Climate change is testing the resilience of native plants to fire, from ash forests to gymea lilies

One year following the 2019/20 fires, this forest has been slow to recover.
Rachael Nolan, CC BY-NC-ND

Rachael Helene Nolan, Western Sydney University; Andrea Leigh, University of Technology Sydney; Mark Ooi, UNSW; Ross Bradstock, University of Wollongong; Tim Curran, Lincoln University, New Zealand; Tom Fairman, The University of Melbourne, and Víctor Resco de Dios, Universitat de LleidaGreen shoots emerging from black tree trunks is an iconic image in the days following bushfires, thanks to the remarkable ability of many native plants to survive even the most intense flames.

But in recent years, the length, frequency and intensity of Australian bushfire seasons have increased, and will worsen further under climate change. Droughts and heatwaves are also projected to increase, and climate change may also affect the incidence of pest insect outbreaks, although this is difficult to predict.

How will our ecosystems cope with this combination of threats? In our recently published paper, we looked to answer this exact question — and the news isn’t good.

We found while many plants are really good at withstanding certain types of fire, the combination of drought, heatwaves and pest insects may push many fire-adapted plants to the brink in the future. The devastating Black Summer fires gave us a taste of this future.

Examples of fire-adapted plants: prolific flowering of pink flannel flowers (upper left), new foliage resprouting on geebung (upper right), seed release from a banksia cone (lower left), and an old man banksia seedling (lower right).
Rachael Nolan

What happens when fires become more frequent?

Ash forests are one of the most iconic in Australia, home to some of the tallest flowering plants on Earth. When severe fire occurs in these forests, the mature trees are killed and the forest regenerates entirely from the seed that falls from the dead canopy.

These regrowing trees, however, do not produce seed reliably until they’re 15 years old. This means if fire occurs again during this period, the trees will not regenerate, and the ash forest will collapse.

This would have serious consequences for the carbon stored in these trees, and the habitat these forests provide for animals.

Southeast Australia has experienced multiple fires since 2003, which means there’s a large area of regrowing ash forests across the landscape, especially in Victoria.

The Black Summer bushfires burned parts of these young forests, and nearly 10,000 football fields of ash forest was at risk of collapse. Thankfully, approximately half of this area was recovered through an artificial seeding program.

Ash to ashes: On the left, unburned ash forest in the Central Highlands of Victoria; on the right, ash forest which has been burned by a number of high severity bushfires in Alpine National Park. Without intervention, this area will no longer be dominated by ash and will transition to shrub or grassland.
T Fairman

What happens when fire seasons get longer?

Longer fire seasons means there’s a greater chance species will burn at a time of year that’s outside the historical norm. This can have devastating consequences for plant populations.

For example, out-of-season fires, such as in winter, can delay maturation of the Woronora beard-heath compared to summer fires, because of their seasonal requirements for releasing and germinating seeds. This means the species needs longer fire-free intervals when fires occur out of season.

The iconic gymea lily, a post-fire flowering species, is another plant under similar threat. New research showed when fires occur outside summer, the gymea lily didn’t flower as much and changed its seed chemistry.

While this resprouting species might persist in the short term, consistent out-of-season fires could have long-term impacts by reducing its reproduction and, therefore, population size.

Out-of-season fires could have long-term impacts on gymea lilies.
Shutterstock

When drought and heatwaves get more severe

In the lead up to the Black Summer fires, eastern Australia experienced the hottest and driest year on record. The drought and associated heatwaves triggered widespread canopy die-off.

Extremes of drought and heat can directly kill plants. And this increase in dead vegetation may increase the intensity of fires.

Another problem is that by coping with drought and heat stress, plants may deplete their stored energy reserves, which are vital for resprouting new leaves following fire. Depletion of energy reserves may result in a phenomenon called “resprouting exhaustion syndrome”, where fire-adapted plants no longer have the reserves to regenerate new leaves after fire.

Therefore, fire can deliver the final blow to resprouting plants already suffering from drought and heat stress.

Drought stressed eucalypt forest in 2019.
Rachael Nolan

Drought and heatwaves could also be a big problem for seeds. Many species rely on fire-triggered seed germination to survive following fire, such as many species of wattles, banksias and some eucalypts.

But drought and heat stress may reduce the number of seeds that get released, because they limit flowering and seed development in the lead up to bushfires, or trigger plants to release seeds prematurely.

For example, in Australian fire-prone ecosystems, temperatures between 40℃ and 100℃ are required to break the dormancy of seeds stored in soil and trigger germination. But during heatwaves, soil temperatures can be high enough to break these temperature thresholds. This means seeds could be released before the fire, and they won’t be available to germinate after the fire hits.

Heatwaves can also reduce the quality of seeds by deforming their DNA. This could reduce the success of seed germination after fire.

Burnt banksia — Many native plants, such as banksia, rely on fire to germinate their seeds.
Shutterstock

What about insects? The growth of new foliage following fire or drought is tasty to insects. If pest insect outbreaks occur after fire, they may remove all the leaves of recovering plants. This additional stress may push plants over their limit, resulting in their death.

This phenomenon has more typically been obverved in eucalypts following drought, where repeated defoliation (leaf loss) by pest insects triggered dieback in recovering trees.

When threats pile up

We expect many vegetation communities will remain resilient in the short-term, including most eucalpyt species.

But even in these resilient forests, we expect to see some changes in the types of species present in certain areas and changes to the structure of vegetation (such as the size of trees).

Resprouting eucalypts, one year on following the 2019-2020 bushfires.
Rachael Nolan

As climate change progresses, many fire-prone ecosystems will be pushed beyond their historical limits. Our new research is only the beginning — how plants will respond is still highly uncertain, and more research is needed to untangle the interacting effects of fire, drought, heatwaves and pest insects.

