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 »

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 »

Food for sex

18 03 2013
Quercus_KakFeed Photo
Kakapo are unique among the ~ 400 parrot species (Psittaciformes) for being flightless, nocturnal and extremely long-lived (up to 100 years!). Additionally, they are herbivorous (seeds, fruits, polen, plants), males can weigh up to 2-4 kg (40% heavier than females), and females lay their eggs on the ground or cavities – i.e., 3 eggs in a single clutch annually, although 2 clutches might occur if the nest fails at the beginning of the reproductive season or if the eggs are taken for artificial incubation.Native to New Zealand, kakapo once inhabited the subalpine fringes of forest and scrub. Polynesians (1000 years ago) and Europeans (mostly in the XIX Century) arrived in the archipelago accompanied by dogs, cats, rats and mustelids that cornered kakapo populations in the Fiordland region (south-west of the South Island) where it was declared extinct in 1989. In 1977, a population of some 200 individuals was found on Stewart Island – this population was already in decline to the claws and jaws of feral cats. By the 1980s, the failure of captive breeding programs prompted the transfer of 60 individuals from Steward to carnivore-free islands. The global (known) population ‘rocketed’ from 50 individuals in 1999 to 126 in the 2012 censuses and, consequently, the kakapo’s IUCN status changed in 2000 from ‘Extinct in the Wild’ to ‘Critically Endangered’. Under the management of the Kakapo Recovery Programme, kakapo are now present on the islands of CodfishAnchor and Little Barrier.

Inbreeding, system shocks caused by fire or cyclones (for example), or demographic stochasticity (by which two or more outcomes are possible) such as how many males and females will be born in a single year, are all factors that threaten the persistence of small and fragmented populations. They can, however, be reverted by conservation actions.

If you have ever taken dancing classes, you will be familiar with the scarcity of male partners and how this can jeopardize group learning. When reproduction, rather than salsa pirouettes, is at stake, a biased sex ratio can compromise the persistence of species. For instance, when females are unable to find males (or vice versa), fertility rates can collapse as a result – a well-known cause of an Allee effect (1). Curiously, natural selection can promote such bias by favouring a species’ investment in litters dominated by one of the two genders. The evolutionary formulation of such scenario is that females can adjust the sex ratio of their offspring depending on the amount of available resources (2) – see contrasting cross-taxa studies on this subject (3-5). Thus, when resources abound (e.g., food), mothers can afford the offspring’s gender requiring more resources to reach adulthood or once adulthood is reached, is less likely to reproduce successfully (6). This predisposition to one gender or another can be key to the conservation of endangered species (7).

The kakapo case

At the end of the 1990s, the New Zealand Department of Conservation placed dispensers of supplementary food in the territories of some kakapo (a rather enormous, flightless parrot Strigops habroptilus) to encourage their reproduction. Back then, only 60 individuals were left of the entire species . Unfortunately, those females with access to the supplemental food conceived 67% of male chicks (so exacerbating the fact that kakapo populations are naturally male-biased), while those females without extra feeding had 71% of female chicks (8). Something wasn’t working. Read the rest of this entry »

The Biodiversity Club

11 10 2012

The International Union for Conservation of Nature (IUCN) Red List of Threatened Species uses 5 quantitative criteria to allocate species to 9 categories of extinction risk. The criteria are based on ecological theory (1, 2), and are therefore subject to modification and critique. With pros and cons (3-6), and intrigues (7, 8), the list has established itself as an important tool for assessing the state of biodiversity globally and, more recently, regionally.

We all carry codes of some sort; that is, unique alphanumeric labels identifying our membership in a collectivity. Some of those codes (e.g., a videoclub customer number) make sense only locally, some do internationally (e.g., passport number). Species are also members of the club of biodiversity and, by virtue of our modern concern for their conservation, the status of many taxa has been allocated to alphanumeric categories under different rationales such as extinction risk or trading schemes (5, 9-13). Contradiction emerges when taxa might be threatened locally but not internationally, or vice versa.

In the journal Biological Conservation, a recent paper (14) has echoed the problem for the seagrass Zostera muelleri. This marine phanerogam occurs in Australia, New Zealand and Papua New Guinea, and is listed as “Least Concern” (LC) with “Stable” population trend by the IUCN. Matheson et al. (14) stated that such status neglects the “substantial loss” of seagrass habitats in New Zealand, and that the attribution of “prolific seed production” to the species reflects the IUCN assessment bias towards Australian populations. The IUCN Seagrass Red List Authority, Fred Short, responded (15) that IUCN species ratings indicate global status (i.e., not representative for individual countries) and that, based on available quantitative data and expert opinion, the declines of Z. muelleri are localised and offset by stable or expanding populations throughout its range. Read the rest of this entry »

Better SAFE than sorry

30 11 2011

Last day of November already – I am now convinced that my suspicions are correct: time is not constant and in fact accelerates as you age (in mathematical terms, a unit of time becomes a progressively smaller proportion of the time elapsed since your birth, so this makes sense). But, I digress…

This short post will act mostly as a spruik for my upcoming talk at the International Congress for Conservation Biology next week in Auckland (10.30 in New Zealand Room 2 on Friday, 9 December) entitled: Species Ability to Forestall Extinction (SAFE) index for IUCN Red Listed species. The post also sets a bit of the backdrop to this paper and why I think people might be interested in attending.

