The Amazon is on fire – here are 5 things you need to know



Huge fires are raging across multiple regions of the Amazon Basin.
Guaira Maia/ISA

Danilo Ignacio de Urzedo, University of Sydney

Record fires are raging in Brazil’s Amazon rainforest, with more than 2,500 fires currently burning. They are collectively emitting huge amounts of carbon, with smoke plumes visible thousands of kilometres away.

Fires in Brazil increased by 85% in 2019, with more than half in the Amazon region, according to Brazil’s space agency.

This sudden increase is likely down to land degradation: land clearing and farming reduces the availability of water, warms the soil and intensifies drought, combining to make fires more frequent and more fierce.




Read more:
Amazon rainforests that were once fire-proof have become flammable


1. Why the Amazon is burning

The growing number of fires are the result of illegal forest clearning to create land for farming. Fires are set deliberately and spread easily in the dry season.

The desire for new land for cattle farming has been the main driver of deforestation in the Brazilian Amazon since the 1970s.

Ironically, farmers may not need to clear new land to graze cattle. Research has found a significant number of currently degraded and unproductive pastures that could offer new opportunities for livestock.

New technical developments also offer the possibility of transforming extensive cattle ranches into more compact and productive farms – offering the same results while consuming less natural resources.

2. Why the world should care

The devastating loss of biodiversity does not just affect Brazil. The loss of Amazonian vegetation directly reduces rain across South America and other regions of the world.

The planet is losing an important carbon sink, and the fires are directly injecting carbon into the atmosphere. If we can’t stop deforestation in the Amazon, and the associated fires, it raises real questions about our ability to reach the Paris Agreement to slow climate change.

The Brazilian government has set an ambitious target to stop illegal deforestation and restore 4.8 million hectares of degraded Amazonian land by 2030. If these goals are not carefully addressed now, it may not be possible to meaningfully mitigate climate change.

3. What role politics has played

Since 2014, the rate at which Brazil has lost Amazonian forest has expanded by 60%. This is the result of economic crises and the dismantling of Brazilian environmental regulation and ministerial authority since the election of President Jair Bolsonaro in 2018.

Bolsonaro’s political program includes controversial programs that critics claim will threaten both human rights and the environment. One of his first acts as president was to pass ministerial reforms that greatly weakened the Ministry of the Environment




Read more:
Amazon deforestation, already rising, may spike under Bolsonaro


Regulations and programs for conservation and traditional communities’ rights have been threatened by economic lobbying.

Over the last months, Brazil’s government has announced the reduction and extinction of environmental agencies and commissions, including the body responsible for combating deforestation and fires.

4. How the world should react

Although Brazil’s national and state governments are obviously on the front line of Amazon protection, international actors have a key role to play.

International debates and funding, alongside local interventions and responses, have reshaped the way land is used in the tropics. This means any government attempts to further dismantle climate and conservation policies in the Amazon may have significant diplomatic and economic consequences.

For example, trade between the European Union and South American trading blocs that include Brazil is increasingly infused with an environmental agenda. Any commercial barriers to Brazil’s commodities will certainly attract attention: agribusiness is responsible for more than 20% of the country’s GDP.

Brazil’s continued inability to stop deforestation has also reduced international funding for conservation. Norway and Germany, by far the largest donors to the Amazon Fund, have suspended their financial support.

These international commitments and organisations are likely to exert considerable influence over Brazil to maintain existing commitments and agreements, including restoration targets.




Read more:
The world protests as Amazon forests are opened to mining


5. There is a solution

Brazil has already developed a pioneering political framework to stop illegal deforestation in the Amazon. Deforestation peaked in 2004, but dramatically reduced following environmental governance, and supply change interventions aiming to end illegal deforestation.

Environmental laws were passed to develop a national program to protect the Amazon, with clearing rates in the Amazon falling by more than two-thirds between 2004 and 2011.

Moreover, private global agreements like the Amazon Beef and Soy Moratorium, where companies agree not to buy soy or cattle linked to illegal deforestation, have also significantly dropped clearing rates.

