Wobbling to extinction

31 08 2009

crashI’ve been meaning to highlight for a while a paper that I’m finding more and more pertinent as a citation in my own work. The general theme is concerned with estimating extinction risk of a particular population, species (or even ecosystem), and more and more we’re finding that different drivers of population decline and eventual extinction often act synergistically to drive populations to that point of no return.

In other words, the whole is greater than the sum of its parts.

In other, other words, extinction risk is usually much higher than we generally appreciate.

This might seem at odds with my previous post about the tendency of the stochastic exponential growth model to over-estimate extinction risk using abundance time series, but it’s really more of a reflection of our under-appreciation of the complexity of the extinction process.

In the early days of ConservationBytes.com I highlighted a paper by Fagan & Holmes that described some of the few time series of population abundances right up until the point of extinction – the reason these datasets are so rare is because it gets bloody hard to find the last few individuals before extinction can be confirmed. Most recently, Melbourne & Hastings described in a paper entitled Extinction risk depends strongly on factors contributing to stochasticity published in Nature last year how an under-appreciated component of variation in abundance leads to under-estimation of extinction risk.

‘Demographic stochasticity’ is a fancy term for variation in the probability of births deaths at the individual level. Basically this means that there will be all sorts of complicating factors that move any individual in a population away from its expected (mean) probability of dying or reproducing. When taken as a mean over a lot of individuals, it has generally been assumed that demographic stochasticity is washed out by other forms of variation in mean (population-level) birth and death probability resulting from vagaries of the environmental context (e.g., droughts, fires, floods, etc.).

‘No, no, no’, say Melbourne & Hastings. Using some relatively simple laboratory experiments where environmental stochasticity was tightly controlled, they showed that demographic stochasticity dominated the overall variance and that environmental variation took a back seat. The upshot of all these experiments and mathematical models is that for most species of conservation concern (i.e., populations already reduced below to their minimum viable populations size), not factoring in the appropriate measures of demographic wobble means that most people are under-estimating extinction risk.

Bloody hell – we’ve been saying this for years; a few hundred individuals in any population is a ridiculous conservation target. People must instead focus on getting their favourite endangered species to number at least in the several thousands if the species is to have any hope of persisting (this is foreshadowing a paper we have coming out shortly in Biological Conservationstay tuned for a post thereupon).

Melbourne & Hastings have done a grand job in reminding us how truly susceptible small populations are to wobbling over the line and disappearing forever.

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





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

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





Burning away ecological ignorance

24 08 2009

This is the last post from the 10th International Congress of Ecology (INTECOL) in Brisbane. I’ve just returned after a long, but good week.

fire

© ABC Landline

Following my last two posts (here and here) from INTECOL, I end with a post about the very final talk of the Congress by a very well-known conservation ecologist, Professor David Lindenmayer of the Australian National University. David is a prolific and highly respected ecologist specialising in long-term ecological studies measuring forest biodiversity change. What made this final talk so compelling (and compelling it had to be after 5 straight days of talks) was not that it was essentially his acceptance ‘speech’ for winning the Ecological Society of Australia‘s Australian Ecology Research Award (AERA), it was the personal side of his science that kept the audience rapt.

As many CB readers will know, Australia (the state of Victoria in particular) suffered earlier this year some of the worst forest fires on record. Many died and many millions in property were damaged. Since then, everyone from Germaine Greer to MP Wilson Tuckey has become a laughably unqualified fire expert, but few have sufficient knowledge or experience to prescribe the most parsimonious fire regime for Victoria’s wet temperate forests.

Now, I think David was unfortunate to lose either friends or family in those fires, and he’s been collecting biodiversity data there and studying the ecology of south Australian fires for over two decades. Suffice it to say, he probably knows what he’s talking about.

So when the baying hounds of public misunderstanding demand that the remaining bush fragments of Victorian forests be cleared to protect people and property (so-called ‘hazard-reduction burning’), I think we should listen instead to David Lindenmayers of this world.

