Surgical conservation: gain requires some pain

21 12 2011

© 2008-2011 ~Hiuki

I apologise to CB readers for the unusually low frequency of posts this month. With the International Congress for Conservation Biology taking up a lot of my time earlier this month, and the standard palaver of xmas preparations (i.e., getting shit done before the end of the year), I’m afraid the blog has taken a back seat. Now officially ‘on leave’ (whatever that means for an academic), I have found a brief window during which I can put a few thoughts together.

For this post I must take you back to October 2011 when, if you were in Australia, you might have heard about the so-called ‘debacle‘ of the Macquarie Island rabbit/rate/mouse-eradication programme in which it was identified that a few thousand seabirds had become the collateral damage.

To recap, an intense poisoning programme was initiated on subantarctic Macquarie Island to eradicate these pests after years of massive environmental degradation had finally forced the government’s (of Tasmania and the Commonwealth) hand to do something. What caught my eye in all this was the sheer stupidity and politicking associated with the programme, in which hyper-conservative Eric Abetz (Liberal Senator for Tasmania) managed to turn this amazing success into a Labor-bashing political sledge-hammer.

Abetz is no stranger to anti-environmentalism and fights vehemently for Tasmania’s forest-raping industry; he considers political parties such as the Greens, environmental groups such as The Wilderness Society and pro-democracy groups such as Get Up! his mortal enemies. He’s even had a go at esteemed author Richard Flanagan for supporting the anti-deforestation movement in Tasmania! Read the rest of this entry »

Twenty landmark papers in biodiversity conservation

13 10 2011

While I can’t claim that this is the first time one of my peer-reviewed papers has been inspired by, I can claim that this is the first time a peer-reviewed paper is derived from the blog.

After a bit of a sordid history of review (isn’t it more and more like that these days?), I have the pleasure of announcing that our paper ‘Twenty landmark papers in biodiversity conservation‘ has now been published as an open-access chapter in the new book ‘Research in Biodiversity – Models and Applications‘ (InTech).

Perhaps not the most conventional of venues (at least, not for me), but it is at the very least ‘out there’ now and freely available.

The paper itself was taken, modified, elaborated and over-hauled from text written in this very blog – the ‘Classics‘ section of Now, if you’re an avid follower of CB, then the chapter won’t probably represent anything terribly new; however, I encourage you to read it anyway given that it is a vetted overview of possibly some of the most important papers written in conservation biology.

If you are new to the field, an active student or merely need a ‘refresher’ regarding the big leaps forward in this discipline, then this chapter is for you.

The paper’s outline is as follows: Read the rest of this entry »

Conservation is all about prioritisation

4 12 2010

Another great guest post from a previous contributor, Piero Visconti.

Biodiversity conservation is about prioritisation – making difficult choices.

With limited money and so many habitats and species in need of protection, deciding where not to expend resources is as important as deciding where to act. Saying ‘no’ will be crucial for ensuring the persistence of biodiversity and ecosystem services, simply because as individuals who value conservation, we will always be tempted to try and save everything.

In the words of Frederick the Great: “He who defends everything, defends nothing.”

As a result, much recent conservation planning research has focused on offering managers general and flexible tools for deciding which conservation features should be the highest priority. Intuitively, we should direct our resources towards areas that have high biodiversity values, and that are likely to be lost if the forces of conservation do not intervene (the most ‘vulnerable’ land parcels). This approach is known as the ‘minimize loss’ approach. Imagine we are worried about the loss of rare native vegetation in the face of ongoing urban expansion (e.g., Melbourne’s western grasslands). To minimize loss, managers would pre-emptively protect sites that are most likely to be developed. But is this decision to race the bulldozers always the best idea? How much does this choice depend on our assumptions about how land is protected, how land developers behave, and the accuracy of our future predictions? Read the rest of this entry »

Classics: Ecological Triage

27 03 2009

It is a truism that when times are tough, only the strongest pull through. This isn’t a happy concept, but in our age of burgeoning biodiversity loss (and economic belt-tightening), we have to make some difficult decisions.In this regard, I suggest Brian Walker’s1992 paper Biodiveristy and ecological redundancy makes the Classics list.

Ecological triage is, of course, taken from the medical term triage used in emergency or wartime situations. Ecological triage refers to the the conservation prioritisation of species that provide unique or necessary functions to ecosystems, and the abandonment of those that do not have unique ecosystem roles or that face almost certain extinction given they fall well below their minimum viable population size (Walker 1992). Financial resources such as investment in recovery programmes, purchase of remaining habitats for preservation, habitat restoration, etc. are allocated accordingly; the species that contribute the most to ecosystem function and have the highest probability of persisting are earmarked for conservation and others are left to their own devices (Hobbs & Kristjanson 2003).

