… some (models) are useful

8 06 2021

As someone who writes a lot of models — many for applied questions in conservation management (e.g., harvest quotas, eradication targets, minimum viable population sizes, etc.), and supervises people writing even more of them, I’ve had many different experiences with their uptake and implementation by management authorities.

Some of those experiences have involved catastrophic failures to influence any management or policy. One particularly painful memory relates to a model we wrote to assist with optimising approaches to eradicate (or at least, reduce the densities of) feral animals in Kakadu National Park. We even wrote the bloody thing in Visual Basic (horrible coding language) so people could run the module in Excel. As far as I’m aware, no one ever used it.

Others have been accepted more readily, such as a shark-harvest model, which (I think, but have no evidence to support) has been used to justify fishing quotas, and one we’ve done recently for the eradication of feral pigs on Kangaroo Island (as yet unpublished) has led directly to increased funding to the agency responsible for the programme.

According to Altmetrics (and the online tool I developed to get paper-level Altmetric information quickly), only 3 of the 16 of what I’d call my most ‘applied modelling’ papers have been cited in policy documents:

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.

Read the rest of this entry »




Conservation paradox – the pros and cons of recreational hunting

20 02 2021
The recovery of species such as mountain zebra (Equus zebra) was partly supported by the economic benefits generated by trophy hunting. © Dr Hayley Clements

Through the leadership of my long-time friend and collaborator, Enrico Di Minin of the Helsinki Lab of Interdisciplinary Conservation Science, as well as the co-leadership of my (now) new colleague, Dr Hayley Clements, I’m pleased to report our new paper in One Earth — ‘Consequences of recreational hunting for biodiversity conservation and livelihoods‘.


My father was a hunter, and by proxy so was I when I was a lad. I wasn’t really a ‘good’ hunter in the sense that I rarely bagged my quarry, but during my childhood not only did I fail to question the morality of recreational hunting, I really thought that in fact it was by and large an important cultural endeavour.

It’s interesting how conditioned we become as children, for I couldn’t possibly conceive of hunting a wild, indigenous species for my own personal satisfaction now. I find the process not only morally and ethically reprehensible, I also think that most species don’t need the extra stress in an already environmentally stressed world.

I admit that I do shoot invasive European rabbits and foxes on my small farm from time to time — to reduce the grazing and browsing pressure on my trees from the former, and the predation pressure on the chooks from the latter. Of course, we eat the rabbits, but I tend just to bury the foxes. My dual perspective on the general issue of hunting in a way mirrors the two sides of the recreational hunting issue we report in our latest paper.

Wild boar (Sus scrofus). Photo: Valentin Panzirsch, CC BY-SA 3.0 AT, via Wikimedia Commons

I want to be clear here that our paper focuses exclusively on recreational hunting, and especially the hunting of charismatic species for their trophies. The activity is more than just a little controversial, for it raises many ethical and moral concerns at the very least. Yet, recreational hunting is frequently suggested as a way to conserve nature and support local people’s livelihoods. 

Read the rest of this entry »




Worried about Earth’s future? Well, the outlook is worse than even scientists can grasp

14 01 2021

Daniel Mariuz/AAP

Corey J. A. Bradshaw, Flinders University; Daniel T. Blumstein, University of California, Los Angeles, and Paul Ehrlich, Stanford University

Anyone with even a passing interest in the global environment knows all is not well. But just how bad is the situation? Our new paper shows the outlook for life on Earth is more dire than is generally understood.

The research published today reviews more than 150 studies to produce a stark summary of the state of the natural world. We outline the likely future trends in biodiversity decline, mass extinction, climate disruption and planetary toxification. We clarify the gravity of the human predicament and provide a timely snapshot of the crises that must be addressed now.

The problems, all tied to human consumption and population growth, will almost certainly worsen over coming decades. The damage will be felt for centuries and threatens the survival of all species, including our own.

Our paper was authored by 17 leading scientists, including those from Flinders University, Stanford University and the University of California, Los Angeles. Our message might not be popular, and indeed is frightening. But scientists must be candid and accurate if humanity is to understand the enormity of the challenges we face.

Girl in breathing mask attached ot plant in container

Humanity must come to terms with the future we and future generations face. Shutterstock

Getting to grips with the problem

First, we reviewed the extent to which experts grasp the scale of the threats to the biosphere and its lifeforms, including humanity. Alarmingly, the research shows future environmental conditions will be far more dangerous than experts currently believe. Read the rest of this entry »





Time for a ‘cold shower’ about our ability to avoid a ghastly future

13 01 2021

I wish it need not have happened in my time,” said Frodo. “So do I,’ said Gandalf, “and so do all who live to see such times. But that is not for them to decide. All we have to decide is what to do with the time that is given us.”