David’s talk was about just this – how the fires are portrayed as the Apocalypse itself by the media, when in reality ecosystems generally bounce back very quickly. Indeed, even in some of the most heavily burnt sites, most of the standing carbon in the vegetation remains (despite appearances). He also explained that our knowledge of temperate fire regimes is rudimentary at best, and that available evidence from the Northern Hemisphere suggests that clearing forests actually can lead to a HIGHER fire proneness, intensity and frequency. He explained how the homogenisation of fire patterns destroy are weakening essential ecosystem functions, and that spatial and temporal fire patchiness is essential to maintain ecosystems and the people living in them.

In summary, we have failed to learn lessons from northern Australia about buggering up the natural fire regime (see previous post). We as a society fall victim to sensationalist and uninformed media reports and develop ill-advised, knee-jerk policies as a result. Ecological considerations for our own welfare have been overlooked too long. It’s time politicians stop fuelling the fires of public ignorance and listen to the ecologists out there who know a thing or two about complex ecosystem structure and the disturbance regimes that create them.

Thanks, David, for a sobering reminder of the importance of our work.

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





Shocking continued loss of Australian mammals

21 08 2009

thylacineAs CB readers know, I’m in Brisbane this week for the 10th International Congress of Ecology (INTECOL). My last post was on a great plenary talk by biodiversity guru, Kevin Gaston of the University of Sheffield, and I’ve got one more before heading back to Adelaide tomorrow.

Today, the last day of INTECOL talks, brought together some great conservation minds in a session in which I was honoured to participate. I spoke on extinction synergies, but I think John Woinarski of the Northern Territory Government stole the show.

I used to live in the NT and have seen John speak many times; however, this was one of the best and most sobering of his talks I’ve seen yet.

In a nutshell, we are STILL experiencing a colossal decline in our mammals. I think many might know that Australia is the WORST country in the world for mammal extinctions already – even more gut-wrenching when you consider that our closest competitors are small islands that have a completely different set of threats. However, many don’t know (and this is John’s point), that we are still losing populations at an outrageous rate.

John’s been working on everything from Conilurus to quolls in the central and northern parts of Australia for over 20 years, and he’s got some of the best data around. Without fail, almost every remaining native small mammal population is in decline, even to the point of local extirpation in over 50 % of all his monitoring sites (and there are a lot of monitoring sites).

If that isn’t worrying enough, much of his data are collected in some of our biggest national parks (e.g., Kakadu National Park) – this basically means that despite restricting habitat loss (our greatest driver of extinction), mammal populations are still in ever-increasing states of buggery.

So, what are the causes? Anyone who’s been to Kakadu National Park, or (even luckier) has been to Arnhem Land, know that we’re literally burning the shit out of these places. Sure, fire is an integral part of northern Australian ecology, but the pervasive paradigm – unless-it’s-burnt-every-year-it’s-bad credence – means that nothing ever has a chance to come back after a population crash caused by a one-off fire.

Sure, things like cane toads and other feral animals might play a role, but it’s the ridiculous burning regime we’ve adopted that’s destroying our already depleted and unique mammalian species assemblage. Unless we reverse this trend NOW, we’ll have more or less condemned our one-of-a-kind mammals to extinction. As an Australian, can you live with that?

A stark reminder of how ridiculous the situation has become, esteemed Professor William Bond of South Africa stated in the question period after John’s talk (I paraphrase):

“When you arrive in Australia, you are bombarded with slogans of sporting victories, great food and fantastic wine [all true], but no one tells you of the biodiversity tragedy that has, and is continuing, to happen in Australia. In Africa, we have managed to convince people to conserve elephants that destroy their crops and kill their families – why can’t Australians realise their are destroying their very heritage? What are you doing to stop the carnage?”

I have no answer. Sorry, William. Sorry, John. Sorry, Australia.

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





The rarity of commonness

18 08 2009

I’m attending the 10th International Congress of Ecology (INTECOL) in Brisbane this week and I have just managed to find (a) an internet connection and (b) a small window to write this post.

I have to say I haven’t been to a good plenary talk for some time – maybe it’s just bad luck, but often plenary talks can be less-than-inspiring.

