I have been unwell lately and struggling a little with my health. This has been the case for the last 30 years, having just passed an unwanted anniversary. I first got sick in 1990, when I was about 21. It has been a hard slog ever since. There are times when it is harder than usual – this is one of those times. I have Chronic Fatigue Syndrome (CFS/ME) – the illness that many say doesn’t exist. That is not something people can tell me. It is a terrible affliction and something I would be gladly done with.
So why this post? Well, I’ll be posting on a very limited basis for the time being. I am struggling to get to work each day and frankly that is more important than my Blogs. I still need to pay the bills, put food on the table, etc, and so my ‘hobby’ will have to be pushed to the side a little. I have at times thought that I should just close the Blogs and websites and be done with it – but I really don’t want this illness to steal something else from me. Perhaps one day it will, but not today.
Australia is a land that has known fire. Our diverse plant and animal species have become accustomed to life with fire, and in fact some require it to procreate.
But in recent decades the pattern of fires – also known as the fire regime – is changing. Individual fires are increasingly hotter, more frequent, happening earlier in the season and covering larger areas with a uniform intensity. And these changes to the fire regime are occurring too fast for our native flora and fauna to adapt and survive.
Many of Australia’s iconic eucalypts are “shade intolerant” species that adapted to exist within a relatively harsh fire regime. These species thrive just after a major fire has cleared away the overstory and prepared an ash bed for their seeds to germinate.
Some of our most majestic trees, like the alpine ash, can only regenerate from seed. Those seeds germinate only on bare earth, where the leaf litter and shrubs have been burnt away.
But if fire is so frequent the trees haven’t matured enough to produce seed, or so intense it destroys the seeds present in the canopy and the ground, then even these fire-adapted species can fail.
The current fires are re-burning some forests that were burnt only a decade ago. Those regenerating trees are too young to survive, but also too young to have started developing seed.
With the disappearance of these tree species, other plants will fill the gap. Acacias (wattles) are potential successors as they mature much earlier than alpine ash. Our tall, majestic forests could easily turn into shrubby bushland with more frequent fires.
Even within a burnt area, there are usually some unburnt patches, which are highly valuable for many types of plants and animals. These patches include gullies and depressions, but sometimes are just lucky coincidences of the terrain and weather. The patches act as reserves of “seed trees” to provide regeneration opportunities.
Recent fires, burning in hotter and drier conditions, are tending to be severe over large areas with fewer unburnt patches. Without these patches, there are no trees in the fire zone to spread seeds for regeneration.
Eucalypt seed is small and without wings or other mechanisms to help the wind disperse it. Birds don’t generally disperse these seeds either. Eucalypt seed thus only falls within 100 – 200 metres of the parent tree. It may take many decades for trees to recolonise a large burnt area.
That means wind-blown or bird-dispersed seeds from other species may fully colonise the burnt area well before the Eucalypts. Unfortunately many of these windblown seeds will be weed species, such as African Love Grass, which may then cover the bare earth and exclude successful Eucalypt regeneration while potentially making fires even hotter and more frequent.
Animals have fewer places to hide
Young animals are significantly more vulnerable to disturbances such as fire than mature individuals. So the best time to give birth is a season when fire is rare.
Spring in the southern zones of Australia has, in the past, been wetter and largely free from highly destructive fires. Both flora and fauna species thus time their reproduction for this period. But as fire seasons lengthen and begin earlier in the year, vulnerable nestlings and babies die where they shelter or starve as the fires burn the fruits and seeds they eat.
Australian fauna have developed behaviours that help them survive fire, including moving towards gullies and depressions, climbing higher, or occupying hollows and burrows (even if not their own) when they sense fire.
But even these behaviours will fail if those refuges are uncharacteristically burning under hotter and drier conditions. Rainforest, marshes and the banks of watercourses were once safe refuges against fire, but we have seen these all burn in recent fires.
All aspects of fire regimes in Australia are clearly changing as a result of our heating and drying climate. But humans can have a deliberate effect, and have done so in the past.
Indigenous burning created a patchwork of burnt areas and impacted on the magnitude and frequency of fires over the landscape. These regular burns kept the understory under control, while the moderate intensity and patchiness allowed larger trees to survive.
There have been repeated calls of late to reintroduce Indigenous burning practices in Australia. But this would be difficult over vast areas. It requires knowledgeable individuals to regularly walk through each forest to understand the forest dynamics at a very fine scale.
More importantly, our landscapes are now filled with dry fuel, and shrubs that act as “ladders” – quickly sending any fire into tree canopies to cause very destructive crown fires. Given these high fuel conditions along with their potentially dangerous distribution, there may be relatively few safe areas to reintroduce Indigenous burning.