As regular readers of CB will know, we published a paper this year in Frontiers in Ecology and the Environment describing a relatively simple metric we called SAFE (Species Ability to Forestall Extinction) that could enhance the information provided by the IUCN Red List of Threatened Species for assessing relative extinction threat. I won’t go into all the detail here (you can read more about it in this previous post), but I do want to point out that it ended up being rather controversial.

The journal ended up delaying final publication because there were 3 groups who opposed the metric rather vehemently, including people who are very much in the conservation decision-making space and/or involved directly with the IUCN Red List. The journal ended up publishing our original paper, the 3 critiques, and our collective response in the same issue (you can read these here if you’re subscribed, or email me for a PDF reprint). Again, I won’t go into an detail here because our arguments are clearly outlined in the response.

What I do want to highlight is that even beyond the normal in-print tête-à-tête the original paper elicited, we were emailed by several people behind the critiques who were apparently unsatisfied with our response. We found this slightly odd, because many of the objections just kept getting re-raised. Of particular note were the accusations that: Read the rest of this entry »

Taxonomy in the clouds

4 07 2011

Another post (see previous here, here and here) by my aspiring science-communicator PhD student, Salvador Herrando-Pérez.

Taxonomy uses rigorous rules of nomenclature to classify living beings, so every known species has a given ‘name’ and ‘surname’. The revision of certain taxonomic groups (particularly through genetic analyses) is favouring the proliferation of nominally new species, often propelled by virtue of their charisma and conservation status.

In secondary school, most of my classmates associated the subject ‘Biology’ with unpronounceable Latin taxonomic names, with which all known living beings are branded — ‘Canis lupus’ reads the identity card of humanity’s best friend. When the Swedish monk Carl Linnaeus proposed such binomial nomenclature, he could hardly imagine that, two hundred years later, his terminology would underpin national and transnational budgets for species conservation. Taxonomic nomenclature allows the classification of species into clusters of the same kind (e.g., diatoms, amanitas, polychaetes, skinks), and the calculation of an indispensable figure for conservation purposes: how many species are there at a given location, range, country, continent, or the entire planet?

Traditionally, taxonomists described species by examining their (external and internal) morphological features, the widest consensus being that two individuals of different species could not hybridise. However, a practical objection to that thinking was that if, for instance, an ocean separated two leopard populations, ethics should prevent us from bringing them in contact only to check if they produce fertile offspring, hence justifying a common-species status. Genetics currently provides a sort of ‘remote check’.

New species, new names

Over the last three decades, the boom of genetics and the global modernisation of environmental policies have fostered alternative criteria to differentiate species, populations, and even individuals. As a result, experts have created a colourful lexicon to label management or conservation units or new taxonomical categories such as that of a subspecies1, e.g., Canis lupus dingo for the wild Australian dog (dingo). These changes have shaken the foundations of taxonomy because several definitions of species (biological, phylogenetic, evolutionary) are forced to live under the umbrella of a common nomenclature. Read the rest of this entry »

Species’ Ability to Forestall Extinction – AudioBoo

8 04 2011

Here’s a little interview I just did on the SAFE index with ABC AM:

Not a bad job, really.

And here’s another one from Radio New Zealand:

CJA Bradshaw

S.A.F.E. = Species Ability to Forestall Extinction

8 01 2011

Note: I’ve just rehashed this post (30/03/2011) because the paper is now available online (see comment stream). Stay tuned for the media release next week. – CJAB

I’ve been more or less underground for the last 3 weeks. It has been a wonderful break (mostly) from the normally hectic pace of academic life. Thanks for all those who remain despite the recent silence.


But I’m back now with a post about a paper we’ve just had accepted in Frontiers in Ecology and Environment. In my opinion it’s a leap forward in how we measure relative threat risk among species, despite some criticism.

I’ve written in past posts about the ‘magic’ minimum number of individuals that should be in a population to reduce the chance of extinction from random events. The so-called ‘minimum viable population (MVP) size’ is basically the abundance of a (connected) population below which random events take over from factors causing sustained declines (Caughley’s distinction between the ‘declining’ and ‘small’ population paradigms).

Up until the last few years, the MVP size was considered to be a population- or species-specific value, and it required very detailed demographic, genetic and biogeographical data to estimate – not something that biologists tend to have at their fingertips for most high-risk species. However, several papers published by our group (Minimum viable population size and global extinction risk are unrelated, Minimum viable population size: a meta-analysis of 30 years of published estimates and Pragmatic population viability targets in a rapidly changing world) have shown that there is in fact little variation in this number among the best-studied species; both demographic and genetic data support a number of around 5000 to avoid crossing the deadly threshold.