Not so for INTECOL this year. I was very pleased to have the opportunity to listen to biodiversity guru Professor Kevin Gaston of the University of Sheffield give a fantastic talk on… common species (?!).

clones

If you have followed any of Kevin’s work, you’ll know he literally wrote the book on rarity – what species rarity is, how to measure it and what it means for preserving biodiversity as a whole.

Now he’s championing (in a very loose sense) the importance of common species because it is these taxa, he argues, that provide the backbone to the persistence of all biodiversity.

Yes, we conservation biologists have tended to focus on the rare and endemic species to make certain we have as much diversity in species (and genetic material) as possible when conserving habitats.

There are a lot more rare species than common ones, and the most common species (i.e., the ones you most often see) tend to have the broadest distributions. We know from much previous work that having a broad distribution reduces extinction risk, so why should we be concerned about common species?

Kevin made a very good point – if you turn the relationship on its head somewhat, you can state that the state of ‘commonness’ is itself ‘rare’. In fact, only about 25 % of the most common species account for about 90-95 % of ALL individuals. He used an interesting (and scary) example to show what this can mean from an extinction perspective. Although very back-of-the-envelope, there are about 2000 individual birds in a km2 of tropical forest; we are losing between 50000 and 120000 km2 of tropical forest per year, so this translates into the loss of about 100 to 240 million individual birds per year; this is the sum total of all birds in Great Britain (a bird-mad country). Yet where do we have the best information about birds? The UK.

Commonness is also geologically transient, meaning that just because you are a common species at some point in your evolutionary history doesn’t mean you have always been or always will be. In fact, most species never do become common.

But it is just these ‘rare’ common that drive the principal patterns we see globally in community structure. The true ‘rare’ species are, in fact, pretty crap predictors of biodiversity patterns. Kevin made a good point – when you look at a satellite image of a forest, it’s not all the little rare species you see, it’s the 2 or 3 most common tree species that make up the forest. Lose those, and you lose everything else.

Indeed, common species also form most trophic structure (the flow of energy through biological communities). Take away these, and ecosystem function degrades. They also tend to have the highest biomass and provide the structure that supports all those millions of rare species. Being common is quite an important job.

Kevin stated that the world is now in a state where many of the so-called common species are in fact, “artificially” common because of how much we’ve changed the planet. It is these benefactors of our world-destroying machinations that are now in decline themselves, and it is for this reason we should be worried.

When you start to see these bastions of ecosystems start to drop off (and the drop is usually precipitous because we don’t tend to notice their loss until they suddenly disappear), then you know we’re in trouble. And yet, even though once common, few, if any, once-common species have come back after a big decline.

So what does this mean for the way we do biodiversity research? Kevin proposes that we need a lot more good monitoring of these essential common species so that we can understand their structuring roles in the community and more importantly, be able to track their change before ecosystem collapse occurs. The monitoring is crucial – it wasn’t the demise of small companies that signalled the 2007 stock market crash responsible for the Global Financial Crisis in which we now find ourselves, the signal was derived from stock data obtained from just a few large (i.e., ‘common’) companies. All the small companies (‘rare’) ones then followed suit.

A very inspiring, worrying and somewhat controversial talk. Watch out for more things ‘Gaston’ on ConservationBytes.com in the near future.

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





Fragmen borealis: degradation of the world’s last great forest

12 08 2009
© energyportal.eu

© energyportal.eu

I have the dubious pleasure today of introducing a recently published paper of ours that was at the same time both intellectually stimulating and demoralising to write. I will make no apologies for becoming emotionally involved in the scientific issues about which my colleagues and I write (as long as I can maintain with absolute sincerity that the data used and conclusions drawn are as objectively presented as I am capable), and this paper probably epitomises that stance more than most I’ve written during my career.

The topic is especially important to me because of its subtle, yet potentially disastrous consequences for biodiversity and climate change. It’s also a personal issue because it’s happening in a place I used to (many, many years ago) call home.

