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Air Quality, Bushfires, Climate Change, Health, Media

Under climate change, winter will be the best time for bush burn-offs – and that could be bad news for public health

Giovanni Di Virgilio, UNSW; Annette Hirsch, UNSW; Hamish Clarke, University of Wollongong; Jason Evans, UNSW; Jason Sharples, UNSW, and Melissa Hart, UNSW

At the height of last summer’s fires, some commentators claimed “greenies” were preventing hazard reduction burns – also known as prescribed burns – in cooler months. They argued that such burns would have reduced the bushfire intensity.

Fire experts repeatedly dismissed these claims. As then NSW Rural Fire Service Commissioner Shane Fitzsimmons noted in January this year, the number of available days to carry out prescribed burns had reduced because climate change was altering the weather and causing longer fire seasons.


Read more: How does bushfire smoke affect our health? 6 things you need to know


This public conversation led our research team to ask: if climate change continues at its current rate, how will this change the days suitable for prescribed burning?

Our results, published today, were unexpected. Climate change may actually increase the number of burn days in some places, but the windows of opportunity will shift towards winter months. The bad news is that burning during these months potentially increases the public health impacts of smoke.

A hot debate

Hazard reduction involves removing vegetation that could otherwise fuel a fire, including burning under controlled conditions. But its effectiveness to subdue or prevent fires is often debated in the scientific community.

Commissioner Fitzsimmons weighs in on a national debate about hazard-reduction burns.

Those with experience on fire grounds, including Fitzsimmons, say it’s an important factor in fire management, but “not a pancea”.

Despite the debate, it’s clear hazard reduction burning will continue to be an important part of bushfire risk management in coming decades.


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


Modelling future weather

Before conducting prescribed burns, firefighting agencies consider factors such as vegetation type, proximity to property, desired rate of spread and possible smoke dispersal over populated areas. But we wanted to distil our investigation down to daily weather factors.

We reduced those factors to five key components. These were maximum temperature, relative humidity, wind speed, fuel moisture and the McArthur forest fire danger index (the index used to forecast fire danger in southeast Australia).

We looked at these elements on prescribed burning days between 2004-2015. We then used climate models to simulate how the conditions would change with global warming over southeast Australia, relative to a baseline historical 20-year period for 1990-2009.

To make a valid 20-year comparison, we compared the historical period to a modelled period from 2060-2079, assuming emissions continue to rise at their current pace.

A controlled burn in bushland, with small flames and lots of smoke.
Under global warming, suitable conditions for prescribed burns will be shifted to late winter and early spring in many places. Shutterstock

Surprisingly, we found, with one regional exception, the number of days suitable for prescribed burning did not change. And in many places, the number increased.

As the fire season lengthened under a warming climate, the number of days suitable for burning just shifted from autumn to winter.

Shifting seasons

Our research indicated that by 2060 there’ll be fewer prescribed burning days during March, April and May. These are the months when most burning happens now.

But there will be significantly more opportunities for burning days from June to October. This is because the conditions that make for a good day for prescribed burning – such as mild and still days – start to shift to winter. Today, weather in these months is unsuitable for conducting burns.

Interestingly, these results aren’t uniform across southeast Australia. For example, much of the Australian east coast and South Australia would see seasonal shifts in burning windows, with around 50% fewer burning days in March to May.

Much of Victoria and in particular the southern regions saw an increase in burning windows during April to May and, in some parts of the state, through September and October as well.

Only the east Queensland coast would see a total reduction in prescribed burn days from April to October.

The smoke trap

This may be good news for firefighters and those agencies who depend on prescribed burning as a key tool in bushfire prevention. But, as so often is the case with climate change, it’s not that simple.

A byproduct of prescribed burning is smoke, and it’s a very significant health issue.

Last year, research showed global warming will strengthen an atmospheric layer that traps pollution close to the land surface, known as the “inversion layer”. This will happen in the years 2060-79, relative to 1990-2009 – especially during winter.


Read more: The smoke from autumn burn-offs could make coronavirus symptoms worse. It’s not worth the risk


Unfortunately, the conditions that create inversion layers – including cool, still air – correspond with conditions suitable for prescribed burning.

For asthmatics and those sensitive to air pollution, smokier burn days could make winter months more difficult and add further stress to the health system.

It also creates an additional challenge for firefighting agencies, which must already consider whether smoke will linger close to the surface and potentially drift into populated regions during prescribed burns.

This is just one factor our firefighting agencies will need to face in the future as bushfire risk management becomes more complex and challenging under climate change.