We have financial, diplomatic and political tools we know will work to stop the whole-sale clearing of the Amazon, and in turn halt these devastating fires. Now it is time to use them.




Read more:
Huge wildfires in the Arctic and far North send a planetary warning


The Conversation


Danilo Ignacio de Urzedo, PhD candidate, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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The summer bushfires you didn’t hear about, and the invasive species fuelling them



File 20190311 86707 1ji5xqu.jpg?ixlib=rb 1.1
Fire has burned through a swathe of the Tjoritja National Park.
Author provided

Christine Schlesinger, Charles Darwin University and Barry Judd, Charles Darwin University

In January 2019, fires burned across a 100-kilometre length of the iconic Tjoritja National Park in the West MacDonnell Ranges, from Ormiston Gorge nearly to the edge of Alice Springs.

These fires affected an area comparable to the recent Tasmanian fires, but attracted relatively little national attention. This is partly because the fires in Tasmania were so unusual – but we believe the fires in central Australia were just as unexpected.




Read more:
Dry lightning has set Tasmania ablaze, and climate change makes it more likely to happen again


In the past, fires of this magnitude have tended to come after heavy rain that powers the growth of native grasses, providing fuel for intense and widespread fires. But our research highlights the new danger posed by buffel grass, a highly invasive foreigner sweeping across inland Australia and able to grow fast without much water.

Far from being pristine, Tjoritja and the Western MacDonnell Ranges are now an invaded landscape under serious threat. Our changing climate and this tenacious invader have transformed fire risk in central Australia, meaning once-rare fires may occur far more often.

Buffel grass in Australia

Buffel grass is tough and fast-growing. First introduced to Australia in the 1870s by Afghan cameleers, the grass was extensively planted in central Australia in the 1960s during a prolonged drought.

Introductions of the drought-resistant plant for cattle feed and dust suppression have continued, and in recent decades buffel grass has become a ubiquitous feature of central Australian landscapes, including Tjoritja.

Buffel grass has now invaded extensive areas in the Northern Territory, Queensland, Western Australia and South Australia and is spreading into New South Wales and Victoria. It was legally recognised as a key threat in 2014, but so far only South Australia has prohibited its sale and created statewide zoning to enforce control or destruction.

Buffel grass crowds out other plants, creating effective “monocultures” – landscapes dominated by a single species. In central Australia, where Aboriginal groups retain direct, active and enduring links to Country, buffel grass makes it hard or impossible to carry out important cultural activities like hunt game species, harvest native plant materials or visit significant sites.

Buffel grass impacts on Anangu Pitjantjatjara Yankunytjatjara communities in central Australia.

But buffel grass isn’t only a threat to biodiversity and Indigenous cultural practices. In January the Tjoritja fires spread along dry river beds choked with buffel, incinerating many large old-growth trees. Much like the alpine forests of Tasmania, the flora of inland river systems has not adapted to frequent and intense fires.

We believe the ability of the fires to spread through these systems, and their increased intensity and size, can be directly attributed to buffel grass.

Fire and buffel grass

Because of the low average rainfall, widespread fires in central Australia have been rare in the recorded past, only following unusual and exceptionally high rainfall.

This extreme rain promoted significant growth of native grasses, which then provided fuel for large fires. There could be decades between these flood and fire cycles. However, since the Tjoritja (previously West MacDonnell Ranges) National Park was established in the 1990s, there have been three large-scale fires in 2001, 2011 and 2019.

What has changed? The 2001-02 and 2011-12 fires both came after heavy rainfall years. In fact, 2011 saw one of the biggest La Niña events on record.

Climate change predictions suggest that central Australia will experience longer and more frequent heatwaves. And although total annual rainfall may stay the same, it’s predicted to fall in fewer days. In other words, we’ll see heavy storms and rainfall followed by long heatwaves: perfect conditions for grass to grow and then dry, creating abundant fuel for intense fires.

The remains of a corkwood tree after an unplanned bushfire in an area heavily invaded by buffel grass near Simpsons Gap. Very few large old corkwood trees now remain in this area.
Author provided

If central Australia, and Tjoritja National Park in particular, were still dominated by a wide variety of native grasses and plants, this might not be such a problem. But buffel grass was introduced because it grows quickly, even without heavy rain.

