Should we bring back the thylacine? We asked 5 experts

17 08 2022
Tasmanian Museum and Art Gallery

Signe Dean, The Conversation

In a newly announced partnership with Texas biotech company Colossal Biosciences, Australian researchers are hoping their dream to bring back the extinct thylacine is a “giant leap” closer to fruition.

Scientists at University of Melbourne’s TIGRR Lab (Thylacine Integrated Genetic Restoration Research) believe the new partnership, which brings Colossal’s expertise in CRISPR gene editing on board, could result in the first baby thylacine within a decade.

The genetic engineering firm made headlines in 2021 with the announcement of an ambitious plan to bring back something akin to the woolly mammoth, by producing elephant-mammoth hybrids or “mammophants”.

But de-extinction, as this type of research is known, is a highly controversial field. It’s often criticised for attempts at “playing God” or drawing attention away from the conservation of living species. So, should we bring back the thylacine? We asked five experts.

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Fallacy of zero-extinction targets

20 05 2022

Nearly a decade ago (my how time flies*), I wrote a post about the guaranteed failure of government policies purporting no-extinction targets within their environmental plans. I was referring to the State of South Australia’s (then) official policy of no future extinctions.

In summary, zero- (or no-) extinction targets at best demonstrate a deep naïvety of how ecology works, and at worst, waste a lot of resources on interventions doomed to fail.

1. Extinctions happen all the time, irrespective of human activity;

2. Through past environmental degradation, we are guaranteed to see future extinctions because of extinction lags;

3. Few, if any, of the indicators of biodiversity change show improvement.

4. Climate change will also guarantee additional (perhaps even most) future extinctions irrespective of Australian policies.

I argued that no-extinction policies are therefore disingenuous to the public in the extreme because they sets false expectations, engender disillusionment after inevitable failure, and ignores the concept of triage — putting our environment-restoration resources toward the species/systems with the best chance of surviving (uniqueness notwithstanding).

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Cartoon guide to biodiversity loss LXXI

11 04 2022

Now that the Australian election has been called for next month, here are a few cartoon reminders of the state of environmental politics in this country (hint: they’re abysmal). I’ve surpassed my normal 6 cartoons/post here in this second set for 2022 because, well, our lives depend on the outcome of 21 May. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.

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Can we resurrect the thylacine? Maybe, but it won’t help the global extinction crisis

9 03 2022


(published first on The Conversation)

Last week, researchers at the University of Melbourne announced that thylacines or Tasmanian tigers, the Australian marsupial predators extinct since the 1930s, could one day be ushered back to life.

The thylacine (Thylacinus cynocephalus), also known as the ‘Tasmanian tiger’ (it was neither Tasmanian, because it was once common in mainland Australia, nor was it related to the tiger), went extinct in Tasmania in the 1930s from persecution by farmers and habitat loss. Art by Eleanor (Nellie) Pease, University of Queensland.
Centre of Excellence for Australian Biodiversity and Heritage

The main reason for the optimism was the receipt of a A$5 million philanthropic donation to the research team behind the endeavour.

Advances in mapping the genome of the thylacine and its living relative the numbat have made the prospect of re-animating the species seem real. As an ecologist, I would personally relish the opportunity to see a living specimen.

The announcement led to some overhyped headlines about the imminent resurrection of the species. But the idea of “de-extinction” faces a variety of technical, ethical and ecological challenges. Critics (like myself) argue it diverts attention and resources from the urgent and achievable task of preventing still-living species from becoming extinct.

The rebirth of the bucardo

The idea of de-extinction goes back at least to the the creation of the San Diego Frozen Zoo in the early 1970s. This project aimed to freeze blood, DNA, tissue, cells, eggs and sperm from exotic and endangered species in the hope of one day recreating them.

The notion gained broad public attention with the first of the Jurassic Park films in 1993. The famous cloning of Dolly the sheep reported in 1996 created a sense that the necessary know-how wasn’t too far off.

