Some say we’ve seen bushfires worse than this before. But they’re ignoring a few key facts



Australia is a bushfire-prone nation. But several factors make this fire season worse than those past.
Victorian Government

Joelle Gergis, Australian National University and Geoff Cary, Australian National University

Every time a weather extreme occurs, some people quickly jump in to say we’ve been through it all before: that worse events have happened in the past, or it’s just part of natural climate variability.

The recent bushfire crisis is a case in point. Writing in The Australian recently, columnist Gerard Henderson said:

In Victoria, there were further huge fires in 1983 and 2009. But until now, there was no suggestion that the state’s future would be one of continuing apocalypse.

Of course, Australia has a long history of bushfires. But several factors make eastern Australia’s recent crisis different to infamous bushfires in the past.

First is the enormous geographic spread of this season’s fires, and second, the absence of El Niño conditions typically associated with previous severe fires.

Thirdly and most important, these fires were preceded by the hottest and driest conditions in Australian history.

Record-breaking hot and dry conditions preceded this fire season.
David Mariuz/AAP

Understanding Australia’s climate

As Australia’s climate has warmed since the 1970s, fire weather conditions have become more extreme, and the length of the fire season has increased across large parts of the nation.

Human-induced warming has been evident in Australian temperatures since 1950. This has contributed to a clear long-term trend toward more dangerous fire weather conditions in many areas.




Read more:
Weather bureau says hottest, driest year on record led to extreme bushfire season


As the planet continues to warm, natural climate variability in the Pacific, Indian and Southern oceans will continue to drive variations in Australian climate.

These natural climate drivers are complex. But taking the time to understand them, and how they interact with human climate influences, is critically important.

Natural climate variability refers to processes such as El Niño and its opposite, La Niña in the Pacific Ocean. Together these are known as the El Niño-Southern Oscillation, or ENSO. Other such processes include phases of the Indian Ocean Dipole (IOD) in the Indian Ocean and fluctuations in the Southern Annular Mode (SAM) across the Southern Ocean.

Australia’s natural climate influences.
Bureau of Meteorology

Right now, ENSO is not active, and a very strong positive IOD event – the strongest since 1997 – has just ended. Positive IOD events typically result in below average winter-spring rainfall over southern and central Australia, and are often associated with more severe bushfire conditions.

There has also been a marked warming of the atmosphere over Antarctica, known as sudden stratospheric warming. This has led to a weakening of the polar vortex, resulting in more negative conditions in the Southern Annular Mode – essentially the north-south movement of the westerly wind belt that loops around Antarctica.

New Australian research has found weakening and warming of the stratospheric polar vortex over Antarctica significantly increases the chances of hot and dry extremes, including more severe fire weather conditions across subtropical eastern Australia than is normal for spring-early summer.




Read more:
The air above Antarctica is suddenly getting warmer – here’s what it means for Australia


This combination of unusual natural variability in the Indian and Southern Oceans, the unprecedented lack of winter rains in 2017, 2018 and 2019, and Australia’s hottest summer on record, have contributed to the extreme drought currently affecting 100% of New South Wales and 67.4% of Queensland.

These factors have combined to bake the landscape dry, even transforming usually wet sub-tropical rainforests into available fuel for this season’s catastrophic bushfire conditions.

Winter rainfall in eastern Australia, 1900–2019.
Bureau of Meteorology

How climate influenced past Australian bushfires

Historically, the most severe Australian bushfire seasons and droughts occurred when the Indian Ocean Dipole combined with El Niño to reinforce dry conditions. Both these climate drivers influence Australian rainfall and soil moisture, with the driest conditions over the southeast, but more broadly across most of the country (with the notable exception of coastal NSW).

As Australia’s climate continues to warm, a range of scientific sources suggest some established relationships between the historical drivers of Australian climate and their impact on rainfall and temperature may be breaking down.




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For example, Australia’s hottest years on record were historically associated with El Niño events, in line with global temperature trends. However, global warming means even traditionally cooler La Niña years are now warmer than many El Niño years of the past. This suggests natural variability may be increasingly swamped by human influences on the climate.

Following Australia’s hottest summer on record, and a record-breaking year of heat and drought, the 2019-2020 bushfire season started as early as winter 2019.

Mount Macedon in Victoria, after the Ash Wednesday bushfires in 1983.
Wikimedia

In September, barely a week into spring, catastrophic bushfires wrought havoc in many areas of southern Queensland and northern NSW.