We need to rapidly reduce carbon emissions before testing the limits of our ecosystems to recover from fire.

Rachael Helene Nolan, Postdoctoral research fellow, Western Sydney University; Andrea Leigh, Associate Professor, Faculty of Science, University of Technology Sydney; Mark Ooi, Senior Research Fellow, UNSW; Ross Bradstock, Emeritus professor, University of Wollongong; Tim Curran, Associate Professor of Ecology, Lincoln University, New Zealand; Tom Fairman, Future Fire Risk Analyst, The University of Melbourne, and Víctor Resco de Dios, Profesor de Incendios y Cambio Global en PVCF-Agrotecnio, Universitat de Lleida

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

Smoke from the Black Summer fires created an algal bloom bigger than Australia in the Southern Ocean

Christina Schallenberg, University of Tasmania; Jakob Weis, University of Tasmania; Joan Llort, Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS); Peter Strutton, University of Tasmania, and Weiyi Tang, Princeton UniversityIn 2019 and 2020, bushfires razed more than 18 million hectares of land in Australia. For weeks, smoke choked major cities, leading to almost 450 deaths, and even circumnavigated the southern hemisphere.

As the aerosols billowed across the oceans many thousands of kilometres away from the fires, microscopic marine algae called phytoplankton had an unexpected windfall: they received a boost of iron.

Our research, published today in Nature, found this caused phytoplankton concentrations to double between New Zealand and South America, until the bloom area became bigger than Australia. And it lasted for four months.

This enormous, unprecedented algal bloom could have profound implications for carbon dioxide levels in the atmosphere and for the marine ecosystem. But so far, the impact is still unclear.

Meanwhile, in another paper published alongside ours in Nature today, researchers from The Netherlands found the amount of carbon dioxide emitted by the fires that summer was more than double previous estimates.

Absorbing 680 million tonnes of carbon dioxide

Iron fertilises phytoplankton and helps them grow, in the same way nutrients added in soil help vegetables grow. And like plants on land, phytoplankton photosynthesise — they absorb CO₂ as they grow and produce oxygen for fish and other marine creatures.

Bushfire smoke is an aerosol made up of many different chemicals, including iron.
Shutterstock

We used satellite data to estimate that for phytoplankton to grow as much as they did in the Southern Ocean, they would have absorbed 680 million tonnes of CO₂. This means the phytoplankton absorbed roughly the same amount of CO₂ as released by the bushfires, according to the latest estimates released today.

The Dutch researchers found the bushfires released 715 million tonnes of CO₂ (or ranging 517–867 million tonnes) between November 2019 and January 2020. This surpasses Australia’s normal annual fire and fossil fuel emissions by 80%.

To put this into perspective, Australia’s anthropogenic CO₂ emissions in 2019 were much less, at 520 million tonnes.

Phytoplankton can have dramatic effects on climate

But that doesn’t mean the phytoplankton growth absorbed the bushfire’s CO₂ emissions permanently. Whether phytoplankton growth extracts and keeps CO₂ from the atmosphere depends on their fate.

If they sink to the deep ocean, then this represents a carbon sink for decades or even centuries — or even longer if phytoplankton are stored in ocean sediments.

But if they’re mostly eaten and decomposed near the ocean’s surface, then all that CO₂ they consumed comes straight back out, with no net effect on the carbon balance in the atmosphere.

Himawari satellite image showing the January aerosol plume stretching over the South Pacific.
Himawari-8, Author provided

In fact, phytoplankton have very likely played a role on millennial time scales in keeping atmospheric CO₂ concentrations down, and can affect the global climate in the long term.

For example, a 2014 study suggests iron-containing dust billowing over the Southern Ocean caused increased phytoplankton productivity, which contributed to reducing atmospheric CO₂ by about 100 parts per million. And this helped transition the planet to ice ages.

Phytoplankton blooms can also have a big impact on the marine ecosystem as they make excellent food for some marine creatures.

For example, more phytoplankton means more food for zooplankton that feed on phytoplankton, with effects up the food chain. It’s also worth noting this huge bloom occurred at a time of year when phytoplankton are usually in decline in this part of the ocean.

But whether there were any long-lasting effects from the bushfire-fuelled phytoplankton on the climate or ecosystem is unclear, because we still don’t know where they ended up.

Using revolutionary data

The link between fire aerosols and the increase in phytoplankton demonstrated in our study is particularly relevant given the intense fire activity around the globe.

Droughts and warming under global climate change are expected to increase the frequency and intensity of wildfires, and the impacts to land-based ecosystems, such as habitat loss and air pollution, will be dramatic. But as we now know, wildfires can also affect marine life thousands of kilometres away from land.

A robotic float being deployed on board the CSIRO RV Investigator.
Jakob Weiss, Author provided

Previous models have predicted the iron-fertilising effect of bushfire aerosols, but this is the first time we’ve observed and demonstrated the connection at a large-scale.

Our study is mainly based on satellite data and observations from robotic floats that roam the oceans and collect data autonomously. These robotic floats are revolutionising our understanding of chemical cycling, oxygen variability and ocean acidification.

During the bushfire period, our smoke tracers reached concentrations at least 300% higher than what had ever been observed in the 22-year satellite record for the region.

Interestingly, you wouldn’t be able to observe the resulting phytoplankton growth in a true-colour satellite image. We instead used more sensitive ocean colour sensors on satellites to estimate phytoplankton concentrations.

So what’s next?

Of course, we need more research to determine the fate of the phytoplankton. But we also need more research to better predict when and where aerosol deposition (such as bushfire smoke) will boost phytoplankton growth.

For example, the Tasman Sea — between Australia and New Zealand — showed only mildly higher phytoplankton concentrations during the bushfire period, even though the smoke cloud was strongest there.

