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Bad fire science can kill our threatened species. It's time to cooperate with nature

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Wednesday, December 14, 2022

ShutterstockFor four years, naturalist Allison Dixon regularly walked from dusk until dawn at the Warrungup Spring bush reserve south of Perth, carefully documenting every western ringtail possum she saw. The possum – or ngwayir in the language of Traditional Owners – is critically endangered. The species is found only in a small area of southwest Australia, including the population of 22 individuals Dixon was monitoring. She knew each possum by name. Their voices and physical features were as familiar to her as human faces. In 2018, a prescribed burn by local authorities was conducted in the Warrungup Spring reserve. Despite burning slowly as planned, it killed 17 of the 22 possums Dixon was monitoring. I document this incident in a new paper and explore how a carefully controlled fuel reduction burn could cause such catastrophic loss. We must move on from bad fire science to prevent similar tragedies. Allison Dixon carefully monitored a population of western ringtail possums. Facebook The fire-intensity equation Prescribed burning occurs when authorities intentionally set fire to a particular area of the landscape under defined conditions. The burns are often used to reduce so-called “fuel loads” – fine biomass such as twigs, leaf litter and bark. As the idea goes, the greater the weight of the fuel load, the more flammable the forest. This theory can be traced back to American fire researcher George Marsden Byram. In 1959, Byram published an equation beautiful in its simplicity: a fire’s heat output (or intensity) was equal to the amount of energy stored in the fuel, multiplied by the amount of fuel, and multiplied again by the speed the fire spreads and consumes it. This theory would shape a central tenet of Australian fire management: that prescribed burns are necessary to reduce fuel loads, to make subsequent bushfires less intense. Prescribed burns are central to Australian fire management. Greg Barnette/The Record Searchlight The influence of Byram’s fire-intensity theory can be seen in an official fire management guide used to inform the burning of ngwayir habitat. The document suggests the animals can survive low-intensity fire – and on the day of the burn that killed 17 ngwayir, weather conditions were conducive to such a fire. But after years of work in fire management, I’ve come to see Byram’s theory – and the management practices flowing from it – as simplistic. In 2016, my colleagues and I published a new way of modelling fire behaviour. In my latest paper, I applied this model to the Warrungup Spring fire. Read more: New modelling on bushfires shows how they really burn through an area The prescribed burn at Warrungup Spring involved igniting patches of balga grasstrees and their surrounds. I investigated what happened to the air around a hollow in a tree where ngwayir were known to live. A balga grasstree burned during the fire was located under the hollow. According to Byram’s theory, the fire would have been classed as low-intensity because it did not spread horizontally. But this thinking does not account for the vertical spread of heat and flames. As depicted in the image below, the supposedly low-intensity fire would have heated the air above it to more than 500℃. This would burn the respiratory tracts of possums inside the hollow in just a few minutes. Byram’s fire-intensity equation might be valuable as a theoretical construct. But using it to inform real-world fire management can be catastrophic. A ngwayir and its hollow located above a balga grasstree set on fire in the prescribed burn. The graph shows the heat penetration into the hollow in increments through the wood, with the hollow temperature in red and the lethal temperature marked by the horizontal line. A. Dixon; P. Zylstra As my latest paper describes, Allison Dixon searched for the western ringtail possums the evening after the fire, and each subsequent evening for two weeks. In some cases, Dixon found the bodies. In others, the presence of flies in high nest hollows indicated the ngwayir inside had perished. Dixon visited surrounding properties and structures in case the possums had fled the fire ground, but no survivors were identified. She also continued weekly monitoring of their habitat. In the end, 17 of the 22 critically endangered possums were presumed dead. A burnt western ringtail possum recorded by Allison Dixon after the prescribed burn in 2018. Source: Allison Dixon But the problem runs even deeper Most fuel load lies in the litter layer on the ground. But we’ve known for decades that burning it away germinates dense understorey regrowth. In fact, WA government records show bushfires are most likely where prescribed burns have occurred, where that regrowth is most dense. In November this year, a prescribed burn was conducted in the Walpole Wilderness, in dense regrowth stimulated by a previous prescribed burn. The fire was reportedly meant to protect quokka habitat. But it escaped containment lines and burnt 25,000 hectares – 10,000 more than originally planned, and at a higher-than-intended severity. A prescribed burn that escaped in the Walpole Wilderness this year. Author provided One peer-reviewed study appears to show less fire in areas where prescribed burning has been undertaken. But research by my colleagues and I has challenged this study. The authors of the study in question compared the amount of wildfire in each six-year period with the amount of prescribed fire in the same period. But this method meant that for some of that period, reduced fire frequency was attributed to prescribed burns that had not yet occurred. Cooperating with nature Australia has the world’s worst record for mammal extinction – and we know fire is one of the main culprits. Yet prescribed burning relies on outdated or even disproved theories and assumptions about fire. Bad fire science is killing our threatened species, but alternatives are available. These approaches reinforce, rather than disrupt, natural ecological controls on forest fire. They include traditional Indigenous fire knowledge, and modern techniques to minimise the extent of dense regrowth in the landscape. By cooperating with nature to minimise fire risk, we can protect species that have persisted through aeons. Read more: Coming of age: research shows old forests are 3 times less flammable than those just burned Philip Zylstra received funding for this study from the NSW Environmental Trust, Curtin University and the San Diego Zoo Wildlife Alliance.

