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 »





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 »




Recreational hunting, conservation and livelihoods: no clear evidence trail

2 03 2021
Enrico Di Minin, University of Helsinki; Anna Haukka, University of Helsinki; Anna Hausmann, University of Helsinki; Christoph Fink, University of Helsinki; Corey J. A. Bradshaw, Flinders University; Gonzalo Cortés-Capano, University of Helsinki; Hayley Clements, Stellenbosch University, and Ricardo A. Correia, University of Helsinki

In some African countries, lion trophy hunting is legal. Riaan van den Berg

In sub-Saharan Africa, almost 1,400,000 km² of land spread across many countries — from Kenya to South Africa — is dedicated to “trophy” (recreational) hunting. This type of hunting can occur on communal, private, and state lands.

The hunters – mainly foreign “tourists” from North America and Europe – target a wide variety of species, including lions, leopards, antelopes, buffalo, elephants, zebras, hippopotamus and giraffes.


Read more: Big game: banning trophy hunting could do more harm than good


Debates centred on the role of recreational hunting in supporting nature conservation and local people’s livelihoods are among the most polarising in conservation today.

On one hand, people argue that recreational hunting generates funding that can support livelihoods and nature conservation. It’s estimated to generate US$200 million annually in sub-Saharan Africa, although others dispute the magnitude of this contribution.

On the other hand, hunting is heavily criticised on ethical and moral grounds and as a potential threat to some species.

Evidence for taking a particular side in the debate is still unfortunately thin. In our recently published research, we reviewed the large body of scientific literature on recreational hunting from around the world, which meant we read and analysed more than 1000 peer-reviewed papers.

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 »




Need to predict population trends, but can’t code? No problem

2 12 2020

Yes, yes. I know. Another R Shiny app.

However, this time I’ve strayed from my recent bibliometric musings and developed something that’s more compatible with the core of my main research and interests.

Welcome to LeslieMatrixShiny!

Over the years I’ve taught many students the basics of population modelling, with the cohort-based approaches dominating the curriculum. Of these, the simpler ‘Leslie’ (age-classified) matrix models are both the easiest to understand and for which data can often be obtained without too many dramas.

But unless you’re willing to sit down and learn the code, they can be daunting to the novice.

Sure, there are plenty of software alternatives out there, such as Bob Lacy‘s Vortex (a free individual-based model available for PCs only), Resit Akçakaya & co’s RAMAS Metapop ($; PC only), Stéphane Legendre‘s Unified Life Models (ULM; open-source; all platforms), and Charles Todd‘s Essential (open-source; PC only) to name a few. If you’re already an avid R user and already into population modelling, you might be familiar with the population-modelling packages popdemo, OptiPopd, or sPop. I’m sure there are still other good resources out there of which I’m not aware.

But, even to install the relevant software or invoke particular packages in R takes a bit of time and learning. It’s probably safe to assume that many people find the prospect daunting.

It’s for this reason that I turned my newly acquired R Shiny skills to matrix population models so that even complete coding novices can run their own stochastic population models.

I call the app LeslieMatrixShiny.

Read the rest of this entry »




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 »





Victoria, please don’t aerial-bait dingoes

10 10 2019

Here’s a submission to Victoria’s proposed renewal of special permission from the Commonwealth to poison dingoes:

dingo with bait

08 October 2019

Honourable Lily D’Ambrosio MP
Minister for Energy, Environment and Climate Change
Level 16, 8 Nicholson Street, East Melbourne, VIC 3002

lily.dambrosio@parliament.vic.gov.au

cc:

The Hon Jaclyn Symes, Minister for Agriculture, Victoria

(jaclyn.symes@parliament.vic.gov.au)

Dr Sally Box, Threatened Species Commissioner

(ThreatenedSpeciesCommissioner@environment.gov.au)

The Hon Sussan Ley MP, Minister for Environment, Australia

(Farrer@aph.gov.au)

RE: RENEWAL OF AERIAL BAITING EXEMPTION IN VICTORIA FOR WILD DOG CONTROL USING 1080

Dear Minister,

The undersigned welcome the opportunity to comment on the proposed renewal of special permission from the Commonwealth under Sections 18 and 18A of the Environment Protection and Biodiversity Conservation Act 1999 (Commonwealth) to undertake aerial 1080 baiting in six Victorian locations for the management of ‘wild dogs’. This raises serious concerns for two species listed as threatened and protected in Victoria: (1) dingoes and (2) spot-tailed quolls (Dasyurus maculatus).

