Why populations can’t be saved by a single breeding pair

3 04 2018

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© Reuters/Thomas Mukoya

I published this last week on The Conversation, and now reproducing it here for CB.com readers.

 

Two days ago, the last male northern white rhino (Ceratotherium simum cottoni) died. His passing leaves two surviving members of his subspecies: both females who are unable to bear calves.

Even though it might not be quite the end of the northern white rhino because of the possibility of implanting frozen embryos in their southern cousins (C. simum simum), in practical terms, it nevertheless represents the end of a long decline for the subspecies. It also raises the question: how many individuals does a species need to persist?

Fiction writers have enthusiastically embraced this question, most often in the post-apocalypse genre. It’s a notion with a long past; the Adam and Eve myth is of course based on a single breeding pair populating the entire world, as is the case described in the Ragnarok, the final battle of the gods in Norse mythology.

This idea dovetails neatly with the image of Noah’s animals marching “two by two” into the Ark. But the science of “minimum viable populations” tells us a different story.

No inbreeding, please

The global gold standard used to assess the extinction risk of any species is the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. Read the rest of this entry »





Predicting sustainable shark harvests when stock assessments are lacking

26 03 2018
srb 1

© Andrew Fox

I love it when a good collaboration bears fruit, and our latest paper is a good demonstration of that principle.

It all started a few years ago with an ARC Linkage Project grant we received to examine how the whaler shark fishing industry in Australia might manage its stocks better.

As I’m sure many are aware, sharks around the world aren’t doing terribly well (surprise, surprise — yet another taxon suffering at the hands of humankind). And while some populations (‘stocks’, in the dissociative parlance of the fishing industry) are doing better than others, and some countries have a better track record in managing these stocks than others, the overall outlook is grim.

One of the main reasons sharks tend to fair worse than bony fishes (teleosts) for the same fishing effort is their ‘slow’ life histories. It doesn’t take an advanced quantitative ecology degree to understand that growing slowly, breeding late, and producing few offspring is a good indication that a species can’t handle too much killing before populations start to dwindle. As is the case for most large shark species, I tend to think of them in a life-history sense as similar to large terrestrial mammals.

Now, you’d figure that a taxon with intrinsic susceptibility to fishing would have heaps of good data with which managers could monitor catches and quotas so that declines could be avoided. However, the reality is generally the inverse, with many populations having poor information regarding vital rates (e.g., survival, fertility), age structure, density feedback characteristics, and even simple estimates of abundance. Without such key information, management tends to be ad hoc and often not very effective. Read the rest of this entry »





Offshore Energy & Marine Spatial Planning

22 02 2018

FishingOffshoreWind

I have the pleasure (and relief) of announcing a new book that’s nearly ready to buy, and I think many readers of CB.com might be interested in what it describes. I know it might be a bit premature to announce it, but given that we’ve just finished the last few details (e.g., and index) and the book is ready to pre-order online, I don’t think it’s too precocious to advertise now.

9781138954533-2

A little history is in order. The brilliant and hard-working Katherine Yates (now at the University of Salford in Manchester, UK) approached me back in 2014 to assist her with co-editing the volume that she wanted to propose for the Routledge Earthscan Ocean series. I admit that I reluctantly agreed at the time, knowing full well what was in store (anyone who has already edited a book will know what I mean). Being an active researcher in energy and biodiversity (perhaps not so much on the ‘planning’ side per se) certainly helped in my decision.

And yes, there were ups and downs, and sometimes it was a helluva lot of work, but Katherine certainly made my life easier, and she has finally driven the whole thing to completion. She deserves most of the credit.

Read the rest of this entry »





Giving a monkey’s about primate conservation

12 12 2017
Urban monkey living (Macaque, Gibraltar) small

Concrete jungle. A Barbary macaque sits in a human-dominated landscape in Gibraltar. Photo: Silviu Petrovan

Saving primates is a complicated business. Primates are intelligent, social animals that have complex needs. They come into conflict with humans when they raid rubbish bins and crops, chew power cables, and in some cases become aggressive towards people.

Humans, however, have the upper hand. While 60% of non-human primate species are threatened, humans grow in numbers and power, building roads through forests, hunting and trapping primates, and replacing their habitat with farms and houses.

