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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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Tags: Australia, co-extinctions, coextinctions, ecological networks, ecology, extinction, extinction cascade, food web, Giovanni Strona, John Llewelyn, Late Pleistocene, megafauna, Naracoorte, Naracoorte Caves, palaeoecology, Sahul, Trophic cascade, trophic web
Categories : anthropocene, Australia, bottom-up ecology, climate change, climate shift, community ecology, ecology, ecosystem, exploitation, extinction, mammal, mathematics, modelling, palaeo-ecology, predation, predator, South Australia, southern Australia, top-down ecology, trophic cascades, World Heritage Area

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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Tags: Alectura, brush turkey, Dasyurus, demographic model, Diprotodon, Dromaius, echidna, emu, extinction, Genyornis, Kangaroo, megafauna, Megalibgwilia, Metasthenurus, model, Notamacropus, Osphranter, Palorchestes, Phascolonus, Procoptodon, Protemnodon, Sahul, Sarcophilus, short-faced kangaroo, Simosthenurus, Sthenurus, Tachyglossus, Tasmanian devil, Thylacine, Thylacinus, Thylacoleo, Vombatus, wallaby, wombat, Zygomaturus
Categories : Australia, birds, climate change, conservation, decline, demography, ecology, evolution, exploitation, extinction, extinction debt, extinction vortex, harvest, kangaroo, mammal, mathematics, minimum viable population, modelling, population dynamics, population viability analysis, predator, PVA, research

Job: Research Associate in Mammalian Morphology-Environment Interactions

15 02 2021

This might be a little outside the realms of ‘conservation’ per se, but put has a lot of ecology-evolution components, with spin-off applications to modern conservation. Please spread the word.

The Research Associate will investigate how the skull of extant mammal populations varies according to their environment, with a focus on the interaction between mega-herbivores and vegetation change.

The project aims to understand the relationship between evolved morphological adaptation and phenotypic plasticity in changing local environments. The Research Associate will extrapolate this knowledge to the iconic extinct Australian megafauna, with the aim of establishing how changing conditions of the past might have contributed to the demise of the Australian megafauna.

The candidate will be expected to work within a large group of collaborators at Flinders University and interstate, and supervise postgraduate students. The collaboration environment includes teams of national and international researchers, and will particularly integrate research in Global Ecology Lab led by Corey Bradshaw, and Chris Johnson‘s lab at the University of Tasmania. The candidate will be expected to liaise with academic, administrative and technical staff according to the University’s policies, practices and standards.

Key position responsibilities

The Research Associate will be responsible for:

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Tags: academic job, apply, Australia, development, ecology, employment, evolution, job, megafauna, morphology, Postdoctoral Fellow
Categories : development, ecology, evolution, jobs

Did people or climate kill off the megafauna? Actually, it was both

10 12 2019

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

—

Earth is now firmly in the grips of its sixth “mass extinction event”, and it’s mainly our fault. But the modern era is definitely not the first time humans have been implicated in the extinction of a wide range of species.

In fact, starting about 60,000 years ago, many of the world’s largest animals disappeared forever. These “megafauna” were first lost in Sahul, the supercontinent formed by Australia and New Guinea during periods of low sea level.

The causes of these extinctions have been debated for decades. Possible culprits include climate change, hunting or habitat modification by the ancestors of Aboriginal people, or a combination of the two.

The main way to investigate this question is to build timelines of major events: when species went extinct, when people arrived, and when the climate changed. This approach relies on using dated fossils from extinct species to estimate when they went extinct, and archaeological evidence to determine when people arrived.

Comparing these timelines allows us to deduce the likely windows of coexistence between megafauna and people.

We can also compare this window of coexistence to long-term models of climate variation, to see whether the extinctions coincided with or shortly followed abrupt climate shifts.

Data drought

One problem with this approach is the scarcity of reliable data due to the extreme rarity of a dead animal being fossilised, and the low probability of archaeological evidence being preserved in Australia’s harsh conditions. Read the rest of this entry »

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Tags: archaeology, climate change, extinction, megafauna, palaeoecology, palaeontology, Sahul
Categories : Australia, biodiversity, climate change, climate shift, conservation, decline, exploitation, extinction, mathematics, modelling, palaeo-ecology, southern Australia, synergies, top-down ecology, water

Climate change and humans together pushed Australia’s biggest beasts to extinction

25 11 2019

people-megafauna Over the last 60,000 years, many of the world’s largest species disappeared forever. Some of the largest that we generally call ‘megafauna’ were first lost in Sahul — the super-continent formed by the connection of Australia and New Guinea during periods of low sea level. The causes of these extinctions have been heavily debated for decades within the scientific community.

