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Like Corey, I am mainly interested in current environmental problems. But now and then I wade into the debate over the extinction of Australia’s Pleistocene megafauna [editor's note: Chris literally wrote the book on Australian mammal extinctions over the last 50,000 years], those huge animals that wandered over the Australian landscape until about 40,000 years ago.

This is an endlessly fascinating topic. The creatures were wonderful and bizarre – it’s great fun doing work that lets you think about marsupial lions, giant kangaroos, geese bigger than emus, echidnas the size of wombats, and the rest. The cause of their extinction is perhaps the biggest mystery, and the most vexed controversy, in the environmental history of Australia. And for reasons that I will explain in a minute, solving this mystery is profoundly important for our understanding of contemporary Australian ecology.

The latest bit of work on this is a paper that a group of us (including Corey’s close colleague, Barry Brook) published in Science. You can see it here (if you don’t have access to Science, email me for a copy). So far, research on this problem has concentrated on dating fossils to find out when megafauna species went extinct. Several recent studies have found evidence for extinction between 40,000 and 50,000 years ago, which is about when people first came to Australia. But the conclusion that people caused a mass extinction of megafauna has been strenuously criticised, because so far it is based on only a few species with good collections of dates. The critics argue that other species disappeared before humans arrived, maybe in an extended series of extinctions caused by something else, like a deteriorating climate.

This argument over fossils will be with us for a long time. Because finding and dating fossils is such hard, slow work, the fossil record will inevitably give a seriously incomplete picture of what happened. One way around this problem would be to analyse the fossil record using mathematical approaches that take into account the problem of incomplete sampling. Corey is lead author of a recent paper that introduced a great new set of tools for this, and we are part of a group that is currently assembling a complete database of all recent dates on Australian fossils so that we can analyse them using these tools. Stay tuned for the result.In our recent study we took a different tack, using an ecological proxy that provides a continuous record of the abundance of big herbivores. We looked at Sporormiella, a fungus that produces spores in the dung of herbivores. Big herbivores produce lots of dung and therefore lots of spores, making Sporormiella a neat proxy for the relative abundance of megafauna. We counted spores in swamp sediments at Lynch’s Crater in northeast Queensland, sampling the last 130,000 years of environmental change at the site. Our results show that megafaunal abundance was stable, despite dramatic shifts in climate, until it crashed about 41,000 years ago, which is about when people appeared in the area. We analysed vegetation as well, and found no change in vegetation leading up to, or coinciding with, the megafauna crash. This makes it clear that climate change was not involved, because if climate had caused the extinction it would have transformed the vegetation too.

And this is where it gets really interesting. The vegetation did change at Lynch’s Crater, and fire increased as well, but not until just after the megafauna declined. These events were well known from previous study of the site, but had always been attributed to landscape burning by people. Our results suggest that they are best explained by the removal of megafauna. This did not surprise me, because I have always suspected that Australia’s megafauna had a large impact on vegetation. This is shown by the structure of the plants themselves. Many Australian Acacia, for example, have spines and densely tangled branches that are classic adaptations for defence of leaves against large browsing mammals. Some trees have preposterous growth strategies whereby they maintain this form until they reach a ghost browse line at about three metres above ground, and then adopt a different, non-defensive, leaf and branch structure.

The existence of these traits suggests that browsing by large mammals drove the evolution of Australian plants. For that to be true, big animals must have had strong effects on the fitness of individual plants. If mega-herbivory did that, it must also have shaped the structure of vegetation communities. The sudden removal of big animals by some external factor (like the appearance of people) would therefore cause a major ecosystem shift. That, I argue, is what we’ve described at Lynch’s Crater.