The next technological leap came in 2008, with the cloning of a dead mouse that had been frozen at –20℃ for 16 years. If frozen individuals could be cloned, re-animation of a whole species seemed possible.

After this achievement, de-extinction began to look like a potential way to tackle the modern global extinction crisis.

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The integrity battlefield: where science meets policy

4 03 2022

Professor Ross Thompson, University of Canberra

On the whole, I am inclined to conclude that my experience of academia and publishing my work has been largely benign. Despite having published 120-odd peer-reviewed papers, I can count the number of major disputes on one hand. Where there have been disagreements, they have centred on issues of content, and despite the odd grumble, things have rarely escalated to the ad hominem. I have certainly never experienced concerted attacks on my work.

But that changed recently. I work in water science, participating in and leading multi-disciplinary teams that do research directly relevant to water policy and management. My colleagues and I work closely with state and federal governments and are often funded by them through a variety of mechanisms. Our teams are a complex blend of scientists from universities, state and federal research agencies, and private-sector consultancies. Water is big business in Australia, and its management is particularly pertinent as the world’s driest inhabited continent struggles to come to terms with the impacts of climate change.

In the last 10 years, Australia has undergone a AU$16 billion program of water reform that has highlighted the extreme pressure on ecosystems, rural communities, and water-dependent industries. In 2019, two documentaries (Cash Splash and Pumped) broadcast by the Australian Broadcasting Corporation were highly critical of the  outcomes of water reform. A group of scientists involved in working on the Murray-Darling Basin were concerned enough about the accuracy of aspects of those stories to support Professor Rob Vertessy from the University of Melbourne in drafting an Open Letter in response. I was a co-author on that letter, and something into which I did not enter lightly. We were very concerned about being seen to advocate for any particular policy position, but were simultaneously committed to contributing to an informed public debate. A later investigation by the Australian Communications and Media Authority also highlighted concerns with the Cash Splash documentary.

Fast forward to 2021 and the publication of a paper by Colloff et al. (2021) in the Australasian Journal of Water Resources. In that paper, the authors were critical of the scientists that had contributed to the Open Letter and claimed they had been subject to “administrative capture” and “issue advocacy”. Administrative capture is defined here as:

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Wondering if you should apply for a DECRA?

7 02 2022

Do you love doing job applications, but wish they were longer and more involved?

If so, applying for an Australian Research Council (ARC) Discovery Early Career Researcher Award (DECRA) should be right up your alley.

If, like most people, you answered a resounding NO! to that question, there are still many good reasons to apply for a DECRA. But there are also some completely valid reasons why you might not apply, so it pays to weigh up the pros and cons if you’re thinking about it.

Let’s go through some of these points, plus tips on how to make a competitive application (I just submitted a DECRA application in the last round, so it’s all painfully fresh in my memory). 

What the hell is a DECRA?

The Discovery Early Career Researcher Awards offered by the Australian Research Council are highly competitive, with success rates of between 12% (ouch!) and 20% across years (but expect especially low success rates in the next round/DECRA23, given the bumper crop of applicants). 

DECRAs are restricted to researchers who are (i) less than 5-years out from their PhD conferral, and (ii) who are proposing non-medical projects.

The 5-year eligibility period is based on time spent ‘research active’, to accommodate the different career pathways people follow. This means that people who haven’t been working 100% in research since completing their PhD can tally up career interruptions (which can relate to illnesses or disability, carer responsibilities, parental leave, unemployment, and employment in non-research positions) and extend their eligibility period.

So even if you are well-over 5 years post PhD (as was the case for me), you might still be eligible to apply. If you’re considering a medical science project, then you need to check out the schemes offered by the National Health and Medical Research Council (NHMRC).

Pros and Cons

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Open Letter from Members of the Australian Research Council College of Experts

25 01 2022

People outside Australia might not have heard about the (unfortunately, not unprecedented) intervention of the acting Minister for Education and Youth to deny funding to six Australian Research Council (ARC: Australia’s main scientific funding body) Discovery Grants that had been assessed and recommended for funding by the College of Experts. As an acting College of Expert member, I joined a long list of my fellow members in protest of this political interference, with whom I co-wrote/co-signed this letter published last week (the ARC Laureate fellows wrote an analogous open letter a few weeks before). I have copied the letter here for your viewing displeasure.