The changed fire conditions still require active management of forests, with trained professionals on the ground. Refuges could be developed throughout forests to provide places where animals can shelter and from which trees can recolonise. Such refuges could be reintroduced by reducing forest biomass (or fuel) using small fires where feasible or by mechanical means.
Biomass collected by machines could be used to produce biochar or other useful products. Biochar could even be used to improve the soil damaged by the fires and excess ash.
Midstory species could be cut down to prevent the development of fire ladders to tree crowns. Even the overstory could be thinned to minimise the potential for crown fires. Seed could also be collected from thinned trees to provide an off-site bank as ecological insurance.
Such active management will not be cheap. But using machinery rather than fire could control biomass quantity and distribution in a much more precise way: leaving some biomass on the ground as habitat for insects and reptiles, and removing other patches to create safer refuges from the fires that will continue to come.
We already know how deadly this summer’s fires have been for mammals, birds, and reptiles across Australia. But beyond this bushfire season, many of those same species – including our bats, which make up around a quarter of all Australian mammal species – are facing another devastating threat to their survival.
Our recent research, published in the journal Austral Ecology, attempted to quantify this risk – and the results are not encouraging. Up to eight bat species occupy caves in south-eastern Australia that provide conditions suitable for the fungus to grow.
Even before this summer’s fires, seven of those types of bats were listed on state or federal legislation as threatened with extinction. This includes the critically endangered southern bent-winged bat (Miniopterus orianae bassanii), a species whose caves would all provide optimal conditions for growth of the fungus.
Millions of bats wiped out in North America
White-nose syndrome was first detected in the United States in 2006 at a popular tourist cave in the state of New York. Since then, the disease has spread across North America, killing millions of bats in its wake, with many local populations experiencing 90 to 100% mortality.
The novel pathogen hypothesis explains why P. destructans has such catastrophic impacts on North American bats: the immune system of these species is evolutionarily naive to this fungal attack. Accordingly, in Europe and Asia, where P. destructans is endemic and widespread, few bats exhibit white‐nose syndrome and mortalities are rare.
Australia’s unique wildlife is inherently at risk from invasive novel pathogens because of its long‐term biogeographical isolation. Thus Australian bats, like their distant North American relatives, probably lack an effective immune response to P. destructans and would be susceptible to developing white-nose syndrome.
Hibernation is the key risk period
Most fungal pathogens grow best at cool temperatures, and a high body temperature in mammals and birds provides an effective barrier against fungal diseases. The fungus causing white-nose syndrome is also cold-loving, ceasing to grow at temperatures above 20°C. The only time it can infect and kill bats is when they hibernate.
Bats go cold (use torpor) during hibernation to prevent starvation over winter in temperate climates. Hibernating bats that are infected by P. destructans rewarm more frequently than normal. These unscheduled bursts of metabolic heat production prematurely burn up the body fat of overwintering bats. Hence, despite the damage caused by white-nose syndrome to the bat’s skin tissue, they apparently die due to starvation or dehydration.
Hibernation is key to predicting the susceptibility of bat populations to mortality from white-nose syndrome: those with less energy to spare over winter are more at risk. Consequently, white-nose syndrome has fuelled a large research program on the winter ecology and hibernation physiology of North American bats.
Bats in south-eastern Australia do enter a period of winter hibernation, but that is about the extent of what we know. This knowledge gap makes it impossible to predict how they will respond if exposed to P. destructans. Even non-lethal impacts, however, will worsen the extinction-bound trajectory of several cave-roosting species, most notably the eastern and southern bent-winged bats.
What can Australia do?
Given the impending arrival of P. destructans in Australia, and our study’s findings of widespread thermal cave suitability in south-eastern Australia, we urge immediate action. This includes tightening biosecurity measures and gaining missing information on bat biology so we are better prepared for a possible white-nose syndrome epidemic.
The importance of this threat has not been missed by Wildlife Health Australia, which has produced guidelines for reporting and response to incursion. Advice is also available from the Commonwealth. Just recently, white-nose syndrome was listed in the national priority list for exotic environmental pests and diseases, ranking in the top five of native animal diseases and their pathogens.
Cave enthusiasts have also been proactive in alerting members to white-nose syndrome and the risk of accidentally introducing P. destructans, especially when returning from overseas caving adventures. And the Australasian Bat Society – a strong advocate for bat conservation – has alerted the public and government agencies to this potential new threat.