The fires this year were extraordinary because there was no unusually high rainfall in the preceding months. They are a portent of the new future of fire in these ecosystems, as native desert plant communities are being transformed into dense near-monocultures of introduced grass.

The fuel that buffel grass creates is far more than native plant communities, and after the fire buffel grass can regenerate more quickly than many native species.

So we now have a situation in which fuel loads can accumulate over much shorter times. This makes the risk of fire in invaded areas so high that bushfire might now be considered a perpetual threat.

Changing fire threat

In spinifex grasslands, traditional Aboriginal burning regimes have been used for millennia to renew the landscape and promote growth while effectively breaking up the landscape so old growth areas are protected and large fires are prevented. Current fire management within Tjoritja “combines traditional and scientific practices”.

However, these fire management regimes do not easily translate to river environments invaded by buffel grass. These environments have, to our knowledge, never been targeted for burning by Aboriginal peoples. Since the arrival of buffel grass, there is now an extremely high risk that control burns can spread and become out-of-control bushfires.

Even when control burns are successful, the rapid regrowth of buffel grass means firebreaks may only be effective for a short time before risky follow-up burning is required. And there may no longer be a good time of year to burn.




Read more:
How invasive weeds can make wildfires hotter and more frequent


Our research suggests that in areas invaded by buffel grass, slow cool winter burns – typical for control burning – can be just as, or more, damaging for trees than fires in hot, windy conditions that often cause fires to spread.

Without more effective management plans and strategies to manage the changing fire threat in central Australia, we face the prospect of a future Tjoritja in which no old-growth trees will remain. This will have a devastating impact on the unique desert mountain ranges.

We need to acknowledge that invasive buffel grass and a changing climate have changed the face of fire risk in central Australia. We need a coordinated response from Australia’s federal and state governments, or it will be too late to stop the ecological catastrophe unfolding before us.


The authors acknowledge the contribution of Shane Muldoon, Sarah White, Erin Westerhuis, CDU Environmental Science and Management students, and NT Parks and Wildlife staff to the research at experimental sites and ongoing tree monitoring in central Australia.The Conversation

Christine Schlesinger, Senior Lecturer in Environmental Science and Ecology, Charles Darwin University and Barry Judd, Professor, Indigenous Social Research, Charles Darwin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

To reduce fire risk and meet climate targets, over 300 scientists call for stronger land clearing laws



File 20190308 150700 3qu1wc.jpg?ixlib=rb 1.1
Without significant tree cover, dry and dusty landscapes can result.
Don Driscoll, Author provided

Martine Maron, The University of Queensland; Andrea Griffin, University of Newcastle; April Reside, The University of Queensland; Bill Laurance, James Cook University; Don Driscoll, Deakin University; Euan Ritchie, Deakin University, and Steve Turton, CQUniversity Australia

Australia’s high rates of forest loss and weakening land clearing laws are increasing bushfire risk, and undermining our ability to meet national targets aimed at curbing climate change.

This dire situation is why we are among the more than 300 scientists and practitioners who have signed a declaration calling for governments to restore, or better strengthen regulations to protect native vegetation.




Read more:
Land clearing on the rise as legal ‘thinning’ proves far from clear-cut


Land clearing laws have been contentious in several states for years. New South Wales relaxed its land clearing controls in 2017, triggering concerns over irreversible environmental damage. Although it is too early to know the impact of those changes, a recent analysis found that land clearing has increased sharply in some areas since the laws changed.

The Queensland Labor government’s 2018 strengthening of land clearing laws came after years of systematic weakening of these protections. Yet the issue has remained politically divisive. While discussing a federal inquiry into the impact of these policies on farmers, federal agriculture minister David Littleproud suggested that the strenthening of regulations may have worsened Queensland’s December bushfires.

We argue such an assertion is at odds with scientific evidence. And, while the conservation issues associated with widespread land clearing are generally well understood by the public, the consequences for farmers and fire risks are much less so.