The reason this should matter to ecologists now is that we need to come to terms with the fact that large herbivores were once a major control on Australian environments, but the continent has recently been transformed into a land without very large animals. That loss provides part of the explanation for why Australia environments are they way they are, and it tells us there is no reason to think that environments like Acacia scrublands, that evolved with big herbivores but are now bereft of them, are in a natural or equilibrial state. One unsettling implication of this knowledge is the idea that, if important interactions between Australian plants and animals were lost with megafaunal extinction, we might be justified in introducing alien species to reinstate those interactions.

This would be a radical and almost heretical proposition if it had not already happened. Europeans have introduced many large mammalian herbivores that have become well-established as wild species in Australia. Some of them seem to make a poor fit with Australian environments, but in other cases that is not quite so clear. For example, one large chunk of the megafauna was made up of large, dry-country kangaroos that browsed on the tough leaves of shrubs and small trees. That ecological role disappeared when those kangaroos went extinct, but it may have been partly re-taken by goats and camels.

While there is no doubt that both species do environmental harm when they are over-abundant, they are also capable of providing environmental benefits, for example by controlling woody weeds. At the Ecological Society of Australia conference in Hobart in December 2011, the central Australian botanist Peter Latz gave a talk arguing that Acacia woodlands were in a healthier condition when browsed by camels than when not. But at present, Australian ecologists and conservation managers see goats and camels only as destructive pests, and would eradicate them if they could. That can’t be done, so the goal of management is usually to reduce their population densities as far as possible.

I suggest that we might manage Australian environments better if we took the long history of large herbivores in Australia to heart [editor's note: a proposition analogous to our ideas about letting dingos do the feral management for us], and re-evaluated the ecological potential of invasive large herbivores. The key to this new thinking would be to estimate, for species like goats and camels, the population densities at which they bring more environmental benefit than harm, then aim to manage populations to hold them close to those densities. I suspect this would be a for more achievable proposition than current pest control operations, because it might often be that the densities at which those species provide ecological benefit are not far below the high densities that result in clear environmental damage. It’s a fine balance and will require a lot of work to ascertain, but it’s probably better than the ad hoc way we manage these species now.

Chris Johnson

© D. Bathory

I’ve just spent the last week at beautiful Linnaeus Estate on the northern NSW coast for my third Australian Centre for Ecological Analysis and Synthesis (ACEAS) (see previous post about my last ACEAS workshop).

This workshop is a little different to my last one, and I’m merely a participant (not the organiser) this time. Alan Cooper and members of his Australian Centre for Ancient DNA (Jeremy Austin, Vicki Thomson & Julien Soubrier) combined forces this week with Craig Mortiz, Margaret Byrne, Steve Donnellan, Tania Laity, Leo Joseph, Xander Xue and Gabriele Cybis. Our task was to examine the mounting evidence that many Australian species appear to show a rather shallow genetic pool from a (or several) major past bottlenecks.

What’s a ‘bottleneck’? In reference to the form after which it was named, a genetic bottleneck is the genetic diversity aftermath after a population declines to a small size and then later expands. The history of this reduction and subsequent expansion is written in the DNA, because inevitably gene ‘types’ are lost as most individuals shuffle off this mortal coil. In a way, it’s like losing a large population of people who all speak different languages – inevitably, you’d lose entire languages and the recovering population would grow out of a reduced ‘pool’ of languages, resulting in fewer overall surviving languages.

Our workshop focus started, as many scientific endeavours do, rather serendipitously. Several years ago, Jeremy Austin noticed that devils who had died out on the mainland several thousand years ago had a very low genetic diversity, as do modern-day devils surviving in Tasmania. He thought it was odd because they should have had more on the mainland given that was their principal distribution prior to Europeans arriving. He mentioned this in passing to Steve Donnellan one day and Steve announced that he had seem the same pattern in echidnas. Now, echidnas cover most of Australia’s surface, so that was equally odd. Then they decided to look at another widespread species – tiger snakes, emus, etc. – and found in many of them, the same patterns were there.

How could such widespread, non-threatened and apparently healthy populations all (or at least, mostly) have such low genetic diversity? Answer: something big and bad happened in the relatively recent history of Australia.