This emotionally empty and accounting-type conservation can be controversial because public favourites like pandas, kakapo and some dolphin species just don’t make the list in many circumstances. As I’ve stated before, it makes no long-term conservation or economic sense to waste money on the doomed and ecologically redundant. Many in the conservation business apply ecological triage without being fully aware of it. Finite pools of money (generally the paltry left-overs from some green-guilty corporation or under-funded government initiative) for conservation mean that we have to set priorities – this is an entire discipline in its own right in conservation biology. Reserve design is just one example of this sacrifice-the-doomed-for-the good-of-the-ecosystem approach.

Walker (1992) advocated that we should endeavour to maintain ecosystem function first, and recommended that we abandon programmes to restore functionally ‘redundant’ species (i.e., some species are more ecologically important than others, e.g., pollinators, prey). But how do you make the choice? The wrong selection might mean an extinction cascade (Noss 1990; Walker 1992) whereby tightly linked species (e.g., parasites-hosts, pollinators-plants, predators-prey) will necessarily go extinct if one partner in the mutualism disappears (see Koh et al. 2004 on co-extinctions). Ecological redundancy is a terribly difficult thing to determine, especially given that we still understand relatively little about how complex ecological systems really work (Marris 2007).

The more common (and easier, if not theoretically weaker) approach is to prioritise areas and not species (e.g., biodiversity hotspots), but even the criteria used for area prioritisation can be somewhat arbitrary and may not necessarily guarantee the most important functional groups are maintained (Orme et al. 2005; Brooks et al. 2006). There are many different ways of establishing ‘priority’, and it depends partially on your predilections.

More recent mathematical approaches such as cost-benefit analyses (Possingham et al. 2002; Murdoch et al. 2007) advocate conservation like a CEO would run a profitable business. In this case the ‘currency’ is biodiversity, and so a fixed financial investment must maximise long-term biodiversity gains (Possingham et al. 2002). This essentially estimates the potential biodiversity saved per dollar invested, and allocates funds accordingly (Wilson et al. 2007). Where the costs outweigh the benefits, conservationists move on to more beneficial goals. Perhaps the biggest drawback with this approach is that it’s particularly data-hungry. When ecosystems are poorly measured, then the investment curve is unlikely to be very realistic.

CJA Bradshaw

Add to FacebookAdd to NewsvineAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to Ma.gnoliaAdd to TechnoratiAdd to Furl

(Many thanks to Lochran Traill and Barry Brook for co-developing these ideas with me)

Captive breeding for conservation

7 08 2008

My first attempt at this potentially rather controversial section of Inspired by my latest post (30/07/2008), I must comment on what I believe is one of the biggest wasters of finite conservation (financial) resources – captive breeding for population recovery. The first laureate of the Toothless category goes to 7 authors (Snyder et al.) who I believe deserve at least a round of beers for their bold paper published way back in 1996 in Conservation BiologyLimitations of captive breeding in endangered species recovery.

The paper describes basically that in most situations, captive breeding for population recovery is ill-conceived, badly planned, overly expensive and done without any notion of the particular species’ minimum viable population size (the population size required to provide a high probability of persistence over a long period). Examples of ridiculous cloning experiments done in the name of ‘conservation’ (one example with which I am familiar is the case of the SE Asian banteng cloning experiment – these conservation-challenged scientists actually claimed “We hope that the birth of these animals will open the way for a new strategy to help maintain valuable biodiversity and to respond to the challenge of large-scale extinctions ahead.” after spending amounts that would make Bill Gates blush). Come on! Minimum viable population sizes number in the thousands to tens of thousands (e.g., Brook et al. 2006; Traill et al. 2007), not to mention the genetic diversity necessary for persistence captive populations generally lack (see Frankham et al. 2004).

In the spirit of ecological triage, we must focus on conservation efforts that have a high probability of changing the extinction risk of species. Wasting millions of dollars to save a handful of inbred individuals (insert your favourite example here) WILL NOT, in most cases, make any difference to population viability (with only a few exceptions). Good on Snyder et al. (1996) for their analysis and conclusions, but zoos, laboratories and other captive-rearing organisations around the world continue to throw away millions using the ‘conservation’ rationale to justify their actions. Rubbish. I’m afraid there is little evidence that the Snyder et al. paper changed anything. (post original published in Toothless 31/07/2008).

CJA Bradshaw

Add to FacebookAdd to NewsvineAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to Ma.gnoliaAdd to TechnoratiAdd to Furl

Wasting precious money on the conservation-irrelevant

30 07 2008
© Michael H.