A new paper explores how a carefully controlled fuel reduction burn killed 17 critically endangered western ringtail possums.

Shutterstock

For four years, naturalist Allison Dixon regularly walked from dusk until dawn at the Warrungup Spring bush reserve south of Perth, carefully documenting every western ringtail possum she saw.

The possum – or ngwayir in the language of Traditional Owners – is critically endangered. The species is found only in a small area of southwest Australia, including the population of 22 individuals Dixon was monitoring.

She knew each possum by name. Their voices and physical features were as familiar to her as human faces.

In 2018, a prescribed burn by local authorities was conducted in the Warrungup Spring reserve. Despite burning slowly as planned, it killed 17 of the 22 possums Dixon was monitoring.

I document this incident in a new paper and explore how a carefully controlled fuel reduction burn could cause such catastrophic loss. We must move on from bad fire science to prevent similar tragedies.

woman in hat leans against tree
Allison Dixon carefully monitored a population of western ringtail possums. Facebook

The fire-intensity equation

Prescribed burning occurs when authorities intentionally set fire to a particular area of the landscape under defined conditions. The burns are often used to reduce so-called “fuel loads” – fine biomass such as twigs, leaf litter and bark.

As the idea goes, the greater the weight of the fuel load, the more flammable the forest. This theory can be traced back to American fire researcher George Marsden Byram.

In 1959, Byram published an equation beautiful in its simplicity: a fire’s heat output (or intensity) was equal to the amount of energy stored in the fuel, multiplied by the amount of fuel, and multiplied again by the speed the fire spreads and consumes it.

This theory would shape a central tenet of Australian fire management: that prescribed burns are necessary to reduce fuel loads, to make subsequent bushfires less intense.

here
Prescribed burns are central to Australian fire management. Greg Barnette/The Record Searchlight

The influence of Byram’s fire-intensity theory can be seen in an official fire management guide used to inform the burning of ngwayir habitat. The document suggests the animals can survive low-intensity fire – and on the day of the burn that killed 17 ngwayir, weather conditions were conducive to such a fire.

But after years of work in fire management, I’ve come to see Byram’s theory – and the management practices flowing from it – as simplistic. In 2016, my colleagues and I published a new way of modelling fire behaviour. In my latest paper, I applied this model to the Warrungup Spring fire.


Read more: New modelling on bushfires shows how they really burn through an area


The prescribed burn at Warrungup Spring involved igniting patches of balga grasstrees and their surrounds. I investigated what happened to the air around a hollow in a tree where ngwayir were known to live. A balga grasstree burned during the fire was located under the hollow.

According to Byram’s theory, the fire would have been classed as low-intensity because it did not spread horizontally. But this thinking does not account for the vertical spread of heat and flames.

As depicted in the image below, the supposedly low-intensity fire would have heated the air above it to more than 500℃. This would burn the respiratory tracts of possums inside the hollow in just a few minutes.

Byram’s fire-intensity equation might be valuable as a theoretical construct. But using it to inform real-world fire management can be catastrophic.