Three potential drivers of these extinctions have been suggested. The first is climate change that assumes an increase in arid conditions that eventually became lethal to megafauna. The second proposed mechanism is that the early ancestors of Aboriginal people who either hunted megafauna species to extinction, or modified ecosystems to put the largest species at a disadvantage. The third and most nuanced proposed driver of extinction is the combination of the first two.

The primary scientific tools we scientists use to determine which of these proposed causes of extinction have the most support are dated fossil records from the extinct species themselves, as well as archaeological evidence from early Aboriginal people. Traditionally, the main way we use these data is to construct a timeline of when the last fossil of a species was preserved, and compare this to evidence indicating when people arrived. We can also reconstruct climate patterns back tens of thousands of years using models similar to the ones used today to predict future climates. Based on the comparison of all of these different timelines, we conclude that abrupt climate changes in the past were influential if they occurred at or immediately before a recorded extinction event. On the other hand, if megafauna extinctions occur immediately after humans are thought to have arrived, we attribute more weight to human arrival as a driver.

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Tags: archaeology, Australia, chronology, climate change, extinction, humans, Late Pleistocene, megafauna, palaeoecology, palaeontology, Pleistocene, Sahul, south-eastern Australia, spatial statistics
Categories : Australia, climate change, climate shift, conservation, ecology, extinction, palaeo-ecology, southern Australia, statistics, top-down ecology

Logbook of Australia’s ancient megafauna

20 11 2019

Australia is home to some of the most unique species worldwide, including egg-laying mammals, tree-climbing, desert-bouncing and and burrow-digging marsupials, and huge flightless birds. While these animals are fascinating, the creatures that used to roam Australia’s landscape thousands of years ago were even more remarkable — these included wombat-like beasts as big as rhinos, birds more than two metres tall, lizards more than seven metres long, and a marsupial lion as big as a leopard.

Just how and why these animals went extinct has been challenging scientists for decades. But examining dated fossil records is one of the primary ways we can look into the past. The ever-increasing number of fossils and the advances in dating techniques have produced a wealth of material we can use to reconstruct the long-lost past.

Even with these data, it has been a struggle to gather enough fossils for large-scale analyses because reports of these records are usually scattered across the scientific literature, with no standardised quality control to make them comparable to each other. Designing a way to standardise these records is therefore important to avoid misleading conclusions.

The FosSahul database was first established in 2016 to try to alleviate these problems — it gathered all the fossil specimens for large animals (excluding humans) from the Late Quaternary (up to ~ 1 million years before present) across the region known as ‘Sahul’, the combined super-continent that included New Guinea and Australia when sea levels were much lower than they are today.

While FosSahul was an important step, the database needed to be updated. First, the quality rating of the fossil dates in the original version was a little subjective and lacked transparency in some cases. This is because the database did not capture enough detail to be able to reproduce all the steps leading to a particular quality rating. Second, given that new fossils are discovered regularly, updates are necessary to include the latest research. Read the rest of this entry »

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Tags: Australia, database, FosSahul, fossils, megafauna, palaeontology, Sahul
Categories : Australia, biodiversity, palaeo-ecology

Increasing human population density drives environmental degradation in Africa

26 06 2019

stumps

Almost a decade ago, I (co-) wrote a paper examining the socio-economic correlates of gross, national-scale indices of environmental performance among the world’s nations. It turned out to be rather popular, and has so far garnered over 180 citations and been cited in three major policy documents.

In addition to the more pedestrian ranking itself, we also tested which of three main socio-economic indicators best explained variation in the environmental rank — a country’s gross ‘wealth’ indicator (gross national income) turned out to explain the most, and there was no evidence to support a non-linear relationship between environmental performance and per capita wealth (the so-called environmental Kuznets curve).