© Michael H.

I’ve just attended the Joint Meeting of Ichthyologists and Herpetologists held in Montréal, Canada (by the way, if you are ever thinking of staying at Le Centre Sheraton in Montréal, my advice is to make a wide berth – one of the least-satisfying, over-priced, deliberately scrooging hotels I have ever had the displeasure of occupying).

The conference itself was interesting, if not somewhat tangential to most of the major conservation issues facing fish, amphibians and reptiles in the modern context (it is only fair though to state that it wasn’t a ‘conservation’ conference per se). One thing that did astound me though was an open-microphone presentation by someone from the Oceanário de Lisboa in Portugal who described the €100000 operation to release a very large (> 3.5 m wingspan) manta ray (Manta birostris) from its restrictive enclosure. Yes, you read correctly – €100000 to save one individual manta ray. Not even a threatened species (currently classified as ‘Near Threatened’ on the IUCN Red List), these good people at what I am sure is an excellent aquarium spent more money on one animal than most projects spend on the conservation of entire species.

Have these people not heard of ecological (or ‘conservation’) triage? Similar to medical triage in emergency or wartime situations, ecological triage directs finite resources to those species that require the most attention and have the highest chance of long-term persistence. I’m not sure who coined the term (perhaps Holt & Viney 2001), but the concept has been developed by a number of excellent conservation planning researchers over the last few years to become the cornerstone of modern conservation investment strategies (see Possingham et al. 2002; Hobbs & Kristjanson 2003; Wilson et al. 2007). Ecological triage essentially means that immediate conservation action and resources are directed toward populations that are highly threatened but where the probability of persistence is high. The flip side is that we shouldn’t waste our precious resources either on irrelevant and useless actions like the one described above.

Saving one manta ray would not change the species’ long-term persistence probability – full stop. In an age where conservation action and research are suffering from human apathy and stupidity, surely we can spend our money more wisely. For example, that €100000 could have purchased some primary rain forest somewhere and saved literally thousands of species from extinction. What a waste.

Add to FacebookAdd to NewsvineAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to Ma.gnoliaAdd to TechnoratiAdd to Furl

50/500 or 100/1000 debate not about time frame

26 06 2014

Not enough individualsAs you might recall, Dick Frankham, Barry Brook and I recently wrote a review in Biological Conservation challenging the status quo regarding the famous 50/500 ‘rule’ in conservation management (effective population size [Ne] = 50 to avoid inbreeding depression in the short-term, and Ne = 500 to retain the ability to evolve in perpetuity). Well, it inevitably led to some comments arising in the same journal, but we were only permitted by Biological Conservation to respond to one of them. In our opinion, the other comment was just as problematic, and only further muddied the waters, so it too required a response. In a first for me, we have therefore decided to publish our response on the arXiv pre-print server as well as here on

50/500 or 100/1000 debate is not about the time frame – Reply to Rosenfeld

cite as: Frankham, R, Bradshaw CJA, Brook BW. 2014. 50/500 or 100/1000 debate is not about the time frame – Reply to Rosenfeld. arXiv: 1406.6424 [q-bio.PE] 25 June 2014.

The Letter from Rosenfeld (2014) in response to Jamieson and Allendorf (2012) and Frankham et al. (2014) and related papers is misleading in places and requires clarification and correction, as follows: Read the rest of this entry »

No-extinction targets are destined to fail

21 09 2012

I’ve been meaning to write about this for a while, and now finally I have been given the opportunity to put my ideas ‘down on paper’ (seems like a bit of an old-fashioned expression these days). Now this post might strike some as overly parochial because it concerns the state in which I live, but the concept applies to every jurisdiction that passes laws designed to protect biodiversity. So please look beyond my navel and place the example within your own specific context.

As CB readers will appreciate, I am firmly in support of the application of conservation triage – that is, the intelligent, objective and realistic way of attributing finite resources to minimise extinctions for the greatest number of (‘important’) species. Note that deciding which species are ‘important’ is the only fly in the unguent here, with ‘importance’ being defined inter alia as having a large range (to encompass many other species simultaneously), having an important ecological function or ecosystem service, representing rare genotypes, or being iconic (such that people become interested in investing to offset extinction.

But without getting into the specifics of triage per se, a related issue is how we set environmental policy targets. While it’s a lovely, utopian pipe dream that somehow our consumptive 7-billion-and-growing human population will somehow retract its massive ecological footprint and be able to save all species from extinction, we all know that this is irrevocably  fantastical.

