The burn legacy: why the science on hazard reduction is contested


Kevin Tolhurst, University of Melbourne

When it comes to reducing the extent of bushfires, scientists disagree on the best way to do it. Hazard-reduction burning (also known as “prescribed burning” or “controlled burning”) is controversial and, depending on the scientific paper, it’s shown to either be effective or not work at all.

Hazard-reduction burning is the process of removing vegetation that would fuel a fire – the “hazard” – through burning, slashing or grazing. It’s one of the ways state governments try to prepare for looming bushfire seasons.




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The Climate Council published a fact sheet in January this year titled “Setting the record straight on hazard reduction”. It concluded that, while important, in future “no amount of hazard reduction will protect human lives, animals and properties from catastrophic fires”.

But this is at odds with empirical studies in Victoria and Western Australia, which found otherwise, after taking a wider view on the issue.

So why are there conflicting views?

Hazard-reduction burns don’t help: a 2015 study

For its report, the Climate Council relied heavily on a 2015 study based on fire and weather records from southeastern Australia over a period of 34 years. This is a relatively short time when it comes to ecosystem cycles – the earth’s natural recycling process of resources like water and carbon.

The researchers of this study used a metric called “leverage” to evaluate the effect of hazard-reduction burning on reducing the extent of wildfires. “Leverage” in this context refers to the ratio between the area burnt by wildfires and the area burnt by prescribed burning.

And they concluded hazard-reduction burning has a statistically significant effect on the extent of wildfires, but only in forested areas with distinct annual drought periods.




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A surprising answer to a hot question: controlled burns often fail to slow a bushfire


The leverage measure implies that prescribed burning only increases the total area burnt, and is therefore ineffective in reducing fire extent.

Like all scientific papers, the conclusions of the 2015 paper are drawn from several assumptions. And while the conclusions are valid for the researchers’ focus, several assumptions don’t work in a land management context. For instance, it’s assumed only the extent of the area burnt is important, rather than the severity.

But the recovery of the plants, animals, nutrients and habitat after low-intensity fire is much quicker than after high-intensity wildfire, according to a long-term Victorian study.

Several other assumptions were also made in the 2015 study, and it is such assumptions that lead to conflicting conclusions with others. While this study is valid within the context in which it was undertaken and includes useful analysis, the conclusions the Climate Council draws from it aren’t supported.

Hazard-reduction burns do help: a 2009 study

A 2009 study looking at 52 years of fire history in southwest Western Australia identified the benefits of hazard-reduction burns. This includes it leading to fewer fires starting and a greater ability to suppress fires in prescribed burnt areas.

A big reason for the different findings is because, unlike the 2009 study, the 2015 study didn’t explicitly consider how past prescribed burns lower the severity of new high-intensity fires when they move in. This helps fire suppression efforts and helps reduce the spread of wildfires.

The 2009 study showed prescribed burning less than about 4% of a million hectares of forested landscape per year wasn’t enough to show trends in reducing wildfires.




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There’s only one way to make bushfires less powerful: take out the stuff that burns


But in the 2015 study the Climate Council used, only included 2% of prescribed burning in the forested landscape of southeast Australia, so a conclusion that prescribed burning was ineffective could have been expected.

In other words, not enough of the landscape was prescribed burnt to have a measureable effect, so it cannot be concluded that prescribed burning is ineffective at reducing the impact of bushfires from this analysis.

The Climate Council should have taken a broader view of the available scientific studies before drawing its conclusions.

So should we use hazard-reduction burns?

There are many dimensions to the debate about whether to use hazard-reduction burns to mitigate and prepare for wildfires. And not all scientific studies will be equally relevant in addressing particular issues.




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To fight the catastrophic fires of the future, we need to look beyond prescribed burning


So before we decide whether hazard-reduction burning for land management is a good thing, we need to consider all of the variables. This includes increased ecosystem resilience, mitigation of wildfire number and extent, impact on human health, economic value, social impact, Traditional Owner culture, and more.