(letter originally posted here)

19 January 2022

To: The Hon Stuart Robert MP
Acting Minister for Education and Youth

CC: Professor Sue Thomas
CEO, Australian Research Council

As members of the Australian Research Council‘s (ARC) College of Experts, we write to express our concern over the Acting Minister for Education and Youth’s decision in late 2021 to reject six Discovery Project grants that were recommended for funding by the ARC.

As explained on its website, the ARC engages a College of Experts to play an essential role in identifying research excellence, in order to support the advancement of knowledge and contribute to national innovation. Its members are experts of international standing drawn from the Australian research community: from higher education, industry, and public sector research organisations. Many College of Experts members have extensive industry and community experience in addition to their specialist research expertise.

The quality of grant proposals submitted to the ARC is extremely high. The ARC runs a rigorous, multi-stage selection process. Each grant eventually recommended to the Minister for funding is first assessed by multiple international experts and multiple College members, and then individually discussed and voted on by College members at the Selection Advisory Committee panel meetings. The 19% of submitted proposals recommended for 2022 were therefore considered to be of the highest calibre measured against international standards for research across disciplines. Each was recommended on the strength not only of quality, innovation and feasibility, but also the wider benefit and value of the proposed research.

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Extinct megafauna prone to ancient hunger games

14 12 2021

I’m very chuffed today to signal the publication of what I think is one of the most important contributions to the persistent conundrum surrounding the downfall of Australia’s megafauna many tens of millennia ago.

Diprotodon optimum. Artwork by palaeontologist and artist Eleanor (Nellie) Pease (commissioned by the ARC Centre of Excellence for Australian Biodiversity and Heritage)

Sure, I’m obviously biased in that assessment because it’s a paper from our lab and I’m a co-author, but if readers had any inkling of the work that went into this paper, I think they might consider adopting my position. In addition, the injection of some actual ecology into the polemic should be viewed as fresh and exciting.

Having waded into the murky waters of the ‘megafauna debate’ for about a decade now, I’ve become a little sensitive to even a whiff of binary polemic surrounding their disappearance in Australia. Acolytes of the climate-change prophet still beat their drums, screaming for the smoking gun of a spear sticking out of a Diprotodon‘s skull before they even entertain the notion that people might have had something to do with it — but we’ll probably never find one given the antiquity of the event (> 40,000 years ago). On the other side are the blitzkriegers who declaim that human hunting single-handedly wiped out the lot.

Well, as it is for nearly all extinctions, it’s actually much more complicated than that. In the case of Sahul’s megafauna disappearances, both drivers likely contributed, but the degree to which both components played a part depends on where and when you look — Fred Saltré demonstrated that elegantly a few years ago.

Palorchestes. Artwork by palaeontologist and artist Eleanor (Nellie) Pease (commissioned by the ARC Centre of Excellence for Australian Biodiversity and Heritage)

So, why does the polemic persist? In my view, it’s because we have largely depended on the crude comparison of relative dates to draw our conclusions. That is, we look to see if some climate-change proxy shifted in any notable way either before or after an inferred extinction date. If a particular study claims evidence that a shift happened before, then it concludes climate change was the sole driver. If a study presents evidence that a shift happened after, then humans did it. Biases in geochronological inference (e.g., spatial, contamination), incorrect application of climate proxies, poor taxonomic resolution, and not accounting for the Signor-Lipps effect all contribute unnecessarily to the debate because small errors or biases can flip relative chronologies on their head and push conclusions toward uncritical binary outcomes. The ‘debate’ has been almost entirely grounded on this simplistically silly notion.

This all means that the actual ecology has been either ignored or merely made up based on whichever pet notion of the day is being proffered. Sure, there are a few good ecological inferences out there from some damn good modellers and ecologists, but these have all been greatly simplified themselves. This is where our new paper finally takes the ecology part of the problem to the next level.