So when legislation is passed that is clearly unattainable, why do we accept it as realistic? My case in point is South Australia’s ‘No Species Loss Strategy‘ (you can download the entire 7.3 Mb document here) that aims to

“…lose no more species in South Australia, whether they be on land, in rivers, creeks, lakes and estuaries or in the sea.”

When I first learned of the Strategy, I instantly thought to myself that while the aims are laudable, and many of the actions proposed are good ones, the entire policy is rendered toothless by the small issue of being impossible. Read the rest of this entry »

The wounded soldiers of biodiversity

10 04 2012

Here’s another great post from Salvador Herrando-Pérez. It is interesting that he’s chosen an example species that was once (a long, long time ago in a galaxy far, far away) of great interest to me (caribou – see ancient papers a, b, c, d). But that is another story. Take it away, Salva.


Figure 1. Caribou (reindeer) are ungulates weighing up to ~ 100 kg. They live in tundra and taiga in Finland, Greenland, Finland, Norway, Mongolia, Russia, Canada and USA (extinct in Sweden). The species is globally stable (‘Least Concern’, IUCN Red List), but the subspecies of woodland caribou (Rangifer tarandus caribou) is threatened in North America. Schneider and colleagues’ 7 study encompasses ~ 3,000 individuals in 12 herds (75 to 450 individuals per herd), occupying ~ 100.000 km2 of conifer forest and peatland (3,000 to 19,000 km2 per herd). Two ecotypes are recognized regionally22, namely migratory mountain herds (mostly from mountains and foothills in west-central Alberta), and non-migratory boreal herds (mostly from peatlands in central and northern Alberta). The photo shows a group of caribous grazing on subalpine vegetation from Tonquin Valley, Jasper National Park (Alberta, Canada). Photo courtesy of Saakje Hazenberg.

As conservation biology keeps incorporating management and economical principles from other disciplines, it stumbles with paradoxes such that investing on the most threatened components of biodiversity might in turn jeopardize the entire assets of biodiversity.

At the end of 2011, newspapers and TVs echoed an IUCN report cataloguing as ‘extinct’ or ‘near extinct’ several subspecies of rhinos in Asia and Africa. To many, such news might have invoked the topic: “how badly governments do to protect the environment”. However if, to avoid those extinctions, politicians had to deviate funds from other activities, what thoughts would come to the mind of workers whose salaries had to be frozen, school directors whose classroom-roof leakages could not be repaired (e.g., last winter at my niece’s school in Spain), colonels whose last acquisition of ultramodern tanks had to be delayed, or our city council’s department who had to cancel Sting’s next performance.

Thus, there are three unquestionable facts regarding species conservation:

  1. the protection of species costs money;
  2. governments and environmental organisations have limited budgets for a range of activities they deem necessary; and
  3. our way of conserving nature is failing because, despite increasing public/private support and awareness, the rate of destruction of biodiversity is not decelerating1,2.

One of the modern debates among conservationists pivots around how to use resources efficiently3-6. Schneider and colleagues7 have dealt with this question for woodland caribou (Rangifer tarandus) in Canada. A total of 18 populations of this ungulate persist in the Canadian province of Alberta, all undergoing demographic declines due to mining extractions (oil, gas and bitumen), logging and wolf predation. The species is listed as ‘threatened’ regionally and nationally. The Alberta Caribou Recovery Plan (2004-2014) is attempting to protect all herds. Under such a framework, Schneider et al.7 predicted that woodland caribou would be regionally extirpated in less than a century.

Furthermore, they estimated the costs of making each herd viable (Fig. 1), with a triple revelation. To save all herds from extinction would need ~ CA$150,000 million (beyond the available budget). The most threatened herds are among the most expensive to protect (within present management approach). Some herds would be secured through modest investment for two decades. Overall, their study suggests that Alberta’s woodland caribou would be eligible for triage, i.e., at the subpopulation level8. Read the rest of this entry »

When the cure becomes the disease

6 02 2012

I’ve always barracked for Peter Kareiva‘s views and work; I particularly enjoy his no-bullshit, take-no-prisoners approach to conservation. Sure, he’s said some fairly radical things over the years, and has pissed off more than one conservationist in the process. But I think this is a good thing.

His main point (as is mine, and that of a growing number of conservation scientists) is that we’ve already failed biodiversity, so it’s time to move into the next phase of disaster mitigation. By ‘failing’ I mean that, love it or loathe it, extinction rates are higher now than they have been for millennia, and we have very little to blame but ourselves. Apart from killing 9 out of 10 people on the planet (something no war or disease will ever be able to do), we’re stuck with the rude realism that it’s going to get a lot worse before it gets better.

