Canberra Day Oration

This paper was prepared by Phil Cheney, a long term, very experienced fire research officer with the CSIRO in Canberra. He described the background to the development of Canberra and how that development contributed to the 2003 fire disaster where a bushfire came right into suburbia.

Canberra: Bush Capital or Bushfire Capital


Based on the ACT Historical Society 2004 Canberra Day Oration

By Phil Cheney

Nearly 14 months ago in January 2003 bushfires burnt into the outskirts of Canberra with devastating consequences. The loss of 4 lives and 500 homes shocked our community to the core. However, a disaster in Canberra was inevitable. Even if these fires had been controlled in the mountains it would only have served to postpone the disaster to some time in the future – almost certainly within the next decade. We in the Bush Capital had set ourselves to burn.

We are not alone. The same factors that predisposed Canberra to disaster occur in other parts of Australia and other parts of the world: almost everywhere in places with a similar climate, where urban development is expanding, and in affluent communities where attitudes to fire, and to fire prevention and mitigation, are changing.

I have spent my entire adult life studying bushfires. It is a field in which the lessons of science, and of history, are hard-won but easily forgotten.

Fire in the bush is not a man-made phenomenon. Fire is an ecological process that has shaped the flora and fauna of the world and is as “natural” as the sun and the rain. It occurs wherever and whenever the climate produces a flammable environment. In Australia bushfires have been around for at least 80 million years and as soon as the eucalypts appeared in the fossil record, charcoal was in there with them.

The vulnerability to bushfire disaster, however, depends not only upon the physical factors of the environment that determine the scale of the event but also on the preparedness of the population. People can modify the environment and their familiarity with fire determines the extent that they are capable of self-help. The most devastating fire disasters occur where the phenomenon is infrequent and the population is unprepared.

Let us examine both the physical nature of fire and the changes that have occurred in the Canberra environment that led us up to January 2003.

Fire is a chaotic chemical reaction that gives off heat and light. It requires dry fuel and some form of ignition. The fuel for a bushfire is primarily the dead grass and accumulated litter of leaves, twigs and woody debris which builds up in our forests and rural areas. Most of the year the fuel is too moist to burn or a substantial source of heat is required to start a fire. But under extreme fire weather the very dry air sucks the last residual moisture from the dead materials and the tiniest spark is capable of starting a fire. Under these conditions, the heat of the fire dries out green vegetation and it too becomes fuel. And when strong winds drive a myriad of sparks into suburbs they ignite the natural and man-made flammable material that occurs around, on and inside our homes. It is a scene repeated almost every year at some place somewhere in Australia.

Australia is a flammable continent. The rolling cycles of wet and dry seasons and periodic droughts provide that sooner or later fire will spread through abundant dry fuel across almost every hectare of the continent. Only the tropical rainforests of north Queensland are spared from widespread burning. In southern Australia the rainfall pattern is such that there is abundant dry fuel ready to burn on 8 of every 10 summers. All that is then needed for a serious bushfire is a weather pattern where strong winds bring hot dry air from the centre of the continent.

We measure fire weather using a scale devised by the pioneering Canberra bushfire scientist Alan McArthur. The scale ranges from an index of one where fires will not burn or if they do they are very easy to suppress, to more than 100 where suppression is impossible. The benchmark weather that computes an index of 100 was the weather in Melbourne during Black Friday January 13 1939 when bushfires ravaged large areas of Victoria and Southern New South Wales and killed 71 people and vast areas of Mountain Ash forest.

The McArthur scale combines measures of seasonal drought, the moisture content of dead fuel and the average speed of the wind into an index of fire danger. There are five fire danger classes – Low, Moderate, High, Very High, and Extreme – familiar to most Australians from the ubiquitous roadside warning signs. The message on the signs is a simple one. They tell you how difficult it will be to extinguish a bushfire should one break out under the present or forecast weather for the day. The “Extreme” category is reached when the fire danger index exceeds 50 on the 1-100 scale.

The fire weather in Canberra on 18 January 2003 was extreme – an index of 80 on the fire danger scale. However, extreme fire weather is not all that uncommon. On average Canberra experiences 3 or 4 extreme days every summer. Nor was this the highest recorded in Australia. On 7 February 1983 (Ash Wednesday) the fire danger peaked at 140 in parts of South Australia and Victoria. However, bushfires still need a source of ignition. If this does not occur, then a day of extreme fire weather passes mostly un-remarked, with people merely observing to one another that it was just another unpleasant, hot, windy day.