The Climate Council’s conclusions are drawn only from the consideration of reduced wildfire extent.

In debating the value or otherwise of prescribed burning, we need to use good scientific evidence, but our decisions must be based on the whole picture, not just a selective part of it.The Conversation

Kevin Tolhurst, Hon. Assoc. Prof., Fire Ecology and Management, University of Melbourne

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

I made bushfire maps from satellite data, and found a glaring gap in Australia’s preparedness



Image courtesy of Greg Harvie, Author provided

Wallace Boone Law, University of Adelaide

On the night of January 9 2020, my wife and I secured our Kangaroo Island home and anxiously monitored the South Australian Country Fire Service (CFS) website for bushfire advice.

After many horrific weeks of bushfires, the winds had again shifted, and the fire front began a slow, nightmarish march eastward into the island’s central farmlands. Official warnings advised that the entire island was potentially under threat.

Landsat-8 false colour image of southwest Kangaroo Island, showing active bushfires on January 9, 2020.
Landsat-8, Author provided

As my good neighbours and volunteer firefighters headed off to battle the flames elsewhere on the island, I desperately wanted to find a way to help. With no firefighting training, I felt I physically had little to offer. But I reasoned that my skills and training in remote sensing and spatial science could potentially turn satellite information into useful maps to track the fires, in more detail than those provided by the Country Fire Service and Geoscience Australia.




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While I was ultimately successful, it wasn’t quite as straightforward as I thought. And what I learned about access to good-quality and up-to-date satellite bushfire information surprised me.

Free satellite imagery is abundant; useful information is not

In principle, there are many good sources of free satellite imagery. But selecting, sourcing, understanding and processing a multilayered satellite image into an accurate burnt area map takes technical know-how that is beyond the reach of the people who need it the most.

We are fortunate to live in a time where satellite images are constantly uploaded to the web, often within hours of acquisition. There are many reputable sources for this information, including NASA Worldview, USGS Earth Explorer, USGS LandLook Viewer, and the Sentinel EO Browser.

These websites are gateways to the world of “big satellite data”, and I quickly found myself on a steep learning curve to efficiently navigate them and find recent imagery.

Once downloaded, the next hurdle I faced was how to process a data-rich satellite image into a meaningful and accurate map of the bushfire area. I scoured the internet for “how to” blogs, academic articles, spatial algorithms, and processing codes; these too are the products of much intellectual investment by global scientists, openly and freely available.

As a spatial scientist, I naturally found all this fascinating. But as a resident of an island under assault from bushfires, I also found it frustratingly time-consuming. I crashed my computer testing algorithms. I maxed out my hard drive. I spent hours on possibilities that turned out to be dead ends.

True colour satellite imagery is often the most accessible and easily understood, but it often lacks sufficient detail to clearly identify burnt areas. In this Sentinel-2 true colour image, approximately 210,000 hectares are burnt, but bushfire-impacted areas are barely visible without advanced image processing.
Sentinel-2, Author provided

Maps help to fight fires and recover from them

In the end, I produced burnt area maps from Sentinel and Landsat satellite images captured during the fires. I learned that this kind of information can indeed help firefighting and ecological recovery efforts, both during and after bushfires.

Initially I gave the maps to a group of farming friends who had been fighting fires around their properties for weeks. They told me the maps helped save time in assessing which areas had already burned, allowing them to focus on defending unburnt areas, and to make decisions on where to move livestock and install firebreaks.

The positive feedback inspired me to customise my processing techniques, so I could provide updates more quickly when new satellite images became available.

I embedded appropriate safety disclaimers into the maps and released them on Twitter and Spatial Points, a blog site managed by my research group at the University of Adelaide.

Within hours, I received messages that the maps were being used for ecological recovery efforts. The maps successfully highlighted remaining patches of habitat where endangered and vulnerable species had found refuge. Several government agencies even contacted me for burnt area information, which I’m told was used to assess infrastructure damage and habitat loss.