First, we must clarify that the terminology ‘wild dog’ is not appropriate when discussing wild canids in Australia. One of the main discussion points at the recent Royal Zoological Society of NSW symposium ‘Dingo Dilemma: Cull, Contain or Conserve’ was that the continued use of the terminology ‘wild dog’ is not justified because wild canids in Australia are predominantly dingoes and dingo hybrids, and not, in fact, feral domestic dogs. In Victoria, Stephens et al. (2015) observed that only 5 out of 623 wild canids (0.008%) sampled were feral domestic dogs with no evidence of dingo ancestry. This same study determined that 17.2% of wild canids in Victoria were pure or likely pure dingoes and 64.4% were hybrids with greater than 60% dingo ancestry. Additionally, comparative studies by Jones (1988, 1990 and 2009) observed that dingoes maintained a strong phenotypic identity in the Victorian highlands over time, and perceptively ‘wild dog’ like animals were more dingo than domestic dog.

As prominent researchers in predator ecology, biology, archaeology, cultural heritage, social science, humanities, animal behaviour and genetics, we emphasise the importance of dingoes in Australian, and particularly Victorian, ecosystems. Dingoes are the sole non-human, land-based, top predator on the Australian mainland. Their importance to the ecological health and resilience of Australian ecosystems cannot be overstated, from regulating wild herbivore abundance (e.g., various kangaroo species), to reducing the impacts of feral mesopredators (cats, foxes) on native marsupials (Johnson & VanDerWal 2009; Wallach et al. 2010; Letnic et al. 20122013; Newsome et al. 2015; Morris & Letnic 2017). Their iconic status is important to First Nations people and to the cultural heritage of all Australians. Read the rest of this entry »





Environmental damage kills children

1 10 2019

Yes, childrenairpollutionit’s a provocative title, I agree. But then again, it’s true.

But I don’t just mean in the most obvious ways. We already have good data showing that lack of access to clean water and sanitation kills children (especially in developing nations), that air pollution is a nasty killer of young children in particular, and now even climate change is starting to take its toll.

These aspects of child health aren’t very controversial, but when we talk about the larger suite of indicators of environmental ‘damage’, such as deforestation rates, species extinctions, and the overall reduction of ecosystem services, the empirical links to human health, and to children in particular, are far rarer.

This is why I’m proud to report the publication today of a paper on which I and team of wonderful collaborators (Sally Otto, Zia Mehrabi, Alicia Annamalay, Sam Heft-Neal, Zach Wagner, and Peter Le Souëf) have worked for several years.

I won’t lie — the path to publishing this paper was long and hard, I think mainly because it traversed so many different disciplines. But we persevered and today published the paper entitled ‘Testing the socioeconomic and environmental determinants of better child-health outcomes in Africa: a cross-sectional study among nations* in the journal BMJ Open.

Read the rest of this entry »





First Australians arrived in large groups using complex technologies

18 06 2019

file-20190325-36276-12v4jq2

One of the most ancient peopling events of the great diaspora of anatomically modern humans out of Africa more than 50,000 years ago — human arrival in the great continent of Sahul (New Guinea, mainland Australia & Tasmania joined during periods of low sea level) — remains mysterious. The entry routes taken, whether migration was directed or accidental, and just how many people were needed to ensure population viability are shrouded by the mists of time. This prompted us to build stochastic, age-structured human population-dynamics models incorporating hunter-gatherer demographic rates and palaeoecological reconstructions of environmental carrying capacity to predict the founding population necessary to survive the initial peopling of late-Pleistocene Sahul.