This post acts mostly an introduction to Peter Kareiva & collaborators’ latest essay on the future of conservation science published in the Breakthrough Institute‘s new journal. While I cannot say I agree with all components (especially the cherry-picked resilience examples), I fundamentally support the central tenet that we have to move on with a new state of play.

In other words, humans aren’t going to go away, ‘pristine’ is as unattainable as ‘infinity’, and reserves alone just aren’t going to cut it. Read the rest of this entry »

Life and death on Earth: the Cronus hypothesis

13 10 2009


Bit of a strange one for you today, but here’s a post I hope you’ll enjoy.

My colleague, Barry Brook, and I recently published a paper in the very new and perhaps controversial online journal , the Journal of Cosmology. Cosmology? According to the journal, ‘cosmology’ is:

“the study and understanding of existence in its totality, encompassing the infinite and eternal, and the origins and evolution of the cosmos, galaxies, stars, planets, earth, life, woman and man”.

The journal publishes papers dealing with ‘cosmology’ and is a vehicle for those who wish to publish on subjects devoted to the study of existence in its totality.

Ok. Quite an aim.

Our paper is part of the November (second ever) issue of the journal entitled Asteroids, Meteors, Comets, Climate and Mass Extinctions, and because we were the first to submit, we managed to secure the first paper in the issue.

Our paper, entitled The Cronus hypothesis – extinction as a necessary and dynamic balance to evolutionary diversification, introduces a new idea in the quest to find that perfect analogy for understanding the mechanisms dictating how life on our planet has waxed and waned over the billions of years since it first appeared.



In the 1960s, James Lovelock conceived the novel idea of Gaia – that the Earth functions like a single, self-regulating organism where life itself interacts with the physical environment to maintain conditions favourable for life (Gaia was the ancient Greeks’ Earth mother goddess). Embraced, contested, denounced and recently re-invigorated, the idea has evolved substantially since it first appeared. More recently (this year, in fact), Peter Ward countered the Gaia hypothesis with his own Greek metaphor – the Medea hypothesis. Essentially this view holds that life instead ‘seeks’ to destroy itself in an anti-Gaia manner (Medea was the siblicidal wife of Jason of the Argonauts). Ward described his Medea hypothesis as “Gaia’s evil twin”.

One can marvel at the incredible diversity of life on Earth (e.g., conservatively, > 4 million protists, 16600 protozoa, 75000-300000 helminth parasites, 1.5 million fungi, 320000 plants, 4-6 million arthropods, > 6500 amphibians, 10000 birds and > 5000 mammals) and wonder that there might be something in the ‘life makes it easier for life’ idea underlying Gaia. However, when one considers that over 99 % of all species that have ever existed are today extinct, then a Medea perspective might dominate.



Enter Cronus. Here we posit a new way of looking at the tumultuous history of life and death on Earth that effectively relegates Gaia and Medea to opposite ends of a spectrum. Cronus (patricidal son of Gaia overthrown by his own son, Zeus, and banished to Hades) treats speciation and extinction as birth and death in a ‘metapopulation’ of species assemblages split into biogeographic realms. Catastrophic extinction events can be brought about via species engineering their surroundings by passively modifying the delicate balance of oxygen, carbon dioxide and methane – indeed, humans might be the next species to fall victim to our own Medean tendencies. But extinction opens up new niches that eventually elicit speciation, and under conditions of relative environmental stability, specialists evolve because they are (at least temporarily) competitive under those conditions. When conditions change again, extinction ensues because not all can adapt quickly enough. Just as all individuals born in a population must eventually die, extinction is a necessary termination.

We think the Cronus metaphor has a lot of advantages over Gaia and Medea. The notion of a community of species as a population of selfish individuals retains the Darwinian view of contestation; self-regulation in Cronus occurs naturally as a result of extinction modifying the course of future evolution. Cronus also makes existing mathematical tools developed for metapopulation theory amenable to broader lines of inquiry.

For example, species as individuals with particular ‘mortality’ (extinction) rates, and lineages with particular ‘birth’ (speciation) rates, could interact and disperse among ‘habitats’ (biogeographical realms). ‘Density’ feedback could be represented as competitive exclusion or symbioses. As species dwindle, feedbacks such as reduced community resilience that further exacerbate extinction risk (Medea-like phase), and stochastic fluctuation around a ‘carrying capacity’ (niche saturation) arising when environmental conditions are relatively stable is the Gaia-like phase. Our Cronus framework is also scale-invariant – it could be applied to microbial diversity on another organism right up to inter-planetary exchange of life (panspermia).