Well, that was then, and this is now. Something that always bothered me about that bit of research was that in some respects, it probably unfairly disadvantaged certain countries that were in more recent phases of the ‘development’ pathway, such that environmental damage long since done in major development pulses many decades or even centuries prior to today (e.g., in much of Europe) probably meant that certain countries got a bit of an unfair advantage. In fact, the more recently developed nations probably copped a lower ranking simply because their damage was fresher.

While I defend the overall conclusions of that paper, my intentions have always been since then to improve on the approach. That desire finally got the better of me, and so I (some might say unwisely) decided to focus on a particular region of the planet where some of the biggest biodiversity crunches will happen over the next few decades — Africa.

Africa is an important region to re-examine these national-scale relationships for many reasons. The first is that it’s really the only place left on the planet where there’s a semi-intact megafauna assemblage. Yes, the great Late Pleistocene megafauna extinction event did hit Africa too, but compared to all other continents, it got through that period relatively unscathed. So now we (still) have elephants, rhinos, giraffes, hippos, etc. It’s a pretty bloody special place from that perspective alone.

Elephants in the Kruger National Park, South Africa (photo: CJA Bradshaw)

Then there’s the sheer size of the continent. Unfortunately, most mercator projections of the Earth show a rather quaint continent nuzzled comfortably in the middle of the map, when in reality, it’s a real whopper. If you don’t believe me, go to truesize.com and drag any country of interest over the African continent (it turns out that its can more or less fit all of China, Australia, USA, and India within its greater borders).

Third, most countries in Africa (barring a few rare exceptions), are still in the so-called ‘development’ phase, although some are much farther along the economic road than others. For this reason, an African nation-to-nation comparison is probably a lot fairer than comparing, say, Bolivia to Germany, or Mongolia to Canada.

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Tags: Africa, agriculture, carbon emissions, deforestation, development, ecological footprint, ecology, environmental performance, environmental sustainability, human population, human population growth, megafauna, sustainability, sustainable development
Categories : Africa, agriculture, anthropocene, biodiversity, biowealth, carbon, cattle, conservation, corruption, deforestation, development, economics, environmental Kuznets curve, environmental policy, environmental science, exploitation, extinction, food, governance, habitat loss, human overpopulation, livestock, logging, mammal, management, modelling, poverty, protected area, societies, sustainability, threatened species, vegetation

Potential conservation nightmare unfolding in South Africa

31 10 2016

Like most local tragedies, it seems to take some time before the news really grabs the overseas audience by the proverbial goolies. That said, I’m gobsmacked that the education tragedy unfolding in South Africa since late 2015 is only now starting to be appreciated by the rest of the academic world.

You might have seen the recent Nature post on the issue, and I do invite you to read that if all this comes as news to you. I suppose I had the ‘advantage’ of getting to know a little bit more about what is happening after talking to many South African academics in the Kruger in September. In a word, the situation is dire.

We’re probably witnessing a second Zimbabwe in action, with the near-complete meltdown of science capacity in South Africa as a now very real possibility. Whatever your take on the causes, justification, politics, racism, or other motivation underlying it all, the world’s conservation biologists should be very, very worried indeed.

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Tags: #feesmustfall, Africa, biodiversity, Education, megafauna, racism, science, South Africa, universities
Categories : Africa, anthropocene, biodiversity, biowealth, conservation, conservation biology, corruption, environmental policy, environmental science, extinction, governance, human overpopulation, management, poaching, poverty, propaganda, research, science

Valuing what we have to prevent it from disappearing

30 09 2016

29 year-old 'Tembo' shows us his grinders © CJA Bradshaw

29 year-old ‘Tembo’ shows us his grinders. Groom Anton is making sure Tembo remains well-rewarded for his good behaviour © CJA Bradshaw

I acknowledge that I’ve been banging on a bit about southern Africa over the last few weeks, but I defend my enthusiasm on the grounds that my first trip to the Kruger National Park profoundly changed the way I view extinction theory and conservation biology.

Today’s post rounds off this mini-series with something I only alluded to in my last: interacting with tame elephants.

I have always been in two minds about the role of animals in captivity, with my opinion that most zoos edge toward the negative because most people who attend them appear to view the animals as a freak-show rather than appreciate their beauty or be fascinated by their behaviour and ecology; add the near-impossible-to-avoid psychological distress to which most captive animals succumb, many zoos in particular are probably better off not existing at all.