Action now is critical
At present, there is little that would prevent P. destructans from making it its way to Australian caves, despite two years passing since experts assessed the risk of incursion as almost certain.
We need effective measures at all levels, from requiring incoming visitors to identify contact with cave environments, to decontamination procedures at caves popular with international tourists.
Predicting the impact of white-nose syndrome on Australian bats is currently not possible because we know so little about their winter biology. We urge the Australian government to fund specific research to gain this information.
The US Fish and Wildlife Service has injected more than US$46 million since 2008 into research and fieldwork to address the threat. Australian researchers can use this work to focus on the critical data needed to inform models that predict the vulnerability of local bat populations.
Why we need bats to survive
Bats are incredibly valuable in their own right. But the world needs healthy bat populations: a single insectivorous bat can eat up to half its body mass in insects each night, and together colonies of bats provide a service with an estimated value to the agricultural industry alone in the billions of dollars per year.
We hope this terrible disease will not threaten Australian bats. But the precautionary principle dictates we should plan and act now, assuming the worst-case scenario. Alarm bells are ringing.
So who’s right? Well, it’s complicated. The short answer is forest thinning is a good way to lower the risk of fire and is a widely-used strategy to improve forest health. However, there are potential downsides. Thinning needs to be carefully planned to avoid effects on soil, water or sensitive habitats.
Unlike clearfell logging and selection harvesting, mechanical thinning for timber involves felling about half the trees in even-aged, uniformly structured forests. Recently, forest managers are using the practice more for ecological outcomes.
If we look to the future, the recent fires have created conditions for forest regeneration on a large scale. These regenerating forests will thin naturally over time, creating more fuel and increased risk of more large-scale fires. Mechanical thinning can remove this potential flammable vegetation.
Forest thinning should be one of the ways we tackle fire management and forest resilience in future, but we need more research to understand the best way to go about it. Here’s what the evidence says.
What is thinning?
Thinning is a natural forest process, where tree numbers in most even-aged forests reduce through competition over time. For example, Mountain ash forests regenerating naturally after a severe fire might have hundreds of thousands of new seedlings per hectare that self-thin to a few thousand after 20 years, and a few hundred after 80 years.
Mechanical thinning for producing timber is a long-standing commercial forestry practice that uses herbicides, chainsaws or mechanical harvesters. It reduces tree numbers and concentrates growth on fewer trees so they reach a valuable size more quickly. This is to improve commercial timber quality, or to more quickly remove trees that would die through natural thinning.
Thinning for ecological outcomes, on the other hand, is a relatively recent practice being tested in many parts of Australia. It can produce more rapid development of “old-growth” forest features, such as large trees, branches, hollows and coarse woody debris – all important wildlife habitats.
Forest managers are using thinning for other reasons, too. For example, to adapt to climate change by reducing stresses on individual trees from increased drought, heat, insects, disease or wildfire because, among other things, thinning takes away the added stress of competition.
Thinning to reduce fire risk is intended to slow the rate fire spreads, lower flame heights and improve recovery after wildfire hits. This was shown in a 2016 extensive review of US research, which found thinning and prescribed burning helped reduce fire severity, tree mortality and crown scorch. A 2018 study on Spanish pine forests had similar results.
Our own research on Australian forests also supported these findings. We found mechanical thinning plus burning in silver top ash reduces fire fuel hazard, with major reductions in dead trees, stumps and understory.
We compared thinned and unthinned alpine ash forests using computer modelling, simulating severe to extreme weather conditions. And we found modelled fire intensity decreased by 30% and the rate of fire spread and spot fires moving ahead of the main fire decreased by 20% with thinning.
Reducing tree density and fuel through thinning can also make it easier and safer for fire-suppression activities, like direct attack with fire hoses, litter raking or back burns, increasing our chances to control the size of wildfires.
Another study from 2015 in East Gippsland forests found that while overall fuel hazard was lower at thinned sites than nearby unthinned sites, larger woody debris from thinning persisted for 15 years or longer.
This is both a good and bad thing. More logs or woody debris may slow fire spreading, but can make it harder to completely extinguish fires after the fire front passes through.
Thinning is potentially costly, but selling the wood or other organic matter may offset the cost. Timber harvesting machines can also disturb soils or wildlife habitat, but these can be minimised with modern equipment and careful planning.
We’ve seen in the media arguments about using thinning to manage bushfire risks. It’s important conservation and bushfire scientists, the timber industry and government bodies understand all concerns and create space for inclusive dialogue to identify where thinning and prescribed burning are best practised.
