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.
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?
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.
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.
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.
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.
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).
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.
How to unleash the wisdom of crowds
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.
John Woinarski, Charles Darwin University; Brendan Wintle, University of Melbourne; Chris Dickman, University of Sydney; David Bowman, University of Tasmania; David Keith, UNSW, and Sarah Legge, Australian National University
Images of desperate, singed koalas in blackened landscapes have come to symbolise the damage to nature this bushfire season. Such imagery has catalysed global concern, but the toll on biodiversity is much more pervasive.
Until the fires stop burning, we won’t know the full extent of the environmental damage. But these fires have significantly increased the extinction risk for many threatened species.
We estimate most of the range and population of between 20 and 100 threatened species will have been burnt. Such species include the long-footed potoroo, Kangaroo Island’s glossy black-cockatoo and the Spring midge orchid.
The fires are exceptional: way beyond normal in their extent, severity and timing. The human and property losses have been enormous. But nature has also suffered profoundly. We must urgently staunch and recover from the environmental losses, and do what it takes to avoid future catastrophes.
Most will have been killed by the fires themselves, or due to a lack of food and shelter in the aftermath.
Some animals survive the immediate fire, perhaps by hiding under rocks or in burrows. But the ferocity and speed of these fires mean most will have perished.
One might think birds and other fast-moving animals can easily escape fires. But smoke and strong winds can badly disorient them, and mass bird deaths in severe bushfires are common.
We saw this in the current fire crisis, when dead birds including rainbow lorikeets and yellow-tailed black-cockatoos washed up on the beach at Mallacoota in Victoria.
Fire impacts are deeply felt in the longer-term. Many habitat features needed by wildlife, such as tree and log hollows, nectar-bearing shrubs and a deep ground layer of fallen leaves, may not develop for decades.
Populations of plant and animal species found only in relatively small areas, which substantially overlap fire-affected areas, will be worst hit. Given the fires are continuing, the precise extent of this problem is still unknown.
We estimate most of the range and population of between 20 and 100 threatened species will have been burnt. The continued existence of such species was already tenuous. Their chances of survival are now much lower again.
For example, the long-footed potoroo exists in a very small range mostly in the forests of Victoria’s East Gippsland. It’s likely intense fires have burnt most of these areas.
On South Australia’s Kangaroo Island, one-third of which burned, there are serious concerns for the Kangaroo Island dunnart, an endangered small marsupial, and the endangered glossy black-cockatoo, whose last refuge was on the island. Both species have lost much of their habitat.
Many threatened plants are also affected: in NSW, fires around Batemans Bay have burnt some of the few sites known for the threatened Spring midge orchid.
Fire has long been a feature of Australian environments, and many species and vegetation types have adapted to fire. But the current fires are in many cases beyond the limits of such adaptation.
The fires are also burning environments that typically go unburnt for centuries, including at least the perimeter of World Heritage rainforests of the Lamington Plateau in south-eastern Queensland. In these environments, recovery – if at all – will be painfully slow.
Many Australian animal species, particularly threatened birds, favour long-unburnt vegetation because these provide more complex vegetation structure and hollows. Such habitat is fast disappearing.
The shortening intervals between fires are also pushing some ecosystems beyond their limits of resilience. Some iconic Alpine Ash forests of Kosciuszko have experienced four fires in 20 or 30 years.
This has reduced a grand wet forest ecosystem, rich in wildlife, to a dry scrub far more flammable than the original forest. Such ecosystem collapse is all but impossible to reverse.
Fires also compound the impacts of other threats. Feral cats and foxes hunt more effectively in burnt landscapes and will inexorably pick off wildlife that may have survived the fire.
In a matter of weeks, the fires have subverted decades of dedicated conservation efforts for many threatened species. As one example, most of the 48,000 hectares of forest reserves in East Gippsland established last year in response to the rapid decline of greater gliders has been burnt. This has further endangered the species and makes the remaining unburnt areas ever more critical.