To help primatologists choose the most effective conservation approaches to resolve these problems, researchers in the Conservation Evidence project teamed up with primate researchers to produce a global database on the effectiveness of primate conservation solutions. This free database, which can also be downloaded as a single pdf, summarizes the evidence for 162 conservation interventions — actions that conservationists might take to conserve primates. The data come from searches of over 170 conservation journals and newsletters, and each study is summarized in a single paragraph in plain English, making it possible for conservationists without access to scientific journals to read the key findings.

Front cover primate synopsisSo what works in primate conservation? Well, the picture is rarely straightforward — partly due to the lack of data — but there are some interesting trends. Reducing hunting is one area where there seem to be a range of potentially effective approaches. Community control of patrolling, banning hunting and removing snares was effective in the three studies in which it was tested, all in African countries.

Further emphasizing the importance of involving local communities, implementing no-hunting community policies or traditional hunting bans also appeared helpful in boosting primate numbers. In other places, a more traditional approach of using rangers to protect primates has proved a winning strategy. Training rangers, providing them with arms, and increasing ranger patrols all worked to protect primates from poachers. Identifying the circumstances in which community led approaches or ranger patrols work will be key to implementing the most appropriate response to each conservation challenge. 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 »





Human population growth, refugees & environmental degradation

7 07 2017

refugeesThe global human population is now over 7.5 billion, and increasing by about 90 million each year. This means that we are predicted to exceed 9 billion people by 2050, with no peak in site this century and a world population of up to 12 billion by 2100. These staggering numbers are the result of being within the exponential phase of population growth since last century, such that some 14% of all human beings that have ever lived on the planet are still alive today. That is taking into account about the past 200,000 years, or 10,000 generations.

Of course just like the Earth’s resources, human beings are not distributed equally around the globe, nor are the population trends consistent among regions or nations. In fact, developing nations are contributing to the bulk of the global annual increase (around 89 million per year), whereas developed nations are contributing a growth of only about 1 million each year. Another demonstration of the disparity in human population distributon is that about half of all human beings live in just seven countries (China, India, USA, Indonesia, Brazil, Pakistan, Nigeria, and Bangladesh), representing just one quarter of the world’s total land area. Read the rest of this entry »





Protecting one of the world’s marine wonders

17 06 2017
IMG_6789

© CJA Bradshaw

While I’m in transit (yet a-bloody-gain) to Helsinki, I wanted to take this opportunity to reflect on one of the most inspiring eco-tourism experiences I recently had in South Australia.

If you are South Australian and have even the slightest interest in wildlife, you will have of course at least heard of the awe-inspiring mass breeding aggregation of giant cuttlefish (Sepia apama) that occur in May-July every year in upper Spencer Gulf near the small town of Whyalla. If you have been lucky enough to go there and see these amazing creatures themselves, then you know exactly what I’m talking about. And if you haven’t yet been there, take it from me that it is so very much worth it to attempt the voyage.

DCIM100GOPROGOPR0121.

Father-daughter giant-cuttlefish-snorkelling selfie. © CJA Bradshaw

Despite having lived in South Australia for nearly a decade now, I only got my chance to see these wonderful creatures when a father at my daughter’s school organised a school trip. After driving for five hours from Adelaide to Whyalla, we hired our snorkelling gear and got into the water the very next morning. 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 »





Transition from the Anthropocene to the Minicene

24 09 2016
Going, going ...

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 50thAnniversary 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 »





Staggering rhino poaching in the Kruger

14 09 2016

rhino-poachingI have the immense honour and pleasure of attending the University of Pretoria’s Mammal Research Institute 50th 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 »





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 »





Rich and stable communities most vulnerable to change

16 08 2016

networkI’ve just read an interesting new study that was sent to me by the lead author, Giovanni Strona. Published the other day in Nature Communications, Strona & Lafferty’s article entitled Environmental change makes robust ecological networks fragile describes how ecological communities (≈ networks) become more susceptible to rapid environmental changes depending on how long they’ve had to evolve and develop under stable conditions.