Despite comprising about a third of the world’s entire forested area and harbouring some of the lowest human densities anywhere, the great boreal forest that stretches across Alaska, Canada, Scandinavia and a huge chunk of Russia is under severe threat.

Surprised that we’re not talking about tropical deforestation for once? Surprised that so-called ‘developed’ nations are pilfering the last great carbon sink and biodiversity haven left on the planet? If you have read any of the posts on this blog, you probably shouldn’t be.

The paper today appeared online in Trends in Ecology and Evolution and is entitled Urgent preservation of boreal carbon stocks and biodiversity (by CJA Bradshaw, IG Warkentin & NS Sodhi). It’s essentially a review of the status of the boreal forest from a biodiversity perspective, and includes a detailed assessment of the degree of its fragmentation, species threat, climate- and human-influenced disturbance regime, and its carbon sequestration/emission status. I’ll summarise some of the main findings below:

borealfire

© NASA

  • Russia contains ~53 % of the boreal forest, followed by Canada (25 %), USA (18 %, mostly in Alaska), Sweden (2 %) and Finland and Norway (~1 % each); there are small areas of boreal forest in northern China and Mongolia.
  • Fire is the main driver of change in the boreal forest. Although clearing for logging and mining abounds, it pales in comparison to the massive driver that is fire.
  • There is evidence that climate change is increasing the frequency and possibly extent of fires in the boreal zone. That said, most fires are started by humans, and this is particularly the case in the largest expanse in Russia (in Russia alone, 7.5 and 14.5 million hectares burnt in 2002 and 2003, respectively).
  • While few countries report an overall change in boreal forest extent, the degree of fragmentation and ‘quality’ is declining – only about 40 % of the total forested area is considered ‘intact’ (defined here as areas ≥ 500 km2, internally undivided by things such as roads, and with linear dimensions ≥ 10 km).
  • Russian boreal forest is the most degraded and least ‘intact’, and has suffered the greatest decline in the last few decades compared to other boreal countries.
  • Boreal countries have only < 10 % of their forests protected from wood exploitation, except Sweden where it’s about 20 %.
  • There are over 20000 species described in the boreal forest – a number much less than that estimated for tropical forests even of much smaller size.
  • 94 % of the 348 IUCN Red Listed boreal species are considered to be threatened with extinction, but other estimates from local assessments compiled together in 2000 (the United Nations’ Temperate and Boreal Forest Resources Assessment) place the percentages of threatened species up to 46 % for some taxa in some countries (e.g., mosses in Sweden). The latter assessment placed the Fennoscandian countries as having the highest proportions of at-risk taxa (ferns, mosses, lichens, vascular plants, butterflies, birds, mammals and ‘other vertebrates’), with Sweden having the highest proportion in almost all categories.
  • Boreal forest ecosystems contain about 30 % of the terrestrial carbon stored on Earth (~ 550 Gigatonnes).
  • © BC Ministry For Range/L. Maclaughlan

    Warmer temperatures have predisposed coniferous forest in western Canada to a severe outbreak of mountain pine beetle (Dendroctonus ponderosae) extending over > 13 M ha. © BC Ministry For Range/L. Maclaughlan

  • Mass insect outbreaks killing millions of trees across the entire boreal region are on the rise.
  • Although considered in the past as a global carbon sink, recent disturbances (e.g., increasing fire and insect outbreak) and refinements of measurement mean that much of the area is probably a carbon source (at least, temporarily).
  • A single insect outbreak in western Canada earlier this decade thought to be the direct result of a warming planet contributed more carbon to the atmosphere than all of that country’s transport industry and fire-caused release combined.
  • Current timber harvest management is inadequately prepared to emulate natural fire regimes and account for shifting fire patterns with climate change.
  • No amount of timber management can offset the damage done by increasing fire – we must manage fire better to have any chance of saving the boreal forest as a carbon sink and biodiversity haven.

Those include the main take-home messages. I invite you to read the paper in full and contact us (the authors) if you have any questions.