That being the case, I won’t simply write off all captive situations as ‘negative’, because if done well, they can have a wonderful educational role to play. Read the rest of this entry »

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Tags: Africa, appreciation, Education, Elephant Whispers, Kruger, Kruger National Park, megafauna, poaching, South Africa, understanding, utility, valuation, value
Categories : Africa, animal welfare, conservation, human-wildlife conflict, poaching

Transition from the Anthropocene to the Minicene

24 09 2016

Going, going … © CJA Bradshaw

I’ve just returned from a life-changing trip to South Africa, not just because it was my first time to the continent, but also because it has redefined my perspective on the megafauna extinctions of the late Quaternary. I was there primarily to attend the University of Pretoria’s Mammal Research Institute 50^thAnniversary Celebration conference.

As I reported in my last post, the poaching rates in one of the larger, best-funded national parks in southern Africa (the Kruger) are inconceivably high, such that for at least the two species of rhino there (black and white), their future persistence probability is dwindling with each passing week. African elephants are probably not far behind.

As one who has studied the megafauna extinctions in the Holarctic, Australia and South America over the last 50,000 years, the trip to Kruger was like stepping back into the Pleistocene. I’ve always dreamed of walking up to a grazing herd of mammoths, woolly rhinos or Diprotodon, but of course, that’s impossible. What is entirely possible though is driving up to a herd of 6-tonne elephants and watching them behave naturally. In the Kruger anyway, you become almost blasé about seeing yet another group of these impressive beasts as you try to get that rare glimpse of a leopard, wild dogs or sable antelope (missed the two former, but saw the latter). Read the rest of this entry »

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Tags: Africa, Anthropocene, elephant, extinction, Holocene, megafauna, persistence, Pleistocene, poaching, rhino, rhinoceros
Categories : Africa, anthropocene, Australia, biodiversity, buffalo, bushmeat, conservation, ecology, ecosystem, ecosystem function, exploitation, extinction, fragmentation, habitat loss, living dead, mammal, management, palaeo-ecology, poaching, poverty, protected area, research, South America, threatened species, trophic cascades

Staggering rhino poaching in the Kruger

14 09 2016

I have the immense honour and pleasure of attending the University of Pretoria’s Mammal Research Institute 50^th Anniversary Celebration conference currently being held in the Kruger National Park. To be rubbing shoulders with some of the greats of African ecology is humbling to say the least, but it’s also a huge opportunity to learn about the wonderful wildlife Africa still has.

Stepping back into what the Pleistocene must have been like in Australia, Europe, and North and South America, I’m moved to near tears by the truly awesome¹ megafauna that still exists here. This is my first time to Africa, and I cannot begin to capture how I feel by seeing these amazing species in the flesh.

But as you probably already know, this last megafauna is under huge threat, and we seriously risk repeating the extinctions of the other continents within less than a century. While the topics associated with the threats are diverse, complex and challenging, one talk here stood out for me among all others: that by Ken Maggs of SANParks.

Kruger holds about 70% of the white (Ceratotherium simum) and black (Diceros bicornis) rhino in South Africa, and about 30% all rhino in the world (98.8% of all white rhino are found in just four countries: South Africa, Namibia, Zimbabwe and Kenya).

So for the ~ 10,000 rhino in Kruger, the following numbers should shock you; Ken showed a slide with the following information: Read the rest of this entry »

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Tags: black rhinoceros, hunting, illegal hunting, Kruger National Park, megafauna, offtake, poach, poaching, rhino, South Africa, white rhinoceros
Categories : Africa, conservation, exploitation

Extinction synergy: deadly combination of human hunting & climate change wrote off Patagonian giants

20 06 2016

Here’s a paper we’ve just had published in Science Advances (Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation). It’s an excellent demonstration of our concept of extinction synergies that we published back in 2008.

—

Giant Ice Age species including elephant-sized sloths and powerful sabre-toothed cats that once roamed the windswept plains of Patagonia, southern South America, were finally felled by a perfect storm of a rapidly warming climate and humans, a new study has shown.

Research published on Saturday in Science Advances, has revealed that it was only when the climate warmed, long after humans first arrived in Patagonia, did the megafauna suddenly die off around 12,300 years ago.

The timing and cause of rapid extinctions of the megafauna has remained a mystery for centuries.