Even the usually moss-covered rainforests of the World Heritage-listed Gondwana Rainforests of Australia burned.

Similarly in Tasmania, the 2016 fires destroyed large areas of ancient Gondwanan forest, triggering a cascade of changes through the entire ecosystem.

Strikingly, the current catastrophic bushfires are occurring in the absence of El Niño conditions typically associated with severe bushfires in the past.

The notorious Ash Wednesday fires that devastated parts of south-eastern Australia in February 1983 occurred during one of the most intense El Niño events on record. Some 75 people were killed across the country’s south-east, and more than 2,000 homes were lost.

Ash Wednesday was also preceded by a positive Indian Ocean Dipole event. Together with the El Niño, this created a “double whammy” of drought conditions which provided the climatic backdrop for the fires.

Average rainfall deciles for total winter-spring rainfall for six positive IOD events that have occurred with El Niño event since 1960.
Bureau of Meteorology

Similarly, the 1994 Sydney fires were also influenced by a combination of El Niño and positive IOD conditions.

However the current drought is affecting areas such as coastal NSW which have not historically been influenced by positive IOD and El Niño events. This suggests other drivers are at play.

Rainfall deficits experienced from 1 July 2018 until 31 December 2019.
Bureau of Meteorology

Perhaps most alarmingly, this summer’s bushfire crisis also differs from the past in the spread and extent of landscape burned. More so than during Victoria’s Ash Wednesday or Black Saturday, this season’s fires have burned large swathes of the country. In some cases, fires merged to form unprecedented “mega fires”. It is sobering to consider what might happen to the Australian landscape the next time an El Niño hits.

Of course it will take time before researchers can pinpoint the full extent to which climate change influenced the current drought and associated bushfires.

But it is already clear to experts that natural variability and human influences on the climate system are now interacting to generate extremes that may have no parallel in Australian history.

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

What this means for bushfire danger

As with land and sea temperatures, Australia has seen rising trends in fire danger indices in recent decades.

In particular, the annual accumulated Forest Fire Danger Index (FFDI) – which takes into account drought, recent rain, air temperature, relative humidity and wind speed – has increased in eastern and southern Australia.




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The bushfire season has become longer and more intense. In fact, the extraordinary conditions experienced during Victoria’s Black Saturday fires in February 2009 later prompted the creation of a new “catastrophic” fire rating, represented by a FFDI of 100 or greater.

On September 6 last year – less than a week out from winter – severe bushfires burned across Queensland and NSW. In most affected areas, daily FFDI values that day (pictured in the bottom right of the graphic below) were higher than anything observed so early in the season since records began in 1950. Astoundingly, a FDDI of 174 was recorded at Murrurundi Gap in the Hunter region of NSW.

Comparison of historical bushfires using the Forest Fire Danger Index for February 16, 1983 (Ash Wednesday, top left), January 6, 1994 (Sydney fires, top right), February 7, 2009 (Black Saturday, bottom left), and September 6, 2019 (bottom right).
Dr Andrew Dowdy, Bureau of Meteorology

Rewriting history

In the past, Australia only had to contend with natural climate variability. Now, our entire weather and climate systems are being altered and amplified by human activity. Climate change is making extreme events even more severe, resulting in unprecedented conditions that are rewriting our nation’s history.

The CSIRO’s most recent climate projections reconfirmed their projections released in 2015 which clearly showed Australia faces more dangerous fire weather conditions in future.

It will take time to understand the exact contribution of each climatic factor in the bushfire season of 2019–2020. However one thing is certain: unless there are global reductions in greenhouse gas emissions, temperatures will continue to rise, increasing the risk that catastrophic bushfire conditions become Australia’s “new normal”.The Conversation

Joelle Gergis, Senior Lecturer in Climate Science, Australian National University and Geoff Cary, Associate Professor, Bushfire Science, Fenner School of Environment and Society, Australian National University

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

Australia’s bushfires could drive more than 700 animal species to extinction. Check the numbers for yourself



Invertebrates out greatly outnumber mammals everywhere, including in bushfire zones.
Michael Lee, CC BY-NC-ND

Mike Lee, Flinders University

The scale and speed of the current bushfire crisis has caught many people off-guard, including biodiversity scientists. People are scrambling to estimate the long-term effects. It is certain that many animal species will be pushed to the brink of extinction, but how many?

One recent article suggested 20 to 100, but this estimate mostly considers large, well-known species (especially mammals and birds).

A far greater number of smaller creatures such as insects, snails and worms will also be imperilled. They make up the bulk of biodiversity and are the little rivets holding ecosystems together.