CJA Bradshaw

Full reference: Bradshaw, CJA, IG Warkentin, NS Sodhi. 2009. Urgent preservation of boreal carbon stocks and biodiversity. Trends in Ecology and Evolution DOI: 10.1016/j.tree.2009.03.019

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





Continuing saga of the frogs’ legs trade

10 08 2009
© D. Bickford

© M. Auliya

In January we had a flurry of media coverage (see here for examples) about one of our papers that had just come out online in Conservation BiologyEating frogs to extinction (Warkentin et al.). I blogged about the paper then (one of ConservationBytes’ most viewed posts) that described the magnitude of the global trade in amphibian parts for human food. Suffice it to say, it’s colossal.

A couple of months ago, John Henley of the Guardian (UK) rang me to discuss the issue some more for a piece he was doing in that newspaper. The article has just come out (along with a companion blog post), and I can honestly say that it’s the most insightful coverage of the issue by the media I’ve seen yet. Thanks, John, for covering it so well. The article is excellently written, poignant and really gets to the heart of the matter – people just don’t know how bad the frog trade really is for amphibian biodiversity.

Short story – don’t eat any more frogs’ legs (you probably won’t be missing much).

I’ve reproduced John’s article below, but please visit the original here.

Why we shouldn’t eat frogs’ legs

In the cavernous community hall of the Vosges spa town of Vittel, a large and lugubrious man, his small, surprisingly chirpy wife, and 450 other people are sitting down to their evening meal. It’s rather noisy. “Dunno why we do it, really,” shouts the man, whose name is Jacky. “Don’t taste of anything, do they? White. Insipid. If it wasn’t for the sauce it’d be like eating some soft sort of rubber. Just the kind of food an Englishman should like, in fact. Hah.”

Outside, the streets are filled with revellers. A funfair is going full swing. The restaurants along the high street are full, and queues have formed before the stands run by the local football, tennis, basketball, rugby and youth clubs.

All offer the same thing: cuisses de grenouilles à la provencale (with garlic and parsley), cuisses de grenouille à la poulette (egg and cream). Seven euros, or thereabouts, for a paper plateful, with fries. Nine with a beer or a glass of not-very-chilled riesling. The more daring are offering cuisses de grenouilles à la vosgienne, à l’andalouse, à l’ailloli. There’s pizza grenouille, quiche grenouille, tourte grenouille. Omelette de grenouilles aux fines herbes. Souffle, cassolette and gratin de grenouilles.

Everywhere you look, people are nibbling greasily on a grenouille, licking their fingers, spitting out little bones. “Isn’t it just great?” yells Jacky’s diminutive wife, Frederique. “Every year we do this. It’s our tradition. Our tribute to the noble frog.”

This is Vittel’s 37th annual Foire aux Grenouilles. According to Roland Boeuf, the 70-year-old president of the Confrererie de Taste-Cuisses de Grenouilles de Vittel, or (roughly) the Vittel Brotherhood of Frog Thigh Tasters, which has organised the event since its inception, the fair regularly draws upwards of 20,000 gourmet frog aficionados to the town for two days of amphibian-inspired jollities. Between them, they consume anything up to seven tonnes of frogs’ legs.

But there’s a problem. When the fair began, its founder René Clément, resistance hero, restaurateur and last of the great Lorraine frog ranchers, could supply all the necessary amphibians from his lakes 20 miles or so away. Nowadays, none of the frogs are even French.

According to Boeuf, Clément, whose real name was Hofstetter, moved to the area in the early 1950s looking to raise langoustines in the Saone river; the water proved too brackish and he turned to frogs instead. A true Frenchman, his catchphrase, oft-quoted around these parts, was that frogs “are like women. The legs are the best bits”.