Was this because nutrients other than iron were lacking, or because there was less deposition? Or perhaps because the smoke didn’t stick around for as long?

Whatever the reason, it’s clear this is only the beginning of exciting new lines of research that link forests, wildfires, phytoplankton growth and Earth’s climate.

Christina Schallenberg, Research Fellow, University of Tasmania; Jakob Weis, Ph.D. student, University of Tasmania; Joan Llort, Oceanógrafo , Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS); Peter Strutton, Professor, Institute for Marine and Antarctic Studies, University of Tasmania, and Weiyi Tang, Postdoc in Biogeochemistry, Princeton University

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

When it comes to preparing for disaster there are 4 distinct types of people. Which one are you?

Agathe Tiana Randrianarisoa, RMIT University and John Richardson, The University of MelbourneImagine it’s summer in Australia and a bushfire is bearing down on your suburb. Are you the pragmatic type – you’ve swapped phone numbers with the neighbours, photocopied your ID and have your emergency plan at the ready? Or are you the sentimental type – you’ve backed up the family photos but forgotten to insure the house, or don’t have an evacuation plan for the cat?

Our research out today shows when it comes to getting ready for disasters, there are four types of people. And this matters, because good disaster preparedness doesn’t just help people during and immediately after a disaster – it can also mean a quicker recovery.

The research, commissioned by Australian Red Cross, examined the experiences of 165 people who lived through a disaster such as fire and flood between 2008 and 2019. We identified a number of steps people wished they’d taken to prepare for disaster, such as protecting sentimental items, planning where the family should meet if separated and better managing stress.

The Black Summer bushfires, this year’s New South Wales floods, the storms around Melbourne and even COVID-19 remind us how disasters can disrupt people’s lives. Hopefully, examining the hard-won lessons of those who’ve lived through the worst life can throw at us will help individuals and communities better prepare and recover from these events.

man, woman and two children in blankets — Examining the hard-won lessons of those who’ve lived through disaster will help others prepare.
Dean Lewins/AAP

Our key findings

The survey questions focused on preparedness actions people took before a disaster, their experience of a disaster and recovery.

Participants were 18 years or older and had experienced a disaster between January 2008 and January 2019. This allowed time for people to experience the challenges and complexity of the recovery process.

Among our key findings were:

feeling prepared leads to a reduction in stress when dealing with the recovery process. And the less people are stressed, the better their recovery up to ten years after a disaster.
generally, the more people do to get prepared, the more they feel prepared. However, one in five respondents who reported not feeling prepared had undertaken actions that should have made them feel prepared. And 3% said they were prepared when they hadn’t undertaken any action, which mostly comes from the lack of knowledge of the most efficient preparedness actions.
the source of advice matters. More of those who received preparedness advice from Australian Red Cross – either directly or through its Get Ready app – had recovered. Those who had no preparedness training or received advice from family or friends were least likely to report having felt in control during the emergency.

man gathers leaves — The research found disaster preparedness, such as clearing fire risk around the home, can be linked to recovery.
Dominica Sanda/AAP

3 ways to prepare

Three distinct groups of preparation actions emerged, which we outline below.

Protect my personal matters:

develop strategies to manage stress levels
protect or back up items of sentimental value
make copies and protect important documents such as identification papers, wills, financial documents
make plans for reunification of family if separated during an emergency.

Build my readiness:

identify sources of information to help prepare for and respond to an emergency
find out what hazards might affect their home and plan for them
use preparedness materials such as bushfire survival plans.

Be pragmatic:

make a plan for pets/livestock/animals
swap phone numbers with neighbours
take out property insurance.

Those who had taken action to prepare for disaster were asked what other actions they wished they’d taken. The top answer was having copies of important documents, such as ID and financial papers, that are potentially complicated to replicate and may be needed during recovery.

The full range of answers is below:

Which preparedness type are you?

Our research showed four types of persona emerged in terms of preparing for a disaster. Hopefully, identifying these groups means preparedness messaging can in future be customised, based on people’s characteristics.

Have a look at the graphic below – is there a type you identify with the most?

The Conversation/author provided data, CC BY-ND

Recovery is complex

Our survey asked if people felt they had recovered from the disaster. Importantly, we did not propose a standard definition of recovery, which allowed respondents to define their recovery in their own way. We then sought to determine how a person’s disaster preparation affected recovery.

Nearly 18% of respondents said they had not recovered at the time of the survey. Surprisingly, 86% of those said they took action to get prepared (compared to 76% of those who had recovered). But those who had not recovered were more likely to feel their preparation actions were not enough. Importantly, 86% also experienced high levels of stress during the recovery, compared to 60% who had already recovered at the time of the survey.

Interestingly, the proportion of respondents who found the recovery process slightly stressful, somewhat stressful or extremely stressful are comparable (15%, 16% and 16% respectively). However, four out of ten respondents reported high levels of stress during the recovery.

What’s more, a greater proportion of those who had not yet recovered required government assistance after the disaster (71%), relative to those who felt they had recovered (38%).

In the group of those not yet recovered, people earning less than A$52,000 a year were over-represented.

children rake branches — Disaster preparedness advice should be tailored to the needs of those receiving it.
Dan Peled/AAP

Ready for anything

Our research shows being prepared can help reduce the long-term impacts of a disaster. The level of disaster preparedness in the Australian population is traditionally low, and so it’s important to demonstrate the benefits to ensure more people get ready for emergencies.

Preparedness programs should have a greater focus on preparing for the long-term impacts of a disaster. And these programs should differ based on people’s characteristics and they type of preparation support they need, particularly focusing on those who have less capacity to prepare and recover from the disruption of disaster.

This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. It is supported by a philanthropic grant from the Paul Ramsay Foundation. Read the rest of the stories here.