Processed Sentinel-2 satellite image. Red areas suggest burnt vegetation. Variation in red hues are caused by dominant vegetation type and soils.
Sentinel-2/W. Boone Law, Author provided

National knowledge gap

My experience shows there is a swag of free and regularly updated satellite imagery available, which when interpreted and presented appropriately can potentially be hugely helpful to firefighting and recovery efforts.

However, I am concerned that neither the general public nor decision-makers seem fully aware of the range of satellite information on offer. Nor is there a good understanding of the advanced technical skills needed to access and process imagery into useful map data.




Read more:
Yes, the Australian bush is recovering from bushfires – but it may never be the same


This leads me to wonder whether I have stumbled upon a glaring knowledge gap in Australia’s bushfire preparedness.

How can we overcome this technological and information bottleneck? I don’t propose to have all the answers, but I do believe it would be sensible for governments, industry and research agencies to invest in the kind of capabilities that I developed while trying to protect my own local community.

As Australia faces a future of more frequent and extreme bushfires, there will doubtless be many people who would be glad of this kind of information when they need it most.The Conversation

Wallace Boone Law, PhD Candidate, University of Adelaide

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

Yes, the Australian bush is recovering from bushfires – but it may never be the same


Grant Williamson, University of Tasmania; Gabi Mocatta, University of Tasmania; Rebecca Harris, University of Tasmania, and Tomas Remenyi, University of Tasmania

As bushfires in New South Wales are finally contained, attention is turning to nature’s recovery. Green shoots are sprouting and animals are returning. But we must accept that in some cases, the bush may never return to its former state.

We’ve all read the devastating figures of destruction this fire season. More than 11 million hectares of land burned across the country over a period of about six months. There is some evidence more than one billion animals perished.

We can take some heart in the regenerative power of the Australian bush.
However, when we read of “recovery” in the media, we feel we must clarify what that might actually look like.

While Australia’s environment has evolved to adapt to fire, our research shows we can no longer assume it will recover completely.




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A fiery future

We are scientists and social science researchers who work in transdisciplinary climate change projects, liaising with park rangers, farmers, policymakers, emergency services and local government.

Our work involves scoping future challenges in land management and developing a range of plausible future climate scenarios for south-east Australia.

Our experience told us something like this catastrophic climatic event was possible, but as researchers we weren’t prepared to see such an inferno this summer.

Although fires are natural in Australia, they’re now occurring at an unprecedented frequency and intensity in areas that, historically, did not burn. This new regime does not allow the effective recovery of natural systems to their pre-fire state.

Alpine ash to ashes

Fires in alpine ash forests (Eucalyptus delegatensis) are a good example of this.

Along with some eucalyptus trees, Australian flowering grass trees (Xanthorrhoea) are pyrophytic plants – which means they are adapted to survive in fire-prone habitats.
Natalie Maguire / Flickr, CC BY-SA

Unlike many eucalypt species which can re-sprout after fire, this species’ only means of recovery is through germination via a seed bank in the canopy, and rapid germination and growth of seedlings after fire.

Multiple fires in quick succession kill seedlings before they reach maturity, disrupting the tree’s reproductive cycle and leading to local extinction of the species in the landscape.

Alpine ash forests have endured repeated fires in recent years. In 2013, a blaze in Victoria burnt more than 31,000 hectares of the Alpine National Park.




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Vast areas have been burnt again in this season’s fires in the same places. Research reveals climate change is increasing the frequency and intensity of fires in the Australian Alps.

This ecosystem will not recover. It will instead transition into a new, different ecosystem, and many species which evolved to live in the original habitat, such as the alpine ash, will no longer be supported. They will be replaced by other vegetation types, such as other eucalyptus woodland, shrubland or grassland.

No more refuge

To further illustrate this point, take the Tasmanian pencil pine Athrotaxis cupressoides.

This slow-growing conifer native to Tasmania can live for up to 1,000 years. They are found in Tasmania’s highlands and sub-alpine regions – historically a Tolkien-esque landscape of moss and emerald green cushion plants, studded with thousands of tiny mountain lakes, called tarns.