Hofstetter/Clément would, says Gisèle Robinet, “provide 150 kg, 200 kg for every fair, all from his lakes and all caught by him”. With her husband Patrick, Robinet runs the Au Pêché Mignon patisserie (tourte aux grenouilles for six, €18; chocolate frogs €13 the dozen) on the Place de Gaulle, across the square from the restaurant Clément used to run, Le Grand Cerf. Now known as Le Galoubet, there’s a plaque commemorating the great frogman outside. “As a child I remember clearly him dismembering and preparing and cleaning his frogs in front of the restaurant,” says Robinet, who sells frog tartlets to gourmet Vitellois throughout the year, but makes a special effort with quiches and croustillants at fair-time. “It’s a big job, you know. Very fiddly. But we were all frog-catchers when I was a kid. Now, of course, that’s not possible any more.”

Boeuf recalls many a profitable frog-hunting expedition in the streams and ponds around Vittel. “One sort, la savatte, you could catch with your bare hands,” he says. “Best time was in spring, when they lay their eggs. They’d gather in their thousands, great wriggling green balls of them. I’ve seen whole streams completely blocked by a mountain of frogs.”

Others, rainettes, would be everywhere at harvest time. Or you could get a square of red fabric and lay it carefully on the water next to a lily pad that happened to have a frog on it, “and she’d just hop straight off and on to the cloth”, Boeuf says. “They love red.”

Pierette Gillet, the longest-standing member of the Brotherhood and, at 81, still a sprightly and committed frog-fancier, remembers heading out at night with a torch in search of so-called mute frogs, harder to catch because they have no larynx and hence emit no croak. “They’d be blinded by the light, and you could whack them over the head,” she says.

But those days are long gone. As elsewhere in the world, the amphibians’ habitat in France – where frogs’ legs have been a recognised and much remarked-upon part of the national diet for the best part of 1,000 years – is increasingly at risk, from pollution, pesticides and other man-made ills. Ponds have been drained and replaced with crops and cattle-troughs. Diseases have taken their toll, and the insects that frogs feed on are disappearing too. Alarmed by a rapid and dramatic fall in frog numbers, the French ministry of agriculture and fisheries began taking measures to protect the country’s species in 1976; by 1980, commercial frog harvesting was banned.

These days, a few regional authorities in France still allow the capture of limited numbers of frogs, strictly for personal consumption and provided they are broiled, fried or barbecued and consumed on the spot (a heresy not even Boeuf is prepared to contemplate). There are poachers who defy the ban; two years ago a court in Vesoul in the Haute-Saone convicted four men of harvesting vast numbers of frogs from the Mille-Etangs or Thousand Lakes area of the Vosges. The ringleader admitted to personally catching at least 10,000, which he sold to restaurants for 32 cents apiece.

By and large, though, France’s tough protection laws, enforceable by fines of up to €10,000 (£8,500) and instant confiscation of vehicles and equipment, seem to be working. As a result, all seven tonnes (officially, at least) of frogs’ legs consumed at this year’s Vittel fair have been imported, pre-prepared, deep-frozen and packed in cardboard boxes, from Indonesia.

Needless to say, this does not much please patriotic Gallic frog-fanciers. “We’d far prefer our frogs to be French, of course we would,” laments Gillet. “Especially here in the Vosges. This really is the heart of frog country.”

A Vittel restaurateur, who for obvious reasons demands anonymity, suggests there are still “ways and means” of securing at least a semi-reliable supply of French frogs for those who demand a true produit du terroir, “but it’s really not very easy, and no one here will tell you anything about it. We’d like to source locally, but the law is the law.”

But the fact that the Foire aux Grenouilles – not to mention the rest of France, and other big frog-consuming nations such as Belgium and the United States – now imports almost all its frogs’ legs has consequences that run deeper than a mere denting of national gastronomic pride. For scientists now believe that, just as with many fish species, we could be well on the way to eating the world’s frogs to extinction. Based on an analysis of UN trade data, researchers think we may now be consuming as many as 1bn wild frogs every year. For already weakened frog populations, that is very bad news indeed.

Scientists have long been aware that while human activity is causing a steady loss of the world’s biodiversity, amphibians seem to be suffering far more severely than any other animal group. It is thought their two-stage life cycle, aquatic and terrestrial, makes them twice as vulnerable to environmental and climate change, and their permeable skins may be more susceptible to toxins than other animals. In recent years, a devastating fungal condition, chytridiomycosis, has caused catastrophic population declines in Australia and the Americas.

