For three years before the Black Summer megafires of 2019–20, cool season rainfall in southeastern Australia was only half that of normal. When fires broke out, intensely dry conditions helped them spread through areas typically resistant to burning, such as wetlands and rainforests.
After the fires came three years of above-average rainfall, and scientific reports charted rapid vegetation regrowth.
It’s easy to think the rains let nature repair itself. But is that the full story? In our new research, we looked at what happened to seven severely burnt plant communities in the Greater Blue Mountains, west of Sydney.
We found a mixed picture. Wet sclerophyll forests supporting tall eucalypts skirted by ferns recovered within five years. But Blue Mountains rainforests did not recover from burns of any severity. Nor did grassy woodlands.
How can we track recovery?
To find out how well forests and other communities recovered from the Black Summer fires, we tracked recovery across the million-hectare Greater Blue Mountains World Heritage Area. Seven severe fires hit this region over the 2019–20 summer. The biggest was the Gospers Mountain fire, which burned an area seven times the size of Singapore – the largest fire from a single ignition point in Australia’s recorded history.
Five years on, if you had looked out across the Blue Mountains landscape you might have thought recovery was well under way. Thick scrub quickly replaced charred undergrowth in many areas. Across our study sites, many burned regions had denser understoreys – the layer of vegetation between forest floor and canopy – than unburnt areas.
But recovery isn’t just about how much vegetation is there. It’s about whether the layers of shrubs and canopy trees that make up a functioning plant community have returned to their previous state.
After fire moves through, some plant species rapidly regrow, outcompeting their rivals for light and water. But these species are often short-lived, failing to survive beyond a few years. On the other hand, species such as eucalypts and banksia may take years to regrow but then live much longer.
This means depending on when we take our measurements, we might mistake a temporary pulse of growth for real recovery.
To address this issue, our study tracked plant growth using a time-series of satellite images. This way, we could see the full trajectory of recovery, not just a snapshot.
A plant community that has fully recovered from burns will look stable year to year and mirror patterns of growth at unburnt sites. Poorly recovered areas, in contrast, will show distinct fluctuations.
We used this method to track recovery from low- to extreme-severity fire at 760 forest, heath and wetland sites in the Greater Blue Mountains region.
What did we find?
An earlier large-scale synthesis two years after the Black Summer fires found wet forests had suffered greater declines than drier plant communities.
Our findings five years after the fires tell a more complex story.
Some wet forests, such as wet sclerophyll, were able to take advantage of the heavy rains to recover fully within five years.
Others were less fortunate. The Blue Mountains are home to rare remnant rainforest, featuring stands of trees such as coachwood, lilly-pilly and sassafras, whose ancestors date back to Gondwana. We found these had not recovered after fires of any severity.
The region’s grassy woodlands also showed no sign of recovery when burned, despite being dry, open areas.
Why? We suggest the intense rains following Black Summer made it difficult for the community’s characteristic grasses and tussocks – adapted to dry conditions – to successfully re-establish.
What if the big dry hadn’t ended?
The years of heavy rain after the Black Summer fires were unusual. If drought had continued, would we have seen different recovery outcomes?
To tease out this question, we modelled what recovery would have looked like for plant communities under drought stress.
Simply put, all would be worse off. In particular, wet sclerophyll forests and freshwater wetlands showed declines five times greater than other plant communities.
This is likely due to the fact that the plant species in these ecosystems need heavy rainfall to re-establish. For instance, freshwater wetlands often need to be completely flooded for species to return.
These communities may be pushed to the point of collapse if drought persists after the next megafire.
What can we do?
Ferocious fires have swept through Europe in recent months and the southern summer is likely to coincide with a strong El Niño event, bringing a higher risk of intense heatwaves, drought and fire.
As climate change accelerates, these extreme conditions will become more common. To protect our plant communities, we must tailor our fire-management strategies. No two communities respond to fire the same way, and recovery outcomes differ greatly depending on whether post-fire conditions are hot and dry or cool and wet. A one-size-fits-all approach won’t work.