Agathe Tiana Randrianarisoa, PhD student and Senior Researcher, RMIT University and John Richardson, Honorary Fellow, Child and Community Wellbeing Unit, Beyond Bushfires Research Program, The University of Melbourne

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

Bushfire survivors just won a crucial case against the NSW environmental watchdog, putting other states on notice

Laura Schuijers, The University of MelbourneThis week was another big one in the land of climate litigation.

On Thursday, a New South Wales court compelled the state Environment Protection Authority (EPA) to take stronger action to reduce greenhouse gas emissions. It’s the first time an Australian court has ordered a government organisation to take more meaningful action on climate change.

The case challenging the EPA’s current failures was brought by a group of bushfire-affected Australians. The group’s president said the ruling means those impacted by bushfires can rebuild their homes, lives, and communities, with the confidence the EPA will also work to do its part by addressing emissions.

The group’s courtroom success shows citizens can play an important role in bringing about change. And it continues a recent trend of successful climate cases that have held government and private sector actors to account for their responsibility to help prevent climate-related harms.

Who are the bushfire survivors?

Members of the group, the Bushfire Survivors for Climate Action, identify as survivors, firefighters and local councillors impacted by bushfires and the continued threat of bushfire posed by climate change.

Their stories paint a picture of devastating loss, and fear of what might be to come. One member, who lost her home, tells of harrowing hours looking for friends and family amid a dark, alien moonscape. Another, a volunteer firefighter, describes the smell of charred and burnt flesh and the silence of the incinerated forests that haunted him.

A person stands in a burnt-out home — Fiona Lee, a member of the Bushfire Survivors group, stands in the ruins of her home after a bushfire swept through.
Bushfire Survivors for Climate Action

The group argues that because the NSW EPA is required, by law, to protect the environment through quality objectives, guidelines and policies, these instruments also need to cover greenhouse gas emissions.

Their reasoning is hard to fault: climate change is one of the environment’s most significant threats. In today’s world, you can’t protect the environment without addressing climate change.

To establish this point, the bushfire survivors presented the latest report from the Intergovernmental Panel on Climate Change, which was released while the trial was being heard. The report describes how the temperature rise in Australia could exceed the global average, and predicts increasingly hotter and drier conditions.

An unperformed duty

The EPA’s statutory duty to protect the environment was already known before the litigation began. That’s because the duty is contained within the EPA’s own legislation.

Bushfire survivors hold signs in front of Parliament House — The Bushfire Survivors brought their case to the NSW Land and Environment Court.
Bushfire Survivors for Climate Action

The EPA protects the environment from other types of pollutants by issuing environment protection licences, monitoring compliance, and imposing fines and clean-up orders. The bushfire survivors were seeking to force the EPA to address greenhouse gas emissions as well.

The EPA unsuccessfully tried to establish it is not required to address any specific environmental problem — i.e. climate change. And it argued that even if it is, it has already done enough.

But the court agreed with the bushfire survivors that the EPA’s instruments already in place aren’t sufficient, leaving the duty “unperformed”.

The court didn’t specify exactly how the EPA should remedy the fact it isn’t adequately addressing climate change, meaning the EPA can decide how it develops its own quality objectives, guidelines and policies, in a way that leads to fewer emissions. It is not the court’s job to make policy.

The EPA might, for example, target the highest-emitting industries and activities, via controls or caps on greenhouse gases.

Importantly, however, the court said the EPA doesn’t have to match its actions with a particular climate scenario, such as a global temperature rise of 1.5℃.

Other states on notice

Although this ruling is specific to NSW, other state environment protection authorities also have legal objectives to protect the environment.

This case may cause other Australian environmental authorities to consider whether their regulatory approaches match what the law requires them to do. This might include a responsibility to protect the environment from climate change.

Another thing we know from the NSW case is that simply having policies and strategies isn’t enough.

The court made it clear aspirational and descriptive plans won’t cut the mustard if there’s nothing to “set any objectives or standards, impose any requirements, or prescribe any action to be taken to ensure the protection of the environment”.

The EPA tried to point to NSW’s Climate Change Framework and Net Zero Plan as a way of showing climate change action. But neither of these was developed by the EPA.

The EPA also presented documents it did develop, including a document about landfill guidelines, a fact sheet on methane, and a regulatory strategy highlighting climate change as a challenge for the EPA.

The court found these weren’t enough to address the threat of climate change and discharge the EPA’s duty, calling the regulatory strategy’s description of climate change “general and trite”.

An Australian first, but not an anomaly

Globally, climate litigation is playing a role in filling gaps in domestic climate governance. Cases in Europe, North and South America, and elsewhere have led to courts pushing governments to do more.

One of the world’s first major successful climate change cases, Massachusetts v EPA, was similar to the bushfire survivors’ case. Back in 2007, the state of Massachusetts, along with other US states, sued the federal US EPA. They were seeking to force regulatory action on greenhouse gas emissions, and a recognition of carbon dioxide as a pollutant under the Clean Air Act.

While the NSW case comes 14 years after the US case, there has been plenty of courtroom action in Australia in the meantime, with cases against the financial sector, government actors, and corporations.

The top of the Santos building in front of a sunny blue sky — The Australasian Centre for Corporate Responsibility just filed a lawsuit against Santos.
Shutterstock

In fact, on the same morning as the bushfire survivors’ case, a lawsuit was filed against oil and gas giant Santos in the Federal Court.

The Australasian Centre for Corporate Responsibility will argue statements made in Santos’s annual report are misleading and deceptive. These statements include that natural gas is a “clean fuel” and that it has a “clear and credible” plan to achieve net-zero emissions by 2040.

Climate change is an inevitable problem, and one that will be costly. Lawsuits seeking to force action now aim to limit how great the costs will be down the track. By targeting those most responsible, they are a means of seeking justice.