What’s the relevance to conservation? We’re struggling to prevent extinction, so understanding how it works is an essential first step. Without the realisation that extinction is necessary (albeit, at rates preferably slower than they are currently), we cannot properly implement conservation triage, i.e., where do we invest in conservation and why?

We had fun with this, and I hope you enjoy it too.

CJA Bradshaw

ResearchBlogging.orgBradshaw, C.J.A., & Brook, B.W. (2009). The Cronus Hypothesis – extinction as a necessary and dynamic balance to evolutionary diversification Journal of Cosmology, 2, 201-209 Other:

Add to FacebookAdd to NewsvineAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to Ma.gnoliaAdd to TechnoratiAdd to Furl

Managing for extinction

9 10 2009

ladderAh, it doesn’t go away, does it? Or at least, we won’t let it.

That concept of ‘how many is enough?’ in conservation biology, the so-called ‘minimum viable population size‘, is enough to drive some conservation practitioners batty.

How many times have we heard the (para-) phrase: “It’s simply impractical to bring populations of critically endangered species up into the thousands”?

Well, my friends, if you’re not talking thousands, you’re wasting everyone’s time and money. You are essentially managing for extinction.

Our new paper out online in Biological Conservation entitled Pragmatic population viability targets in a rapidly changing world (Traill et al.) shows that populations of endangered species are unlikely to persist in the face of global climate change and habitat loss unless they number around 5000 mature individuals or more.

After several meta-analytic, time series-based and genetic estimates of the magic minimum number all agreeing, we can be fairly certain now that if a population is much less than several thousands (median = 5000), its likelihood of persisting in the long run in the face of normal random variation is pretty small.

We conclude essentially that many conservation biologists routinely underestimate or ignore the number of animals or plants required to prevent extinction. In fact, aims to maintain tens or hundreds of individuals, when thousands are actually needed, are simply wasting precious and finite conservation resources. Thus, if it is deemed unrealistic to attain such numbers, we essentially advise that in most cases conservation triage should be invoked and the species in question be abandoned for better prospects

A long-standing idea in species restoration programs is the so-called ‘50/500’ rule; this states that at least 50 adults are required to avoid the damaging effects of inbreeding, and 500 to avoid extinctions due to the inability to evolve to cope with environmental change. Our research suggests that the 50/500 rule is at least an order of magnitude too small to stave off extinction.

This does not necessarily imply that populations smaller than 5000 are doomed. But it does highlight the challenge that small populations face in adapting to a rapidly changing world.

We are battling to prevent a mass extinction event in the face of a growing human population and its associated impact on the planet, but the bar needs to be a lot higher. However, we shouldn’t necessarily give up on critically endangered species numbering a few hundred of individuals in the wild. Acceptance that more needs to be done if we are to stop ‘managing for extinction’ should force decision makers to be more explicit about what they are aiming for, and what they are willing to trade off, when allocating conservation funds.

CJA Bradshaw

(with thanks to Lochran Traill, Barry Brook and Dick Frankham)

Add to FacebookAdd to NewsvineAdd to DiggAdd to Del.icio.usAdd to StumbleuponAdd to RedditAdd to BlinklistAdd to Ma.gnoliaAdd to TechnoratiAdd to Furl

This post was chosen as an Editor's Selection for

Traill, L.W., Brook, B.W., Frankham, R.R., & Bradshaw, C.J.A. (2009). Pragmatic population viability targets in a rapidly changing world Biological Conservation DOI: 10.1016/j.biocon.2009.09.001

We’re sorry, but 50/500 is still too few

28 01 2014

too fewSome of you who are familiar with my colleagues’ and my work will know that we have been investigating the minimum viable population size concept for years (see references at the end of this post). Little did I know when I started this line of scientific inquiry that it would end up creating more than a few adversaries.

It might be a philosophical perspective that people adopt when refusing to believe that there is any such thing as a ‘minimum’ number of individuals in a population required to guarantee a high (i.e., almost assured) probability of persistence. I’m not sure. For whatever reason though, there have been some fierce opponents to the concept, or any application of it.

Yet a sizeable chunk of quantitative conservation ecology develops – in various forms – population viability analyses to estimate the probability that a population (or entire species) will go extinct. When the probability is unacceptably high, then various management approaches can be employed (and modelled) to improve the population’s fate. The flip side of such an analysis is, of course, seeing at what population size the probability of extinction becomes negligible.

‘Negligible’ is a subjective term in itself, just like the word ‘very‘ can mean different things to different people. This is why we looked into standardising the criteria for ‘negligible’ for minimum viable population sizes, almost exactly what the near universally accepted IUCN Red List attempts to do with its various (categorical) extinction risk categories.