Led by Global Ecology and CABAH postdoctoral fellow, John Llewelyn, and guided by modelling guru Giovanni Strona at University of Helsinki, the paper Sahul’s megafauna were vulnerable to plant-community changes due to their position in the trophic network has just been published online in Ecography. Co-authors include Kathi Peters, Fred Saltré, and me from Flinders Global Ecology, Matt McDowell and Chris Johnson from UTAS, Daniel Stouffer from University of Canterbury (NZ), and Sara de Visser from University of Groningen (Netherlands).

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Animating models of ecological change

6 12 2021

Flinders University Global Ecology postdoc, Dr Farzin Shabani, recently created this astonishing video not only about the results of his models predicting vegetation change in northern Australia as a function of long-term (tens of thousands of years) climate change, but also on the research journey itself!

He provides a brief background to how and why he took up the challenge:

Science would be a lot harder to digest without succinct and meaningful images, graphs, and tables. So, being able to visualise both inputs and outputs of scientific models to cut through the fog of data is an essential element of all science writing and communication. Diagrams help us understand trends and patterns much more quickly than do raw data, and they assist with making comparisons.

During my academic career, I have studied many different topics, including natural hazards (susceptibility & vulnerability risks), GIS-based ensemble modelling, climate-change impacts, environmental modelling at different temporal and spatial scales, species-distribution modelling, and time-series analysis. I use a wide range of graphschartsplotsmaps and tables to transfer the key messages.

For my latest project, however, I was given the opportunity to make a short animation and visualise my results and the journey itself. I think that my animation inspires a sense of wonder, which is among the most important goals of science education. I also think that my animation draws connections to real-life problems (e.g., ecosystem changes as a product of climate change), and also develops an appreciation of the scientific process itself.

Take a look at let me know what you think!

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An eye on the past: a view to the future

29 11 2021

originally published in Brave Minds, Flinders University’s research-news publication (text by David Sly)

Clues to understanding human interactions with global ecosystems already exist. The challenge is to read them more accurately so we can design the best path forward for a world beset by species extinctions and the repercussions of global warming.

This is the puzzle being solved by Professor Corey Bradshaw, head of the Global Ecology Lab at Flinders University. By developing complex computer modelling and steering a vast international cohort of collaborators, he is developing research that can influence environmental policy — from reconstructing the past to revealing insights of the future.

As an ecologist, he aims both to reconstruct and project how ecosystems adapt, how they are maintained, and how they change. Human intervention is pivotal to this understanding, so Professor Bradshaw casts his gaze back to when humans first entered a landscape – and this has helped construct an entirely fresh view of how Aboriginal people first came to Australia, up to 75,000 years ago.

Two recent papers he co-authored — ‘Stochastic models support rapid peopling of Late Pleistocene Sahul‘, published in Nature Communications, and ‘Landscape rules predict optimal super-highways for the first peopling of Sahul‘ published in Nature Human Behaviour — showed where, how and when Indigenous Australians first settled in Sahul, which is the combined mega-continent that joined Australia with New Guinea in the Pleistocene era, when sea levels were lower than today.

Professor Bradshaw and colleagues identified and tested more than 125 billion possible pathways using rigorous computational analysis in the largest movement-simulation project ever attempted, with the pathways compared to the oldest known archaeological sites as a means of distinguishing the most likely routes.

The study revealed that the first Indigenous people not only survived but thrived in harsh environments, providing further evidence of the capacity and resilience of the ancestors of Indigenous people, and suggests large, well-organised groups were able to navigate tough terrain.

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And this little piggy went extinct

24 11 2021

Back in June of this year I wrote (whinged) about the disappointment of writing a lot of ecological models that were rarely used to assist real-world wildlife management. However, I did hint that another model I wrote had assistance one government agency with pig management on Kangaroo Island.