Laura Schuijers, Research Fellow in Environmental Law, The University of Melbourne

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

Some animals have excellent tricks to evade bushfire. But flames might be reaching more animals naive to the dangers

Dale Nimmo, Charles Sturt University; Alex Carthey, Macquarie University; Chris J Jolly, Charles Sturt University, and Daniel T. Blumstein, University of California, Los AngelesThe new report by the Intergovernmental Panel on Climate Change paints a sobering picture of the warming climate in coming decades. Among the projections is an increase in fire weather, which will expose Earth’s landscapes to more large and intense megafires.

In our paper, published today in Global Change Biology, we considered what this fiery future might mean for the planet’s wildlife. We argue a lot can be learned by looking at how wildlife responds to a very different threat: predators.

Australia has seen the brutal consequences that occur when native wildlife is exposed to introduced predators. Australian animals have not evolved alongside introduced predators, such as cats and foxes, and some are what scientists call “predator naive” — they simply aren’t equipped with the evolutionary instincts to detect and respond to introduced predators before it’s too late.

Now, let’s take that idea and apply it to fires. Some animals have evolved excellent tricks to detect when a bushfire is nearby. But some areas where infernos were once rare are growing increasingly bushfire-prone, thanks to climate change. The wildlife in these spots may not have the evolutionary know-how to detect a fire before it’s too late.

Just as being “predator naive” has decimated Australian wildlife, will being “fire naive” wreak havoc on our native species?

Behaviour forged in fire

A growing list of studies show the tricks animals from fire-prone areas use to survive the flames.

Sleepy lizards have been shown to panic at the smell of burnt pastry, reed frogs leap away from the crackling sounds of fire, and bats and marsupials wake from torpor after smelling smoke.

And one study found that, when exposed to smoke, Mediterranean lizards from fire-prone areas reacted more strongly than Mediterranean lizards from areas where fire was rare.

These studies show some animals can recognise the threat of fire, and behave in a way that increases their chance of survival. Those that can are more likely to live through fire and pass on those abilities to their offspring.

That’s where the parallels between fire and predation become striking — and potentially worrying.

Reading the cues

It’s well known predators and prey are in an ongoing evolutionary race to outmanoeuvre one another.

One tool prey draw upon to avoid becoming predator food is to recognise cues — such as smells, sights and sounds — that indicate a predator is lurking nearby. Once they do, prey can change their behaviour to minimise the risk of becoming dinner.

Research showed the Mediterranean skink can smell a fire. — Research has shown the Mediterranean skink can smell a fire.
By Balles2601 / Wikimedia Commons / CC BY-SA 4.0, CC BY-SA 4.0, CC BY

Decades of research has shown that when prey evolve alongside a predator, they can become highly adept at recognising their predator’s cues, such as a scent markings or territorial calls.

But what about animals that haven’t evolved alongside these lethal threats?

When a new predator enters an ecosystem, prey that have not evolved with it can be naive to its cues. They might fail to recognise the threat implied by the new predator’s scents, signs, or sounds, placing them at substantial risk.

This “predator naivety” helps explain why introduced predators are global drivers of extinction. Naive prey just don’t hear, smell, or see them coming.

Which species are ‘fire naive’?

Research on how animals respond to fire cues has focused on animals from fire-prone regions, probably because that’s where you’d expect to find the strongest responses. But more research is needed about animals from regions that rarely burn.

Do these animals also recognise the cues of fire as an approaching lethal threat?

Do they have finely tuned behaviours that help them survive fire?

Are they “fire naive”?

We don’t know. And that’s a worry because recent changes in global fire activity, triggered by a warming and drying climate, are seeing fires enter ecosystems long regarded as “fire-free”.

If they are naive to fire, species in these ecosystems might be more at risk than previously thought.

The search for fire naivety

We urge researchers around the world to assess fire naivety of animals, particularly in areas experiencing a change in their fire regimes, such as from rare to frequent fire or increased fire severity.

Evidence suggests recognition of predator cues is at least partly genetic. It will be important to determine whether the capacity to recognise and respond to fire also has a genetic basis.

If those behaviours can be passed on from one generation to the next, then perhaps we could take fire-savvy individuals from fire-prone areas and place them into fire naive populations, in the hope their favourable behaviours will spread rapidly via genes passed onto their offspring. Scientists call this “targeted gene flow”.

As the world continues to warm and megafires rage across the globe, we will need all the knowledge and tools at our disposal to help avoid an acceleration of Earth’s biodiversity crisis.

Dale Nimmo, Associate Professor in Ecology, Charles Sturt University; Alex Carthey, Macquarie University Research Fellow, Macquarie University; Chris J Jolly, Postdoctoral Research Fellow, Charles Sturt University, and Daniel T. Blumstein, Professor in the Department of Ecology and Evolutionary Biology and the Institute of the Environment and Sustainability, University of California, Los Angeles

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

You may have heard the ‘moon wobble’ will intensify coastal floods. Well, here’s what that means for Australia

Mark Gibbs, Australian Institute of Marine ScienceExtreme floods this month have been crippling cities worldwide. This week in China’s Henan province, a year’s worth of rain fell in just three days. Last week, catastrophic floods swept across western Germany and parts of Belgium. And at home, rain fell in Perth for 17 days straight, making it the city’s wettest July in 20 years.

But torrential rain isn’t the only cause of floods. Many coastal towns and cities in Australia would already be familiar with what are known as “nuisance” floods, which occur during some high tides.

A recent study from NASA and the University of Hawaii suggests even nuisance floods are set to get worse in the mid-2030s as the moon’s orbit begins another phase, combined with rising sea levels from climate change.

The study was conducted in the US. But what do its findings mean for the vast lengths of coastlines in Australia and the people who live there?