Using the Avida Digital Evolution Platform (a free, open-source scientific software platform for doing virtual experiments with self-replicating and evolving computer programs), they programmed evolving host-parasite pairs in a virtual community to examine how co-extinction rate (i.e., extinctions arising in dependent species — in this case, parasites living off of hosts) varied as a function of the complexity of the interactions between species.

Starting from a single ancestor digital organism, the authors let evolve several artificial life communities for hundred thousands generation under different, stable environmental settings. Such communities included both free-living digital organisms and ‘parasite’ programs capable of stealing their hosts’ memory. Throughout generations, both hosts and parasites diversified, and their interactions became more complex. Read the rest of this entry »





Environmental Arsehats

3 03 2016

arsehatI’m starting a new series on ConservationBytes.com — one that exposes the worst environmental offenders on the planet.

I’ve taken the idea from an independent media organisation based in Australia — Crikey — who has been running the Golden Arsehat of the Year awards since 2008. It’s a hilarious, but simultaneously maddening, way of shaming the worst kinds of people.

So in the spirit of a little good fun and environmental naming-and-shaming, I’d like to put together a good list of candidates for the inaugural Environmental Arsehat of the Year awards.

So I’m keen to receive your nominations, either privately via e-mail, the ConservationBytes.com message service, or even in the comments stream of this post. Once I receive a good list of candidates, I’ll do separate posts on particularly deserving individuals, followed by an online poll where you can vote for your (least) favourite Arsehat.

There are a few nomination rules, however. Read the rest of this entry »





Bad science

10 02 2016

Head in HandsIn 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 »





It’s not always best to be the big fish

3 02 2016

obrien_fish_2Loosely following the theme of last week’s post, it’s now fairly well established that humans tend to pick on the big species first.

From fewer big trees, declines of big carnivores, elephant & rhino poaching, to fishing down the web, big species tend to cop it hardest when it comes to human-caused ecological disturbance.

While there are a lot of different combinations of traits that make some species more vulnerable to extinction than others (see examples for legumes, amphibians, sharks & teleosts, and mammals), one of the main ones is species size.

Generally speaking, larger species tend to produce fewer offspring and breed later in life than smaller species. This means that despite larger species tending to live longer than their smaller counterparts, their ‘slow’ reproductive output means that they are generally more susceptible to rapid environmental change (mainly via human intervention). In other words, their capacity for self-replacement is often too low to counteract the offtake from direct exploitation or habitat loss.

Despite a reasonable scientific understanding of this extinction-risk principle, the degree to which human disturbance affects species’ distributions is much less well quantified, and this is especially true for marine species.

I’m proud to announce another fascinating paper led by my postdoc, Camille Mellin, that has just come out online in Nature CommunicationsHumans and seasonal climate variability threaten large-bodied coral reef fish with small ranges.

With the world’s largest combined dataset of coral reef fish surveys for the entire Indo-Pacific (including the coral reef fish biodiversity hotspot — the Coral Triangle), we examined which conditions best described the distribution of fishes over a range of body sizes. Read the rest of this entry »





No evidence climate change is to blame for Australian megafauna extinctions

29 01 2016

bw spear throwingLast 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 SaltréClimate 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 »





Getting your conservation science to the right people

22 01 2016

argument-cartoon-yellingA perennial lament of nearly every conservation scientist — at least at some point (often later in one’s career) — is that the years of blood, sweat and tears spent to obtain those precious results count for nought in terms of improving real biodiversity conservation.

Conservation scientists often claim, especially in the first and last paragraphs of their papers and research proposals, that by collecting such-and-such data and doing such-and-such analyses they will transform how we manage landscapes and species to the overall betterment of biodiversity. Unfortunately, most of these claims are hollow (or just plain bullshit) because the results are either: (i) never read by people who actually make conservation decisions, (ii) not understood by them even if they read the work, or (iii) never implemented because they are too vague or too unrealistic to translate into a tangible, positive shift in policy.

A depressing state of being, I know.

