fire-safe and healthy to use.
A combination of hard-nosed research and traditional wisdom, borne of the school of hard knocks, has resulted in an extensive checklist of items to consider when building a new home or renovating an old one.
Before building, researchers advocate planning the landscape. Dwellings can be protected from wind-driven embers using natural or artificial land forms and shelter belts.
Use low-flammability plants that drop little litter.
Clear fuel from under trees and shrubs and remove lower branches, loose bark, twigs and leaves.
Surround buildings with open spaces – mown lawns, grazed paddocks and driveways or paths.
Use hills or gullies, or construct earth mounds and cut-and-fill terraces or retaining walls to block heat radiation and deflect embers and wind-driven debris.
Plant hedges and windbreaks using largish trees and shrubs of low flammability and with dense foliage to catch embers and debris and reduce wind.
Keep trees at least 20 metres from dwellings.
Building design strategies
Scientists today also know which building designs and construction materials are safest. From plan shapes to roofs, and walls to windows, there’s a wealth of advice that includes the following:
Avoid building on hilltops as fires travel faster uphill.
Minimise corners and vulnerable junctions such as verandahs or pergolas where embers might lodge. Separate pergolas from dwellings.
Simplify roof profiles, but keep them relatively steep to help shed leaf litter or burning debris. Clad them in metal or fibre-cement and ensure they have no crevices or valleys; seal roof spaces and cavities.
Use sarking waterproof sheets to cover gaps in roof coverings. Roof cladding and supporting structures should withstand gale-force winds.
Eliminate roof gutters, if possible, and instead collect rainwater in trenches. Or make gutters wide to facilitate cleaning and fit leaf guards.
Provide fire plugs for filling downpipes and roof gutters with water.
Use concrete slab constructions to eliminate underfloor spaces but if this is impossible, enclose spaces beneath timber floors, or line undersides with fire-resistant materials.
Use non-combustible materials for walls, columns and posts supporting floors. If columns and posts are combustible, use metal sheaths.
Use concrete or steel grates for decks and steps.
Make external doors and windows flush with the external edges to stop litter gathering. Cover screen door thresholds and window sills with metal mesh.
Use double glazing and toughened glass in windows or wired glass or glass bricks.
Use non-combustible shutters for outside glass doors and windows and to cover leadlight windows. Treat timber window frames and other exposed timbers with weather-resistant fire retardant.
Beware of flammable outbuildings and storage facilities that are too close to the house.
Provide adequate, reliable and independent supplies of water and power including a diesel generator.
External sprinkler systems should have metal – not soft-soldered – pipes and be capable of saturation.
Store gas tanks out of harm’s way and point vents away from walls.
Use non-combustible fences.
(Sources: Landscape and Building Design for Bushfire Areas, Fire Protection Association Australia)
Some high-density timbers that need no fire retardant include blackbutt, kwila (merbau), red ironbark, river red gum, silvertop ash, spotted gum and turpentine. Some varieties of acacia are relatively fire-resistant and thus suited for use as firebreaks.