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But we have scant data on how many species of small creatures have been wiped out in the fires, and detailed surveys comparing populations before and after the fires will not be forthcoming. So how can we come to grips with this silent catastrophe?

This native bee (Amphylaeus morosus) has been devastated by the bushfires across much of its range. It plays important roles in pollinating plants and as part of the food web, but has no common name, and its plight is so far unheralded.
Reiner Richter https://www.ala.org.au/

Using the information that is available, I calculate that at least 700 animal species have had their populations decimated – and that’s only counting the insects.

This may sound like an implausibly large figure, but the calculation is a simple one. I’ll explain it below, and show you how to make your own extinction estimate with only a few clicks of a calculator.

Using insects to estimate true extinction numbers

More than three-quarters of the known animal species on Earth are insects. To get a handle on the true extent of animal extinctions, insects are a good place to start.

My estimate that 700 insect species are at critical risk involves extrapolating from the information we have about the catastrophic effect of the fires on mammals.

We can work this out using only two numbers: A, how many mammal species are being pushed towards extinction, and B, how many insect species there are for each mammal species.

To get a “best case” estimate, I use the most conservative estimates for A and B below, but jot down your own numbers.

How many mammals are critically affected?

A recent Time article lists four mammal species that will be severely impacted: the long-footed potoroo, the greater glider, the Kangaroo Island dunnart, and the black-tailed dusky antechinus. The eventual number could be much greater (e.g the Hastings River mouse, the silver-headed antechinus), but let’s use this most optimistic (lowest) figure (A = 4).

Make your own estimate of this number A. How many mammal species do you think would be pushed close to extinction by these bushfires?

We can expect that for every mammal species that is severely affected there will be a huge number of insect species that suffer a similar fate. To estimate exactly how many, we need an idea of insect biodiversity, relative to mammals.

How many insect species are out there, for each mammal species?

The world has around 1 million named insect species, and around 5,400 species of land mammals.

So there are at least 185 insect species for every single land mammal species (B = 185). If the current bushfires have burnt enough habitat to devastate 4 mammal species, they have probably taken out around 185 × 4 = 740 insect species in total. Along with many species of other invertebrates such as spiders, snails, and worms.

There are hundreds of insect species for every mammal species.
https://imgbin.com/

For your own value for B, use your preferred estimate for the number of insect species on earth and divide it by 5,400 (the number of land mammal species).

One recent study suggests there are at least 5.5 million species of insects, giving a value of B of around 1,000. But there is reason to suspect the real number could be much greater.




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How do our estimates compare?

My “best case” values of A = 4 and B = 185 indicate at least 740 insect species alone are being imperilled by the bushfires. The total number of animal species impacted is obviously much bigger than insects alone.

Feel free to perform your own calculations. Derive your values for A and B as above. Your estimate for the number of insect species at grave risk of extinction is simply A × B.

Post your estimate and your values for A and B please (and how you got those numbers if you wish) in the Comments section and compare with others. We can then see what the wisdom of the crowd tells us about the likely number of affected species.




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Why simplistic models can still be very useful

The above calculations are a hasty estimate of the magnitude of the current biodiversity crisis, done on the fly (figuratively and literally). Technically speaking, we are using mammals as surrogates or proxies for insects.

To improve these estimates in the near future, we can try to get more exact and realistic estimates of A and B.

Additionally, the model itself is very simplistic and can be refined. For example, if the average insect is more susceptible to fire than the average mammal, our extinction estimates need to be revised upwards.

Also, there might be an unusually high (or low) ratio of insect species compared to mammal species in fire-affected regions. Our model assumes these areas have the global average – whatever that value is!

And most obviously, we need to consider terrestrial life apart from insects – land snails, spiders, worms, and plants too – and add their numbers in our extinction tally.

Nevertheless, even though we know this model gives a huge underestimate, we can still use it to get an absolute lower limit on the magnitude of the unfolding biodiversity crisis.

This “best case” is still very sad. There is a strong argument that these unprecedented bushfires could cause one of biggest extinction events in the modern era. And these infernos will burn for a while longer yet.The Conversation

Mike Lee, Professor in Evolutionary Biology (jointly appointed with South Australian Museum), Flinders University

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

You can leave water out for wildlife without attracting mosquitoes, if you take a few precautions



Leaving water out for wildlife is important during droughts and bushfires but if it’s not changed regularly it can be a breeding ground for mosquitoes.
Roger Smith/Flickr, CC BY-NC

Cameron Webb, University of Sydney

Australia is in for a long, hot summer. The recent bushfires have been devastating for communities and wildlife. Drought is also impacting many regions.