Now the fourth paper in this series has just been accepted (sorry, no link yet, but I’ll let you all know as soon as it is available), and it was organised and led by Reuben Clements, and co-written by me, Barry Brook and Bill Laurance.

The idea is fairly simple and it somewhat amazes me that it hasn’t been implemented before. The SAFE (Species Ability to Forestall Extinction) index is simply the distance a population is (in terms of abundance) from its MVP. In the absence of a species-specific value, we used the 5000-individual threshold. Thus, Read the rest of this entry »

Humans 1, Environment 0

27 09 2010


While travelling to our Supercharge Your Science workshop in Cairns and Townsville last week (which, by the way, went off really well and the punters gave us the thumbs up – stay tuned for more Supercharge activities at a university near you…), I stumbled across an article in the Sydney Morning Herald about the state of Australia.

That Commonwealth purveyor of numbers, the Australian Bureau of Statistics (ABS), put together a nice little summary of various measures of wealth, health, politics and environment and their trends over the last decade. The resulting Measures of Australia’s Progress is an interesting read indeed. I felt the simple newspaper article didn’t do the environmental components justice, so I summarise the salient points below and give you my tuppence as well. Read the rest of this entry »

Global erosion of ecosystem services

14 09 2010

A few months ago I was asked to give a lecture about erosion of ecosystem services to students in the University of Adelaide‘s Issues in Sustainable Environments unit. I gave that lecture last week and just uploaded a slidecast of the presentation (with audio) today.

I’ve reproduced the lecture here for your viewing pleasure. I hope you find the 45-minute presentation useful. Note that the first few minutes cover me referring to the Biodiversity film short that I posted not too long ago.

CJA Bradshaw

The biodiversity extinction numbers game

4 01 2010

© Ferahgo the Assassin

Not an easy task, measuring extinction. For the most part, we must use techniques to estimate extinction rates because, well, it’s just bloody difficult to observe when (and where) the last few individuals in a population finally kark it. Even Fagan & Holmes’ exhaustive search of extinction time series only came up with 12 populations – not really a lot to go on. It’s also nearly impossible to observe species going extinct if they haven’t even been identified yet (and yes, probably still the majority of the world’s species – mainly small, microscopic or subsurface species – have yet to be identified).

So conservation biologists do other things to get a handle on the rates, relying mainly on the species-area relationship (SAR), projecting from threatened species lists, modelling co-extinctions (if a ‘host’ species goes extinct, then its obligate symbiont must also) or projecting declining species distributions from climate envelope models.

But of course, these are all estimates and difficult to validate. Enter a nice little review article recently published online in Biodiversity and Conservation by Nigel Stork entitled Re-assessing current extinction rates which looks at the state of the art and how the predictions mesh with the empirical data. Suffice it to say, there is a mismatch.

Stork writes that the ‘average’ estimate of losing about 100 species per day has hardly any empirical support (not surprising); only about 1200 extinctions have been recorded in the last 400 years. So why is this the case?

As mentioned above, it’s difficult to observe true extinction because of the sampling issue (the rarer the individuals, the more difficult it is to find them). He does cite some other problems too – the ‘living dead‘ concept where species linger on for decades, perhaps longer, even though their essential habitat has been destroyed, forest regrowth buffering some species that would have otherwise been predicted to go extinct under SAR models, and differing extinction proneness among species (I’ve blogged on this before).

Of course, we could just all be just a pack of doomsday wankers vainly predicting the end of the world ;-)

Well, I think not – if anything, Stork concludes that it’s all probably worse than we currently predict because of extinction synergies (see previous post about this concept) and the mounting impact of rapid global climate change. If anything, the “100 species/day” estimate could look like a utopian ideal in a few hundred years. I do disagree with Stork on one issue though – he claims that deforestation isn’t probably as bad as we make it out. I’d say the opposite (see here, here & here) – we know so little of how tropical forests in particular function that I dare say we’ve only just started measuring the tip of the iceberg.

CJA Bradshaw

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This post was chosen as an Editor's Selection for

ResearchBlogging.orgStork, N. (2009). Re-assessing current extinction rates Biodiversity and Conservation DOI: 10.1007/s10531-009-9761-9

Carbon = biodiversity

21 12 2009

I’ve decided to blog this a little earlier than I would usually simply because the COP15 is still fresh in everyone’s minds and the paper is now online as an ‘Accepted Article’, so it is fully citable.

The paper published in Conservation Letters by Strassburg and colleagues is entitled Global congruence of carbon storage and biodiversity in terrestrial ecosystems is noteworthy because it provides a very useful answer to a very basic question. If one were to protect natural habitats based on their carbon storage potential, would one also be protecting the most biodiversity (and of course, vice versa)?

Turns out, one would.

Using a global dataset of ~ 20,000 species of mammal, bird and amphibian, they compared three indices of biodiversity distribution (species richness, species threat & range-size rarity) to a new global above- and below-ground carbon biomass dataset. It turns out that at least for species richness, the correlations were fairly strong (0.8-ish, with some due to spatial autocorrelation); for threat and rarity indices, the correlations were rather weaker (~0.3-ish).