When fires do burn during extreme weather the speed of their development is staggering. Above a fire danger index of 100 (imagine a day when the temperature is 38 degrees, the fuels are dry and the average wind is 50 gusting to 90 km/hour) grassfires can travel at an average of 20 kilometers per hour. Forest fires are slower, burning at around 10 – 12 kilometers per hour but they can throw spot fires 10 – 15 kilometers ahead. From a single ignition on a day of extreme fire danger, both forest and grass fires can burn out more than 100 000 ha in 8 hours. That’s an area 50 by 20 kilometers wide.

There are many unpredictable elements in a bushfire. For example, when the next big fire occurs in the ACT or NSW, Canberra residents may not have had 10 days notice between the fire starting and it hitting the suburbs. But other elements are predictable. We can predict with certainty that the situation will again be chaotic. Communications will break down. Power and water supplies will fail. There will not be enough fire fighters, and they will be able to attend to only a small fraction of the families and houses under threat.

It is also entirely predictable that the extent of the damage will depend on the number of people who recognised the fuel around their homes before the fire occurred (and had taken steps to reduce it) and who are physically and mentally prepared to defend their own homes when the fire arrives.

There are of course no guarantees. The best-prepared and defended house may still burn down from an undetected spark that lodges in the building. In other cases property owners may be prevented from defending their property by forced evacuation. Many Australians demand the right to assess the risk for themselves and stay and defend their home. In my opinion, this right should be enshrined in law for all Australians as it is in Victoria. Victoria regularly has the most severe fire weather of anywhere in Australia.

The physics of combustion are well known. The intensity of a fire, or the rate it emits heat, depends on the amount of fuel consumed every second, which in turn depends on the speed of the fire and the amount of fuel available for combustion. At the top end of the scale, heat is released at a rate of 100 000 kW along every metre of fire edge. By comparison, a large household bar radiator emits 1 kW.

Our ability to quell the sort of heat generated by an intense bushfire is puny. Under favorable conditions tough and skillful firefighters can put out a fire of 2000 kW/m. But this is only 2 % of the maximum rate. This means that under extreme conditions it is simply impossible to put out a bushfire unless it is tackled within a minute or two of ignition or until it runs out of fuel. When a forest or grass fire runs into a suburb the mass of embers generated can easily cross bare roads. They then seek out the fine fuel accumulated in the gardens and on and around our homes. The fire stops only when the fuel is sufficiently discontinuous so that people can suppress each new spot fire as it starts.

There is a great irony that in developing Canberra into a Bush Capital we were sowing the seeds of bushfire disaster. Developing bush meant also developing bushfire fuel. Most Canberra people did not understand this – “the bush” was something out in the country.

But Canberra was not always the Bush Capital. The vision of the city’s great planner Walter Burley Griffin in 1913 was, “to relieve the surface tension of city life by placing within reach and enjoyment of every city dweller some attendant delights of the country”.

As Governor General Lord Denman said the same year. “Let us hope that here a city may arise where those responsible for government of this country in the future may seek to find inspiration in its noble buildings, its broad avenues, it’s shaded parks and sheltered gardens — a city, perhaps, bearing some resemblance to the City Beautiful of our dreams”.

Onto the treeless plains of the Molonglo and the surrounding areas the Garden City was established. Broad avenues and shaded parks were planted, mostly with exotic species, in particular the deciduous hardwoods trees of the northern hemisphere. Home gardens were prescribed. Front fences were banned and government workers trimmed hedges to the prescribed height and size. When, in 1952, trimming by the government was deemed too expensive many of the public responded by either pulling out the hedges or allowing them to grow unchecked.

By the mid-1960s the growing fascination for Australian plants reached Canberra. Streetscapes changed their character.   Street trees, which had been predominantly deciduous hardwoods, with an occasional smattering of eucalypts, now were planted to native species. In the suburb of Aranda, established in the peripheral woodland of Black Mountain, every street tree was a eucalypt. In Weston Creek eucalypts also dominated the street planting. On the median strips of the broader avenues, the stately cedars, oaks and elms on irrigated lawns were now filled with mixed plantings of native species including Eucalypts, Acacias, Melaleucas and Casuarinas with extensive mulching to reduce the areas of dry grass needing to be mown and which would become unsightly in late summer.

Many residents followed suit. The classical older Canberra gardens with fine specimen trees, weeded flowerbeds and green lawns gave way in the new suburbs to native trees and shrubs, and mulches of natural litter or woodchips. Like-minded residents would run their gardens together producing continuous areas of “bushland” often right up to the house and with minimal areas of mown grass. By the 1980s bushland fuel had arrived in the bush capital.