Tree loss can increase fire risk

During December’s heatwave in northern Queensland, some regions were at “catastrophic” bushfire risk for the first time since ratings began. Even normally wet rainforests, such as at Eungella National Park inland from Mackay, sustained burns in some areas during “unprecedented” fire conditions.

There is no evidence to support the suggestion that 2018’s land clearing law changes contributed to the fires. No changes were made to how vegetation can be managed to reduce fire risk. This is governed under separate laws, which remained unaltered.

In fact, shortly after the fires, Queensland’s land clearing figures were released. They showed that in the three years to June 2018, an area equivalent to roughly 570,000 Melbourne Cricket Grounds (1,138,000 hectares) of bushland was cleared, including 284,000 hectares of remnant (old-growth) ecosystems.

Tree clearing can worsen fire risk in several ways. It can affect the regional climate. In parts of eastern Australia, tree cover reductions are estimated to have increased summer surface temperatures by up to 2℃ and southwest Western Australia by 0.4–0.8℃, reduced rainfall in southeast Australia, and made droughts hotter and longer.

Removing forest vegetation depletes soil moisture. Large, intact areas of forest typically have cooler, wetter microclimates buffered from extreme temperatures. Over time, some forest types can even become fire-resistant, but smaller patches of trees are typically drier and more flammable.

Trees also form a natural windbreak that can slow the spread of bushfires. An analysis of the 2005 Wangary fire in South Australia found that fires spread most rapidly through paddocks, rather than through areas lined with native trees.

Trends from 1978 to 2017 in the annual (July to June) sum of the daily Forest Fire Danger Index, an indicator of the severity of fire weather conditions. Positive trends, shown in the yellow to red colours, indicate increasing length and intensity of the fire weather season. Areas where there are sparse data coverage, such as central parts of Western Australia, are faded.
CSIRO/Bureau of Meteorology/State of the Climate 2018

Finally, Australia’s increasing risk of bushfire and worsening drought are driven by global climate change, to which land clearing is a major contributor.

Farmers on the frontline of environmental risk

Extensive tree clearing also leads to problems for farmers, including rising salinity, reduced water quality, and soil erosion. Governments and rural communities spend significant money and labour redressing the aftermath of excessive clearing.

Sensible regulation of native vegetation removal does not restrict existing agriculture, but rather seeks to support sustainable production. Retained trees can help deal with many environmental risks that hamper agricultural productivity, including animal health, long-term pasture productivity, risks to the water cycle, pest control, and human well-being.

Rampant tree clearing is undoing climate policy too. Much of the federal government’s A$2.55 billion Emissions Reduction Fund has gone towards tree planting. But it would take almost this entire sum just to replace the trees cleared in Queensland since 2012.




Read more:
Stopping land clearing and replanting trees could help keep Australia cool in a warmer future


In 2019, Australians might reasonably expect that our relatively wealthy and well-educated country has moved beyond a frontier-style reliance on continued deforestation, and we would do well to better acknowledge and learn lessons from Indigenous Australians with respect to their land management practices.

Yet the periodic weakening of land clearing laws in many parts of Australia has accelerated the problem. The negative impacts on industry, society and wildlife are numerous and well established. They should not be ignored.The Conversation

Martine Maron, ARC Future Fellow and Associate Professor of Environmental Management, The University of Queensland; Andrea Griffin, Senior Lecturer, School of Psychology, University of Newcastle; April Reside, Researcher, Centre for Biodiversity and Conservation Science, The University of Queensland; Bill Laurance, Distinguished Research Professor and Australian Laureate, James Cook University; Don Driscoll, Professor in Terrestrial Ecology, Deakin University; Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, and Steve Turton, Adjunct Professor of Environmental Geography, CQUniversity Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How a bushfire can destroy a home


Douglas Brown, Western Sydney University

Ten years after the devastation of Black Saturday, building design has largely been unrecognised as an area worthy of research. We have advanced our knowledge of the materials used in the construction of homes in bushfire-prone areas but we continue to use the design model of the suburban home.

This needs to change. An initial starting point is to consider the way previous bushfires have damaged and destroyed buildings.