Frodo Baggins and Gandalf, The Fellowship of the Ring

Today, 16 high-profile scientists and I published what I describe as a ‘cold shower’ about society’s capacity to avoid a ghastly future of warfare, disease, inequality, persecution, extinction, and suffering.

And it goes way beyond just the plight of biodiversity.

No one who knows me well would mistake me for an optimist, try as I might to use my colleagues’ and my research for good. Instead, I like to describe myself as a ‘realist’. However, this latest paper has made even my gloomier past outputs look downright hopeful.

And before being accused of sensationalism, let me make one thing abundantly clear — I sincerely hope that what we describe in this paper does not come to pass. Not even I am that masochistic.

I am also supportive of every attempt to make the world a better place, to sing about our successes, regroup effectively from our failures, and maintain hope in spite of evidence to the contrary.

But failing to acknowledge the magnitude and the gravity of the problems facing us is not just naïve, it is positively dangerous and potentially fatal.

It is this reason alone that prompted us to write our new paper “Underestimating the challenges of
avoiding a ghastly future
” just published in the new journal, Frontiers in Conservation Science.

Read the rest of this entry »




The only constant is change

27 07 2020

I just wrote a piece for the Flinders University alumnus magazine — Encounter — and I thought I’d share it here.

encounter-2020_Page_01

As an ecologist concerned with how life changes and adapts to the vagaries of climate and pervasive biological shuffling, ‘constant change’ is more than just a mantra — it is, in fact, the mathematical foundation of our entire discipline.

But if change is inevitable, how can we ensure it is in the right direction?

Take climate change for example. Since the Earth first formed it has experienced abrupt climate shifts many times, both to the detriment of most species in existence at any given time, and to the advantage of those species evolving from the ashes.

For more than 3.5 billion years, species have evolved and gone extinct, such that more than 99% of all species that have ever existed are now confined, permanently, to the vaults of the past.

Read the rest of this entry »





Extinction cascades

3 06 2020

A recent online interview I did on the role of extinction cascades in mass extinctions:





Extinction Anxiety

21 05 2020

Earlier this week, the SBS show The Feed did a short segment called ‘Extinction Anxiety’ where I talked with host Alice Matthews about biodiversity extinctions. Given that it has so far only been available in Australia, I made a copy here for others to view.

For more information on the state of global biodiversity, see this previous post.

 

 

CJA Bradshaw





In pursuit of an ecological resilience in the Anthropocene

3 03 2020

Changing TidesAn excerpt from Alejandro Frid‘s new book, Changing Tides: An Ecologist’s Journey to Make Peace with the Anthropocene (published first in Sierra, with photos courtesy of New Society Publishers)

The birth of my daughter, in 2004, thrust upon me a dual task: to be scientifically realistic about all the difficult changes that are here to stay, while staying humanly optimistic about the better things that we still have.

By the time my daughter turned eleven, I had jettisoned my nos­talgia for the Earth I was born into in the mid-196os—a planet that, of course, was an ecological shadow of Earth 100 years before, which in turn was an ecological shadow of an earlier Earth. The pragmatist in me had embraced the Anthropocene, in which humans dominate all biophysical processes, and I ended up feeling genuinely good about some of the possible futures in which my daughter’s generation might grow old.

It was a choice to engage in a tough situation. An acknowledgement of rapid and uninvited change. A reaffirmed commitment to everything I have learned, and continue to learn, as an ecologist working with Indigenous people on marine conservation. Fundamental to this perspective is the notion of resilience: the ability of someone or something—a culture, an ecosystem, an economy, a person—to absorb shocks yet still maintain their essence.

But what is essence? Read the rest of this entry »





Unlikely the biodiversity crisis will improve any time soon

6 02 2020

hopelessAround a fortnight ago I wrote a hastily penned post about the precarious state of biodiversity — it turned out to be one of the most-read posts in ConservationBytes‘ history (nearly 22,000 views in less than two weeks).

Now, let’s examine whether this dreadful history is likely to get any better any time soon.

Even if extinction rates decline substantially over the next century, I argue that we are committed to an intensifying biodiversity extinction crisis. The aggregate footprint from the growing human population notwithstanding, we can expect decades, if not centuries, of continued extinctions from lag effects alone (extinction debts arising from previous environmental damage engendering extinctions in the future)1.

Global vegetation cover and production are also likely to decline even in the absence of continued habitat clearing — the potential benefit of higher CO2 concentrations for plant photosynthesis is more than offset by lower availability of water in the soil, heat stress, and the frequency of disturbances such as droughts2. Higher frequencies and intensities of disturbance events like catastrophic bushfire will also exacerbate extinction rates3.