A ngwayir and its hollow located above a balga grasstree set on fire in the prescribed burn. The graph shows the heat penetration into the hollow in increments through the wood, with the hollow temperature in red and the lethal temperature marked by the horizontal line. A. Dixon; P. Zylstra

As my latest paper describes, Allison Dixon searched for the western ringtail possums the evening after the fire, and each subsequent evening for two weeks.

In some cases, Dixon found the bodies. In others, the presence of flies in high nest hollows indicated the ngwayir inside had perished.

Dixon visited surrounding properties and structures in case the possums had fled the fire ground, but no survivors were identified. She also continued weekly monitoring of their habitat. In the end, 17 of the 22 critically endangered possums were presumed dead.

burnt possum lies in ash
A burnt western ringtail possum recorded by Allison Dixon after the prescribed burn in 2018. Source: Allison Dixon

But the problem runs even deeper

Most fuel load lies in the litter layer on the ground. But we’ve known for decades that burning it away germinates dense understorey regrowth. In fact, WA government records show bushfires are most likely where prescribed burns have occurred, where that regrowth is most dense.

In November this year, a prescribed burn was conducted in the Walpole Wilderness, in dense regrowth stimulated by a previous prescribed burn.

The fire was reportedly meant to protect quokka habitat. But it escaped containment lines and burnt 25,000 hectares – 10,000 more than originally planned, and at a higher-than-intended severity.

smoke fills the sky above hills
A prescribed burn that escaped in the Walpole Wilderness this year. Author provided

One peer-reviewed study appears to show less fire in areas where prescribed burning has been undertaken. But research by my colleagues and I has challenged this study.

The authors of the study in question compared the amount of wildfire in each six-year period with the amount of prescribed fire in the same period. But this method meant that for some of that period, reduced fire frequency was attributed to prescribed burns that had not yet occurred.

Cooperating with nature

Australia has the world’s worst record for mammal extinction – and we know fire is one of the main culprits. Yet prescribed burning relies on outdated or even disproved theories and assumptions about fire.

Bad fire science is killing our threatened species, but alternatives are available. These approaches reinforce, rather than disrupt, natural ecological controls on forest fire. They include traditional Indigenous fire knowledge, and modern techniques to minimise the extent of dense regrowth in the landscape.

By cooperating with nature to minimise fire risk, we can protect species that have persisted through aeons.


Read more: Coming of age: research shows old forests are 3 times less flammable than those just burned


The Conversation

Philip Zylstra received funding for this study from the NSW Environmental Trust, Curtin University and the San Diego Zoo Wildlife Alliance.

Read the full story here.
Photos courtesy of

Are the jobs created by the Inland Empire warehouse boom built to last?

The main justification for the explosion of warehouses in the Inland Empire has been their economic benefits, primarily around job creation. But the wages they provide barely keep people out of poverty, and this work may soon disappear altogether because of automation. Is the region prepared for what comes next?