What could that big, bad event be? A likely candidate is the last glacial maximum (LGM) between 28 and 15 thousand years ago (i.e., the ‘Ice Age’) when Australia became a dry, cold place (but with very little ice – this is not the Northern Hemisphere). Temperatures dropped by about 10 degrees C on average, and this dry country became substantially drier. Many things would have likely perished.

Of course, it’s more complicated than just this, but there seems to be a general pattern that during (and perhaps before) the LGM, many now-widespread Australian species retracted to very small population ‘refugia’, and then subsequently respread to occupy their former distributions. We’re currently working out WHO showed this pattern, WHEN it likely happened (based on how so-called ‘molecular clocks’ that tell us how far back in time lineages were lost) and WHERE the refugia were.

One pattern that seems to have some evidence is that south-west Western Australia was a site of many refugia. We’re currently trying to get our heads around why.

The reason this work is so important is that it demonstrates that even our widespread, apparently ‘healthy’ species might actually be in a lot more trouble than anyone has previously thought. We currently rush to save the rare and declining species, but what do we do about the widespread, but genetically depauperate ones? I don’t think Australians would swallow threat-listing emus, echidnas and tiger snakes, but we might have to consider how to legislate their poor conservation status from the genetic perspective.

Before I leave this unfinished business, I want again to extol the virtues of the venue itself. I’ve blogged before about Linnaeus Estate, but every time I come here I become more impressed. In a nutshell, Linnaeus is a group of long-term thinkers how want to save a beautiful, highly biodiverse section of coastline from the urban devastation to the north (Gold Coast) and south (everything from Sydney to Grafton). They do this by applying conservation convenants to land that must be held within families (intergenerational covenants) for at least 150 years. With the ugly sprawl of the east coast claiming more and more native habitats each year, we really need more like-minded endeavours.

Well done, Linnaeus Estate trustees, and thanks for hosting us during a terrific week of well-pampered science!

CJA Bradshaw

Filed under: Allee effect, Australia, biodiversity, climate change, conservation, decline, genetic diversity, genetics, inbreeding depression, threatened species ]]> http://conservationbytes.com/2012/05/25/ghosts-of-bottlenecks-past/feed/ 0 -34.917731 138.603034 -34.917731 138.603034 CJAB http://conservationbytes.com/2012/05/18/can-australia-afford-the-dingo-fence/ http://conservationbytes.com/2012/05/18/can-australia-afford-the-dingo-fence/#comments Fri, 18 May 2012 00:50:44 +0000 CJAB http://conservationbytes.com/?p=7167 ]]> I wrote this last night with Euan Ritchie of Deakin University in response to some pretty shoddy journalism that misrepresented my comments (and Euan’s work). Our article appeared first in The Conversation this morning (see original article).

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We feel we have to set the record straight after some of our (Bradshaw’s) comments were taken grossly out of context, or not considered at all (Ritchie’s). A bubbling kerfuffle in the media over the last week compels us to establish some facts about dingoes in Australia, and more importantly, about how we as a nation choose to manage them.

A small article in the News Ltd. Adelaide Advertiser appeared on 11 May in which one of us (Bradshaw) was quoted as advocating the removal of the dingo fence because it was not “cost effective” (sic). Despite nearly 20 minutes on the telephone explaining to the paper the complexities of feral animal management, the role of dingoes in suppressing feral predators, and the “costs” associated with biodiversity enhancement and feral control, there wasn’t a single mention of any of this background or justification.

Another News Ltd. article denouncing Ritchie’s work on the role of predators in Australian ecosystems appeared in The Weekly Times the day before, to which Ritchie responded in full.

So it’s damage control, and mainly because we want to state categorically that our opinion is ours alone, and not that of our respective universities, schools, institutes or even Biosecurity SA (which some have claimed or insinuated, falsely, that we represent). Biosecurity SA is responsible for, inter alia, the dingo fence in South Australia. Although our opinions differ on its role, we are deeply impressed, grateful and supportive of their work in defending us from biological problems.