As with the hedges of the fifties, maintenance of the new bush gardens also became costly and was reduced. There was also a decline in standards of maintenance of ACT’s pine plantations. Pruning of the lower branches was reduced and the plantations were invaded by garden escapes, like the exotic shrub species of cotoneaster and pyracantha. These made access more difficult, and more importantly supported the needle litter above the ground producing a more hazardous bushfire fuel bed. The older group plantings of conifers and other tree species within the suburbs were left to fend for themselves, often unpruned and accumulating a highly hazardous fuel of suspended litter that extended from the surface up into the green tree crowns.

Initially, Canberra’s suburban edge abutted grazing land where the grassy pastures were well eaten down by sheep during the summer months. As Canberra expanded to the north, south and west, the dangerous western perimeter (where bushfire entry was most likely) was protected by new urban development, where for a while there was little fuel in the gardens or parkland reserves. But then grazing was withdrawn from the hills as the houses encroached, and former farmland was converted to nature reserves. Residents on the fringes of the major parks extended their gardens onto public land, in places planting up the strips that had been cleared to provide a fuel break between the park and the suburban gardens. When the western expansion finally stopped the suburban edge now fronted onto maturing pine plantations and hilly bushland reserves.

There were other changes. The suburbs established in the Sixties gentrified. Short-lived native plants died. Rental properties became more common and dead fuels accumulated in neglected gardens. Species such as Cypress, and other exotic conifers which retain extensive dead material within an outer mask of green, were older, larger and even more flammable. Thirty years of lifestyle detritus, including old tires, lumber, plastics and flammable chemicals, had accumulated in almost every suburban backyard.

But there was another more insidious and ultimately more damaging change afoot. Fire was disappearing from the consciousness of Australians.

In the early days, the rural lessees on farmland in the ACT commonly used fire. Paddocks of stubble were burnt each year before the new crops were sown. Graziers regularly burnt the dry forests of the foothills and the Cotter Valley to regenerate the native grasses. Rural residents burnt firebreaks around their homes each summer. When major fires burnt through the Brindabella Mountains in January 1939 under extreme weather their spread was restricted by extensive areas of recently burnt forest in the Cotter Valley and by grasslands which had been heavily grazed by sheep, and in some cases denuded by rabbits. Although burning firebrands were thrown up to 15 km downwind from the Brindabella range, they could only ignite new fires in a few isolated areas of bushland fuel near Tharwa and Williamsdale. The 1939 fires were Australia’s worst bushfire event; Canberra was threatened, but survived.

In earlier times, Canberra residents used wood fires for domestic heating and regularly burnt wastes in the garden incinerator. Bushfires were also part of the local scene. In 1952 a magpie flew into powerlines along Cotter Road near the present location of the Australian Mint. This fire burnt over the grazed pastures of the Red Hill reserve and the newly developed federal golf course, and reached the Tinderry ranges 30 km south of Queanbeyan in a few hours. Another fire, started by lightning near Huntley, burnt over the pine forests on Mount Stromlo destroying the Observatory. It was contained when it came out into the grasslands. Neither fire encroached directly on suburban Canberra, but they were events which entered the city consciousness and influenced attitudes to fire at that time.

There were two other significant events in 1952. Mervyn Victor Richardson developed the first Australian rotary mower in his suburban garage in Sydney and CSIRO began the widespread introduction of myxomatosis to control the rabbit plague.

On the one hand the Victa mower provided a means for Australian homeowners to turn grass into lawn and to a large extent removed the need for the tiresome task of burning-off grass around the home when it first cured in early summer. On the other hand, the dramatic reduction of the rabbit population removed enormous grazing pressure from both the grassland and the forest vegetation, particularly during drought, and accelerated the buildup of fuel. From that time on, even in severe drought, the grassland in and around Canberra was never as bare again as it had been in 1939.

Even into the early 1970s Canberra residents were unconcerned about burning off in the forests and woodlands of the ACT. Every summer between 1962 and 1970, I conducted experimental burning on the foothills of Black Mountain and Bruce Ridge to collect data on fire behaviour and to train forestry students from the ANU. We burnt experimental fires in crop stubble on the plains of the Woden valley and even burnt fires in paddocks surrounded by suburbs at McKellar and Stirling before they too were built upon. I do not remember one complaint or unfavourable comment in the media.

I have already mentioned Alan McArthur, the Canberra scientist now recognised as the father of bushfire science in Australia. In 1960 (when I was one of his students at the Australian Forestry School in Yaralumla) McArthur advocated the prescribed burning of ACT’s forests and woodlands for fuel reduction as a measure for mitigating future bushfire damage. Aerial ignition of prescribed burns was introduced in Western Australia in 1966 and in 1967 I carried out the first operational aerial ignition of forests in the mountainous terrain of the Brindabella ranges. Over the next 10 years extensive prescribed burning every autumn laid smoke, clearly visible from the city, over the mountain country. The media ignored our burning and while we advised the rural lessees and the police there was never to my knowledge any complaint from the public about the fires or the smoke.