During the Black Summer fires, a team of firefighters protected the last wild stand of the ancient, fire-averse Wollemi pine in the Blue Mountains.
To help rainforests and other fire-averse plant communities survive, we will need technologies that help us rapidly detect and suppress new fires – and long-term monitoring programs to let us know when species are at risk.
In other landscapes, we must rethink our reliance on fuel-reduction burns. This is because plants are at higher risk of damage from fire if they have been frequently burnt in the past. When we repeatedly burn an area, we inflate this risk and condemn many plants and animals to staggering losses in future fires.
Of course, all these efforts won’t matter if we fail to tackle the underlying reason why fires are getting more frequent and severe – climate change.
Emily Simpson receives funding from the Ecological Society of Australia.
Aaron Greenville receives funding from the NSW Department of Climate Change, Energy, the Environment and Water.
Glenda Wardle receives funding from the Australian Research Council and the Terrestrial Ecosystem Research Network. She is a WWF-Australia director and a member of the Australasian Network for Plant Conservation.
Chris Dickman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
Seventy beaches across New South Wales are part of the $34m dawn-to-dusk drone-monitoring program, which one expert has called ‘the best technology we have at the moment’
On the morning of August 26, a section of mountain near Langtang Lirung peak in Nepal suddenly collapsed.
A huge mass of rock, ice and debris plunged roughly 1,200 metres into the valley below, producing a hugely destructive flood on the Lhende Khola river. The flow travelled almost 100 kilometres downstream, washing villages and bridges away. Almost 1,000 people died and thousands more are still missing across the Nepal-China border.
What caused it? At first, it looked like a glacier collapse. But emerging satellite and photographic evidence suggests a more complex picture – an avalanche of rock and ice, rather than a simple glacier collapse.
The mountain face now has a sharply defined scar after the collapse, clearly marking the boundary between the remaining slope and the section which failed.
This isn’t the first rock-ice avalanche in the Himalayas, but it is by far the most devastating. Unfortunately, it is unlikely to be the last. Rising temperatures due to climate change mean the permanently frozen slopes of mountains in the region may begin to melt and destabilise.
How did a mountain collapse?
The steep mountain face was topped by a glacier – a heavy river of ice. It’s likely that the steep slope of bedrock collapsed first, followed by the overhang of ice.
As this enormous mass fell into the valley, it created a tremendous amount of energy. This would likely have melted the ice in the avalanche and any in the valley, adding large volumes of faster-moving water to the flow and intensifying the debris flood.
The rugged Himalayan terrain made the disaster even worse by providing a steep, confined pathway, accelerating the mass of water, rock, dirt and ice as it flowed into the river.
A landslide followed the first collapse and a small lake has formed within the newly created depression in the valley. The site will remain unstable for some time.
Now that we know more about how the Langtang collapse became a cascading disaster, we can find parallels.
The closest example is the February 2021 rock-ice avalanche in Chamoli, India, which began when a huge landslide down Ronti Peak triggered an avalanche carrying an estimated 27 million cubic metres of rock and ice. This became a fast-moving debris flowing down a river valley. Over 200 people were killed or left missing.
The high mountains are changing
The Himalayas are the best known feature of the High Mountain Asia region – a large area with an average elevation of 4,000 metres which includes mountain ranges and the Tibetan plateau.
Despite its height, the region is not safe from climate change. In fact, change is happening faster here.
As air temperatures warm past 0°C more often, glaciers are beginning to melt. Snow and rainfall patterns are changing.
Permafrost – long-frozen earth and rock – is also becoming vulnerable. This matters most for steep mountain slopes, where fractured rock can be held together by ice.
When the ice melts, these ice-rock bonds can break. Water can begin to move down through long-frozen mountain slopes and bedrock. That means long-stable slopes can suddenly fail.
It’s common to picture glaciers as a slow-moving river of ice in a valley. But this high region is home to many hanging glaciers and smaller ice masses perched on steep mountain slopes.