So what does this all mean for policy? Biodiversity hotspots – those areas around the globe with the highest biodiversity and greatest threats – have some of the greatest potential to store carbon as well as guard against massive extinctions if we prioritise them for conservation. Places such as the Amazon, Borneo Sumatra and New Guinea definitely fall within this category.

However, not all biodiversity hotspots are created equal; areas such as Brazil’s Cerrado or the savannas of the Rift Valley in East Africa have relatively lower carbon storage, and so carbon-trading schemes wouldn’t necessarily do much for biodiversity in these areas.

The overall upshot is that we should continue to pursue carbon-trading schemes such as REDD (Reduced Emissions from Deforestation and forest Degradation) because they will benefit biodiversity (contrary to what certain ‘green’ organisations say about it), but we can’t sit back and hope that REDD will solve all of biodiversity’s problems world wide.


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ResearchBlogging.orgStrassburg, B., Kelly, A., Balmford, A., Davies, R., Gibbs, H., Lovett, A., Miles, L., Orme, C., Price, J., Turner, R., & Rodrigues, A. (2009). Global congruence of carbon storage and biodiversity in terrestrial ecosystems Conservation Letters DOI: 10.1111/j.1755-263X.2009.00092.x

Crap environmental reporting

13 11 2009

EvilWe do a lot in our lab to get our research results out to a wider community than just scientists – this blog is just one example of how we do that. But of course, we rely on the regular media (television, newspaper, radio) heavily to pick up our media releases (see a list here). I firmly believe it goes well beyond shameless self promotion – it’s a duty of every scientist I think to tell the world (i.e., more than just our colleagues) about what we’re being paid to do. And the masses are hungry for it.

However, the demise of the true ‘journalist’ (one who investigates a story – i.e., does ‘research’) in favour of the automaton ‘reporter’ (one who merely regurgitates, and then sensationalises, what he/she is told or reads) worldwide (and oh, how we are plagued with reporters and deeply in need of journalists in Australia!) means that there is some horrendous stories out there, especially on scientific issues. This is mainly because most reporters have neither the training nor capacity to understand what they’re writing about.

This issue is also particular poignant for the state of the environment, climate change and biodiversity loss – I’ve blogged about this before (see Poor media coverage promotes environmental apathy and untruths).

But after a 30-minute telephone interview with a very friendly American food journalist yesterday, I expected a reasonable report on the issue of frog consumption because, well, I explained many things to her as best I could. What was eventually published was appalling.

Now, in all fairness, I think she was trying to do well, but it’s as though she didn’t even listen to me. The warning bells should have rung loudly when she admitted she hadn’t read my blog “in detail” (i.e., not at all?). You can read the full article here, but let me just point out some of the inconsistencies:

  • She wrote: “That’s a problem, Bradshaw adds, because nearly one half of frog species are facing extinction.”

Ah, no. I told her that between 30 and 50 % of frogs could be threatened with extinction (~30 % officially from the IUCN Red List). It could be as much as half given the paucity of information on so many species. A great example of reporter cherry-picking to add sensationalism.

  • She wrote: “Bradshaw attributes the drop-off to global warming and over-harvesting.”

Again, no, I didn’t. I clearly told her that the number one, way-out-in-front cause of frog declines worldwide is habitat loss. I mentioned chytrid fungus as another major contributor, and that climate change exacerbates the lot. Harvesting pressure is a big unknown in terms of relative impact, but I suspect it’s large.

  • She continued: “Bradshaw has embarked on a one-man campaign to educate eaters about the frog leg industry”

Hmmm. One man? I had a great team of colleagues co-write the original paper in Conservation Biology. I wasn’t even the lead author! Funny how suddenly I’m a lone wolf on a ‘campaign’. Bloody hell.

“Aghast”, was I? I don’t recall being particularly emotional when I told her that I found a photo of Barack Obama eating frog legs during his election campaign. I merely pointed this out to show that the product is readily available in the USA. I also mentioned absolutely nothing about whales or their loins.

So, enough of my little humorous whinge. My point is really that there are plenty of bad journalists out there with little interest in reporting the truth on environmental issues (tell us something we don’t know, Bradshaw). If you want to read a good story about the frog consumption issue, check out a real journalist’s perspective here.

CJA Bradshaw

Raise targets to prevent extinction

12 11 2009

I know I’ve blogged recently about this, but The Adelaidean did a nice little article that I thought I’d reproduce here. The source can be found here.

Adelaidean story Nov 2009

Not so ‘looming’ – Anthropocene extinctions

4 11 2009


© ABC 2009

Yesterday I was asked to do a quick interview on ABC television (Midday Report) about the release of the 2009 IUCN Red List of Threatened Species. I’ve blogged about the importance of the Red List before, but believe we have a lot more to do with species assessments and getting prioritisation right with respect to minimum viable population size. Have a listen to the interview itself, and read the IUCN’s media release reproduced below.