Unfortunately for bushfire managers, during the late 1970s smoke became unpopular. It started with discouragement and later banning of backyard incinerators and burning of autumn leaves and other garden debris. Wood fires became the next target, and residents were encouraged to fight air pollution by converting to gas and oil. They were not told that gas and oil produces the same primary combustion products but without the tell-tale visible particulates of woodsmoke. Thus people could ignore the massive consumption of fossil carbon reserves associated with this change.

The onset in the late 1970s of environmentalism, and its concern for conservation of native species saw the beginning of a great decline in broad-acre prescribed burning for fuel reduction in the ACT and nearby NSW. Environmentalists vilified the burning of native bushland, but without any understanding of the essential role that fire plays in the regeneration of native species and creating habitat for native fauna. Moreover, Canberra’s demographic profile was changing dramatically at this time: increasingly the population was city bred, or immigrant from countries where intense forest fires were rare. These people had absolutely no comprehension of the destructive power of the Australian bushfire.

Large bush fires had occurred in and around the ACT in the years 1960-1990, but these were out in the country or skirted around the Canberra suburbs. In 1965 a fire started north of Goulburn and burnt to the coast near Jervis Bay in a single day, a distance of 90 km. On the same day a fire burnt across Kosciusko National Park from the Tumut River in the west to the backwaters of Eucumbene Dam. Canberra was in between and also experienced extreme fire weather, but we were lucky – no fires started.

In 1985 two fires started on the eastern side of the city and burnt away from the suburbs to Foxlow near Captains Flat. The back of both these fires burnt slowly into the prevailing westerly wind and threatened backyard fences in the suburbs of Hackett and Garren, but gave residents little indication of the speed and intensity of the head fire that trapped and killed a firefighter at Burra.

As often happens in Australia, a period of high fire activity was followed by many mild years. There were no serious fires in the ACT for another 18 years. During this time, the bushfire agencies became better equipped and more efficient at suppressing small fires. The community became complacent – fire disasters were something that happened somewhere else. It seemed unnecessary for individual home owners to take actions to protect themselves.

The attitude of the media also changed dramatically. Fire became theatre. With access to the helicopter and the telephoto lens even a mild fire could be turned into a dramatic spectacle. In this scenario, there was no interest in the root cause of the problem. The spotlight turned to suppression and to the heroics of the volunteers. Few people reading the newspaper or watching the television news realised that fire fighting, particularly in the forest, is a hard, tough and dirty job, and is only successful when the flames are less than a metre high. And when firefighters put out fires when they were small there was no news and no plaudits.

Land managers and firefighters made plea after plea for more prescribed burning to reduce fuel loads to make their job safer and easier and to extend the window of weather conditions where they could suppress a fire before extreme conditions arrived. But prescribed burning was unpopular and emergency service agencies turned to technology and particularly to helicopters without emphasising that they are only a support tool for the firefighters on the ground. All this was despite the fact that the USA, the richest and most powerful country in the world with almost unlimited resources, was losing the battle against wildfires in heavy fuel. During the 1990s the point was reached where the USA had to import fire fighters from Australia and New Zealand to assist them, but still they have experienced increasingly severe and damaging bushfires.

All around the world the message was the same: suppression fails where heavy fuel is too extensive.

The only way to prevent widespread conflagration fire is to use fire to reduce fuel loads well before the extreme weather hits. This is not new. When the Aborigines arrived the climate was probably not much different that we have today. They soon recognised the consequences of widespread continuous fuel and extreme weather. Having little capacity for suppression – I am sure they were tough but there is only so much you can do with a green branch and no clothes – they resorted to burning. There is now little doubt that they burnt the bush frequently and extensively and in my opinion burnt primarily to protect themselves and their food resources by creating an extensive patchwork of recently burnt ground that limited the spread of intense fire under severe weather.

In Southern Australia we cannot now re-create the pattern of Aboriginal burning even if we wanted to. However, we can create a pattern of fuel-reduced areas that, if combined with efficient suppression, will provide for the need to manage our forests for catchment protection, timber production and recreation, our parks for the conservation of our flora and fauna and beyond the forest edge to provide for the protection of our farms and homes.

Broad-scale prescribed burning is essential in our forests to allow fire-fighters the opportunity to suppress fire before it becomes too large and to provide a balance of age classes after fire for the maintenance of biodiversity. It is also of critical importance to enhance the safety of our firefighters themselves.