But most reasonable people are likely to agree that < 1 % chance of going extinct over many generations (40, in the case of our suggestion) is an acceptable target. I’d feel pretty safe personally if my own family’s probability of surviving was > 99 % over the next 40 generations.

Some people, however, baulk at the notion of making generalisations in ecology (funny – I was always under the impression that was exactly what we were supposed to be doing as scientists – finding how things worked in most situations, such that the mechanisms become clearer and clearer – call me a dreamer).

So when we were attacked in several high-profile journals, it came as something of a surprise. The latest lashing came in the form of a Trends in Ecology and Evolution article. We wrote a (necessarily short) response to that article, identifying its inaccuracies and contradictions, but we were unable to expand completely on the inadequacies of that article. However, I’m happy to say that now we have, and we have expanded our commentary on that paper into a broader review. Read the rest of this entry »

Who’s responsible for climate change? Not ecologists, right?

19 06 2012

It’s sometimes difficult to take a long, hard look in the mirror and admit one’s failings. Today’s post is a thought-provoking challenge to all ecologists (indeed, all scientists) who gaily flit all over the known universe in the name of science. I’m certainly in one of the upper guilt echelons on this issue – and while I tell myself each January that “this year I’ll fly much less frequently”, I usually end up breaking my resolution by month’s end.

In some defence of my sins, I have to state that while I should always endeavour to fly less, I am convinced that strategic, well-planned (and usually small) meetings are some of the best ways to advance scientific ideas. As CB readers might know, I am particularly impressed with the results of dedicated workshops in this regard.

I also think that even if all aeroplanes suddenly fell from the sky and one could no longer enjoy that transcontinental G & T, we’d still be in a terribly climate-change mess – we need BIG solutions beyond simple consumption reduction.

Now I’m just making excuses. Thanks again to Alejandro Frid for providing this challenge to me and our colleagues.

Recently I asked a math savvy graduate student at Simon Fraser University, in Western Canada, to proofread an equation. ‘No problem’, she replied, ‘but could you wait a few days? I am about to fly to Korea for a conference but I will return shortly.’

Hmmmm? So this is what the system promotes: gallivanting halfway around the world and back within a week, burning extraordinary amounts of fossil fuels, all in the name of scientific career advancement. Who are the climate change culprits? Not us ecologists, right?

Of course I am being unfair to Ms. Maths Savvy. Most of us are equally guilty of boarding that big ol’ jet airliner in the name of scientific meetings or the pursuit of ecological knowledge in far off study sites. Yet the inconvenient truth, according to a recent editorial in Nature Climate Change1, is that “international air travel accounts for about 5% of global warming”. Flying all over the world in the name of ecology and conservation therefore implies that we believe that (i) there are no alternative means to accomplish the same goal with far less emissions, and (ii) that the benefits of our work outweigh the atmospheric impacts of flying. Think again.

For insight into these issues, I interviewed Kevin Anderson, deputy director of the Tyndall Centre for Climate Change Research at the University of Manchester and arguably the climate conscience of scientists. I was attracted to Anderson’s perspective because of its blunt honesty. He calls air travel “…the most emission profligate activity per hour”2 and has little patience for the irony that “international climate jamborees”, otherwise known as climate science meetings, have contributed far more to increasing carbon emissions than to any meaningful action on climate change. His recent commentary in Nature3 makes it amply clear that buying carbon offsets when flying may ease our perceived guilt but not emission rates. Read the rest of this entry »

Not magic, but necessary

18 10 2011

In April this year, some American colleagues of ours wrote a rather detailed, 10-page article in Trends in Ecology and Evolution that attacked our concept of generalizing minimum viable population (MVP) size estimates among species. Steve Beissinger of the University of California at Berkeley, one of the paper’s co-authors, has been a particularly vocal adversary of some of the applications of population viability analysis and its child, MVP size, for many years. While there was some interesting points raised in their review, their arguments largely lacked any real punch, and they essentially ended up agreeing with us.

Let me explain. Today, our response to that critique was published online in the same journal: Minimum viable population size: not magic, but necessary. I want to take some time here to summarise the main points of contention and our rebuttal.

But first, let’s recap what we have been arguing all along in several papers over the last few years (i.e., Brook et al. 2006; Traill et al. 2007, 2010; Clements et al. 2011) – a minimum viable population size is the point at which a declining population becomes a small population (sensu Caughley 1994). In other words, it’s the point at which a population becomes susceptible to random (stochastic) events that wouldn’t otherwise matter for a small population.