A triple whammy

We know average sea levels are rising from climate change, and we know small rises in average sea levels amplify flooding during storms. From the perspective of coastal communities, it’s not if a major flood will occur, it’s when the next one will arrive, and the next one after that.

But we know from historical and paleontological records of flooding events that in many, if not most, cases the coastal flooding we’ve directly experienced in our lifetimes are simply the entrée in terms of what will occur in future.

Flooding is especially severe when a storm coincides with a high tide. And this is where NASA and the University of Hawaii’s new research identified a further threat.

Researchers looked at the amplification phase of the natural 18.6-year cycle of the “wobble” in the moon’s orbit, first identified in 1728.

The orbit of the moon around the sun is not quite on a flat plane (planar); the actual orbit oscillates up and down a bit. Think of a spinning plate on a stick — the plate spins, but also wobbles up and down.

When the moon is at particular parts of its wobbling orbit, it pulls on the water in the oceans a bit more. This means for some years during the 18.6-year cycle, some high tides are higher than they would have otherwise been.

This results in increases to daily tidal rises, and this, in turn, will exacerbate coastal flooding, whether it be nuisance flooding in vulnerable areas, or magnified flooding during a storm.

View of Earth from the Moon — The moon’s orbit isn’t on a flat plane. It oscillates up and down, like a plate would when it spins on a stick.
Shutterstock

A major wobble amplification phase will occur in the mid-2030s, when climate change will make the problem become severe in some cases.

The triple whammy of the wobble in the moon’s orbit, ongoing upwards creep in sea levels from ocean warming, and more intense storms associated with climate change, will bring the impacts of sea-level rise earlier than previously expected — in many locations around the world. This includes in Australia.

So what will happen in Australia?

The locations in Australia where tides have the largest range, and will be most impacted by the wobble, aren’t close to the major population centres. Australia’s largest tides are close to Broad Sound, near Hay Point in central Queensland, and Derby in the Kimberley region of Western Australia.

However, many Australian cities host suburbs that routinely flood during larger high tides. Near my home in Meanjin (Brisbane), the ocean regularly backs up through the storm water drainage system during large high tides. At times, even getting from the front door to the street can be challenging.

Derby, WA, has one of the biggest tidal ranges in Australia.
Shutterstock

Some bayside suburbs in Melbourne are also already exposed to nuisance flooding. But a number of others that are not presently exposed may also become more vulnerable from the combined influence of the moon wobble and climate change — even when the weather is calm. High tide during this lunar phase, occurring during a major rainfall event, will result in even greater risk.

In high-income nations like Australia, sea-level rise means increasing unaffordability of insurance for coastal homes, followed by an inability to seek insurance cover at all and, ultimately, reductions in asset values for those unable or unwilling to adapt.

The prognosis for lower-income coastal communities that aren’t able to adapt to sea-level rise is clear: increasingly frequent and intense flooding will make many aspects of daily life difficult to sustain. In particular, movement around the community will be challenging, homes will often be inundated, unhealthy and untenable, and the provision of basic services problematic.

What do we do about it?

While our hearts and minds continue to be occupied by the pandemic, threats from climate change to our ongoing standard of living, or even future viability on this planet, haven’t slowed. We can pretend to ignore what is happening and what is increasingly unstoppable, or we can proactively manage the increasing threat.

Some coastal communities, such as in Melbourne’s bayside suburbs, may experience flooding, even if they never have before.
Shutterstock

Thankfully, approaches to adapting the built and natural environment to sea-level rise are increasingly being applied around the world. Many major cities have already embarked on major coastal adaptation programs – think London, New York, Rotterdam, and our own Gold Coast.

However, the uptake continues to lag behind the threat. And one of the big challenges is to incentivise coastal adaptation without overly impacting private property rights.

Perhaps the best approach to learning to live with water is led by the Netherlands. Rather than relocating entire communities or constructing large barriers like sea walls, this nation is finding ways to reduce the overall impact of flooding. This includes more resilient building design or reducing urban development in specific flood retention basins. This means flooding can occur without damaging infrastructure.

There are lessons here. Australia’s adaptation discussions have often focused on finding the least worst choice between constructing large seawalls or moving entire communities — neither of which are often palatable. This leads to inaction, as both options aren’t often politically acceptable.

The seas are inexorably creeping higher and higher. Once thought to be a problem for our grandchildren, it is becoming increasingly evident this is a challenge for the here and now. The recently released research confirms this conclusion.

Mark Gibbs, Principal Engineer: Reef Restoration, Australian Institute of Marine Science

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

Biggest Earthquakes

Spiders are cloaking Gippsland with stunning webs after the floods. An expert explains why

Lizzy Lowe, Macquarie UniversityStunning photographs of vast, ghostly spider webs blanketing the flood-affected region of Gippsland in Victoria have gone viral online, prompting many to muse on the wonder of nature.

But what’s going on here? Why do spiders do this after floods and does it happen everywhere?

The answer is: these webs have nothing to do with spiders trying to catch food. Spiders often use silk to move around and in this case are using long strands of web to escape from waterlogged soil.

This may seem unusual, but these are just native animals doing their thing. It’s crucial you don’t get out the insecticide and spray them. These spiders do important work managing pests, so by killing them off you would be increasing the risk that pests such as cockroaches and mosquitoes will get out of control.

Using silk to move around

What you’re seeing online, or in person if you live locally, is an amazing natural phenomena but it’s not really very complicated.

We are constantly surrounded by spiders, but we don’t usually see them. They are hiding in the leaf litter and in the soil.

Spider webs blanket the ground in Gippsland — When floods happen, spiders use silk to evacuate quickly.
Darren Carney

When these flood events happen, they need evacuate quickly up out of holes they live in underground. They come out en masse and use their silk to help them do that.