As ecological modellers, we are often asked by other scientists to attempt to render the highly complex mechanisms of entire ecosystems tractable for virtual manipulation and hypothesis testing through the inevitable simplification that is ‘a model’. When we work with scientists studying long-since-disappeared ecosystems, the challenges multiply.

Add some multidisciplinary data and concepts into the mix, and the complexity can quickly escalate.

We do have, however, some powerful tools in our modelling toolbox, so as the Modelling Node for the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CABAH), our role is to link disparate fields like palaeontology, archaeology, geochronology, climatology, and genetics together with mathematical ‘glue’ to answer the big questions regarding Australia’s ancient past.

This is how we tackled one of these big questions: just how did the first anatomically modern Homo sapiens make it to the continent and survive?

At that time, Australia was part of the giant continent of Sahul that connected New Guinea, mainland Australia, and Tasmania at times of lower sea level. In fact, throughout most of last ~ 126,000 years (late Pleistocene and much of the Holocene), Sahul was the dominant landmass in the region (see this handy online tool for how the coastline of Sahul changed over this period).

Read the rest of this entry »





Influential conservation ecology papers of 2018

17 12 2018

e35f9ddeada029a053a15cd023abadf5
For the last five years I’ve published a retrospective list of the ‘top’ 20 influential papers of the year as assessed by experts in F1000 Prime — so, I’m doing so again for 2018 (interesting side note: six of the twenty papers highlighted here for 2018 appear in Science magazine). See previous years’ posts here: 2017, 20162015, 2014, and 2013.

Read the rest of this entry »





Sex on the beach

2 10 2018
Female green turtles (Chelonia mydas) spawning (top) and diving (bottom) on Raine Island (Great Barrier Reef, Queensland, Australia) — photos courtesy of Ian Bell. This species is ‘Endangered’ globally since 1982, mainly from egg harvesting (poaching conflict in Mexico for olive ridley Lepidochelys olivacea featured by National Geographic’s video here), despite the success of conservation projects (39). Green turtles inhabit tropical and subtropical seas in all oceans. Adults can grow > 150 kg and live for up to ~ 75 years. Right after birth, juveniles venture into the open sea to recruit ultimately in coastal areas until sexual maturity. They then make their first reproductive migration, often over 1000s of km (see footage of a real dive of a camera-equipped green turtle), to reach their native sandy beaches where pregnant females will lay their eggs. Each female can deposit more than one hundred eggs in her nest, and in several clutches in the same season because they can store the sperm from multiple mating events.

When sex is determined by the thermal environment, males or females might predominate under sustained climatic conditions. A study about marine turtles from the Great Barrier Reef illustrates how feminisation of a population can be partitioned geographically when different reproductive colonies are exposed to contrasting temperatures.

Fortunately, most people in Western societies already perceive that we live in a complex blend of sexual identities, far beyond the kind of genitals we are born with. Those identities start to establish themselves in the embryo before the sixth week of pregnancy. In the commonest scenario, for a human foetus XY with one maternal chromosome (X) and one paternal (Y) chromosome, the activation of the Sry gen (unique to Y) will trigger the differentiation of testicles and, via hormonal pathways, the full set of male characteristics (1).

Absence of that gene in an XX embryo will normally lead to a woman. However, in just one of many exceptions to the rule, Sry-expression failure in XY individuals can result in sterile men or ambiguous genitals — along a full gradient of intermediate sexes and, potentially, gender identities. A 2015 Nature ‘News’ feature echoes two extraordinary cases: (i) a father of four children found to bear a womb during an hernia operation, and (ii) a pregnant mother found to host both XX and XY cells during a genetic test – with her clinical geneticist stating “… that’s the kind of science-fiction material for someone who just came in for an amniocentesis” (2). These real-life stories simply reflect that sex determination is a complex phenomenon.