“Patagonia turns out to be the Rosetta Stone – it shows that human colonisation didn’t immediately result in extinctions, but only as long as it stayed cold”. “Instead, more than 1000 years of human occupation passed before a rapid warming event occurred, and then the megafauna were extinct within a hundred years.”

The researchers, including from the University of Colorado Boulder, University of New South Wales and University of Magallanes in Patagonia, studied ancient DNA extracted from radiocarbon-dated bones and teeth found in caves across Patagonia, and Tierra del Fuego, to trace the genetic history of the populations. Species such as the South American horse, giant jaguar and sabre-toothed cat, and the enormous one-tonne short-faced bear (the largest land-based mammalian carnivore) were found widely across Patagonia, but seemed to disappear shortly after humans arrived. Read the rest of this entry »

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Tags: climate change, extinction, extinction synergy, glaciation, Ice Age, megafauna, synergies
Categories : biodiversity, climate change, climate shift, DNA, ecology, extinction, genetics, South America

How to find fossils

30 03 2016

Many palaeontologists and archaeologists might be a little put out by the mere suggestion that they can be told by ecologists how to do their job better. That is certainly not our intention.

Like fossil-hunting scientists, ecologists regularly search for things (individuals of species) that are rare and difficult to find, because surveying the big wide world for biodiversity is a challenge that we have faced since the dawn of our discipline. In fact, much of the mathematical development of ecology stems from this probabilistic challenge — for example, species distribution models are an increasingly important component of both observational and predictive ecology.

But the palaeo types generally don’t rely on mathematical models to ‘predict’ where fossils might be hiding just under the surface. Even I’ve done what most do when trying to find a fossil — go to a place where fossils have already been found and start fossicking. I’ve done this now with very experienced sedimentary geologists in the Flinders Rangers looking for 550 million year-old Ediacaran fossils, and most recently searching for Jurassic fossils (mainly ammonites) on the southern coast of England (Devon’s Jurassic Coast). My prized ammonite find is shown in the photo to the left.

If you’ve read anything on this blog before, you’ll probably know that I’m getting increasingly excited about palaeo-ecology, with particular emphasis on Australia’s late-Pleistocene and early Holocene mass-extinction of megafauna. So with a beautiful, brand-new, shiny, and quality-rated megafauna dataset¹, we cheekily decided to take fossil hunting to the next level by throwing mathematics at the problem.

Just published² in PloS One, I’m happy to announce our newest paper entitled Where to dig for fossils: combining climate-envelope, taphonomy and discovery models.

Of course, we couldn’t just treat fossil predictions like ecological ones — there are a few more steps involved because we are dealing with long-dead specimens. Our approach therefore involved three steps: Read the rest of this entry »

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Tags: Fossil, Genyornis, megafauna, species distribution model
Categories : bioclimatic envelope, climate change, extinction, modelling, palaeo-ecology

Bad science

10 02 2016

In addition to the surpassing coolness of reconstructing long-gone ecosystems, my new-found enthusiasm for palaeo-ecology has another advantage — most of the species under investigation are already extinct.

That might not sound like an ‘advantage’, but let’s face it, modern conservation ecology can be bloody depressing, so much so that one sometimes wonders if it’s worth it. It is, of course, but there’s something marvellously relieving about studying extinct systems for the simple reason that there are no political repercussions. No self-serving, plutotheocratic politician can bugger up these systems any more. That’s a refreshing change from the doom and gloom of modern environmental science!

But it’s not all sweetness and light, of course; there are still people involved, and people sometimes make bad decisions in an attempt to modify the facts to suit their creed. The problem is when these people are the actual scientists involved in the generation of the ‘facts’.

As I alluded to a few weeks ago with the publication of our paper in Nature Communications describing the lack of evidence for a climate effect on the continental-scale extinctions of Australia’s megafauna, we have a follow-up paper that has just been published online in Proceedings of the Royal Society B — What caused extinction of the Pleistocene megafauna of Sahul? led by Chris Johnson of the University of Tasmania.