Read more:
Where to take refuge in your home during a bushfire


Elements of a bushfire

A bushfire has five different elements: smoke, wind, embers, flames, and radiant heat (the latter two are collectively called the “fire front”).

Smoke and wind are usually present throughout a fire, but are particularly high when the fire burns at its most intense levels. Depending on the type of vegetation burning, isolated flying embers may arrive hours before a fire front. Intense ember attacks usually occur 15-30 minutes before a fire front arrives, and may persist for up to 8 hours after the fire front moves on.

Radiant heat at a level that makes it impossible to survive outside will persist during the passage of the fire front, which may last anywhere between 2 and 15 minutes. However, if consequential fires are ignited by the main fire front, the radiant heat may remain at non-survivable levels for much longer.

The smoke of a bushfire reduces visibility and can turn a bright day into night. A change in wind direction can renew a threat residents thought had already passed them.

How will a bushfire attack your home?

Most people would expect that the most destructive element of a bushfire is the fire front, but rather surprisingly that’s not the case. Ember entry and associated spot fires, rather than direct flame contact, accounts for 75-80% of homes destroyed by bushfires.

Embers can be large strips of burning bark, or a tiny spark as small as a pinhead, and depending on wind speed these can travel up to 10 kilometres ahead of the fire front.

Australian research over the past 75 years has revealed more than 20 different parts of a house and its surrounding area that are vulnerable to bushfire attack. Much of this knowledge has now been incorporated into a recently updated Australian Standard: Construction of buildings in bushfire-prone areas.

These guidelines aim to reduce the vulnerability of each part of a house, and thus make the structure as a whole more resistant to bushfire damage. The Standard applies across Australia for new homes and renovations.

The known building ignition points

The known weak parts of a building are referred to as the “building ignition points”. Several are considered below:

Roof cavity

In domestic homes the roof cavity is the large open space under the roof and above the ceiling. Embers in this space can cause fire to spread rapidly, making the whole building vulnerable to ceiling collapse.

Any gap in the roof, such as a poorly secured tile, can allow flying embers to enter. The burning crown of a nearby tree, pushed onto a roof by high-speed winds, can also ignite the house.

When people choose to shelter in their bathrooms they often forget the ceiling is particularly vulnerable there. It’s difficult to access a roof cavity with a fire hose, and extinguishing embers and fire invariably damages electrical wiring, plasterwork, and home contents.

Regular inspection and maintenance of roof elements can help reduce ember entry. Avoiding trees close to your house, and removing any overhanging branches, can also help reduce this bushfire risk.

Gutters

Overhanging trees can cause compacted leaf litter to build up in gutters. During a bushfire flying embers land in this material, catch alight and spread flames to combustible parts of the roof structure such as wooden facia boards, rafters, roof battens, and eaves.

It’s a good idea to clear out your gutters each year as part of seasonal bushfire preparation. Some people choose to wait until a bushfire is approaching to do this, but going onto your roof for the first time in semi-darknes while embers are flying at you can put you at risk, and endanger your life.

If you’re building a new structure you can consider extending the roof line and having a water collection system on the ground to remove the need for gutters.

Vents and weep holes

Together vents and weep holes allow for fresh air to pass through a building and for excess moisture to leave, reduce condensation and mould. They are necessary for our comfort and health, and maintaining the integrity of a building.

However in a bushfire these types of external openings can allow flying embers to enter the building and start spot fires. Having steel or other non-combustible mesh with small holes in front or behind vents and weep holes can reduce the bushfire risk while still allowing air and moisture to pass through.

Subfloors

Often houses constructed in bushfire-prone areas are built on a sloping block of land. The area under the building (the subfloor) is left open rather than being enclosed, and combustible materials are often stored there. The danger is similar in scale to embers in the roof cavity. When embers or flames take hold in this subfloor area they can spread under the entire building and allow the fire to move up.

Plants and mulched garden beds next to the home

Garden beds and timber steps near a house are a potential danger during a bushfire. Plants with dense foliage can burn intensely and cause radiant heat damage, cracking and imploding nearby windows and glass doors.

Garden beds which have been recently mulched can trap flying embers and spread fire to timber subfloors. It’s much better to have a non-combustible paved area next to your home, with pots containing either succulents or plants with thin foliage.