These are at particular risk because they often sit high above valleys. If their rock support collapses, they can too. If they take rock, sediment and water with them, a simple glacial collapse can become a much larger avalanche or debris flow.
As the climate heats up, warmer air can lead to faster melting of the glacier and change how tightly it is coupled to its rocky bed. A small change in conditions at the glacier’s base can make it unstable.
Which areas are at highest risk?
Predicting the next big mountain or glacier collapse is a very complex task.
But we can improve our understanding of the landscapes and environmental conditions associated with such failures. Recent analysis of large rock and ice avalanches across the High Mountain Asia region gives us important insight.
Of the 60 avalanches analysed, 86% began on slopes steeper than 30° and at elevations above 3,000 metres. Almost two-thirds (65%) began in areas where permafrost was probable.
Earthquakes, underlying rock types and structures, and changes to rainfall can also make these avalanches more likely.
Across this region, rock–ice avalanches have been documented to occur more often in the Western Himalayas, including the Karakoram and Pamir Ranges, and across southern and eastern Tibet.
We will need to treat these rock-ice avalanches as a cascading hazard separate to isolated glacier collapses or landslides.
Could we be forewarned?
Footage from the disaster shows many people were caught unaware. If we could predict which glaciers or mountain faces are at highest risk, we could potentially save lives.
It is not an easy task. Signs a collapse is imminent such as rock deformation or fractures can often be subtle.
One approach could be combining field observations and seismic monitoring with data from satellites equipped with sensors able to observe changes in mountain faces and make optical and thermal infrared observations. New techniques such as the use of drones to monitor inaccessible or dangerous terrain are also worth exploring.
Observations must feed into early-warning systems capable of rapidly communicating the danger to communities downstream.
Because many Himalayan rivers cross national boundaries, nations will have to work together to strengthen data sharing, joint monitoring and coordinated early-warning systems.
The task is increasingly urgent. Climate change is loading the dice for more disasters in this high, cold region.
Tirthankar Ghosh is affiliated with the Indian Institute of Technology Bombay.
Levan Tielidze receives funding from the Australian Research Council's Special Research Initiative on Securing Antarctica's Environmental Future.
Who dreams of having a Euro summer now when staying in an ancient, uncooled building in the Old Town is like trying to sleep in a wood-fired pizza oven?
This week the Euro summer comes to an end – and so does a certain type of posting on Instagram.
Waiting at the bus stop in the grey winter dawn, a slanting rain soaking your trouser leg, you can warm yourself by scrolling your feed and seeing pictures of Australians enjoying a Euro summer. There it is again – azure Greek coves, plates of barbecued sardines, the yachts rented by the hour, and selfies on the balcony of some Paris Airbnb, drinking wine in the long, blue night.
Australia’s Macquarie Island lies deep in the Southern Ocean, about 1,500 kilometres southeast of Tasmania. This World Heritage-listed sanctuary is a haven for species such as elephant and fur seals, penguins, albatrosses and petrels, and a key site for wildlife researchers.
But it is not safe from H5N1 bird flu. This lethal virus is rapidly spreading across the Australian mainland and Southern Ocean, already hitting other sub-Antarctic islands including Heard Island.
However, the Australian government has decided to withdraw all 24 expeditioners – including scientists, tradespeople and support staff – from the site. It says this is mainly to protect them from the psychosocial risks – the psychological harms of working in stressful or traumatic conditions – associated with living through a potential H5N1 outbreak and the wildlife casualties it may cause.
Those risks are real. Witnessing mass wildlife deaths could be deeply distressing for any person. But taking everyone off the island means the scientists who work there cannot document an outbreak as it unfolds, or understand what is happening to wildlife populations we have studied for decades.
At Macquarie, monitoring is vital
Scientists have worked at Macquarie Island for more than 70 years, and withdrawing all personnel will disrupt long-term wildlife, climate, atmospheric and geological monitoring, well beyond the bird flu response.