Three ways of doing it

In nature, there are three main strategies of sex determination (3) — see scheme here: Read the rest of this entry »





Legacy of human migration on the diversity of languages in the Americas

12 09 2018

quechua-foto-ale-glogsterThis might seem a little left-of-centre for CB.com subject matter, but hang in there, this does have some pretty important conservation implications.

In our quest to be as transdisciplinary as possible, I’ve team up with a few people outside my discipline to put together a PhD modelling project that could really help us understand how human colonisation shaped not only ancient ecosystems, but also our own ancient cultures.

Thanks largely to the efforts of Dr Frédérik Saltré here in the Global Ecology Laboratory, at Flinders University, and in collaboration with Dr Bastien Llamas (Australian Centre for Ancient DNA), Joshua Birchall (Museu Paraense Emílio Goeldi, Brazil), and Lars Fehren-Schmitz (University of California at Santa Cruz, USA), I think the student could break down a few disciplinary boundaries here and provide real insights into the causes and consequences of human expansion into novel environments.

Interested? See below for more details?

Languages are ‘documents of history’ and historical linguists have developed comparative methods to infer patterns of human prehistory and cultural evolution. The Americas present a more substantive diversity of indigenous language stock than any other continent; however, whether such a diversity arose from initial human migration pathways across the continent is still unknown, because the primary proxy used (i.e., archaeological evidence) to study modern human migration is both too incomplete and biased to inform any regional inference of colonisation trajectories. Read the rest of this entry »





Greater death rates for invasive rabbits from interacting diseases

30 05 2018

When it comes to death rates for invasive European rabbits (Oryctolagus cuniculus) in Australia, it appears that 1 + 1 = 2.1.

Pt tagged rab with RHD+myxo 1 10-08

Tagged European rabbit kitten infected with myxoma virus, but that died from rabbit haemorrhagic virus disease (RHDV). Photo by David Peacock, Biosecurity South Australia.

“Canberra, we have a problem” — Sure, it’s an old problem and much less of one than it used to be back in the 1950s, but invasive rabbits are nonetheless an ecological, conservation, and financial catastrophe across Australia.

relative rabbit abundance South Australia

Semi-schematic diagram, redrawn using data from Saunders and others and extended to include the recent spread of RHDV2, showing changes in rabbit abundance in relation to the introduction of biological control agents into north-eastern South Australia. Dotted lines indicate uncertainty due to lack of continuous annual data. The broken line indicates a level of about 0.5 rabbits ha-1, below which rabbits must be held to ensure recovery of native pastures and shrubs (from B. Cooke 2018 Vet Rec doi:10.1136/vr.k2105)

Rabbits used to reach plague numbers in much of agricultural and outback Australia, but the introduction and clever manipulation of two rather effective rabbit-specific viruses and insect vectors — first, myxoma virus in 1950, European rabbit fleas in the 1960s to help spread the virus, then Spanish rabbit fleas in the 1990s to increase spread into arid areas, and then rabbit haemorrhagic disease virus (RHDV) in 1995 — have been effective in dropping rabbit abundances by an estimated 75-80% in South Australia alone since the 1950s.

Read the rest of this entry »





Four decades of fragmentation

27 09 2017

fragmented

I’ve recently read perhaps the most comprehensive treatise of forest fragmentation research ever compiled, and I personally view this rather readable and succinct review by Bill Laurance and colleagues as something every ecology and conservation student should read.

The ‘Biological Dynamics of Forest Fragments Project‘ (BDFFP) is unquestionably one of the most important landscape-scale experiments ever conceived and implemented, now having run 38 years since its inception in 1979. Indeed, it was way ahead of its time.

Experimental studies in ecology are comparatively rare, namely because it is difficult, expensive, and challenging in the extreme to manipulate entire ecosystems to test specific hypotheses relating to the response of biodiversity to environmental change. Thus, we ecologists tend to rely more on mensurative designs that use existing variation in the landscape (or over time) to infer mechanisms of community change. Of course, such experiments have to be large to be meaningful, which is one reason why the 1000 km2 BDFFP has been so successful as the gold standard for determining the effects of forest fragmentation on biodiversity.