In any case, whether you’re for or against the practice, more research is needed to determine how much we should use it. In 2017, the Federal Government funded mechanical fuel reduction trials in three states. But these trials must be expanded to a national program.
This can be done in using adaptive management – trialling the practice at larger scale and monitoring the outcomes.
The evidence from Australia and overseas is compelling, but we need careful planning and thoughtful discussion about how to use thinning to its full potential as part of our strategy in addressing the escalating risks of bushfires in a changing climate.
To delve deeper into the conservation impact, we used publicly available satellite imagery to look at the burnt areas (up to January 7, 2020) and see how they overlapped with the approximate distributions of all the threatened animals and plants listed under the Environment Protection and Biodiversity Conservation Act.
We restricted our analysis to the mediterranean and temperate zone of south-east and south-west Australia.
The bad news
We found that 99% of the area burned in the current fires contains potential habitat for at least one nationally listed threatened species. We conservatively estimate that six million hectares of threatened species habitat has been burned.
Given that many fires are still burning and it is not yet clear how severe the burning has been in many areas, the number of species affected and the extent of the impact may yet change.
What we do know is that these species are already on the brink of extinction due to other threats, such as land clearing, invasive species, climate change, disease, or previous fires.
Approximately 70 nationally threatened species have had at least 50% of their range burnt, while nearly 160 threatened species have had more than 20% of their range burnt.
More threatened plants have been affected than other groups: 209 threatened plant species have had more than 5% of their range burnt compared to 16 mammals, ten frogs, six birds, four reptiles, and four freshwater fish.
Twenty-nine of the 30 species that have had more than 80% of their range burnt are plants. Several species have had their entire range consumed by the fires, such as the Mountain Trachymene, a fire-sensitive plant found in only four locations in the South Eastern Highlands of NSW.
Other species that have been severely impacted include the Kangaroo Island dunnart and the Kangaroo Island glossy black cockatoo. These species’ entire populations numbered only in the hundreds prior to these bushfires that have burned more than 50% of their habitat.
Glossy black cockatoos have a highly specialised diet. They eat the seeds of the drooping sheoak (Allocasuarina verticillata). These trees may take anywhere from 10 to 50 years to recover enough to produce sufficient food for the black cockatoos.
The populations of many species will need careful management and protection to give their habitats enough time to recover and re-supply critical resources.
The figures above do not account for cumulative impacts of previous fires. For example, the critically endangered western ground parrot had around 6,000 hectares of potential habitat burnt in these fires, which exacerbates the impact of earlier extensive fires in 2015 and early 2019.
Threatened species vary in their ability to cope with fire. For fire-sensitive species, almost every individual dies or is displaced. The long-term consequences are likely to be dire, particularly if vegetation composition is irrevocably changed by severe fire or the area is subject to repeat fires.
More than 50% of the habitat of several species known to be susceptible to fire has been burnt – these include the long-footed potoroo and Littlejohn’s tree frog.
Some species are likely to thrive after fire. Indeed, of the top 30 most impacted species on our list, almost 20% will likely flourish due to low competition in their burnt environments – these are all re-sprouting plants. Others will do well if they are not burnt again before they can set seed.
Rising from the ashes
For fire-sensitive threatened species, these fires could have substantially increased the probability of extinction by virtue of direct mortality in the fires or reducing the amount of suitable habitat. However, after the embers settle, with enough investment and conservation actions, guided by evidence-based science, it may be possible to help threatened species recover.
Protection and conservation-focussed management of areas that have not burned will be the single most important action if threatened species are to have any chance of persistence and eventual recovery.
Management of threatening processes (such as weeds, feral predators, introduced herbivores, and habitat loss through logging or thinning) must occur not just at key sites, but across the landscapes they sit in. Maintaining only small pockets of habitat in a landscape of destruction will lock many species on the pathway to extinction.
In some cases, rigorous post-fire restoration will be necessary to allow species to re-colonise burnt areas. This may include intensive weed control and assisted regeneration of threatened flora and specific food sources for fauna, installing nest boxes and artificial cover, or even targeted supplementary feeding.
Unconventional recovery actions will be needed because this unique situation calls for outside-the-box thinking.
We are in a moment of collective grief for what has been lost. A species lost is not just a word on a page, but an entire world of unique traits, behaviours, connections to other living things, and beauty.
These losses do not need to be in vain. We have an opportunity to transform our collective grief into collective action.
Australians are now personally experiencing climate impacts in an unprecedented way. We must use this moment to galvanise our leaders to act on climate change, here in Australia and on the world stage.
The futures of our beloved plants and animals, and our own, depend on it.