Read more: How does bushfire smoke affect our health? 6 things you need to know The Conversation


Giovanni Di Virgilio, Research associate, UNSW; Annette Hirsch, Post Doctoral Research Fellow, UNSW; Hamish Clarke, Research Fellow, University of Wollongong; Jason Evans, Professor, UNSW; Jason Sharples, Professor of Bushfire Dynamics, School of Science, UNSW Canberra, UNSW, and Melissa Hart, Graduate Director, ARC Centre of Excellence for Climate Extremes, UNSW

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

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Bushfires, Emergency Management

Black Summer – how the NSW community responded to the 2019-20 bushfire season

The 2019-20 bushfire season saw unprecedented, destructive bushfires across New South Wales (NSW). After an early start to the fire season in August 2019, fires spread south from the Queensland border to the Victorian border over the course of spring and summer. Tens of thousands of people were displaced by the fires, including residents, tourists and visitors to affected areas. Significant rainfall in early February 2020 helped contain the fires by February 13 and brought an end to the most deadly and destructive fire season in NSW history. Tragically, 26 people lost their lives in the fires, including four NSW RFS volunteers and three US aerial firefighters. Many more people were affected by smoke, including in regional areas and major population centres such as the north coast, Sydney, Canberra, Newcastle and Wollongong. By season’s end, fires had burned a record 5.5 million hectares of NSW and destroyed 2,448 homes (NSW RFS 2020). Community and commercial buildings and infrastructure were also significantly impacted on. The fires adversely affected many industries, including agriculture, forestry and tourism. The NSW RFS engaged the Bushfire and Natural Hazards Cooperative Research Centre to conduct research into community preparedness, warnings and responses to the 2019-20 NSW bushfires. The NSW RFS identified eight key themes for investigation, including: (i) risk communication; (ii) effect of prolonged and repeated exposure to bushfire on planning, preparation and responses; (iii) effect of previous experience and exposure to bushfire on planning, preparation and responses; (iv) sheltering practices; (v) experiences of tourists and visitors; (vi) awareness and attitudes toward bushfire risk reduction; (vii) building standards; and (viii) community recovery and resilience. This report presents findings from research into community attitudes and experiences of the 2019-20 bushfire season undertaken for the NSW RFS. The NSW RFS Statement of Work identified the following themes and questions for investigation:

  • Risk communication
  • Effect of prolonged and/or repeated exposure to bushfire
  • Effect of previous experiences and exposure to bushfire
  • Sheltering practices
  • Experience of tourists and visitors
  • Awareness and attitudes toward bushfire risk reduction activities
  • Building standards
  • Community recover and resilience
Bushfire and Natural Hazards CRC 2021 - (Whittaker, J., Haynes, K., Wilkinson, C., Tofa, M., Dilworth, T., Collins, J., Tait)

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Bushfires, Flora and Fauna, Media, Threatened Species

5 remarkable stories of flora and fauna in the aftermath of Australia’s horror bushfire season

hamiltonphillipa/iNaturalist, CC BY-NC-SA
Will Cornwell, UNSW; Casey Kirchhoff, UNSW, and Mark Ooi, UNSW

Around one year ago, Australia’s Black Summer bushfire season ended, leaving more than 8 million hectares across south-east Australia a mix of charcoal, ash and smoke. An estimated three billion animals were killed or displaced, not including invertebrates.

The impact of the fires on biodiversity was too vast for professional scientists alone to collect data. So in the face of this massive challenge, we set up a community (citizen) science project through the iNaturalist website to help paint a more complete picture of which species are bouncing back — and which are not.

Almost 400 community scientists living near or travelling across the firegrounds have recorded their observations of flora and fauna in the aftermath, from finding fresh wombat droppings in blackened forests, to hearing the croaks of healthy tree frogs in a dam choked with debris and ash.

Each observation is a story of survival against the odds, or of tragedy. Here are five we consider particularly remarkable.

Greater gliders after Australia’s largest ever fire

The Gospers Mountain fire in New South Wales was the biggest forest fire in Australian history, razing an area seven times the size of Singapore. This meant there nothing in history scientists could draw from to predict the animals’ response.

So it came as a huge surprise when a community scientist observed greater gliders deep within the heart of the Gospers Mountain firegrounds in Wollemi National Park, far from unburned habitat. Greater gliders are listed as “vulnerable” under national environment law. They’re nocturnal and live in hollow-bearing trees.

A greater glider with shining eyes at night
A citizen scientist snapped this photo of a greater glider in the heart of the the Gospers Mountain firegrounds. Mike Letnic/iNaturalist, CC BY-NC

How gliders survived the fire is still unknown. Could they have hidden in deep hollows of trees where the temperature is relatively cooler while the fire front passed? And what would they have eaten afterwards? Greater gliders usually feed on young leaves and flowers, but these foods are very rare in the post-fire environment.

Finding these gliders shows how there’s still so much to learn about the resilience of species in the face of even the most devastating fires, especially as bushfires are forecast to become more frequent.

Rare pink flowers burnishing the firegrounds

The giant scale of the 2019-20 fires means post-fire flowering is on display in grand and gorgeous fashion. This is a feature of many native plant species which need fire to stimulate growth.

Excitingly, community scientists recorded a long-dormant species, the pink flannel flower (Actinotus forsythii), that’s now turning vast areas of the Blue Mountains pink.