Well, now that report has been published online and I’m permitted to talk about it. I’m also very happy to report that, in the words of the Government of South Australia’s Department of Primary Industries and Regions (PIRSA),

Modelling by the Flinders University Global Ecology Laboratory shows the likelihood and feasibility of feral pig eradication under different funding and eradication scenarios. With enough funding, feral pigs could be eradicated from Kangaroo Island in 2 years.

This basically means that because of the model, PIRSA was successful in obtaining enough funding to pretty much ensure that the eradication of feral pigs from Kangaroo Island will be feasible!

Why is this important to get rid of feral pigs? They are a major pest on the Island, causing severe economic and environmental impacts both to farms and native ecosystems. On the agricultural side of things, they prey on newborn lambs, eat crops, and compete with livestock for pasture. Feral pigs damage natural habitats by up-rooting vegetation and fouling waterholes. They can also spread weeds and damage infrastructure, as well as act as hosts of parasites and diseases (e.g., leptospirosis, tuberculosis, foot-and-mouth disease) that pose serious threats to industry, wildlife, and even humans.

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PhD opportunity in control strategies of feral deer

30 09 2021

In collaboration with Biosecurity South Australia, the Global Ecology Lab at Flinders University is happy to announce a wonderful new PhD opportunity in feral deer control strategies for South Australia.

The project is tentatively entitled: Refining models of feral deer abundance and distribution to inform culling programs in South Australia

Feral fallow deer (Dama dama) digging in a mallee fowl (Leipoa ocellata) mound © Lee Williams

The project brief follows:

South Australian legislation requires that all landholders cull feral deer on their properties. Despite this, feral deer abundance and distribution are increasing across South Australia. This arises because culling by land managers and government organisations is not keeping pace with rates of population growth, and some landholders are harbouring deer for hunting, whereas some deer escape from deer farms.

There are an estimated 40,000 feral deer in South Australia, and state government agencies are working to ramp up programs to cull feral deer before their numbers reach a point where control is no longer feasible.

Planning such large-scale and costly programs requires that government agencies engage economists to measure the economic impacts of feral deer, and to predict the value of these impacts in the future. That modelling is done regularly by governments, and in the case of pest-control programs, the modelling draws on models of feral deer population growth, farmer surveys about the economic, social, and environmental impacts of feral deer, and analyses of culling programs and trials of new culling techniques.

The economic models predict and compare both the current and future costs of:

  • deer impacts on pastures, crops, native plants, and social values (including illegal hunting)
  • culling programs that achieve different objectives (e.g., contain vs. reduce vs. eradicate)

The outputs of the models also inform whether there are sufficient public benefits from the investment of public funds into the culling of feral deer.

This PhD project will collate published and unpublished data to refine models of feral deer distribution and abundance under various culling scenarios. This project will drive both high-impact publications and, because this project builds extensive collaborations with government agencies, the results will inform the management of feral deer in South Australia.

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It’s a tough time for young conservation scientists

24 08 2021

Sure, it’s a tough time for everyone, isn’t it? But it’s a lot worse for the already disadvantaged, and it’s only going to go downhill from here. I suppose that most people who read this blog can certainly think of myriad ways they are, in fact, still privileged and very fortunate (I know that I am).

Nonetheless, quite a few of us I suspect are rather ground down by the onslaught of bad news, some of which I’ve been responsible for perpetuating myself. Add lock downs, dwindling job security, and the prospect of dying tragically due to lung infection, many have become exasperated.

I once wrote that being a conservation scientist is a particularly depressing job, because in our case, knowledge is a source of despair. But as I’ve shifted my focus from ‘preventing disaster’ to trying to lessen the degree of future shittyness, I find it easier to get out of bed in the morning.

What can we do in addition to shifting our focus to making the future a little less shitty than it could otherwise be? I have a few tips that you might find useful:

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Pest plants and animals cost Australia around $25 billion a year — and it will get worse

2 08 2021

Corey J. A. Bradshaw, Flinders University and Andrew Hoskins, CSIRO

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

Shamefully, Australia has one of the highest extinction rates in the world.
And the number one threat to our species is invasive or “alien” plants and animals.