Beyond counting the wildlife casualties, responses are needed to help environmental recovery. Priorities may differ among species and regions, but here is a general list:
quickly protect unburnt refuge patches in otherwise burnt landscapes
increase control efforts for pest animals and weeds that would magnify the impacts of these fires on wildlife
strategically establish captive breeding populations of some threatened animals and collect seeds of threatened plants
provide nest boxes and in special circumstances plant vegetation providing critical food resources
care for and rehabilitate injured wildlife and establish monitoring programs to chart a hoped-for recovery.
Some of these actions may be mere pinpricks in the extent of loss. But any useful action will make a small difference, and perhaps help alleviate the community’s profound sense of dismay at the damage wrought by these fires.
Governments, conservation groups and landholders must all play a role. Recovery actions should be thoughtfully coordinated, and form part of the broader social and economic post-fire recovery program.
Critically, we must also reduce the likelihood of similar catastrophes in future. Some have blamed the fires on national parks and a lack of hazard reduction burning. Skilful and fine-scale application of preventative burning does have merit. But such measures would not have stopped these fires, and the number of days suitable for such burning is diminishing.
Increasingly severe drought and extreme heat, associated with global warming, are the immediate causes of these wildfires and their ferocity. To prevent this fire-ravaged summer becoming the new normal, we must take drastic measures to tackle climate change.
A caption in an earlier version of this article said the glossy black cockatoo was extinct on the mainland. It was referring to the South Australian subspecies found on Kangaroo Island. The caption has been amended to clarify this.
John Woinarski, Professor (conservation biology), Charles Darwin University; Brendan Wintle, Professor Conservation Ecology, University of Melbourne; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; David Bowman, Professor of Pyrogeography and Fire Science, University of Tasmania; David Keith, Professor of Botany, UNSW, and Sarah Legge, Professor, Australian National University
The concept of a canary in a coal mine – a sensitive species that provides an alert to danger – originated with British miners, who carried actual canaries underground through the mid-1980s to detect the presence of deadly carbon monoxide gas. Today another bird, the Emperor Penguin, is providing a similar warning about the planetary effects of burning fossil fuels.
As a seabird ecologist, I develop mathematical models to understand and predict how seabirds respond to environmental change. My research integrates many areas of science, including the expertise of climatologists, to improve our ability to anticipate future ecological consequences of climate change.
Most recently, I worked with colleagues to combine what we know about the life history of Emperor Penguins with different potential climate scenarios outlined in the 2015 Paris Agreement, to combat climate change and adapt to its effects. We wanted to understand how climate change could affect this iconic species, whose unique life habits were documented in the award-winning film “March of the Penguins.”
Our newly published study found that if climate change continues at its current rate, Emperor Penguins could virtually disappear by the year 2100 due to loss of Antarctic sea ice. However, a more aggressive global climate policy can halt the penguins’ march to extinction.
As many scientific reports have shown, human activities are increasing carbon dioxide concentrations in Earth’s atmosphere, which is warming the planet. Today atmospheric CO2 levels stand at slightly over 410 parts per million, well above anything the planet has experienced in millions of years.
If this trend continues, scientists project that CO2 in the atmosphere could reach 950 parts per million by 2100. These conditions would produce a very different world from today’s.
Emperor Penguins are living indicators whose population trends can illustrate the consequences of these changes. Although they are found in Antarctica, far from human civilization, they live in such delicate balance with their rapidly changing environment that they have become modern-day canaries.
I have spent almost 20 years studying Emperor Penguins’ unique adaptations to the harsh conditions of their sea ice home. Each year, the surface of the ocean around Antarctica freezes over in the winter and melts back in summer. Penguins use the ice as a home base for breeding, feeding and molting, arriving at their colony from ocean waters in March or April after sea ice has formed for the Southern Hemisphere’s winter season.
In mid-May the female lays a single egg. Throughout the winter, males keep the eggs warm while females make a long trek to open water to feed during the most unforgiving weather on Earth.
When female penguins return to their newly hatched chicks with food, the males have fasted for four months and lost almost half their weight. After the egg hatches, both parents take turns feeding and protecting their chick. In September, the adults leave their young so that they can both forage to meet their chick’s growing appetite. In December, everyone leaves the colony and returns to the ocean.
Throughout this annual cycle, the penguins rely on a sea ice “Goldilocks zone” of conditions to thrive. They need openings in the ice that provide access to the water so they can feed, but also a thick, stable platform of ice to raise their chicks.