And successful it has been. A quick search for ‘BDFFP’ in the Web of Knowledge database identifies > 40 peer-reviewed articles and a slew of books and book chapters arising from the project, some of which are highly cited classics in conservation ecology (e.g., doi:10.1046/j.1523-1739.2002.01025.x cited > 900 times; doi:10.1073/pnas.2336195100 cited > 200 times; doi:10.1016/j.biocon.2010.09.021 cited > 400 times; and doi:10.1111/j.1461-0248.2009.01294.x cited nearly 600 times). In fact, if we are to claim any ecological ‘laws’ at all, our understanding of fragmentation on biodiversity could be labelled as one of the few, thanks principally to the BDFFP. Read the rest of this entry »





Noses baffled by ocean acidification

18 04 2017

Clown fish couple (Amphiprion percula) among the tentacles of anemone Heteractis magnifica in Kimbe Bay (Papua New Guinea) – courtesy of Mark McCormick. Clownfish protect anemones from predators and parasites in exchange of shelter and food. The fish tolerates the host’s venom because its skin is protected by a mucus layer some 2-3× thicker than phylogenetically related species (12); clownfish fabricate the mucus themselves and seem to obtain anemone antigens through a period of acclimation (13), but whether protection is acquired or innate is still debated. Clownfish are highly social bony fish, forming groups with one reproductive pair (up to 11 cm in length each) and several smaller, non-reproductive males. Reproduction is protandrous (also known as sequential hermaphroditism), so larvae are born male and, as soon as the reproductive female dies, her widower becomes female and the largest of the subsidiary males becomes the alpha male. The IUCN lists clownfish, generically named ‘anemone fish’, as threatened by the pet-trade industry and habitat degradation, although surprisingly, only 1 species has been assessed (A. sandaracinos). The clown anemone fish A. ocellaris is the species that inspired Nemo in the 2003 Academy-Award fiction movie – contrary to the logical expectation that the Oscars Red Carpet would generate support for conservation on behalf of Hollywood, of the 1568 species represented in the movie, only 16 % of those evaluated are threatened (14).

Smell is like noise, the more scents we breathe in one sniff, the more difficult it is to distinguish them to the point of olfactory saturation. Experimental work with clownfish reveals that the increase in dissolved carbon dioxide in seawater, mimicking ocean acidification, alters olfactory physiology, with potential cascading effects on the demography of species.

Places such as a restaurant, a hospital or a library have a characteristic bouquet, and we can guess the emotional state of other people by their scents. Smell is critical between predators and prey of many species because both have evolved to detect each other without the aid of vision. At sea, the smell of predators dissolves in water during detection, attack, capture, and ingestion of prey, and many fishes use this information to assess the risk of ending up crunched by enemy teeth (1, 2). But predator-prey interactions can be modified by changes in the chemical composition of seawater and are therefore highly sensitive to ongoing ocean acidification (see global measuring network here). Experts regard ocean acidification as the ‘other CO2 problem’ of climate change (3) — just to emphasize that anthropogenic climate-change impacts terrestrial and aquatic ecosystems alike. Acidification occurs because the ocean absorbs CO2 at a rate proportional with the concentration of this gas in the atmosphere and, once dissolved, CO2 becomes carbonic acid (H2CO3), which in turn releases protons (H+) — in simple terms, pH is the concentration of protons (see video about ocean acidification): Read the rest of this entry »





Job: Research Fellow in Palaeo-Ecological Modelling

13 04 2017

© seppo.net

I have another postdoctoral fellowship to advertise! All the details you need for applying are below.