But invasive species don’t just cause extinctions and biodiversity loss – they also create a serious economic burden. Our research, published today, reveals invasive species have cost the Australian economy at least A$390 billion in the last 60 years alone.

Our paper – the most detailed assessment of its type ever published in this country – also reveals feral cats are the worst invasive species in terms of total costs, followed by rabbits and fire ants.

Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.

Feral cats are Australia’s costliest invasive species. Source: Adobe Stock/240188862

Huge economic burden

Invasive species are those not native to a particular ecosystem. They are introduced either by accident or on purpose and become pests.

Some costs involve direct damage to agriculture, such as insects or fungi destroying fruit. Other examples include measures to control invasive species like feral cats and cane toads, such as paying field staff and buying fuel, ammunition, traps and poisons.

Our previous research put the global cost of invasive species at A$1.7 trillion. But this is most certainly a gross underestimate because so many data are missing.

Read more:
Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill

As a wealthy nation, Australia has accumulated more reliable cost data than most other regions. These costs have increased exponentially over time – up to sixfold each decade since the 1970s.

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Killing (feral) cats quickly (and efficiently)

20 05 2021

I’m pleased to announce the publication of a paper led by Kathryn Venning (KV) that was derived from her Honours work in the lab. Although she’s well into her PhD on an entirely different topic, I’m overjoyed that she persevered and saw this work to publication.

Here, killa, killa, killa, killa …

As you probably already know, feral cats are a huge problem in Australia. The are probably the primary reason Australia leads the world in mammal extinctions in particular, and largely the reason so many re-introduction attempts of threatened marsupials fail miserably only after a few years.

Feral cats occupy every habitat in the country, from the high tropics to the deserts, and from the mountains to the sea. They adapt to the cold just as easily as they adapt to the extreme heat, and they can eat just about anything that moves, from invertebrates to the carcases of much larger animals that they scavenge.

Cats are Australia’s bane, but you can’t help but be at least a little impressed with their resilience.

Still, we have to try our best to get rid of them where we can, or at least reduce their densities to the point where their ecological damage is limited.

Typically, the only efficient and cost-effective way to do that is via lethal control, but by using various means. These can include direct shooting, trapping, aerial poison-baiting, and a new ‘smart’ method of targeted poison delivery via a prototype device known as a Felixer™️. The latter are particularly useful for passive control in areas where ground-shooting access is difficult.

A live Felixer™️ deployed on Kangaroo Island (photo: CJA Bradshaw 2020)

A few years back the federal government committed what might seem like a sizeable amount of money to ‘eradicate’ cats from Australia. Yeah, good luck with that, although the money has been allocated to several places where cat reduction and perhaps even eradication is feasible. Namely, on islands.

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Mapping the ‘super-highways’ the First Australians used to cross the ancient land

4 05 2021

Author provided/The Conversation, Author provided

There are many hypotheses about where the Indigenous ancestors first settled in Australia tens of thousands of years ago, but evidence is scarce.

Few archaeological sites date to these early times. Sea levels were much lower and Australia was connected to New Guinea and Tasmania in a land known as Sahul that was 30% bigger than Australia is today.

Our latest research advances our knowledge about the most likely routes those early Australians travelled as they peopled this giant continent.

Read more: The First Australians grew to a population of millions, much more than previous estimates

We are beginning to get a picture not only of where those first people landed in Sahul, but how they moved throughout the continent.

Navigating the landscape

Modelling human movement requires understanding how people navigate new terrain. Computers facilitate building models, but they are still far from easy. We reasoned we needed four pieces of information: (1) topography; (2) the visibility of tall landscape features; (3) the presence of freshwater; and (4) demographics of the travellers.

We think people navigated in new territories — much as people do today — by focusing on prominent land features protruding above the relative flatness of the Australian continent. Read the rest of this entry »

Population of First Australians grew to millions, much more than previous estimates

30 04 2021

Shutterstock/Jason Benz Bennee

We know it is more than 60,000 years since the first people entered the continent of Sahul — the giant landmass that connected New Guinea, Australia and Tasmania when sea levels were lower than today.