For more than 60 years, scientists have extensively studied one Emperor Penguin colony in Antarctica, called Terre Adélie. This research has enabled us to understand how sea ice conditions affect the birds’ population dynamics. In the 1970s, for example, the population experienced a dramatic decline when several consecutive years of low sea ice cover caused widespread deaths among male penguins.
Over the past 10 years, my colleagues and I have combined what we know about these relationships between sea ice and fluctuations in penguin life histories to create a demographic model that allows us to understand how sea ice conditions affect the abundance of Emperor Penguins, and to project their numbers based on forecasts of future sea ice cover in Antarctica.
Once we confirmed that our model successfully reproduced past observed trends in Emperor Penguin populations around all Antarctica, we expanded our analysis into a species-level threat assessment.
When we used a climate model linked to our population model to project what is likely to happen to sea ice if greenhouse gas emissions continue on their present trend, we found that all 54 known Emperor Penguin colonies would be in decline by 2100, and 80% of them would be quasi-extinct. Accordingly, we estimate that the total number of Emperor Penguins will decline by 86% relative to its current size of roughly 250,000 if nations fail to reduce their carbon dioxide emissions.
However, if the global community acts to reduce greenhouse gas emissions and succeeds in stabilizing average global temperatures at 1.5 degrees Celsius (3 degrees Faherenheit) above pre-industrial levels, we estimate that Emperor Penguin numbers would decline by 31% – still drastic, but viable.
Less-stringent cuts in greenhouse gas emissions, leading to a global temperature rise of 2°C, would result in a 44% decline.
Our model indicates that these population declines will occur predominately in the first half of this century. Nonetheless, in a scenario in which the world meets the Paris climate targets, we project that the global Emperor Penguin population would nearly stabilize by 2100, and that viable refuges would remain available to support some colonies.
In a changing climate, individual penguins may move to new locations to find more suitable conditions. Our population model included complex dispersal processes to account for these movements. However, we find that these actions are not enough to offset climate-driven global population declines. In short, global climate policy has much more influence over the future of Emperor Penguins than the penguins’ ability to move to better habitat.
Our findings starkly illustrate the far-reaching implications of national climate policy decisions. Curbing carbon dioxide emissions has critical implications for Emperor Penguins and an untold number of other species for which science has yet to document such a plain-spoken warning.
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John Woinarski, Charles Darwin University; Brett Murphy, Charles Darwin University; Dale Nimmo, Charles Sturt University; Michael F. Braby, Australian National University; Sarah Legge, Australian National University, and Stephen Garnett, Charles Darwin University
It’s well established that unsustainable human activity is damaging the health of the planet. The way we use Earth threatens our future and that of many animals and plants. Species extinction is an inevitable end point.
It’s important that the loss of Australian nature be quantified accurately. To date, putting an exact figure on the number of extinct species has been challenging. But in the most comprehensive assessment of its kind, our research has confirmed that 100 endemic Australian species living in 1788 are now validly listed as extinct.
Alarmingly, this tally confirms that the number of extinct Australian species is much higher than previously thought.
Counts of extinct Australian species vary. The federal government’s list of extinct plants and animals totals 92. However 20 of these are subspecies, five are now known to still exist in Australia and seven survive overseas – reducing the figure to 60.
An RMIT/ABC fact check puts the figure at 46.
The states and territories also hold their own extinction lists, and the International Union for Conservation of Nature keeps a global database, the Red List.
Our research collated these separate listings. We excluded species that still exist overseas, such as the water tassel-fern. We also excluded some species that, happily, have been rediscovered since being listed as extinct, or which are no longer recognised as valid species (such as the obscure snail Fluvidona dulvertonensis).
We concluded that exactly 100 plant and animal species are validly listed as having become extinct in the 230 years since Europeans colonised Australia:
Our tally includes three species listed as extinct in the wild, with two of these still existing in captivity.
The mammal toll represents 10% of the species present in 1788. This loss rate is far higher than for any other continent over this period.