KEY PURPOSE 

Scientific data such as fossil and archaeological records used as proxy to reconstruct past environments and biological communities (including humans) are sparse, often ambiguous or contradictory when establishing any consensus on timing or routes of initial human arrival and subsequent spread, the timing or extent of major changes in climate and other environmental perturbations, or the timing or regional pattern of biological extinctions.

The Research Fellow (Palaeo-Ecological Modelling) will assist in addressing these problems by developing state-of-the-art analytical and simulation tools to infer regional pattern of both the timing of human colonisation and megafauna extinction based on incomplete and sparse dataset, and investigating past environmental changes and human responses to identify their underlying causes and consequences on Australia’s landscapes, biodiversity and cultural history.

ORGANISATIONAL ENVIRONMENT 

The position will be based in the School of Biological Sciences in the Faculty of Science & Engineering at Flinders University. Flinders University boasts a world-class Palaeontology Research Group (PRG) and the new Global Ecology Research Laboratory that have close association with the research-intensive South Australian Museum. These research groups contribute to building a dynamic research environment that explores the continuum of environmental and evolutionary research from the ancient to modern molecular ecology and phylogeography. The School of Biological Sciences is an integrated community researching and teaching biology, and has a long history of science innovation. The appointee will join an interdisciplinary school of approximately 45 academic staff. The teaching and research activities of the School are supported by a range of technical and administrative infrastructure services.

KEY RESPONSIBILITIES

The key responsibilities and selection criteria identified for this position should be read in conjunction with the Flinders University Academic Profiles for the relevant academic classification (scroll down to Academic Profiles).

The Research Fellow (Palaeo-Ecological Modelling) will work under the direction of the Project Chief Investigator, and will be required to: Read the rest of this entry »





Limited nursery replenishment in coral reefs

27 03 2017

Haemulon sciurus

blue-striped grunt (Haemulon sciurus)

Coral reef fishes are wonderfully diverse in size, form, and function, as well as their need for different habitats throughout the life cycle. Some species spend all of their life in the same kind of coral habitat, while others need different places to breed and feed.

Fishes requiring different habitats as they progress through life often have what we call ‘nurseries’ in which adults lay eggs and the subsequent juveniles remain, and these places are often dominated by mangroves or seagrasses (i.e., they are not part of the coral reef).

While we’ve known for quite some time that when these nursery habitats are not around, adjacent coral reefs have few, if any, of these nursery-dependent species. What we haven’t known until now is just how far the influence of nurseries extends along a coral reef.

In other words, if a nursery is present, just how many new recruits do different areas of a reef receive from it? Read the rest of this entry »





Multiculturalism in the lab

23 02 2017

8294047fabf352ce46f4fd9a89d4a93dWith all the nasty nationalism and xenophobia gurgling nauseatingly to the surface of our political discoursethese days, it is probably worth some reflection regarding the role of multiculturalism in science. I’m therefore going to take a stab, despite being in most respects a ‘golden child’ in terms of privilege and opportunity (I am, after all, a middle-aged Caucasian male living in a wealthy country). My cards are on the table.

I know few overtly racist scientists, although I suspect that they do exist. In fact, most scientists are of a more liberal persuasion generally and tend to pride themselves on their objectivity in all aspects of being human, including the sociological ones. In other words, we tend to think of ourselves as dispassionate pluralists who only judge the empirical capabilities of our colleagues, with their races, genders, sexual persuasions and other physical attributes irrelevant to our assessment. We generally love to travel and interact with our peers from all nations and walks of life, and we regularly decorate our offices and with cultural paraphernalia different to our own.

But are we as unbiased and dispassionate as we think we are? Do we take that professed pluralism and cultural promiscuity with us to the lab each day? Perhaps we could, and should, do better. Read the rest of this entry »





Inexorable rise of human population pressures in Africa

31 08 2016

© Nick Brandt

© Nick Brandt

I’ve been a bit mad preparing for an upcoming conference, so I haven’t had a lot of time lately to blog about interesting developments in the conservation world. However, it struck me today that my preparations provide ideal material for a post about the future of Africa’s biodiversity.