My basic stance is that we’ve only just started to assess the number of species on the planet (under 50000), yet there are many millions of species still largely under-studied and/or under-described (e.g., extant species richness = > 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 – see Bradshaw & Brook 2009 J Cosmol for references). What we’re looking at here is a refinement of knowledge (albeit a small one). We are indeed in the midst of the Anthropocene mass extinction event – there is nothing ‘looming’ about it. We are essentially losing species faster than we can assess them. I believe it’s important to make this clearer to those not working directly in the field of biodiversity conservation.

CJA Bradshaw

Extinction crisis continues apace – IUCN

Gland, Switzerland, 3 November, 2009 (IUCN) – The latest update of the IUCN Red List of Threatened Species™ shows that 17,291 species out of the 47,677 assessed species are threatened with extinction.

The results reveal 21 percent of all known mammals, 30 percent of all known amphibians, 12 percent of all known birds, and 28 percent of reptiles, 37 percent of freshwater fishes, 70 percent of plants, 35 percent of invertebrates assessed so far are under threat.

“The scientific evidence of a serious extinction crisis is mounting,” says Jane Smart, Director of IUCN’s Biodiversity Conservation Group. “January sees the launch of the International Year of Biodiversity. The latest analysis of the IUCN Red List shows the 2010 target to reduce biodiversity loss will not be met. It’s time for governments to start getting serious about saving species and make sure it’s high on their agendas for next year, as we’re rapidly running out of time.”

Of the world’s 5,490 mammals, 79 are Extinct or Extinct in the Wild, with 188 Critically Endangered, 449 Endangered and 505 Vulnerable. The Eastern Voalavo (Voalavo antsahabensis) appears on the IUCN Red List for the first time in the Endangered category. This rodent, endemic to Madagascar, is confined to montane tropical forest and is under threat from slash-and-burn farming.

There are now 1,677 reptiles on the IUCN Red List, with 293 added this year. In total, 469 are threatened with extinction and 22 are already Extinct or Extinct in the Wild. The 165 endemic Philippine species new to the IUCN Red List include the Panay Monitor Lizard (Varanus mabitang), which is Endangered. This highly-specialized monitor lizard is threatened by habitat loss due to agriculture and logging and is hunted by humans for food. The Sail-fin Water Lizard (Hydrosaurus pustulatus) enters in the Vulnerable category and is also threatened by habitat loss. Hatchlings are heavily collected both for the pet trade and for local consumption.

“The world’s reptiles are undoubtedly suffering, but the picture may be much worse than it currently looks,” says Simon Stuart, Chair of IUCN’s Species Survival Commission. “We need an assessment of all reptiles to understand the severity of the situation but we don’t have the $2-3 million to carry it out.”

The IUCN Red List shows that 1,895 of the planet’s 6,285 amphibians are in danger of extinction, making them the most threatened group of species known to date. Of these, 39 are already Extinct or Extinct in the Wild, 484 are Critically Endangered, 754 are Endangered and 657 are Vulnerable.

The Kihansi Spray Toad (Nectophrynoides asperginis) has moved from Critically Endangered to Extinct in the Wild. The species was only known from the Kihansi Falls in Tanzania, where it was formerly abundant with a population of at least 17,000. Its decline is due to the construction of a dam upstream of the Kihansi Falls that removed 90 percent of the original water flow to the gorge. The fungal disease chytridiomycosis was probably responsible for the toad’s final population crash.

The fungus also affected the Rabb’s Fringe-limbed Treefrog (Ecnomiohyla rabborum), which enters the Red List as Critically Endangered. It is known only from central Panama. In 2006, the chytrid fungus (Batrachochytrium dendrobatidis) was reported in its habitat and only a single male has been heard calling since. This species has been collected for captive breeding efforts but all attempts have so far failed.

Of the 12,151 plants on the IUCN Red List, 8,500 are threatened with extinction, with 114 already Extinct or Extinct in the Wild. The Queen of the Andes (Puya raimondii) has been reassessed and remains in the Endangered category. Found in the Andes of Peru and Bolivia, it only produces seeds once in 80 years before dying. Climate change may already be impairing its ability to flower and cattle roam freely among many colonies, trampling or eating young plants.

There are now 7,615 invertebrates on the IUCN Red List this year, 2,639 of which are threatened with extinction. Scientists added 1,360 dragonflies and damselflies, bringing the total to 1,989, of which 261 are threatened. The Giant Jewel (Chlorocypha centripunctata), classed as Vulnerable, is found in southeast Nigeria and southwest Cameroon and is threatened by forest destruction.

Scientists also added 94 molluscs, bringing the total number assessed to 2,306, of which 1,036 are threatened. Seven freshwater snails from Lake Dianchi in Yunnan Province, China, are new to the IUCN Red List and all are threatened. These join 13 freshwater fishes from the same area, 12 of which are threatened. The main threats are pollution, introduced fish species and overharvesting.

There are now 3,120 freshwater fishes on the IUCN Red List, up 510 species from last year. Although there is still a long way to go before the status all the world’s freshwater fishes is known, 1,147 of those assessed so far are threatened with extinction. The Brown Mudfish (Neochanna apoda), found only in New Zealand, has been moved from Near Threatened to Vulnerable as it has disappeared from many areas in its range. Approximately 85-90 percent of New Zealand’s wetlands have been lost or degraded through drainage schemes, irrigation and land development.