The 100 extinctions are drawn from formal lists. But many extinctions have not been officially registered. Other species disappeared before their existence was recorded. More have not been seen for decades, and are suspected lost by scientists or Indigenous groups who knew them best. We speculate that the actual tally of extinct Australian species since 1788 is likely to be about ten times greater than we derived from official lists.
And biodiversity loss is more than extinctions alone. Many more Australian species have disappeared from all but a vestige of their former ranges, or persist in populations far smaller than in the past.
Dating of extinctions is not straightforward. For a few Australian species, such as the Christmas Island forest skink, we know the day the last known individual died. But many species disappeared without us realising at the time.
Our estimation of extinction dates reveals a largely continuous rate of loss – averaging about four species per decade.
Continuing this trend, in the past decade, three Australian species have become extinct – the Christmas Island forest skink, Christmas Island pipistrelle and Bramble Cay melomys – and two others became extinct in the wild.
The extinctions occurred over most of the continent. However 21 occurred only on islands smaller than Tasmania, which comprise less than 0.5% of Australia’s land mass.
This trend, repeated around the world, is largely due to small population sizes and vulnerability to newly introduced predators.
The 100 recognised extinctions followed the loss of Indigenous land management, its replacement with entirely new land uses and new settlers introducing species with little regard to detrimental impacts.
Introduced cats and foxes are implicated in most mammal extinctions; vegetation clearing and habitat degradation caused most plant extinctions. Disease caused the loss of frogs and the accidental introduction of an Asian snake caused the recent loss of three reptile species on Christmas Island.
The causes have changed over time. Hunting contributed to several early extinctions, but not recent ones. In the last decade, climate change contributed to the extinction of the Bramble Cay melomys, which lived only on one Queensland island.
The prospects for some species are helped by legal protection, Australia’s fine national reserve system and threat management. But these gains are subverted by the legacy of previous habitat loss and fragmentation, and the ongoing damage caused by introduced species.
Our own population increase is causing further habitat loss, and new threats such as climate change bring more frequent and intense droughts and bushfires.
But now is not the time to weaken environment laws further. The creation of modern Australia has come at a great cost to nature – we are not living well in this land.
The study on which this article is based was also co-authored by Andrew Burbidge, David Coates, Rod Fensham and Norm McKenzie.
John Woinarski, Professor (conservation biology), Charles Darwin University; Brett Murphy, Associate Professor / ARC Future Fellow, Charles Darwin University; Dale Nimmo, Associate professor/ARC DECRA fellow, Charles Sturt University; Michael F. Braby, Associate Professor, Australian National University; Sarah Legge, Professor, Australian National University, and Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University
For more than 3.5 billion years, living organisms have thrived, multiplied and diversified to occupy every ecosystem on Earth. The flip side to this explosion of new species is that species extinctions have also always been part of the evolutionary life cycle.
But these two processes are not always in step. When the loss of species rapidly outpaces the formation of new species, this balance can be tipped enough to elicit what are known as “mass extinction” events.
A mass extinction is usually defined as a loss of about three quarters of all species in existence across the entire Earth over a “short” geological period of time. Given the vast amount of time since life first evolved on the planet, “short” is defined as anything less than 2.8 million years.
Since at least the Cambrian period that began around 540 million years ago when the diversity of life first exploded into a vast array of forms, only five extinction events have definitively met these mass-extinction criteria.
These so-called “Big Five” have become part of the scientific benchmark to determine whether human beings have today created the conditions for a sixth mass extinction.
These five mass extinctions have happened on average every 100 million years or so since the Cambrian, although there is no detectable pattern in their particular timing. Each event itself lasted between 50 thousand and 2.76 million years. The first mass extinction happened at the end of the Ordovician period about 443 million years ago and wiped out over 85% of all species.
The Ordovician event seems to have been the result of two climate phenomena. First, a planetary-scale period of glaciation (a global-scale “ice age”), then a rapid warming period.
The second mass extinction occurred during the Late Devonian period around 374 million years ago. This affected around 75% of all species, most of which were bottom-dwelling invertebrates in tropical seas at that time.
This period in Earth’s past was characterised by high variation in sea levels, and rapidly alternating conditions of global cooling and warming. It was also the time when plants were starting to take over dry land, and there was a drop in global CO2 concentration; all this was accompanied by soil transformation and periods of low oxygen.