Read more:
How can we build houses that better withstand bushfires?


Deciding whether to stay and defend a home or leave early is a difficult and contentious choice. Hopefully, knowing more about some parts of your house which are most vulnerable to bushfire attack will make that decision easier.The Conversation

Douglas Brown, Casual Academic, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Summer forecast: scorching heat and heightened bushfire risk


Catherine Ganter, Australian Bureau of Meteorology

Large parts of Australia are facing a hotter and drier summer than average, according to the Bureau of Meteorology’s summer outlook.

Drier than average conditions are likely for much of northern Australia. Most of the country has at least an 80% chance of experiencing warmer than average day and night-time temperatures.

The threat of bushfire will remain high, with few signs of the sustained rain needed to reduce fire risk or make a significant dent in the ongoing drought.

Expect extreme heat

Large parts of Western Australia, most of Queensland and the Top End of the Northern Territory are expected to be drier than usual. Further south, the rest of the country shows no strong push towards a wetter or drier than average summer, which is a change for parts of the southeast compared to recent months.


Bureau of Meteorology

Queensland has already seen some extraordinary record-breaking heat in recent days, with summer yet to truly begin. With the summer outlook predicting warmer days and nights, combined with recent dry conditions and our long-term trend of increasing temperatures, some extreme highs are likely this summer.


Bureau of Meteorology

All of this means above-normal bushfire potential in eastern Australia, across New South Wales, Victoria and Queensland. The bushfire outlook, also released today, notes that rain in areas of eastern Australia during spring, while welcome, was not enough to recover from the long-term dry conditions. The current wet conditions across parts of coastal New South Wales will help, but it will not take long once hot and dry conditions return for vegetation to dry out.




Read more:
Sydney storms could be making the Queensland fires worse


What about El Niño?

The Bureau is currently at El Niño ALERT, which means a roughly 70% chance of El Niño developing this season.




Read more:
Australia moves to El Niño alert and the drought is likely to continue


However, not all the ducks are lined up. While ocean temperatures have already warmed to El Niño levels, to declare a proper “event” there must also be a corresponding response in the atmosphere to reinforce the ocean – this hasn’t happened yet.

That said, climate models expect this event to arrive in the coming months. The outlook has factored in that chance, and the conditions predicted are largely consistent with what we would expect during El Niño. In summer, this includes drier weather in parts of northern Australia, and warmer summer days.

Once an El Niño is in place, weather systems across southern Australia tend to be more mobile. This can mean shorter but more intense heatwaves in Victoria and southern South Australia. However, in New South Wales and Queensland, El Niño is associated with both longer and more intense heat waves.

The exact reason why the states are affected differently is complicated, but relates to the fast-moving cold fronts and troughs that sweep through Victoria and South Australia in the summertime, creating cool changes. These weather systems don’t influence areas further north so when hot air arrives, it takes longer to clear.




Read more:
Drought, wind and heat: when fire seasons start earlier and last longer


The heavy rains seen in parts of eastern Australia in October and November have provided some welcome short-term relief to drought-stricken farmers, but longer-term rainfall relief has not arrived yet. If El Niño arrives, this widespread relief may only be on the cards in autumn.The Conversation

Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Australia: NSW – Solid Fuel Fires Banned Until Further Notice


The link below is to a media release concerning the banning of solid fuel fires in State Forests throughout NSW due to bushfire concerns.

For more visit:
http://www.forestrycorporation.com.au/about/releases/solid-fuel-fires-banned-in-state-forests

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Firestorms: the bushfire/thunderstorm hybrids we urgently need to understand


Jason Sharples, UNSW Australia

The journal Climatic Change has published a special edition of review papers discussing major natural hazards in Australia. This article is one of a series looking at those threats in detail.


Fire has been a driving force across Australia for millennia. Indeed, the health of many of our ecosystems is intrinsically dependent on fire. But bushfires are also one of our most frequent natural hazards, with a total cost estimated at A$340 million per year.