And we have to address the fuel within the city. The most concentrated fire disaster in recent history was the Oakland-Berkley Hills fire in California on October 20 1991. It started and burnt entirely within an established suburban area, with homes intermixed with closely spaced Australian eucalypts and Monterey pines – better known to us as the Radiata pine we grow in our plantations – that over-topped many of the houses with an understorey of flammable Californian native shrubs. The fire weather was slightly less severe than experienced in Canberra on 18 January 2003, with hot dry winds that averaged 35 km per hour and gusts to 80 km per hour. Although it burnt only 650 ha it destroyed 2449 single-family dwellings and 437 apartment buildings and killed 27 people. It built up so rapidly after ignition that 790 homes were burnt in the first hour.

A similar situation occurred in Como and Janali, suburbs deep inside the built-up area of Southern Sydney a few months later in January 1992. These suburbs were thought to be protected on the western side by the Woronora river but firebrands traveled more than a kilometer across the river and started three spotfires into a mere 30 hectares of bushland reserve between the river and the houses. The bushland was long unburnt, and carrying very heavy fuels. The resulting fires could not be controlled before they had burned around 200 homes.

The only way to have people understand fire is to expose them to it on a regular basis. Fire should be used to reduce fuels in our national parks and pine forests. This is not the ecological disaster that some people would depict. For example, low-intensity prescribed fire on Black Mountain every 5 years would protect the green canopy of the trees and regenerate the understorey shrubs. With fire exclusion many shrubs like the Black Mountain Wattle become scraggy and die out. Some of the beautiful-flowered pea bushes live only for 7 to 10 years and in many areas only persist as seed in the soil. These species do not need high-intensity fire but can be safely and successfully regenerated by low-intensity fire applied at the right time of the year.

The most attractive carpet of yellow orchids I have ever seen on Black Mountain came up after a spring burn in 1965. Perhaps when the responses of our native plants are even better known we can burn to achieve a floral display on demand.

There is a downside of course. The weather conditions that are most favorable for precision burning are stable and will result in a layer of smoke moving into and through urban areas. And to some people smoke is a severe irritant and may precipitate asthma and other allergic reactions. But in the divine scheme of things smoke was not put there just to irritate the human race. Smoke stimulates flowering of many native plant species and has a role in breaking the dormancy of the seed of many others. Smoke is part of that ecological process called fire and a natural part of the ecosystem we call earth.

I consider that a forest subjected to mild prescribed fire, where the scene is one of freshly regenerated shrubs under an intact canopy is far more attractive and far better for the conservation of biodiversity than long-unburned forest with its sickly understorey of moribund shrubs and massive accumulations of Tussock grasses and leaf litter.

I believe we must limit the areas burnt by conflagration fires. Biodiversity must surely also be lost in forest subjected to extensive high-intensity wildfire, where defoliated blackened trees are unable ever to reach the full expression of their natural form. In an intense fire there is massive death of wildlife, isolated populations become vulnerable to extinction, soils are baked and vulnerable to erosion, increasingly precious water catchments are compromised, the capacity of our storage reservoirs reduced and we have the attendant trauma of fire in the suburbs, country towns and farms.

Fuel reduction burning will not stop fires – at least not after 12 to 18 months from the burning. But it does reduce the speed and intensity of a fire. I have measured a reduction in speed and intensity of forest fires in fuels 11 years after burning compared with a 20-year-old fuel. Normally bushfire scientists would recommend burning every 5 years for a dry eucalypt forest like that occurring on Black Mountain. Fuel reduction burning at the interface between the city and the bush will reduce the impact of fire on the suburbs.

Residents too have to play their part and reduce the flammable dead fuels in their gardens and make wise choices of trees and shrubs that do not collect abundant dead material in their structure. People who want to have native gardens should be encouraged to safely burn excessive fuel – if only to expose them to the nature of fire and have them appreciate what constitutes fuel for a bushfire.

If the ‘City Beautiful of our dreams’ is to have the character of the Australian bush we have to accept that fire is part and parcel of that character. We have to manage fire and the only thing that we can manage to reduce fire damage is the fuel. We have to accept that prescribed fire used to reduce fuel loads also produces a natural response that is part of the bushland ecosystem. We have to accept that bushfire smoke is also an integral part of the Australian environment and people who are sensitive to smoke need to take individual actions to protect themselves just as people sensitive to skin cancer need to take individual protection from the damaging rays of the sun.

If we do not accept this, the alternatives are bleak. We must either create an environment of tar and cement, or a city of exotic trees and irrigated lawns……. or face the prospect of increasingly severe bushfire disasters in the future.