In summary The main justification for the explosion of warehouses in the Inland Empire has been their economic benefits, primarily around job creation. But the wages they provide barely keep people out of poverty, and this work may soon disappear altogether because of automation. Is the region prepared for what comes next? Much of the debate over warehouse construction in the Inland Empire – where the boom has been explosive in recent years – revolves around a single word: jobs. Are the jobs worth it? Warehouses are, after all, both a job creator and an inconvenience. They take up large amounts of land that could be used for other purposes, from housing to open space. They are serviced by trucks, sometimes 24 hours a day. And with those trucks come traffic, air pollution and noise. They are not especially good neighbors. But that’s true of a lot of economic activity. People don’t necessarily love to live near schools or hospitals, but they accept them as necessary parts of any community. What makes warehouses worth it, at least some of the time, is the jobs that they produce. So, how great is the economic benefit in terms of jobs that warehouses bring to Riverside and San Bernardino counties, where the number of these buildings has been geometrically expanding?  It is both significant and significantly worrisome.  Matt Englhard is a developer and leader of the National Association of Office Parks, known as NAIOP. He’s been building projects in Southern California, including the Inland Empire, for decades. He sees warehouses as a crucial link in the region’s economy, both in terms of their importance to international trade and for the local jobs they create. “Warehousing is one of the better entry jobs in the region,” he said in a recent interview. Yes, many of those warehouse jobs begin at or near minimum wage, but those are appealing to many young people seeking their first employment.  Moreover, entry-level jobs offer paths for promotion. Warehouse workers can become forklift drivers, electricians, truck drivers or warehouse supervisors – all with significant income potential. There’s nothing novel or wrong about starting at a low wage and moving up.  With warehouses moving adjacent to some of the Inland Empire’s wealthier neighborhoods, residents have complained that minimum-wage employment will hardly allow those workers to live nearby. That means they come from far away, creating traffic and air pollution. Englhard concedes that some of those homes will be out of reach to new workers. But that’s hardly new. After all, he asked, “how many 18 to 30 year-olds are buying $700,000 homes?” The new jobs created by warehouses, said Englhard and Jonathan Sharldow, another NAIOP leader, help explain why the Inland Empire has demonstrated economic resiliency in recent years. They pointed to a 2019 study by the Metropolitan Policy Program of the Brookings Institute that concluded, among other things, that the “Inland Empire’s logistics and manufacturing industries are crucial drivers of economic growth and prosperity.”  That economic foundation, the authors concluded, helped the region withstand the recession in the early 2000s and produce “unexpectedly swift jobs recovery.”  An Amazon warehouse in San Bernardino on Feb. 16, 2023. Warehouses in the Inland Empire have grown at an exponentially high pace. Photo by Pablo Unzueta for CalMatters But that same report also lamented the uneven nature of that recovery, with only very wealthy residents showing economic gains. By 2016, some 41% of Inland Empire families were classified as “struggling.” The region’s poverty rate rose from 13% in 2005 to 16% in 2016.  That’s despite the explosive growth of warehouses. In 1980, there were 234 warehouses across the Inland Empire. Since then, the number has roughly doubled every 10 years. Today, there are more than 4,000, and they take up roughly 1 billion square feet of land.  The logistics industry, anchored by warehouses, employs more than 200,000 people in the Inland Empire.  Those jobs have helped some young people find work and have supplied opportunities for others to promote. But they have not dented poverty rates, nor have they helped reduce inequality. “The argument we hear all the time is ‘these jobs are better than no jobs,’” said Susan Phillips, a professor of environmental analysis at Pitzer College and director of the Robert Redford Conservancy. But that, she said, is a false choice that suggests warehouses are the region’s only option. And these jobs, most of them close to minimum wage, come at a cost: the lost opportunity to develop other parts of the economy, which might be more prosperous or resilient.  “One of the problems with warehouses is that they take up a lot of land,” Phillips said. “They crowd out the room for anything else to grow.” There is yet another problem to consider. Many types of work are subject to stress these days. Generative artificial intelligence is threatening writers and lawyers and all manner of other workers, and automation is transforming others. Warehouse employment is particularly vulnerable to both trends.  Automation already has become so sophisticated that manufacturers already dream of “dark warehouses,” which are facilities powered by robots and AI and don’t need lights (robots are happy to work in the dark).  Those warehouses won’t replace current ones tomorrow – the investment costs are significant – but they may not be far away.  “We need to be prepared,” said Johannes Moenius, a professor at the University of Redlands and director of the Institute for Spatial Economic Analysis. “Within the next 10 years, the warehouse sector will undergo tremendous changes.” “Within the next 10 years, the warehouse sector will undergo tremendous changes.”Johannes Moenius, University of Redlands professor and director of the Institute for Spatial Economic Analysis He’s not exaggerating. One study by the institute concluded that some 75% of warehouse jobs are “susceptible to automation.”  That suggests that the warehouse boom may keep pace with automation for a time – new warehouses going up fast enough to compensate for jobs being automated – but then begin to decline. And once that decline begins, it will be fast and steep.  As Moenius noted, the bigger the employment base, the larger the drop. When 300,000 jobs drop by 75%, that could mean the loss of more than 200,000 workers in a very short period. There will be, Moenius emphasized – and apologies for his glumness – “substantial unemployment.” So which is it? Are warehouses the lifeblood of the Inland Empire, supplying it with badly needed employment to help it power through a recession and COVID? Or are they providing wages that barely keep pace with poverty and that may soon go away altogether?  The answer is both – and that should be cause for concern.

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