Pink flannel flowers are bushfire ephemerals, which means their seeds only germinate after fire. Margaret Sky/iNaturalist, CC BY-NC

Pink flannel flowers are not considered threatened, but they are very rarely seen.

Individuals of this species spend most of their life as a seed in the soil. Seeds require a chemical found in bushfire smoke, and the right seasonal temperatures, to germinate.

Rediscovering the midge orchid

Much of Australia’s amazing biodiversity is extremely local. Some species, particularly plants, exist only in a single valley or ridge. The Black Summer fires destroyed the entire range of 100 Australian plant species, incinerating the above-ground parts of every individual. How well a species regenerates after fire determines whether it recovers, or is rendered extinct.

The midge orchid. Nick Lambert/iNaturalist, CC BY-NC

One of these is a species of midge orchid, which grows in a small area of Gibraltar Range National Park, NSW.

All of the midge orchid’s known sites are thought to have burned in late 2019. The species fate was unknown until two separate community scientists photographed it at five sites in January 2021, showing its recovery.

Like many of Australia’s terrestrial orchids, this species has an underground tuber (storage organ) which may have helped part of it avoid the flames’ lethal heat.


Read more: After last summer's fires, the bell tolls for Australia’s endangered mountain bells


Don’t forget about insects

Despite their incredible diversity and tremendous value to society, insects tend to be the forgotten victims of bushfires and other environmental disasters.

Many trillions of invertebrates would have been killed in the fires of last summer. A common sight during and after the bushfire season was a deposit of dead insects washed ashore. Some died from the flames and heat, while others died having drowned trying to escape.

Dead insects washed up on the beach was a common sight in the fire aftermath. BlueBowerStudio/iNaturalist, CC BY-NC

One dead insect deposit — one of hundreds that washed up near Bermagui, NSW on Christmas Eve — included a range of species that have critical interactions with other organisms.

This includes orchid dupe wasps (Lissopimpla excelsa), the only known pollinator of the orchid genus Cryptostylis. Transverse ladybirds (Coccinella transversalis), an important predator of agricultural pests such as aphids, also washed up. As did metallic shield bugs (Scutiphora pedicellata), spectacular iridescent jewel bugs that come in green and blue hues.

Some insects died from the flames and heat, while others died having drowned trying to escape the flames. BlueBowerStudio/iNaturalist, CC BY-NC

The unlikely survival of the Kaputar slug

Creatures such as kangaroos or birds have a chance to flee bushfires, but smaller, less mobile species such as native slugs and snails have a much tougher time of surviving.

The 2019-2020 bushfire season significantly threatened the brilliantly coloured Mount Kaputar pink slug, found only on the slopes of Mount Kaputar, NSW. When fires ripped through the national park in October and November 2019, conservationists feared the slug may have been entirely wiped out.


Read more: Photos from the field: zooming in on Australia's hidden world of exquisite mites, snails and beetles


But park ranger surveys in January 2020 found at least 60 individuals managed to survive, likely by sheltering in damp rock crevices. Community scientists have spotted more individuals since then, such as the one pictured here found in September 2020.

But the slug isn’t out of the woods yet, and more monitoring is required to ensure the population is not declining.

Bright pink slug
A community scientist spotted this rare slug in firegrounds. Taylor/iNaturalist, CC BY-NC

Continuing this work

While community scientists have been documenting amazing stories of recovery all across Australia, there are still many species which haven’t been observed since the fires. Many more have been observed only at a single site.

The Snowy River westringia (Westringia cremnophila), for instance, is a rare flowering shrub found on cliffs in Snowy River National Park, Victoria. No one has reported observing it since the fire.

So far these community scientist observations have contributed to one scientific paper, and three more documenting the ability for species to recover post-fire are in process.

Recovery from Black Summer is likely to take decades, and preparing a body of scientific data on post-fire recovery is vital to inform conservation efforts after this and future fires. We need more observations to continue this important work.


Read more: Summer bushfires: how are the plant and animal survivors 6 months on? We mapped their recovery The Conversation


Will Cornwell, Associate Professor in Ecology and Evolution, UNSW; Casey Kirchhoff, PhD Candidate, UNSW, and Mark Ooi, Senior Research Fellow, UNSW

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

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Bushfires, Flora and Fauna, Threatened Species

A preliminary assessment of the impact of the 2019/2020 fires on NSW plants of national significance

Auld T.D., Mackenzie B.D.E., Le Breton T.D, Keith D.A., Ooi M.K.J., Allen S., Gallagher R.V. (2020) A preliminary assessment of the impact of the 2019/2020 fires on NSW plants of national significance. Report to NSW Government Department of Planning, Industry and Environment.

The impacts of the 2019/2020 fires on NSW plant species were assessed using an expert-derived framework that addressed 11 key factors likely to drive risk to plants from fire or during post-fire recovery. This assessment builds on the national assessment of risk to plants as a results of these fires (Gallagher 2020) by providing additional NSW data, determining how species identified as at high or medium risk relate to current conservation measures in NSW, and framing priority conservation priority species and management actions for NSW.

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