“Amphibians are the most threatened animal group; about one third of all amphibian species are now listed as threatened, against 23% of mammals and 12% of birds,” says Corey Bradshaw, an associate professor at the Environment Institute of the University of Adelaide and a member of the team that carried out the research into human frog consumption that was published earlier this year in the journal Conservation Biology. “The principle drivers of extinction, we always assumed, were habitat loss and disease. Human harvesting, we thought, was minor. Then we started digging, and we realised there’s this massive global trade that no one really knows much about. It’s staggering. So as well as destroying where they live, we’re now eating them to death.”

France is the main culprit: according to government figures, while the French still consume 70 tonnes a year of domestically gathered legs each year, they have been shipping in as many as 4,000 tonnes annually since 1995. Besides popular, essentially local events such as the Foire aux Grenouilles, frogs’ legs are mostly a delicacy reserved for restaurants with gastronomic pretensions; one three-star chef, Georges Blanc, has at one time or another developed 19 different recipes for them at his celebrated restaurant in the Ain village of Vonnas, baking and skewering and skilleting them in everything from cream to apples.

Belgium and Luxembourg are also noted connoisseurs, but perhaps surprisingly, the country that runs France closest in the frog import stakes is the US. Frogs’ legs are particularly popular in the former French colony of Louisiana, where the city of Rayne likes to call itself Frog Capital of the World, but are also consumed with relish in Arkansas and Texas, where they are mostly served breaded and deep-fried. Bradshaw has a picture on his blog of President Barack Obama tucking with apparent gusto into a plate of frogs’ legs.

The world’s most avid frog eaters, though, are almost certainly in Asia, in countries such as Indonesia, China, Thailand and Vietnam. South America, too, is a big market. “People may think frogs’ legs are some kind of epicurean delicacy consumed by a handful of French gourmets, but in many developing countries they are a staple,” Bradshaw says.

Indonesia is today the world’s largest exporter of frogs by far, shipping more than 5,000 tonnes each year. Some of these may be farmed, but not many. Commercial frog-farming has been tried in both the US and Europe, but with little success: for a raft of reasons, including the ease with which frogs can fall prey to disease, feeding issues and basic frog biology, it is a notoriously risky and uneconomic business. Frogs are farmed in Asia, but rarely on an industrial scale; most are small, artisan affairs with which rural families try to supplement their income.

The vast majority of frogs that end up on a plate are harvested from the wild. Bradshaw and his colleagues estimate that Indonesia, to take just one exporting country, is probably consuming between two and seven times as many frogs as it sends abroad. “We have the legally recorded, international trade figures, but none of the local business is recorded,” Bradshaw says. “It’s back-of-an-envelope work. That’s what’s so alarming.”

The scientists’ biggest concern, he says, is that because of the almost complete lack of data, no one knows in what proportion different frog species are being taken. If, as they suspect, some 15 or 20 frog species are at any given moment supplying most of world demand, the consequences could be catastrophic. For while overharvesting for human consumption may not in itself be quite enough to drive a frog species to extinction, combined with all the other threats frogs face it certainly could be.

“The thing is, it isn’t a gradual process,” Bradshaw warns. “There’s a threshold, you cross it, and the whole thing crashes because you’ve just completely changed the composition of the whole community. There’s a tipping point. It’s exactly what happened with the overexploitation of cod in the North Atlantic. And with frogs, there’s no data, no tracking, no stock management. We really should have learned our lesson with fish, but it seems we haven’t. This is a wake-up call.”

Back in Vittel, Boeuf says he had no idea frogs were in such trouble. “They’re an endangered species here, I know,” he says. “That’s why we have to be careful, and we are. But if we can buy them in such quantities from Indonesia, surely it must be all right. They’re being careful there too, aren’t they?” Sadly, it would seem they are not. And all for a few greasy scraps of limp, bland flesh.

People say frogs taste like a cross between fish and chicken. In fact, they taste of frog: in other words, precious little bar the sauce they are served in.