I’ve been lucky enough to be invited to the University of Pretoria Mammal Research Unit‘s 50th Anniversary Celebration conference to be held from 12-16 September this year in Kruger National Park. Not only will this be my first time to Africa (I know — it has taken me far too long), the conference will itself be in one of the world’s best-known protected areas.

While decidedly fortunate to be invited, I am a bit intimidated by the line-up of big brains that will be attending, and of the fact that I know next to bugger all about African mammals (in a conservation science sense, of course). Still, apparently my insight as an outsider and ‘global’ thinker might be useful, so I’ve been hard at it the last few weeks planning my talk and doing some rather interesting analyses. I want to share some of these with you now beforehand, although I won’t likely give away the big prize until after I return to Australia.

I’ve been asked to talk about human population pressures on (southern) African mammal species, which might seem simple enough until you start to delve into the complexities of just how human populations affect wildlife. It’s simply from the perspective that human changes to the environment (e.g., deforestation, agricultural expansion, hunting, climate change, etc.) do cause species to dwindle and become extinct faster than they otherwise would (hence the entire field of conservation science). However, it’s another thing entirely to attempt to predict what might happen decades or centuries down the track. Read the rest of this entry »





Sensitive numbers

22 03 2016

toondoo.com

A sensitive parameter

You couldn’t really do ecology if you didn’t know how to construct even the most basic mathematical model — even a simple regression is a model (the non-random relationship of some variable to another). The good thing about even these simple models is that it is fairly straightforward to interpret the ‘strength’ of the relationship, in other words, how much variation in one thing can be explained by variation in another. Provided the relationship is real (not random), and provided there is at least some indirect causation implied (i.e., it is not just a spurious coincidence), then there are many simple statistics that quantify this strength — in the case of our simple regression, the coefficient of determination (R2) statistic is a usually a good approximation of this.

In the case of more complex multivariate correlation models, then sometimes the coefficient of determination is insufficient, in which case you might need to rely on statistics such as the proportion of deviance explained, or the marginal and/or conditional variance explained.

When you go beyond this correlative model approach and start constructing more mechanistic models that emulate ecological phenomena from the bottom-up, things get a little more complicated when it comes to quantifying the strength of relationships. Perhaps the most well-known category of such mechanistic models is the humble population viability analysis, abbreviated to PVA§.

Let’s take the simple case of a four-parameter population model we could use to project population size over the next 10 years for an endangered species that we’re introducing to a new habitat. We’ll assume that we have the following information: the size of the founding (introduced) population (n), the juvenile survival rate (Sj, proportion juveniles surviving from birth to the first year), the adult survival rate (Sa, the annual rate of surviving adults to year 1 to maximum longevity), and the fertility rate of mature females (m, number of offspring born per female per reproductive cycle). Each one of these parameters has an associated uncertainty (ε) that combines both measurement error and environmental variation.

If we just took the mean value of each of these three demographic rates (survivals and fertility) and project a founding population of = 10 individuals for 1o years into the future, we would have a single, deterministic estimate of the average outcome of introducing 10 individuals. As we already know, however, the variability, or stochasticity, is more important than the average outcome, because uncertainty in the parameter values (ε) will mean that a non-negligible number of model iterations will result in the extinction of the introduced population. This is something that most conservationists will obviously want to minimise.

So each time we run an iteration of the model, and generally for each breeding interval (most often 1 year at a time), we choose (based on some random-sampling regime) a different value for each parameter. This will give us a distribution of outcomes after the 10-year projection. Let’s say we did 1000 iterations like this; taking the number of times that the population went extinct over these iterations would provide us with an estimate of the population’s extinction probability over that interval. Of course, we would probably also vary the size of the founding population (say, between 10 and 100), to see at what point the extinction probability became acceptably low for managers (i.e., as close to zero as possible), but not unacceptably high that it would be too laborious or expensive to introduce that many individuals. Read the rest of this entry »