“Creatures living in freshwater have long been neglected. This year we have again added a large number of them to the IUCN Red List and are confirming the high levels of threat to many freshwater animals and plants. This reflects the state of our precious water resources. There is now an urgency to pursue our effort but most importantly to start using this information to move towards a wise use of water resources,” says Jean-Christophe Vié, Deputy Head of the IUCN Species Programme.

“This year’s IUCN Red List makes for sobering reading,” says Craig Hilton-Taylor, Manager of the IUCN Red List Unit. “These results are just the tip of the iceberg. We have only managed to assess 47,663 species so far; there are many more millions out there which could be under serious threat. We do, however, know from experience that conservation action works so let’s not wait until it’s too late and start saving our species now.”

The status of the Australian Grayling (Prototroctes maraena), a freshwater fish, has improved as a result of conservation efforts. Now classed as Near Threatened as opposed to Vulnerable, the population has recovered thanks to fish ladders which have been constructed over dams to allow migration, enhanced riverside vegetation and the education of fishermen, who now face heavy penalties if found with this species.

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)

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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

Not-so-scary maths and extinction risk

27 08 2009

© P. Horn

© P. Horn

Population viability analysis (PVA) and its cousin, minimum viable population (MVP) size estimation, are two generic categories for mathematically assessing a population’s risk of extinction under particular environmental scenarios (e.g., harvest regimes, habitat loss, etc.) (a personal plug here, for a good overview of general techniques in mathematical conservation ecology, check out our new chapter entitled ‘The Conservation Biologist’s Toolbox…’ in Sodhi & Ehrlich‘s edited book Conservation Biology for All by Oxford University Press [due out later this year]). A long-standing technique used to estimate extinction risk when the only available data for a population are in the form of population counts (abundance estimates) is the stochastic exponential growth model (SEG). Surprisingly, this little beauty is relatively good at predicting risk even though it doesn’t account for density feedback, age structure, spatial complexity or demographic stochasticity.

So, how does it work? Well, it essentially calculates the mean and variance of the population growth rate, which is just the logarithm of the ratio of an abundance estimate in one year to the abundance estimate in the previous year. These two parameters are then resampled many times to estimate the probability that abundance drops below a certain small threshold (often set arbitrarily low to something like < 50 females, etc.).

It is simple (funny how maths can become so straightforward to some people when you couch them in words rather than mathematical symbols), and rather effective. This is why a lot of people use it to prescribe conservation management interventions. You don’t have to be a modeller to use it (check out Morris & Doak’s book Quantitative Conservation Biology for a good recipe-like description).

But (there’s always a but), a new paper just published online in Conservation Letters by Bruce Kendall entitled The diffusion approximation overestimates extinction risk for count-based PVA questions the robustness when the species of interest breeds seasonally. You see, the diffusion approximation (the method used to estimate that extinction risk described above) generally assumes continuous breeding (i.e., there are always some females producing offspring). Using some very clever mathematics, simulation and a bloody good presentation, Kendall shows quite clearly that the diffusion approximation SEG over-estimates extinction risk when this happens (and it happens frequently in nature). He also offers a new simulation method to get around the problem.

Who cares, apart from some geeky maths types (I include myself in that group)? Well, considering it’s used so frequently, is easy to apply and it has major implications for species threat listings (e.g., IUCN Red List), it’s important we estimate these things as correctly as we can. Kendall shows how several species have already been misclassified for threat risk based on the old technique.

So, once again mathematics has the spotlight. Thanks, Bruce, for demonstrating how sound mathematical science can pave the way for better conservation management.

CJA Bradshaw

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Few people, many threats – Australia’s biodiversity shame

31 07 2009

bridled_nailtail_400I bang on a bit about human over-population and how it drives biodiversity extinctions. Yet, it isn’t always hordes of hungry humans descending on the hapless species of this planet  – Australia is a big place, but has few people (just over 20 million), yet it has one of the higher extinction rates in the world. Yes, most of the country is covered in some fairly hard-core desert and most people live in or near the areas containing the most species, but we have an appalling extinction record all the same.

A paper that came out recently in Conservation Biology and was covered a little in the media last week gives some telling figures for the Oceania region, and more importantly, explains that we have more than enough information now to implement sound, evidence-based policy to right the wrongs of the past and the present. Using IUCN Red List data, Michael Kingsford and colleagues (paper entitled Major conservation policy issues for biodiversity in Oceania), showed that of the 370 assessed species in Australia, 80 % of the threatened ones are listed because of habitat loss, 40 % from invasive species and 30 % from pollution. As we know well, it’s mainly habitat loss we have to control if we want to change things around for the better (see previous relevant posts here, here & here).