You’ll often see juvenile spiders let out a long strand of silk which is caught by the wind and lifted up. The web catches onto another object such as a tree and allows the spider to climb up.

That’s how baby spiders (spiderlings!) disperse when they emerge from their egg sacs — it’s called ballooning. They have to disperse as quickly as possible because they are highly cannibalistic so they need to move away from each other swiftly and find their own sites to hunt or build their webs.

Small spiders have been seen on a post in Gippsland after floods.
AAP Image/JEFF HOBBS

That said, I doubt these webs are from baby spiders. It is more likely to be a huge number of adult spiders, of all different types, sizes and species. They’re all just trying to escape the flood waters. These are definitely spiders you don’t usually see above ground so they are out of their comfort zone, too.

This mass evacuation of spiders, and associated blankets of silk, is not a localised thing. It is seen in other parts of Australia and around the world after flooding.

It just goes to show how versatile spider silk can be. It’s not just used for catching food, it’s also used for locomotion and is even used by some spiders to lay a trail so they don’t get lost.

Don’t spray them!

The most important thing I need readers to know is that this is not anything to be worried about. The worst thing you could do is get out the insecticide and spray them.

These spiders are making a huge contribution to pest control and you would have major pest problems if you get rid of all the spiders. The spiders will disperse on their own very quickly. In general, spiders don’t like being in close proximity to each other (or humans!) and they want to get back to their homes underground.

If you live in Gippsland, you probably don’t even need to clear the webs away with a broom. There’s no danger in doing so if you wish, but I am almost certain these webs will disperse on their own within days.

Until then, enjoy this natural spectacle. I wish I could come down to see them with my own eyes!

Lizzy Lowe, Researcher, Macquarie University

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

Native forest logging makes bushfires worse – and to say otherwise ignores the facts

Philip Zylstra, University of Wollongong; Grant Wardell-Johnson, Curtin University; James Watson, The University of Queensland, and Michelle Ward, The University of QueenslandThe Black Summer bushfires burned far more temperate forest than any other fire season recorded in Australia. The disaster was clearly a climate change event; however, other human activities also had consequences.

Taking timber from forests dramatically changes their structure, making them more vulnerable to bushfires. And, crucially for the Black Summer bushfires, logged forests are more likely to burn out of control.

Naturally, the drivers of the fires were widely debated during and after the disaster. Research published earlier this month, for example, claimed native forest logging did not make the fires worse.

We believe these findings are too narrowly focused and in fact, misleading. They overlook a vast body of evidence that crown fire – the most extreme type of bushfire behaviour, in which tree canopies burn – is more likely in logged native forests.

Logged forest — The authors say logging increases the risk of intense crown fires.
Australian National University

Crown fires vs scorch

The Black Summer fires occurred in the 2019-20 bushfire season and burned vast swathes of Australia’s southeast. In some cases, fire spread through forests with no recorded fire, including some of the last remnants of ancient Gondwanan rainforests.

Tragically, the fires directly killed 33 people, while an estimated 417 died due to the effects of smoke inhalation. A possible three billion vertebrate animals perished and the risk of species extinctions dramatically increased.

Much of the forest that burned during Black Summer experienced crown fires. These fires burn through the canopies of trees, as well as the undergrowth. They are the most extreme form of fire behaviour and are virtually impossible to control.

Crown fires pulse with such intense heat they can form thunderstorms which generate lightning and destructive winds. This sends burning bark streamers tens of kilometres ahead of the fire, spreading it further. The Black Summer bushfires included at least 18 such storms.

Various forest industry reports have recognised logging makes bushfires harder to control.

And to our knowledge, every empirical analysis so far shows logging eucalypt forests makes them far more likely to experience crown fire. The studies include:

A 2009 paper suggesting changes in forest structure and moisture make severe fire more likely in logging regrowth compared to undisturbed forest
2012 research concluding the probability of crown fires was higher in recently logged areas than in areas logged decades before
A 2013 study that showed the likelihood of crown fire halved as forests aged after a certain point
2014 findings that crown fire in the Black Saturday fires likely peaked in regrowth and fell in mature forests
2018 research into the 2003 Australian Alps fires, which found the same increase in the likelihood of crown fire during regrowth as was measured following logging.

The findings of these studies are represented in the image below. The lines a, b and c refer to the 2013, 2014 and 2018 studies respectively.

Graph showing the likelihood of crown fire relative to years since logging or fire — Author supplied

Crown fires take lives

The presence of crown fire is a key consideration in fire supression, because crown fires are very hard to control.

However, the study released last week – which argued that logging did not worsen the Black Summer fires – focused on crown “scorch”. Crown scorch is very different to crown fire. It is not a measure of how difficult it is to contain the fire, because even quite small flames can scorch a drought-stressed canopy.

Forestry studies tend to focus more on crown scorch, which damages timber and is far more common than crown fires.

But the question of whether logging made crown scorch worse is not relevant to whether a fire was uncontrollable, and thus was able to destroy homes and lives.

Importantly, when the study said logging had a very small influence on scorch, this was referring to the average scorch over the whole fire area, not just places that had been logged. That’s like asking how a drought in the small town of Mudgee affects the national rainfall total: it may not play a large role overall, but it’s pretty important to Mudgee.

The study examined trees in previously logged areas, or areas that had been logged and burned by fires of any source. It found they were as likely to scorch on the mildest bushfire days as trees in undisturbed forests on bad days. These results simply add to the body of evidence that logging increases fire damage.

Timber plantation after fire — Forestry industry studies tend to focus on crown scorch.
Richard Wainwright/AAP

Managing forests for all

Research shows forests became dramatically less likely to burn when they mature after a few decades. Mature forests are also less likely to carry fire into the tree tops.