After our paper published earlier this month, this title might seem a bit rhetorical, so I want to highlight some of the reasons why we wrote the review. Read the rest of this entry »

Comments : 2 Comments »
Tags: Australia, Climate, climate change, EPICA, fossils, human hunting, Judith Field, megafauna, Michael Archer, Signor-Lipps effect, Stephen Wroe, taphonomy
Categories : anthropocene, Australia, climate change, climate shift, conservation, environmental science, exploitation, extinction, science, scientific publishing, synergies

No evidence climate change is to blame for Australian megafauna extinctions

29 01 2016

Last July I wrote about a Science paper of ours demonstrating that there was a climate-change signal in the overall extinction pattern of megafauna across the Northern Hemisphere between about 50,000 and 10,000 years ago. In that case, it didn’t have anything to do with ice ages (sorry, Blue Sky Studios); rather, it was abrupt warming periods that exacerbated the extinction pulse instigated by human hunting.

Contrary to some appallingly researched media reports, we never claimed that these extinctions arose only from warming, because the evidence is more than clear that humans were the dominant drivers across North America, Europe and northern Asia; we simply demonstrated that warming periods had a role to play too.

A cursory glance at the title of this post without appreciating the complexity of how extinctions happen might lead you to think that we’re all over the shop with the role of climate change. Nothing could be farther from the truth.

Instead, we report what the evidence actually says, instead of making up stories to suit our preconceptions.

So it is with great pleasure that I report our new paper just out in Nature Communications, led by my affable French postdoc, Dr Frédérik Saltré: Climate change not to blame for late Quaternary megafauna extinctions in Australia.

Of course, it was a huge collaborative effort by a crack team of ecologists, palaeontologists, geochronologists, paleo-climatologists, archaeologists and geneticists. Only by combining the efforts of this diverse and transdisciplinary team could we have hoped to achieve what we did. Read the rest of this entry »

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Tags: Aboriginal, Aborigine, Australia, ecology, extinction, geochronology, GRIWM, megafauna, modelling, palaeontology, Signor-Lipps effect
Categories : Australia, climate change, conservation, exploitation, extinction, harvest, modelling, science, synergies

Ice Age? No. Abrupt warmings and hunting together polished off Holarctic megafauna

24 07 2015

Oh shit oh shit oh shit …

Did ice ages cause the Pleistocene megafauna to go extinct? Contrary to popular opinion, no, they didn’t. But climate change did have something to do with them, only it was global warming events instead.

Just out today in Science, our long-time-coming (9 years in total if you count the time from the original idea to today) paper ‘Abrupt warmings drove Late Pleistocene Holarctic megafaunal turnover‘ demonstrates for the first time that abrupt warming periods over the last 60,000 years were at least partially responsible for the collapse of the megafauna in Eurasia and North America.

You might recall that I’ve been a bit sceptical of claims that climate changes had much to do with megafauna extinctions during the Late Pleistocene and early Holocene, mainly because of the overwhelming evidence that humans had a big part to play in their demise (surprise, surprise). What I’ve rejected though isn’t so much that climate had nothing to do with the extinctions; rather, I took issue with claims that climate change was the dominant driver. I’ve also had problems with blanket claims that it was ‘always this’ or ‘always that’, when the complexity of biogeography and community dynamics means that it was most assuredly more complicated than most people think.

I’m happy to say that our latest paper indeed demonstrates the complexity of megafauna extinctions, and that it took a heap of fairly complex datasets and analyses to demonstrate. Not only were the data varied – the combination of scientists involved was just as eclectic, with ancient DNA specialists, palaeo-climatologists and ecological modellers (including yours truly) assembled to make sense of the complicated story that the data ultimately revealed. Read the rest of this entry »

Comments : 7 Comments »
Tags: bison, cave bear, cave lion, climate change, climatology, extinction, Global warming, GRIWM, Ice Age, mammoth, megafauna, muskox, Neandertal, Signor-Lipps effect
Categories : anthropocene, Arctic, Asia, biodiversity, biogeography, boreal, Canada, climate change, climate shift, connectivity, conservation, decline, DNA, ecology, ecosystem, Europe, extinction, genetics, harvest, mammal, mathematics, metapopulation, minimum viable population, modelling, Russia, synergies, USA

Cleaning up the rubbish: Australian megafauna extinctions

15 11 2013

A few weeks ago I wrote a post about how to run the perfect scientific workshop, which most of you thought was a good set of tips (bizarrely, one person was quite upset with the message; I saved him the embarrassment of looking stupid online and refrained from publishing his comment).

As I mentioned at the end of post, the stimulus for the topic was a particularly wonderful workshop 12 of us attended at beautiful Linnaeus Estate on the northern coast of New South Wales (see Point 5 in the ‘workshop tips’ post).