Kingsford and colleagues proceed to give a good set of policy recommendations for each of the drivers identified:

Habitat loss and degradation

  • Implement legislation, education, and community outreach to stop or reduce land clearing, mining, and unsustainable logging through education, incentives, and compensation for landowners that will encourage private conservation
  • Establish new protected areas for habitats that are absent or poorly represented
  • In threatened ecosystems (e.g., wetlands), establish large-scale restoration projects with local communities that incorporate conservation and connectivity
  • Establish transparent and evidence-based state of environment reporting on biodiversity and manage threats within and outside protected areas.
  • Protect free-flowing river systems (largely unregulated by dams, levees, and diversions) within the framework of the entire river basin and increase environmental flows on regulated rivers

Invasive species

  • Avoid deliberate introduction of exotic species, unless suitable analyses of benefits outweigh risk-weighted costs
  • Implement control of invasive species by assessing effectiveness of control programs and determining invasion potential
  • Establish regulations and enforcement for exchange or treatment of ocean ballast and regularly implement antifouling procedures

Climate change

  • Reduce global greenhouse gas emissions
  • Identify, assess, and protect important climate refugia
  • Ameliorate the impacts of climate change through strategic management of other threatening processes
  • Develop strategic plans for priority translocations and implement when needed


  • Implement restrictions on harvest of overexploited species to maintain sustainability
  • Implement an ecosystem-based approach for fisheries, based on scientific data, that includes zoning the ocean; banning destructive fishing; adopting precautionary fishing principles that include size limits, quotas, and regulation with sufficient resources based on scientific assessments of stocks and; reducing bycatch through regulation and education
  • Implement international mechanisms to increase sustainability of fisheries by supporting international treaties for fisheries protection in the high seas; avoiding perverse subsidies and improve labelling of sustainable fisheries; and licensing exports of aquarium fish
  • Control unsustainable illegal logging and wildlife harvesting through local incentives and cessation of international trade


  • Decrease pollution through incentives and education; reduce and improve treatment of domestic, industrial, and agriculture waste; and rehabilitate polluted areas
  • Strengthen government regulations to stop generation of toxic material from mining efforts that affects freshwater and marine environments
  • Establish legislation and regulations and financial bonds (international) to reinforce polluter-pays principles
  • Establish regulations, education programs, clean ups, labelling, and use of biodegradable packaging to reduce discarded fishing gear and plastics


  • Establish early-detection programs for pathological diseases and biosecurity controls to reduce translocation
  • Identify causes, risk-assessment methods, and preventative methods for diseases
  • Establish remote communities of organisms (captive) not exposed to disease in severe outbreaks


  • Establish regional population policies based on ecologically sustainable human population levels and consumption
  • Ensure that all developments affecting the environment are adequately analysed for impacts over the long term
  • Promote economic and societal benefits from conservation through education
  • Determine biodiversity status and trends with indicators that diagnose and manage declines
  • Invest in taxonomic understanding and provision of resources (scientific and conservation) to increase capacity for conservation
  • Increase the capacity of government conservation agencies
  • Focus efforts of nongovernmental organisations on small island states on building indigenous capacity for conservation
  • Base conservation on risk assessment and decision support
  • Establish the effectiveness of conservation instruments (national and international) and their implementation

A very good set of recommendations that I hope we can continue to develop within our governments.

CJA Bradshaw

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Destroyed or Destroyer?

23 03 2009

Last year our group published a paper in Journal of Ecology that examined, for the first time, the life history correlates of a species’ likelihood to become invasive or threatened.

The paper is entitled Threat or invasive status in legumes is related to opposite extremes of the same ecological and life-history attributes and was highlighted by the Editor of the journal.

The urgency and scale of the global biodiversity crisis requires being able to predict a species’ likelihood of going extinct or becoming invasive. Why? Well, without good predictive tools about a species’ fate, we can’t really prepare for conservation actions (in the case of species more likely to go extinct) or eradication (in the case of vigorous invasive species).

We considered the problem of threat and invasiveness in unison based on analysis of one of the largest-ever databases (8906 species) compiled for a single plant family (Fabaceae = Leguminosae). We chose this family because it is one of the most speciose (i.e., third highest number of species) in the Plant kingdom, its found throughout all continents and terrestrial biomes except Antarctica, its species range in size from dwarf herbs to large tropical trees, and its life history, form and functional diversity makes it one of the most important plant groups for humans in terms of food production, fodder, medicines, timber and other commercial products. Choosing only one family within which to examine cross-species trends also makes the problem of shared evolutionary histories less problematic from the perspective of confounded correlations.

We found that tall, annual, range-restricted species with tree-like growth forms, inhabiting closed-forest and lowland sites are more likely to be threatened. Conversely, climbing and herbaceous species that naturally span multiple floristic kingdoms and habitat types are more likely to become invasive.

Our results support the idea that species’ life history and ecological traits correlate with a fate response to anthropogenic global change. In other words, species do demonstrate particular susceptibility to either fate based on their evolved traits, and that traits generally correlated with invasiveness are also those that correlate with a reduced probability of becoming threatened.