But where the earliest people moved across the landscape, how fast they moved, and how many were involved, have been shrouded in mystery.

Our latest research, published today shows the establishment of populations in every part of this giant continent could have occurred in as little as 5,000 years. And the entire population of Sahul could have been as high as 6.4 million people.

This translates to more than 3 million people in the area that is now modern-day Australia, far more than any previous estimate.

Read more: We mapped the ‘super-highways’ the First Australians used to cross the ancient land

The first people could have entered through what is now western New Guinea or from the now-submerged Sahul Shelf off the modern-day Kimberley (or both).

But whichever the route, entire communities of people arrived, adapted to and established deep cultural connections with Country over 11 million square kilometres of land, from northwestern Sahul to Tasmania.

A map showing a much larger landmass as Australia is joined to both Tasmania and New Guinea due to lower sea levels

Map of what Australia looked like for most of the human history of the continent when sea levels were lower than today. Author provided

This equals a rate of population establishment of about 1km per year (based on a maximum straight-line distance of about 5,000km from the introduction point to the farthest point).

That’s doubly impressive when you consider the harshness of the Australian landscape in which people both survived and thrived.

Previous estimates of Indigenous population

Various attempts have been made to calculate the number of people living in Australia before European invasion. Estimates vary from 300,000 to more than 1,200,000 people. Read the rest of this entry »

No, you can’t argue the Medieval warm period is evidence that today’s climate change isn’t all that bad

23 04 2021
As this reconstructed village shows, Vikings made it as far as Newfoundland during the Medieval warm period. Wikimedia/Dylan Kereluk, CC BY-SA

Frédérik Saltré, Flinders University and Corey J. A. Bradshaw, Flinders University

What was the Medieval warm period? What caused it, and did carbon dioxide play a role?

We are living in a world that is getting warmer year by year, threatening our environment and way of life.

But what if these climate conditions were not exceptional? What if it had already happened in the past when human influences were not part of the picture?

The often mentioned Medieval warm period seems to fit the bill. This evokes the idea that if natural global warming and all its effects occurred in the past without humans causing them, then perhaps we are not responsible for this one. And it does not really matter because if we survived one in the past, then we can surely survive one now.

But it’s just not that simple.

Read more: 2,000 years of records show it’s getting hotter, faster

The Medieval climate anomaly

This Medieval period of warming, also known as the Medieval climate anomaly, was associated with an unusual temperature rise roughly between 750 and 1350 AD (the European Middle Ages). The available evidence suggests that at times, some regions experienced temperatures exceeding those recorded during the period between 1960 and 1990. Read the rest of this entry »

Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill

19 04 2021


They’re one of the most damaging environmental forces on Earth. They’ve colonised pretty much every place humans have set foot on the planet. Yet you might not even know they exist.

We’re talking about alien species. Not little green extraterrestrials, but invasive plants and animals not native to an ecosystem and which become pests. They might be plants from South America, starfish from Africa, insects from Europe or birds from Asia.

These species can threaten the health of plants and animals, including humans. And they cause huge economic harm. Our research, recently published in the journal Nature, puts a figure on that damage. We found that globally, invasive species cost US$1.3 trillion (A$1.7 trillion) in money lost or spent between 1970 and 2017.

The cost is increasing exponentially over time. And troublingly, most of the cost relates to the damage and losses invasive species cause. Meanwhile, far cheaper control and prevention measures are often ignored.

Yellow crazy ants attacking a gecko
Yellow crazy ants, such as these attacking a gecko, are among thousands of invasive species causing ecological and economic havoc. Dinakarr, CC0, Wikimedia Commons

An expansive toll

Invasive species have been invading foreign territories for centuries. They hail from habitats as diverse as tropical forests, dry savannas, temperate lakes and cold oceans.

They arrived because we brought them — as pets, ornamental plants or as stowaways on our holidays or via commercial trade.