But why did a group of ecological modellers (me, Barry Brook, Salvador Herrando-Pérez, Fréd Saltré, Chris Johnson, Nick Beeton), geneticists, palaeontologists (Gav Prideaux), fossil dating specialists (Dizzy Gillespie, Bert Roberts, Zenobia Jacobs) and palaeo-climatologists (Michael Bird, Chris Turney [in absentia]) get together in the first place? Hint: it wasn’t just the for the beautiful beach and good wine.

I hate to say it – mainly because it deserves as little attention as possible – but the main reason is that we needed to clean up a bit of rubbish. The rubbish in question being the latest bit of excrescence growing on that accumulating heap produced by a certain team of palaeontologists promulgating their ‘it’s all about the climate or nothing’ broken record.

Read the rest of this entry »

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Tags: Ancient DNA, Australasia, Australia, climate change, Extinctions, Fossil, hunting, megafauna, over-exploitation, Sahul
Categories : Australia, climate change, conservation, disease, DNA, exploitation, extinction, genetics, harvest, mathematics, metapopulation, minimum viable population, modelling, population dynamics, population viability analysis, South America, synergies

It couldn’t have been us!

29 05 2012

A few months ago I asked Chris Johnson of the University of Tasmania to put together a post on his recent Science paper regarding Australian megafaunal extinctions. It seems that it stirred, yet again, some controversy among those who refuse to accept (mainly archaeologists) that humans could have had anything to do with pre-European extinctions. Indeed, how could humans possibly have anything to do with extinctions?!

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Like Corey, I am mainly interested in current environmental problems. But now and then I wade into the debate over the extinction of Australia’s Pleistocene megafauna [editor’s note: Chris literally wrote the book on Australian mammal extinctions over the last 50,000 years], those huge animals that wandered over the Australian landscape until about 40,000 years ago.

This is an endlessly fascinating topic. The creatures were wonderful and bizarre – it’s great fun doing work that lets you think about marsupial lions, giant kangaroos, geese bigger than emus, echidnas the size of wombats, and the rest. The cause of their extinction is perhaps the biggest mystery, and the most vexed controversy, in the environmental history of Australia. And for reasons that I will explain in a minute, solving this mystery is profoundly important for our understanding of contemporary Australian ecology.

The latest bit of work on this is a paper that a group of us (including Corey’s close colleague, Barry Brook) published in Science. You can see it here (if you don’t have access to Science, email me for a copy). So far, research on this problem has concentrated on dating fossils to find out when megafauna species went extinct. Several recent studies have found evidence for extinction between 40,000 and 50,000 years ago, which is about when people first came to Australia. But the conclusion that people caused a mass extinction of megafauna has been strenuously criticised, because so far it is based on only a few species with good collections of dates. The critics argue that other species disappeared before humans arrived, maybe in an extended series of extinctions caused by something else, like a deteriorating climate.

This argument over fossils will be with us for a long time. Because finding and dating fossils is such hard, slow work, the fossil record will inevitably give a seriously incomplete picture of what happened. One way around this problem would be to analyse the fossil record using mathematical approaches that take into account the problem of incomplete sampling. Corey is lead author of a recent paper that introduced a great new set of tools for this, and we are part of a group that is currently assembling a complete database of all recent dates on Australian fossils so that we can analyse them using these tools. Stay tuned for the result. Read the rest of this entry »

Comments : 5 Comments »
Tags: Aboriginal, Aborigine, Australia, Chris Johnson, extinction, megafauna, Sporormiella
Categories : Australia, bushmeat, climate change, conservation, decline, ecosystem function, exploitation, extinction, fire, harvest, invasive species, mammal

Why and how did Pleistocene megafauna go extinct?

27 05 2010

Just a quick post to say that I’m currently at Duke University in the USA attending a special National Evolutionary Synthesis Centre ‘Catalysis Meeting’ entitled: Integrating datasets to investigate megafaunal extinction in the Late Quaternary.

The meeting is basically about nailing down some of the remaining mysteries and controversies surrounding the extinction of many species during periods of rapid climate change 11-60 thousand years ago.

It’s been fun so far, and a lot of exciting analysis will ensue, but for the meantime I’ll just summarise what we’re trying to do. Read the rest of this entry »