For southern elephant seals, the stakes are particularly high. The species is considered “vulnerable” on the IUCN Red List and under Australia’s Environment Protection and Biodiversity Conservation Act. Decades of monitoring show numbers of breeding females at Macquarie’s major colony have fallen sharply, dropping from 9,400 in 1949 to 2,550 in 2023. The federal recovery plan for this species identifies disease outbreaks as a threat and calls for regular, scientifically robust monitoring.
Bird flu is precisely this type of threat.
At Australia’s Heard Island, more than 13,000 elephant seal pups died during a recent H5N1 outbreak, while the number of breeding females fell by almost half at monitored sites on Britain’s South Georgia. The Australian Antarctic Division itself identified the need for 2026-27 population data to assess the impact of bird flu on Macquarie Island. But the government has now reversed course in withdrawing the island’s staff.
But avoiding exposure to loss isn’t the only answer. Guidance from the World Health Organisation emphasises preparation, training and dedicated mental health and psychosocial support for personnel working in difficult emergency environments.
Other nations have already faced this problem. At other sub-Antarctic islands such as South Georgia, Crozet and Kerguelen and the Falklands, authorities boosted biosecurity measures – including providing personal protective equipment and guidance on wildlife sampling – to maintain essential science and disease surveillance. Similarly, the international Scientific Committee for Antarctic Research Action Group on Wildlife Health recommends assessing which activities should continue during outbreaks and outlines appropriate protective measures.
This raises important questions about how Australia reached its decision. Did the government seek advice from other programs that have successfully monitored outbreaks? Could a smaller specialist team remain with additional training, shorter deployments and dedicated psychological support?
The government hasn’t indicated what the long-term plan will be. Bird flu may not arrive this summer. Elsewhere in the Southern Ocean, outbreaks have recurred across multiple years. If the virus arrives next year or stretches over several years, will expeditioners be withdrawn indefinitely?
Biological sampling during the recent H5N1 outbreak at South Georgia.Jane Younger
Can cameras replace scientists?
After Australia’s personnel leave, the government may rely on live cameras, drones and satellites to monitor Macquarie Island. These tools will be useful. At Heard Island, drones were invaluable for measuring the enormous scale of mortality.
But remote monitoring cannot replace biological sampling. A camera cannot swab a freshly dead pup, collect blood from a surviving animal or conduct a postmortem.
Across Crozet, Kerguelen, Heard, South Georgia and the Falkland Islands, scientists sampled dead and apparently healthy wildlife during major outbreaks. These samples confirmed infections, detected antibodies in survivors and enabled viral sequencing. In our recent research, 104 new virus genomes collected across six sub-Antarctic and Antarctic locations allowed us to map transmission over thousands of kilometres and show how the virus continues to evolve, including adapting to mammals.
Without field samples, we lose crucial information about how the virus is evolving and spreading, limiting our ability to anticipate what happens next.
Royal penguins are endemic to Macquarie Island, where they live in large colonies.Richard McManus/Getty
Remote should not mean out of sight and out of mind
Surveillance, testing and reporting have been a top priority in our bird flu response on the Australian mainland. It should be no different on Macquarie Island, even though it is a remote location.
We cannot stop animals from dying if the lethal virus strain arrives. But we can understand which species are affected, which animals survive and where the virus may travel next.
We have monitored Macquarie’s declining elephant seal population for decades. We should not avert our eyes now.
We say this as scientists who have studied bird flu outbreaks and witnessed devastating wildlife losses firsthand. We are prepared for the difficult reality of studying wildlife disease. But what is much harder to accept is being forced to look away when science could still make a difference.
Jane Younger receives funding from the Australian Research Council, National Geographic Society, Rolex, WIRES, the Marine Megafauna Research Fund and Lindblad-National Geographic. She is affiliated with the University of Tasmania.
Augustin Clessin receives funding from France's Agence Nationale de la Recherche. He is affiliated with France's Centre d’Ecologie Fonctionnelle et Evolutive, Centre National de la Recherche Scientifique, Université de Montpellier, École Pratique des Hautes Études and Institut de Recherche pour le Développement.
Amandine Gamble does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