However, perhaps the least-appreciated element of potential extinctions arising from climate change is that they are vastly underestimated when only considering a species’ thermal tolerance4. In fact, climate disruption-driven extinction rates could be up to ten times higher than currently predicted4 when extinction cascades are taken into account5. Read the rest of this entry »





The state of global biodiversity — it’s worse than you probably think

24 01 2020

Chefurka biomass slide

I often find myself in a position explaining to non-professionals just how bad the state of global biodiversity really is. It turns out too that even quite a few ecologists seem to lack an appreciation of the sheer magnitude of damage we’ve done to the planet.

The loss of biodiversity that has occurred over the course of our species’ time on Earth is staggering. This loss is now truly planetary in scale and caused by human actions, albeit the severity of which is unequally distributed across the globe1. While Sandra Díaz and company recently summarised the the extent of the biodiversity crisis unfolding1 well in their recent synopsis of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES)2 report, I’m going to repeat some of the salient summary statements here, and add a few others. Read the rest of this entry »





Cartoon guide to biodiversity loss LVIII

4 01 2020

The first set of six biodiversity cartoons for 2020. This special, Australia-is-burning-down-themed set is dedicated to Scott Morrison and his ilk. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


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Influential conservation ecology papers of 2019

24 12 2019

Bradshaw-Waves breaking on rocks Macquarie Island
As I’ve done for the last six years, I am publishing a retrospective list of the ‘top’ 20 influential papers of 2019 as assessed by experts in F1000 Prime (in no particular order). See previous years’ lists here: 20182017, 20162015, 2014, and 2013.

Read the rest of this entry »





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

10 12 2019

When freshwater dried up, so did many megafauna species.
Centre of Excellence for Australian Biodiversity and Heritage, Author provided

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.


Read more: What is a ‘mass extinction’ and are we in one now?


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.


Read more: An incredible journey: the first people to arrive in Australia came in large numbers, and on purpose


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 »





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

25 11 2019

people-megafaunaOver 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.

Read the rest of this entry »





What is a ‘mass extinction’ and are we in one now?

13 11 2019

(reproduced from The Conversation)

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.


Read more: Climate change is killing off Earth’s little creatures


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.

An ammonite fossil found on the Jurassic Coast in Devon. The fossil record can help us estimate prehistoric extinction rates. Corey Bradshaw, Author provided

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Cartoon guide to biodiversity loss LVII

6 11 2019

The sixth set of six biodiversity cartoons for 2019. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


Read the rest of this entry »





Respecting Aboriginal culture through language

16 10 2019

(originally posted on the GE.blog)

GEL Logo KaurnaWhat’s in a name? Well, rather a lot, I think.

Names have meanings, and not just in the way that they tag people, places or objects. I am of the opinion that names go to the core of culture and personal identity in a way that our corporate/fast-food/market-driven society often fails to appreciate or espouse.

This is why we decided to seek cultural permission to have our lab’s name translated into the local Kaurna Language. Like many Aboriginal languages around Australia, Kaurna needs support, respect, and value among Aboriginal and non-Aboriginal people alike if it is to survive. And to me, the extinction of even one language is akin to the extinction of a species. Gone forever, never to be renewed.

But some people probably do not understand why this is important, which was brought home to me last night when a good friend asked why we decided to seek permission to have the lab’s name translated.

“Well,”, I said, “whenever I travel to other countries where multiple languages are spoken, be that in New Zealand1, South Africa2, Canada3, or southern Finland4, almost every official building, place, object, or document has a translation in different languages of the region.”

“Why don’t we seem to do that in Australia very much?”, I said.

After all, it is, at the very least, a sign of respect and recognition of the rightful custodians of the places and land; it recognises that there isn’t only one culture that usurps all others, and that there is multiple meaning and value in that place or object. Read the rest of this entry »





The Great Dying

30 09 2019

Here’s a presentation I gave earlier in the year for the Flinders University BRAVE Research and Innovation series:

There is No Plan(et) B — What you can do about Earth’s extinction emergency

Earth is currently experiencing a mass extinction brought about by, … well, … us. Species are being lost at a rate similar to when the dinosaurs disappeared. But this time, it’s not due to a massive asteroid hitting the Earth; species are being removed from the planet now because of human consumption of natural resources. Is a societal collapse imminent, and do we need to prepare for a post-collapse society rather than attempt to avoid one? Or, can we limit the severity and onset of a collapse by introducing a few changes such as removing political donations, becoming vegetarians, or by reducing the number of children one has?

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Cartoon guide to biodiversity loss LVI

4 09 2019

The fifth set of six biodiversity cartoons for 2019. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


Read the rest of this entry »