But large fires across Tasmania’s pencil pine habitat in recent years, including those in 2016, reduced hundreds of isolated pencil pine communities to blackened skeletons. The stands of trees that remain are struggling to survive in a drying and warming climate.

Pencil pines, widely found in Tasmania, are not fire-adapted and are killed by bushfires.
David Bowman

All this is occurring in areas that historically did not experience fire, which allowed a suite of ancient, fire-sensitive species to persist.

As climate change worsens, the pencil pine will be restricted to even smaller areas. Higher temperatures and increased fuel loads increase the likelihood of destruction by fire. Areas where pencil pines have historically been protected will diminish in number and size.

Irreplaceable loss

In these cases and many others, animal species relying on these trees and their ecosystems are profoundly affected.

Well before the latest fires, Australia had an abysmal record on vertebrate extinctions. This summer’s fires have brought some animal species, including the Kangaroo Island dunnart, closer to extinction.




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Future fire seasons will not be normal events, or even some kind of stable “new normal”, to which humans and nature will readily adapt. We’re seeing a trajectory of change in which our climate will shift faster than most living things can tolerate.

The Australian environment evolved with fire and in past conditions, could recover from fire. However climate change has altered the rules irrevocably.

We can no longer rest assured that nature will bounce back, and that knowledge should be a wake-up call for the world.The Conversation

Grant Williamson, Research Fellow in Environmental Science, University of Tasmania; Gabi Mocatta, Research Fellow in Climate Change Communication, University of Tasmania; Rebecca Harris, Climate Research Fellow, University of Tasmania, and Tomas Remenyi, Climate Research Fellow, Climate Futures Programme, University of Tasmania

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

Here are 5 practical ways trees can help us survive climate change



Shutterstock

Gregory Moore, University of Melbourne

As the brutal reality of climate change dawned this summer, you may have asked yourself a hard question: am I well-prepared to live in a warmer world?

There are many ways we can ready ourselves for climate change. I’m an urban forestry scientist, and since the 1980s I’ve been preparing students to work with trees as the planet warms.

In Australia, trees and urban ecosystems must be at the heart of our climate change response.

Governments have a big role to play – but here are five actions everyday Australians can take as well.




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Go native: why we need ‘wildlife allotments’ to bring species back to the ‘burbs


1. Plant trees to cool your home

At the current rate of warming, the number of days above 40℃ in cities including Melbourne and Brisbane, will double by 2050 – even if we manage to limit future temperature rises to 2℃.

Trees can help cool your home. Two medium-sized trees (8-10m tall) to the north or northwest of a house can lower the temperature inside by several degrees, saving you hundreds of dollars in power costs each year.

Trees can cool your home by several degrees.
Shutterstock

Green roofs and walls can reduce urban temperatures, but are costly to install and maintain. Climbing plants, such as vines on a pergola, can provide great shade, too.

Trees also suck up carbon dioxide and extend the life of the paint on your external walls.

2. Keep your street trees alive

Climate change poses a real threat to many street trees. But it’s in everyone’s interests to keep trees on your nature strip alive.

Adequate tree canopy cover is the least costly, most sustainable way of cooling our cities. Trees cool the surrounding air when their leaves transpire and the water evaporates. Shade from trees can also triple the lifespan of bitumen, which can save governments millions each year in road resurfacing.

Tree roots also soak up water after storms, which will become more extreme in a warming climate. In fact, estimates suggest trees can hold up to 40% of the rainwater that hits them.

But tree canopy cover is declining in Australia. In Melbourne, for instance, it falls by 1-1.5% annually, mainly due to tree removals on private land.

Governments are removing trees from public and private land at the time we need them most.
Shutterstock

This shows state laws fail to recognise the value of trees, and we’re losing them when we need them most.

Infrastructure works such as level crossing removals have removed trees in places such as the Gandolfo Gardens in Melbourne’s inner north, despite community and political opposition. Some of these trees were more than a century old.