Read the rest of this entry »

The biggest and slowest don’t always bite it first

13 04 2021

For many years I’ve been interested in modelling the extinction dynamics of megafauna. Apart from co-authoring a few demographically simplified (or largely demographically free) models about how megafauna species could have gone extinct, I have never really tried to capture the full nuances of long-extinct species within a fully structured demographic framework.

That is, until now.

But how do you get the life-history data of an extinct animal that was never directly measured. Surely, things like survival, reproductive output, longevity and even environmental carrying capacity are impossible to discern, and aren’t these necessary for a stage-structured demographic model?

Thylacine mum & joey. Nellie Pease & CABAH

The answer to the first part of that question “it’s possible”, and to the second, it’s “yes”. The most important bit of information we palaeo modellers need to construct something that’s ecologically plausible for an extinct species is an estimate of body mass. Thankfully, palaeontologists are very good at estimating the mass of the things they dig up (with the associated caveats, of course). From such estimates, we can reconstruct everything from equilibrium densities, maximum rate of population growth, age at first breeding, and longevity.

But it’s more complicated than that, of course. In Australia anyway, we’re largely dealing with marsupials (and some monotremes), and they have a rather different life-history mode than most placentals. We therefore have to ‘correct’ the life-history estimates derived from living placental species. Thankfully, evolutionary biologists and ecologists have ways to do that too.

The Pleistocene kangaroo Procoptodon goliah, the largest and most heavily built of the  short-faced kangaroos, was the largest and most heavily built kangaroo known. It had an  unusually short, flat face and forwardly directed 
eyes, with a single large toe on each foot  (reduced from the more normal count of four). Each forelimb had two long, clawed fingers  that would have been used to bring leafy branches within reach.

So with a battery of ecological, demographic, and evolutionary tools, we can now create reasonable stochastic-demographic models for long-gone species, like wombat-like creatures as big as cars, birds more than two metres tall, and lizards more than seven metres long that once roamed the Australian continent. 

Ancient clues, in the shape of fossils and archaeological evidence of varying quality scattered across Australia, have formed the basis of several hypotheses about the fate of megafauna that vanished during a peak about 42,000 years ago from the ancient continent of Sahul, comprising mainland Australia, Tasmania, New Guinea and neighbouring islands.

There is a growing consensus that multiple factors were at play, including climate change, the impact of people on the environment, and access to freshwater sources.

Just published in the open-access journal eLife, our latest CABAH paper applies these approaches to assess how susceptible different species were to extinction – and what it means for the survival of species today. 

Using various characteristics such as body size, weight, lifespan, survival rate, and fertility, we (Chris Johnson, John Llewelyn, Vera Weisbecker, Giovanni Strona, Frédérik Saltré & me) created population simulation models to predict the likelihood of these species surviving under different types of environmental disturbance.

Simulations included everything from increasing droughts to increasing hunting pressure to see which species of 13 extinct megafauna (genera: Diprotodon, Palorchestes, Zygomaturus, Phascolonus, Procoptodon, Sthenurus, Protemnodon, Simosthenurus, Metasthenurus, Genyornis, Thylacoleo, Thylacinus, Megalibgwilia), as well as 8 comparative species still alive today (Vombatus, Osphranter, Notamacropus, Dromaius, Alectura, Sarcophilus, Dasyurus, Tachyglossus), had the highest chances of surviving.

We compared the results to what we know about the timing of extinction for different megafauna species derived from dated fossil records. We expected to confirm that the most extinction-prone species were the first species to go extinct – but that wasn’t necessarily the case.

While we did find that slower-growing species with lower fertility, like the rhino-sized wombat relative Diprotodon, were generally more susceptible to extinction than more-fecund species like the marsupial ‘tiger’ thylacine, the relative susceptibility rank across species did not match the timing of their extinctions recorded in the fossil record.

Indeed, we found no clear relationship between a species’ inherent vulnerability to extinction — such as being slower and heavier and/or slower to reproduce — and the timing of its extinction in the fossil record.

In fact, we found that most of the living species used for comparison — such as short-beaked echidnas, emus, brush turkeys, and common wombats — were more susceptible on average than their now-extinct counterparts.

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