In the past decade or so, extreme bushfires in southeastern Australia have burned more than a million hectares, claiming more than 200 lives and over 4,000 homes. Similar losses in other major urban areas have prompted questions about whether we are seeing a shift towards a significantly more hazardous fire regime, characterised by increasing fire frequency and intensity, and the development of catastrophic “firestorms”.

While these extreme bushfires account for only a very small percentage of fire events, they are responsible for the lion’s share of bushfire-related losses.

In contrast to typical bushfires, which spread across the landscape as well-defined burning fronts with smoke plumes perhaps a few kilometres high, extreme bushfires exhibit deep and widespread flaming and produce smoke plumes that can extend 10-15km into the atmosphere.

At these altitudes, bushfire plumes can actually develop into thunderstorms (hence the term “firestorm”). As such, extreme bushfires become much more difficult for emergency services to handle, making them all but impossible to suppress and their spread difficult to predict.

A firestorm blots out the sky in Victoria’s Grampians.
Randall Bacon, Author provided

Beyond hot, dry and windy

Like other dangerous bushfires, firestorms are driven by hot, dry and windy weather. But to spawn a firestorm, a range of other conditions must also be met; these can include a rugged landscape, particularly nasty weather events that produce “spikes” in fire danger, and conditions in the upper atmosphere that allow fire plumes to grow to considerable heights.

While previous studies have considered past and projected changes in the hot, dry and windy aspect of fire danger, less research has been done on the future projections for these other types of conditions. This means that we have quite a poor understanding of how extreme bushfires might affect us in the future.

As part of a series of reviews produced by the Australian Energy and Water Exchange initiative, my colleagues and I have taken a closer look at the most catastrophic bushfire cases and the factors that drive them, beyond the usual hot, dry and gusty weather.

There has been an overall increase in the frequency of major bushfire events in southeastern Australia since the mid-19th century. In particular, in the past 15 years a major fire event has occurred every 5 years or less. While some of this increase is due to changes in land use since European colonisation, there is also strong evidence of climate-driven changes.

We found that besides increases in dangerous surface fire danger conditions, upper atmospheric conditions have also become more conducive to explosive fire growth. High levels of the c-Haines index, which signals greater potential for a fire’s plume to rise high into the atmosphere, have become considerably more prevalent since the 1980s. The effects of droughts and widespread heatwaves have also contributed to the occurrence of extreme bushfires.

Looking into the future, high c-Haines values are projected to grow more prevalent still, albeit more gradually than over recent decades. Frontal weather patterns associated with particularly bad fire days are also projected to become more frequent during this century, and rainfall is projected to decrease over southwest and southeastern Australia.

All of this suggests that extreme bushfires will become a more common occurrence into the future.

What we still don’t know

Our methods for assessing fire danger do not explicitly account for the effects of extended drought and heatwaves on larger fuel elements such as branches and logs, and so may not properly account for their effects on fire spread and heat release into the atmosphere.

There is also considerable uncertainty about how fuel loads will change into the future. It is possible that the higher fire intensities expected to result from the direct effects of a warmer, drier climate may be offset by lower fuel loads.

Our understanding of extreme fire occurrence is also hampered by the lack of long-term and prehistoric climate data, which makes it hard to work out what the “normal” level of extreme bushfires has been in the past. While charcoal records show promise in this regard, we still don’t know enough about how charcoal is generated, deposited and subsequently preserved during extreme fires.

To predict the future occurrence of extreme bushfires, we also have more work to do in understanding how the trends forecast by global climate models will play out in terms of creating regional-scale fire weather conditions. And we still need to figure out the likely effects of other large-scale patterns such as El Niño.

Given the relatively recent advances that have been made in understanding the key drivers of extreme bushfires, the field is now ready for targeted studies that will help us estimate the future risk of extreme bushfires – and how best we can confront the threat.


_This article was amended on November 11, 2016, to correct the figure for the cost of bushfire-related damage. The correct figure is A$340 million, not A$8.5 billion which is the annual cost of all fire-related damage in Australia.

The Conversation

Jason Sharples, Associate Professor, School of Physical, Environmental and Mathematical Sciences, UNSW Australia, UNSW Australia

This article was originally published on The Conversation. Read the original article.