For example during the Black Saturday fires in 2009, the Kilmore East fire north of Melbourne consumed all before it as a crown fire. Then it reached the old, unlogged mountain ash forests on Mount Disappointment and dropped to the ground, spreading as a slow surface fire.

The trees were scorched. But they were too tall to ignite, and instead blocked the high winds and slowed the fire down. Meanwhile, logged ash forests drove flames high into the canopy.

Despite decades of opportunity to show otherwise, the only story for eucalypt forests remains this: logging increases the impact of bushfires. This fact should inform forest management decisions on how to reduce future fire risk.

We need timber, but it must be produced in ways that don’t endanger human lives or the environment.

Philip Zylstra, Adjunct Associate Professor at Curtin University, Honorary Fellow at University of Wollongong, University of Wollongong; Grant Wardell-Johnson, Associate Professor, Environmental Biology, Curtin University; James Watson, Professor, The University of Queensland, and Michelle Ward, PhD Candidate, The University of Queensland

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

New research finds native forest logging did not worsen the Black Summer bushfires

David Bowman, University of TasmaniaThe Black Summer bushfires shocked the world and generated enormous global media interest. Fire scientists like myself found themselves filling a role not unlike sport commentators, explaining the unfolding drama in real time.

Scientists who engaged with the media during the crisis straddled two competing imperatives. First was their duty to share their knowledge with the community while knowing their understanding is imperfect. Second was the ethical obligation to rigorously test hypotheses against data analysis and peer review – the results of which could only be known long after the fires were out.

One area where this tension emerged was around the influential idea that logging exacerbated the bushfire disaster. During the fire crisis and in the months afterwards, some scientists suggested logging profoundly affected the fires’ severity and frequency. There were associated calls to cease native forestry and shift wood production to plantations.

But there is no scientific consensus about the possible effects of logging on fire risk. In fact, research by myself and colleagues, published in Nature Ecology and Evolution today, shows logging had little if any effect on the Black Summer bushfires. Rather, the disaster’s huge extent and severity were more likely due to unprecedented drought and sustained hot, windy weather.

These findings are significant for several reasons. Getting to the bottom of the bushfires’ cause is essential for sustainable forest management. And, more importantly, our research confirms the devastating role climate change played in the Black Summer fires.

Firefighters recover after battling blazes at Kangaroo Island on 10 January 2019.
David Mariuz/AAP

Looking for patterns

Our research focused on 7 million hectares of mostly eucalyptus forests, from the subtropics to temperate zones, which burned between August 2019 and March 2020.

There is some evidence to suggest logged areas are more flammable that unlogged forests. Proponents of this view say logging regimes make the remaining forests hotter and drier, and leave debris on the ground that increases the fuel load.

In our research, we wanted to determine:

the relative roles logging and other factors such as climate played in fires that destroyed or completely scorched forest canopies
whether plantations are more vulnerable to canopy scorch than native forests.

To do so, we used landscape ecology techniques that could compare very large areas with different patterns of land use and fire severity. We sampled 32% of the area burnt in three regions spanning the geographic range of the fires.

firefighters run past fire — The research used landscape ecology techniques to compare large areas.
Shutterstock

What we found

Fire intensity is classified according to the vertical layer of vegetation burnt. A scorched tree canopy suggests the most intense type of fire, where the heat extended from the ground to the treetops.

We found several predictors of canopy damage. First, completely scorched canopy, or canopy consumed by fire, typically occurred across connected swathes of bushland. This most likely reflected instances where the fire made a “run”, driven by localised winds.

Extreme weather fire conditions were the next most important predictor of canopy damage. The drought had created vast areas of tinder-dry forests. Temperatures during the fire season were hot and westerly winds were strong.

Southeast Australia’s climate has changed, making such extreme fire weather more frequent, prolonged and severe.

Logging activity in the last 25 years consistently ranked “low” as a driver of fire severity. This makes sense for several reasons.

As noted above, fire conditions were extraordinarily extreme. And there was mismatch between the massive area burnt and the comparatively small areas commercially logged in the last 25 years (4.5% in eastern Victoria, 5.3% in southern NSW and 7.8% in northern NSW).

Fire severity is also related to landscape features: fire on ridges is generally worse than in sheltered valleys.

Our research also found timber plantations were as prone to severe fire as native forestry areas. In NSW (the worst-affected state) one-quarter of plantations burned – than 70% severely. This counteracts the suggestion using plantations, rather than logging native forest, can avoid purported fire hazards.

plantation forest divided by road — Plantation forests were found to be highly flammable.
Shutterstock

A challenge awaits

Our findings are deeply concerning. They signal there is no quick fix to the ongoing fire crisis afflicting Australia and other flammable landscapes.

The crisis is being driven by relentless climate change. Terrifyingly, it has the potential to turn forests from critical stores of carbon into volatile sources of carbon emissions released when vegetation burns.

Under a rapidly warming and drying climate, fuel loads are likely to become less important in determining fire extent and severity. This will make it increasingly difficult, if not impossible, to lower fuel loads in a way that will limit bushfire severity.

A massive challenge awaits. We must find socially and environmentally acceptable ways to make forests more resilient to fire while the also produce sustainable timber products, store carbon, provide water and protect biodiversity.

The next step is a real-world evaluation of management options. One idea worth exploring is whether the fire resistance of native forests can be improved in specific areas by altering tree density, vegetation structure or fuel loads, while sustaining biodiversity and amenity.

Commercial forestry could potentially do this, with significant innovation and willingness to let go of current practices.

Through collective effort, I’m confident we can sustainably manage of forests and fire. Our study is but a small step in a much bigger, zig-zagging journey of discovery.

forest regenerating after fire — Forests must become fire-resilient while performing other functions.
Shutterstock

David Bowman, Professor of Pyrogeography and Fire Science, University of Tasmania

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

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