So what can you do to help? Ask your local council if they keep a register of important trees of your suburb, and whether those trees are protected by local planning schemes. Depending on the council, you can even nominate a tree for protection and significant status.

But once a development has been approved, it’s usually too late to save even special trees.

3. Green our rural areas

Outside cities, we must preserve remnant vegetation and revegetate less productive agricultural land. This will provide shade and moderate increasingly strong winds, caused by climate change.

Planting along creeks can lower water temperatures, which keeps sensitive native fish healthy and reduces riverbank erosion.

Strategically planting windbreaks and preserving roadside vegetation are good ways to improve rural canopy cover. This can also increase farm production, reduce stock losses and prevent erosion.

To help, work with groups like Landcare and Greening Australia to vegetate roadsides and river banks.

4. Make plants part of your bushfire plan

Climate change is bringing earlier fire seasons and more intense, frequent fires. Fires will occur where they hadn’t in the past, such as suburban areas. We saw this in the Melbourne suburbs of Bundoora, Mill Park, Plenty and Greensborough in December last year.

It’s important to have a fire-smart garden. It might seem counter-intuitive to plant trees around the house to fortify your fire defences, but some plants actually help reduce the spread of fire – through their less flammable leaves and summer green foliage – and screen your house from embers.




Read more:
Low flammability plants could help our homes survive bushfires


Depending on where you live, suitable trees to plant include crepe myrtle, the hybrid flame tree, Persian ironwood, some fruit trees and even some native eucalypts.

Gardens play a role in mitigating fire risk to your home.
Shutterstock

If you’re in a bushfire-prone area, landscape your garden by strategically planting trees, making sure their canopies don’t overhang the house. Also ensure shrubs do not grow under trees, as they might feed fire up into the canopy.

And in bad fire conditions, rake your garden to put distance between fuel and your home.




Read more:
Keeping the city cool isn’t just about tree cover – it calls for a commons-based climate response


5. What if my trees fall during storms?

The fear of a whole tree falling over during storms, or shedding large limbs, is understandable. Human injury or death from trees is extremely rare, but tragedies do occur.

Make sure your trees are healthy, and their root systems are not disturbed when utility services such as plumbing, gas supplies and communication cables are installed.

Coping with a warming world

Urban trees are not just ornaments, but vital infrastructure. They make cities liveable and sustainable and they allow citizens to live healthier and longer lives.

For centuries these silent witnesses to urban development have been helping our environment. Urban ecosystems depend on a healthy urban forest for their survival, and so do we.The Conversation

Gregory Moore, Doctor of Botany, University of Melbourne

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

These plants and animals are now flourishing as life creeps back after bushfires


Flickr

Kathryn Teare Ada Lambert, University of New England

As the east coast bushfire crisis finally abates, it’s easy to see nothing but loss: more than 11 million hectares of charcoal and ash, and more than a billion dead animals.

But it is heartening to remember that bushfire can be a boon to some plants and animals. We’re already seeing fresh green shoots as plants and trees resprout. Beetles and other insects are making short work of animal carcasses; they will soon be followed by the birds which feed on them.

Australia’s worsening fire regimes are challenging even these tolerant species. But let’s take a look at exactly how life is returning to our forests now, and what to expect in coming months.

Life is returning to fire-ravaged landscapes.
Flickr, CC BY

The science of resprouting

Of course, bushfires kill innumerous trees – but many do survive. Most of us are familiar with the image of bright green sprouts shooting from the trunks and branches of trees such as eucalypts. But how do they revive so quickly?

The secret is a protected “bud bank” which lies behind thick bark, protected from the flames. These “epicormic” buds produce leaves, which enables the tree to photosynthesise – create sugar from the sun so the tree can survive.

Under normal conditions, hormones from shoots higher in the tree suppress these buds. But when the tree loses canopy leaves due to fire, drought or insect attack, the hormone levels drop, allowing the buds to sprout.