Conservation managers can therefore benefit from these insights by being able to rank certain plant species according to their risk of becoming threatened. When land-use changes are imminent, poorly documented species can essentially be ranked according to those traits that predispose them to respond negatively to habitat modification. Here, species inventories combined with known or expected life history information (e.g., from related species) can identify which species may require particular conservation attention. The same approach can be used to rank introduced plant species for their probability of spreading beyond the point of introduction and threatening native ecosystems, and to prioritise management interventions.

I hope more taxa are examined with such scrutiny so that we can have ready-to-go formulae for predicting a wider array of potential fates.

CJA Bradshaw

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Rare just tastes better

11 02 2009

I had written this a while ago for publication, but my timing was out and no one had room to publish it. So, I’m reproducing it here as an extension to a previous post (That looks rare – I’ll kill that one).

As the international market for luxury goods expands in value, extent and diversity of items (Nueno & Quelch 1998), the world’s burgeoning pool of already threatened species stands to worsen. Economic theory predicts that harvested species should eventually find refuge from over-exploitation because it simply becomes too costly to find the last remaining wild individuals (Koford & Tschoegl 1998). However, the self-reinforcing cycle of human greed (Brook & Sodhi 2006) can make rare species increasingly valuable to a few select consumers such that mounting financial incentives drive species to extinction (Courchamp et al. 2006). The economic and ecological arguments are compelling, but to date there has been little emphasis on how the phenomenon arises in the human thought process, nor how apparently irrational behaviour can persist. Gault and colleagues (2008) have addressed this gap in a paper published recently in Conservation Letters by examining consumer preferences for arguably one of the most stereotypical luxury food items, caviar from the 200-million-year-old sturgeon (Acipenser spp.).

Sturgeon (6 genera) populations worldwide are in trouble, with all but two of the 27 known species threatened with extinction (either Near Threatened, Vulnerable, Endangered or Critically Endangered) according to the International Union for Conservation of Nature and Natural Resources’ (IUCN) Red List of Threatened Species. Despite all 27 species also having strict international trade restrictions imposed by the Convention on International Trade in Endangered Species (CITES) (Gault et al. 2008), intense commercial pressure persists for 15 of these at an estimated global value exceeding US$200 million annually (Pikitch et al. 2005). The very existence of the industry itself and the luxury good it produces are therefore, at least for some regions, unlikely to endure over the next decade (Pala 2007). What drives such irrational behaviour and why can we not seem to prevent such coveted species from spiralling down the extinction vortex?

Gault and colleagues addressed this question specifically in an elegantly simple set of preference experiments targeting the very end-consumers of the caviar production line – French connoisseurs. Some particularly remarkable results were derived from presentations of identical caviar; 86 % of attendees of luxury receptions not only preferred falsely labelled ‘rarer’ Siberian caviar (A. baeri) after blind tasting experiments, they also scored what they believed was caviar from the rarer species as having a higher ‘gustative quality’. These high-brow results were compared to more modest consumers in French supermarkets, with similar conclusions. Not only were unsuspecting gourmands fooled into believing the experimental propaganda, subjects in both cases stated a preference for seemingly rarer caviar even prior to tasting.

The psycho-sociological implications of perceived rarity are disturbing themselves; but Gault and colleagues extended their results with a mathematical game theory model demonstrating how irrational choices drive just such a harvested species to extinction. The economic implications of attempting to curb exploitation as species become rarer when the irrationality of perceived rarity was taken into consideration were telling – there is no payoff in delaying exploitation as more and more consumers are capable of entering the market. In other words, the assumption that consumers apply a positive temporal discount rate to their payoff (Olson & Bailey 1981) is wrong, with the demographic corollary that total depletion of the resource ensues. The authors contend that such artificial value may drive the entire luxury goods market based mainly on the self-consciousness and social status of consumers able to afford these symbols of affluence.

The poor record of species over-exploitation by humans arising from the Tragedy of the Commons (Hardin 1968) is compounded by this new information. This anthropogenic Allee effect (Courchamp et al. 2006) provides a novel example mechanism for how small populations are driven ever-downward because low densities ensure declining fitness. Many species may follow the same general rules, from bluefin tuna, Napoleon wrasse lips and shark fins, to reptile skins and Tibetan antelope woollen shawls. Gault and colleagues warn that as the human population continues to expand and more people enter the luxury-goods market, more wildlife species will succumb to this Allee effect-driven extinction vortex.

The authors suggest that a combination of consumer education and the encouragement of farmed substitute caviar will be more effective than potentially counter-productive trading bans that ultimately encourage illegal trade. However, the preference results suggest that education might not promote positive action given that reluctance of affluent consumers to self-limit. I believe that the way forward instead requires a combination of international trade bans, certification schemes for ‘sustainable’ goods that flood markets to increase supply and reduce price, better controls on point-of-origin labelling, and even state-controlled ‘warning’ systems to alert prospective consumers that they are enhancing the extinction risk of the very products they enjoy. A better architecture for trading schemes and market systems that embrace long-term persistence can surely counteract the irrationality of the human-induced destruction of global ecosystem services. We just need to put our minds and pocketbooks to the task.

CJA Bradshaw

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