This isn’t any sort of novel revelation, for we’ve been discussing the divide between policy makers and scientists for donkey’s years. Regardless, the whinges can be summarised succinctly: Read the rest of this entry »





Outright bans of trophy hunting could do more harm than good

5 01 2016

In July 2015 an American dentist shot and killed a male lion called ‘Cecil’ with a hunting bow and arrow, an act that sparked a storm of social media outrage. Cecil was a favourite of tourists visiting Hwange National Park in Zimbabwe, and so the allegation that he was lured out of the Park to neighbouring farmland added considerable fuel to the flames of condemnation. Several other aspects of the hunt, such as baiting close to national park boundaries, were allegedly done illegally and against the spirit and ethical norms of a managed trophy hunt.

In May 2015, a Texan legally shot a critically endangered black rhino in Namibia, which also generated considerable online ire. The backlash ensued even though the male rhino was considered ‘surplus’ to Namibia’s black rhino populations, and the US$350,000 generated from the managed hunt was to be re-invested in conservation. Together, these two incidents have triggered vociferous appeals to ban trophy hunting throughout Africa.

These highly politicized events are but a small component of a large industry in Africa worth > US$215 million per year that ‘sells’ iconic animals to (mainly foreign) hunters as a means of generating otherwise scarce funds. While to most people this might seem like an abhorrent way to generate money, we argue in a new paper that sustainable-use activities, such as trophy hunting, can be an important tool in the conservationist’s toolbox. Conserving biodiversity can be expensive, so generating money is a central preoccupation of many environmental NGOs, conservation-minded individuals, government agencies and scientists. Making money for conservation in Africa is even more challenging, and so we argue that trophy hunting should and could fill some of that gap. Read the rest of this entry »





Australia’s perfect storm of negligence

17 03 2015

If, for the purposes of some sick and twisted thought experiment, you were to design policies that would ensure the long-term failure of a wealthy, developed nation, you wouldn’t have to look farther than Australia’s current recipe for future disaster. I’m not trying to be provocative, but the warning signs are too bold and flashy to ignore. Let’s just run through some of the main ones:

1. As the lambasted and thoroughly flawed 2015 Intergenerational Report clearly demonstrates, our current government has no idea about the future threats of climate change. Dragged kicking and screaming into only a symbolic recognition of some ‘distant and currently irrelevant problem’, the Abbott-oir and his intergenerational criminals are well known for killing the carbon-pricing scheme, dismantling the Department of Climate Change, pulling out of major international talks on climate-change mitigation and installing a half-arsed, ineffective policy that will do nothing to stem our emissions. Combine that with comments like “coal is good for humanity“, and it’s easy to see how our current leaders have little idea about the future mess they’re creating.

2. Not content just to kick the shit out of any meaningful climate action, our government has also turned its back on any renewable energy target, and facilitated the fossil-fuel barons to dig more coal out of the ground. While South Australia’s Royal Commission on the nuclear fuel cycle is a welcome candle in the climate change-mitigation darkness here, it is far from becoming a national priority any time soon.

3. As has been well documented, the Abbott-oir ship of fools has also done whatever it can to turn back decades of environmental protections in less than six months of taking office. Everything from opening up national parks for exploitation, failing to protect marine sanctuaries, limiting environmental checks to promoting logging in World Heritage Areas, there is little room for hope that our crumbling environmental system will improve at all in the near to long term. Read the rest of this entry »





Earth’s second lung has emphysema

19 02 2015
© WWF

© WWF

Many consider forests as the ‘lungs’ of the planet – the idea that trees and other plants take up carbon and produce oxygen (the carbon and oxygen cycles). If we are to be fair though, the oceans store about 93% of the Earth’s carbon pool (excluding the lithosphere and fossil fuels) and oceanic phytoplankton produces between 50 and 80% of the oxygen in the atmosphere. For comparison, the terrestrial biosphere – including forests – stores only about 5% of the Earth’s carbon, and produces most of the remainder of atmospheric oxygen.

So there’s no denying that the biggest player in these cycles is the ocean, but that’s not the topic of today’s post. Instead, I’m going to focus on the terrestrial biosphere, and in particular, the carbon storage and flux of forests.

Now it’s pretty well established that tropical forests are major players in the terrestrial carbon cycle, with the most accepted estimates of about 55% the terrestrial carbon stock stored therein. The extensive boreal forest, covering most of the northern half of North America, most of Scandinavia and a huge chunk of Russia, comes in globally at about 33%, and temperate forests store most of the remainder.

That is, until now. Read the rest of this entry »