Insect influx

This summer’s fires left in their wake a mass of decaying animal carcasses, logs and tree trunks. While such a loss can be devastating for many species – particularly those that were already vulnerable – many insects thrive in these conditions.

For example, flies lay eggs in the animal carcasses; when the maggots hatch, the rotting flesh provides an ample food source. This process helps break down the animal’s body – reducing bacteria, disease and bad smells. Flies are important decomposers and their increased numbers also provide food for birds, reptiles and other species.




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Similarly, beetles such as the grey furrowed rosechafer, whose grubs feed on decaying logs and tree trunks, add nutrients to the soil when they defecate which helps plants grow again.

Insects also benefit from the mass of new leaves on trunks and branches. For example, native psyllids – an insect similar to aphids – feed on the sap from leaves and so thrive on the fresh growth.

Animal carcasses are a sad consequence of bushfire, but provide a boon to some insect species.
Sean Davey/AAP

Then come the birds

Once insects start to move back into an area from forested areas nearby, the birds that eat them will follow.

An increase in psyllids encourages honeyeaters – such as bell miners and noisy miners – to return. These birds are considered pests.

A CSIRO study after bushfires in Victoria’s East Gippsland in 1983 found several native bird species – flame and scarlet robins, the buff-rumped thornbill and superb fairy-wren – increased quickly to levels greater than before fire. As shrubs in the understorey regrow, other species will move in, slowly increasing biodiversity.




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Since the recent bushfire in woodland near Moonbi in New South Wales, numerous bird species have returned. On a visit over this past weekend, I observed currawongs landing in the canopy, saw fairy wrens darting in and out of foliage sprouting from the ground, and heard peep wrens in tufts of foliage on bark and high branches.

Honeyeaters moved between burnt and intact trees on the edge of the blackened forest and butterflies visited new plants flowering after recent rain.

The presence of the currawong, while a pest species, shows birdlife is returning to the bush.
Flickr, CC BY

Weeds can help

Weeds usually benefit when fire opens up the tree canopy and lets in light. While this has a downside – preventing native plants from regenerating – weeds can also provide cover for native animal species.

A study I co-authored in 2018 found highly invasive Lantana camara provided habitat for small mammals such as the brown rat in some forests. Mammal numbers in areas where lantana was present were greater than where it was absent.

Lantana often grows quickly after fire due to the increase in light and its ability to suppress other plant growth.

Lantana provides cover for animal species.
Flickr, CC BY

Is there hope for threatened species?

Generalist species – those that thrive in a variety of environments – can adapt to burnt forest. But specialist species need particular features of an ecosystem to survive, and are far less resilient.

The critically endangered Leadbeater’s possum lives only in small pockets of forest in Victoria.

It requires large fires to create a specific habitat: big dead trees provide hollows for shelter and nesting, and insects feeding on burnt wood and carcasses provide a food source.

But for the Leadbeater’s possum to benefit from the fire regime, bushfires should be infrequent – perhaps every 75 years – allowing time for the forest to grow back. If fires are too frequent, larger trees will not have time to establish and hollows will not be created, causing the species’ numbers to decline.

Similarly in NSW, at least 50% and up to 80% of the habitat of threatened species such as the vulnerable rufous scrub-bird was burnt in the recent fires, an environmental department analysis found.

Looking ahead

Only time will tell whether biodiversity in these areas is forever damaged, or will return to its former state.

Large fires may benefit some native species but they also provide food and shelter for predatory species, such as feral cats and foxes. The newly open forest leaves many native mammals exposed, changing the foodweb, or feeding relationships, in an ecosystem.

This means we may see a change in the types of birds, reptiles and mammals found in forests after the fires. And if these areas don’t eventually return to their pre-fire state, these environments may be changed forever – and extinctions will be imminent.




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Fire almost wiped out rare species in the Australian Alps. Feral horses are finishing the job


The Conversation


Kathryn Teare Ada Lambert, Adjunct Lecturer/ Ecologist, University of New England

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