Consider the great auk (Pinguinus impennis), a formerly widespread and abundant North Atlantic species that was reduced by intensive hunting throughout its range. How did it eventually go extinct? The last remaining population blew up in a volcanic explosion off the coast of Iceland (Halliday 1978). Had the population been large, the small dent in the population due to the loss of those individuals would have been irrelevant.

But what is ‘large’? The empirical evidence, as we’ve pointed out time and time again, is that large = thousands, not hundreds, of individuals.

So this is why we advocate that conservation targets should aim to keep at or recover to the thousands mark. Less than that, and you’re playing Russian roulette with a species’ existence. Read the rest of this entry »


10 07 2008

periodicalsThis page highlights a growing list of what I (and others) believe are some of the classic studies that have assisted in biodiversity conservation. The first link per topic takes you to the post, the highlighted paper and link takes you to the paper’s source.

Allee, W.C. (1931). Animal Aggregations: A Study in General Sociology, University of Chicago Press, Chicago, IL

MacArthur, R.H. & Wilson, E.O. (1967). The Theory of Island Biogeography. Princeton University Press, Princeton, NJ

Hardin, G. (1968). The tragedy of the commons Science, 162, 1243-1248

Shaffer, M.L. (1981). Minimum population sizes for species conservation. BioScience 31, 131–134

Ehrlich, P.R., H. A. Mooney. (1983). Extinction, substitution, and ecosystem services. BioScience 33, 248-254

Diamond, J.M. (1984). ‘Normal’ extinction of isolated populations In: Extinctions, M.H. Nitecki (Ed.), 191-246, Chicago University Press, Chicago, USA

Wilcox, B.A., Murphy D.D. (1985). Conservation strategy: the effects of fragmentation on extinction. American Naturalist, 125, 879-887

Soulé, M. E., Bolger, D. T., Alberts, A. C., Sauvajot, R. S., Wright, J., Sorice, M. & Hill, S. (1988) Reconstructed dynamics of rapid extinctions of chaparral-requiring birds in urban habitat islands. Conservation Biology, 2, 75-92

Lande, R. (1988). Genetics and demography in biological conservation. Science, 241, 1455-1460

Mace, G.M. & Lande, R. (1991). Assessing extinction threats: toward a re-evaluation of IUCN threatened species categories. Conservation Biology, 51, 148-157

Walker, B. H. (1992) Biodiversity and ecological redundancy. Conservation Biology, 6, 18-23

Caughley, G. (1994). Directions in conservation biology. Journal of Animal Ecology, 63, 215-244

Tilman, D., May, R.M., Lehman, C.L., Nowak, M.A. (1994) Habitat destruction and the extinction debt. Nature 371, 65-66

Frankham, R. (1995). Effective population size/adult population size ratios in wildlife: a review. Genetical Research, 66, 95-107

Pauly, D. (1995). Anecdotes and the shifting baseline syndrome of fisheries Trends in Ecology and Evolution, 10, 430

Pauly, D., Christensen, V., Dalsgaard, J., Froese, R. & Torres Jr., F. (1998). Fishing down marine food webs. Science, 279, 860-863

Simberloff, D. & Von Holle, B. (1999). Positive interactions of nonindigenous species: invasional meltdown? Biological Invasions, 1, 21-32

Myers, N., Mittermeier, R.A., Mittermeier, C.G., da Fonseca, G.A.B. & Kent, J. (2000). Biodiversity hotspots for conservation priorities. Nature, 403, 853-858

Thomas, C.D., Cameron, A., Green, R.E., Bakkenes, M., Beaumont, L.J., Collingham, Y.C., Erasmus, B.F.N., de Siqueira, M.F., Grainger, A., Hannah, L., Hughes, L., Huntley, B., van Jaarsveld, A.S., Midgley, G.F., Miles, L., Ortega-Huerta, M.A., Peterson, A.T., Phillips, O.L., & Williams, S.E. (2004) Extinction risk from climate change. Nature, 427, 145-148

Recent Media

2 07 2008




1I didn’t actually say anywhere in this interview that climate change would ‘save’ grey nurse sharks; I did say that increased population connectivity resulting from warming waters might reduce extinction risk. I loathe how reporters ‘quote’ scientists even when they never actually said these words. Ah, the sensationalism of scientific media!

2Another corker of bad ‘journalism’. See post here for explanation

3My comments on another paper.

4What? It’s not about climate pollution – it’s a bloody environmental degradation metric. Did these people even read the paper? Another classic example of hack-and-regurgitate reporting.

5While the article isn’t too awful, the title misses the point of the paper entirely.