Understandably, people want to leave water out for thirsty birds and animals.

Health authorities generally warn against collecting and storing water in backyards as one measure to protect against mosquito bites and mosquito-borne diseases caused by, for example, dengue and Ross River viruses.




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But it’s possible to leave water out for wildlife – and save water for your garden – without supplying a breeding ground for mosquitoes, if you take a few precautions.

For some mozzies, any water will do

Mosquitoes often look for wetlands and ponds to lay their eggs. But sometimes, anything that holds water – a bucket, bird bath, drain or rainwater tank – will do.

When the immature stages of mosquitoes hatch out of those eggs, they wriggle about in the water for a week or so before emerging to fly off in search of blood.

While there are many mosquitoes found in wetlands and bushland areas, Aedes notoscriptus and Culex quinquefasciatus are the mosquitoes most commonly found in our backyards and have been shown to transmit pathogens that cause mosquito-borne disease.

The Australian backyard mosquito (Aedes notoscriptus) is quick to take advantage of water-filled containers around the home.
Cameron Webb (NSW Health Pathology)

In central and north Queensland, mosquitoes such as Aedes aegypti can bring more serious health threats, such as dengue, to some towns.




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Mosquitoes can also impact our quality of life through bites as well as the nuisance of simply buzzing about our bedrooms and backyards.

So how can you stop mozzies making a home in your backyard?

Empty water containers once a week

Mosquitoes need access to standing water for about a week or so. Reduce the number of water-filled containers available or how long that water is available to mosquitoes.

Emptying a water-filled container once a week will stop the immature mosquitoes from completing their development and emerging as adults.

If you’re leaving water out for pets or wildlife, use smaller volume containers that will allow for easy emptying once a week. You can tip any remaining water into the garden, as mosquito larvae won’t survive if they’re “stranded” on soil.

For larger or heavier items, such as bird baths, flushing them out once a week with the hose will knock out most of the wrigglers and stop the mosquitoes completing their life cycle.

Make sure garden water doesn’t slosh about

Be careful with self-watering planter boxes. These often have a reservoir of water in their base and, while it may seem like a water-wise idea, these can turn into tiny mozzie hotels!

A simple trick to keep water available to plants, but not mosquitoes, is to fill your potted plant saucers with sand. The sand traps and stores some moisture but there is no water sloshing about for mosquitoes.

If you’re collecting water from showers, baths, or washing machines (commonly known as grey water), use it immediately on the garden, don’t store it outside in buckets or other containers.




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Gutters, ponds, tanks and pools

Make sure your roof gutters and drains are free of leaves and other debris that will trap water and provide opportunities for mosquitoes.

Ensure rainwater tanks (and other large water-storage containers) are appropriately screened to prevent access by mosquitoes.

Rainwater tanks can be a useful way to conserve water in our cities but they can also be a source of mosquitoes.
Cameron Webb (NSW Health Pathology)

A well maintained swimming pool won’t be a source of mosquitoes. But if it’s turning “green”, through neglect and not intent, it may become a problem. Mosquitoes don’t like the chlorine or salt treatments typically used for swimming pools but when there is a build up of leaves and other detritus, as well as algae, the mosquitoes will move in.




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For backyard ponds, introducing native fish can help keep mosquito numbers down.

But if you want your pond to be a home for frogs, avoid fish as they may eat the tadpoles. Instead, try to encourage other wildlife that may help keep mosquito numbers down by creating habitats for spiders and other predatory insects, reptiles, frogs, birds, and bats.

Avoiding excessive use of insecticides around the backyard will help encourage and protect that wildlife too.

Mozzies can still come

There isn’t much that can be done about those mosquitoes flying in from over the back fences from local bushland or wetland areas.

Mosquitoes are generally most active at dusk and dawn so keep that in mind when planning time outdoors. But when mosquito populations are peaking, they’ll be active almost all day long.

Applying an insect repellent can be a safe and effective way to stop those bites.




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Covering up with long pants, long-sleeved shirt and shoes will provide a physical barrier to mosquitoes. If you’re spending a lot of time outdoors, perhaps even consider treating your clothing with insecticide to add that extra little bit of protection.

Make sure insect screens are installed, and in good condition, on windows and doors. Mosquitoes outdoors can be bad; you don’t want them inside as well.The Conversation

Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney

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