The third and most devastating of the Big Five occurred at the end of the Permian period around 250 million years ago. This wiped out more than 95% of all species in existence at the time.
Some of the suggested causes include an asteroid impact that filled the air with pulverised particle, creating unfavourable climate conditions for many species. These could have blocked the sun and generated intense acid rains. Some other possible causes are still debated, such as massive volcanic activity in what is today Siberia, increasing ocean toxicity caused by an increase in atmospheric CO₂, or the spread of oxygen-poor water in the deep ocean.
Fifty million years after the great Permian extinction, about 80% of the world’s species again went extinct during the Triassic event. This was possibly caused by some colossal geological activity in what is today the Atlantic Ocean that would have elevated atmospheric CO₂ concentrations, increased global temperatures, and acidified oceans.
The last and probably most well-known of the mass-extinction events happened during the Cretaceous period, when an estimated 76% of all species went extinct, including the non-avian dinosaurs. The demise of the dinosaur super predators gave mammals a new opportunity to diversify and occupy new habitats, from which human beings eventually evolved.
The most likely cause of the Cretaceous mass extinction was an extraterrestrial impact in the Yucatán of modern-day Mexico, a massive volcanic eruption in the Deccan Province of modern-day west-central India, or both in combination.
The Earth is currently experiencing an extinction crisis largely due to the exploitation of the planet by people. But whether this constitutes a sixth mass extinction depends on whether today’s extinction rate is greater than the “normal” or “background” rate that occurs between mass extinctions.
This background rate indicates how fast species would be expected to disappear in absence of human endeavour, and it’s mostly measured using the fossil record to count how many species died out between mass extinction events.
The most accepted background rate estimated from the fossil record gives an average lifespan of about one million years for a species, or one species extinction per million species-years. But this estimated rate is highly uncertain, ranging between 0.1 and 2.0 extinctions per million species-years. Whether we are now indeed in a sixth mass extinction depends to some extent on the true value of this rate. Otherwise, it’s difficult to compare Earth’s situation today with the past.
In contrast to the the Big Five, today’s species losses are driven by a mix of direct and indirect human activities, such as the destruction and fragmentation of habitats, direct exploitation like fishing and hunting, chemical pollution, invasive species, and human-caused global warming.
If we use the same approach to estimate today’s extinctions per million species-years, we come up with a rate that is between ten and 10,000 times higher than the background rate.
Even considering a conservative background rate of two extinctions per million species-years, the number of species that have gone extinct in the last century would have otherwise taken between 800 and 10,000 years to disappear if they were merely succumbing to the expected extinctions that happen at random. This alone supports the notion that the Earth is at least experiencing many more extinctions than expected from the background rate.
It would likely take several millions of years of normal evolutionary diversification to “restore” the Earth’s species to what they were prior to human beings rapidly changing the planet. Among land vertebrates (species with an internal skeleton), 322 species have been recorded going extinct since the year 1500, or about 1.2 species going extinction every two years.
If this doesn’t sound like much, it’s important to remember extinction is always preceded by a loss in population abundance and shrinking distributions. Based on the number of decreasing vertebrate species listed in the International Union for Conservation of Nature’s Red List of Threatened Species, 32% of all known species across all ecosystems and groups are decreasing in abundance and range. In fact, the Earth has lost about 60% of all vertebrate individuals since 1970.
Australia has one of the worst recent extinction records of any continent, with more than 100 species of vertebrates going extinct since the first people arrived over 50 thousand years ago. And more than 300 animal and 1,000 plant species are now considered threatened with imminent extinction.
Although biologists are still debating how much the current extinction rate exceeds the background rate, even the most conservative estimates reveal an exceptionally rapid loss of biodiversity typical of a mass extinction event.
In fact, some studies show that the interacting conditions experienced today, such as accelerated climate change, changing atmospheric composition caused by human industry, and abnormal ecological stresses arising from human consumption of resources, define a perfect storm for extinctions. All these conditions together indicate that a sixth mass extinction is already well under way.
Frédérik Saltré, Research Fellow in Ecology & Associate Investigator for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University and Corey J. A. Bradshaw, Matthew Flinders Fellow in Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University