It is probably surprising to most Australians that introduced species (and the mismanagement thereof) in this country have devastated many elements of our native ecosystems. With over 20 million pigs, 18 million cats, 7 million foxes, 2 million goats, 1 million camels, 300,000 swamp buffalo, 200,000 deer (from six species) and millions of rabbits, our native biodiversity has suffered immensely. Indeed, Australia has the worst record for mammal extinctions in the world, mainly due to foxes and cats.

Furthermore, pigs, camels, buffalo and goats have heavily damaged millions of square kilometres of outback Australia. Even in northern Australia, where deforestation has been relatively light compared to the south, native animals are on the decline in part from introduced species. And guess what? We are no closer to controlling them now than anytime in our past.

So why do we invest billions of dollars in feral animal control and the subsequent recovery plans for endangered wildlife using the same techniques for decades, when a more proactive and natural alternative exists? It’s a solution mired in controversy because it involves yet another “introduced” predator – the dingo.

The dingo has long evoked fear and loathing in the hearts of Australians. Ever since we learnt that it was introduced around 4000 years ago by Southeast Asian visitors to our northern shores, we have developed an irrational opinion that this sheep-killing, baby-stealing, thylacine- and devil-displacing feral from Asia is a menace that should be eradicated at all costs.

But when you look at the evidence, you are compelled to question that image. Despite some high-profile incidences of attacks on humans, they are perhaps one of the least-dangerous species to humans in Australia. The entirely coincidental disappearance of thylacines (Tasmanian tigers) and devils from mainland Australia when the dingo appeared also ignores that the climate was changing and Aboriginal populations began booming at the same time.

So, what did we do? We built a fence, of course! Over 5500 km long and possibly the world’s longest human-built structure, the dingo fence is a monument to predator xenophobia. Its role is controversial, because while it certainly has prevented an influx of a large number of dingoes into southern and eastern Australia, it has also seen a proliferation of competing native (kangaroos) and non-native (rabbits) herbivores where dingoes are absent or in low abundance.

While the roughly $10 million it costs each year to maintain the fence is lower than the cited $48 million per year pastoralists claim to lose to “wild dogs”, these costs don’t include the labour-intensive and expensive additional poisoning that accompanies the fencing. And poisoning is not the answer either. In addition to killing non-target native species, baiting dingoes might in fact result in increased dingo densities due to social breakdown of the pack, resulting in increasing attacks on stock, not to mention a higher likelihood of hybridisation with feral dogs. Baiting also leads to more juvenile dingoes. These less-efficient predators tend to target calves more than adult dingoes do.

And of course the “costs” also don’t include the unquantifiable costs to our biodiversity. How many millions per year do we spend on native species recovery, and how many billions are lost from depleted ecosystem services?

There’s also the issue of the fence’s effectiveness – today dingoes are penetrating farther and farther south due to camel damage to the fence itself, and other weaker areas where dingoes can penetrate.

It turns out that the dingo is in fact a sorely under-utilised weapon in our feral-animal arsenal. Pretty much everywhere we’ve looked across Australia, when dingoes are abundant, foxes and cats aren’t, and native marsupials are. It’s called the “mesopredator” effect, and highlights the important role of predators in maintaining healthy ecosystems.

There are other advantages to dingoes that might not seem obvious. Dingoes reduce herbivore densities and this can reduce the effects of climate change-induced drought by increasing available plant cover. Dingoes can also benefit graziers by providing more vegetation to produce stronger, healthier cattle that can resist attack (indeed, dingoes prefer more passive prey such as kangaroos).

Unfortunately, most pest management in Australia lacks an integrated approach. We remove foxes, and cats increase; we remove cats, and rabbits increase. We remove dingoes, and we have more herbivore competition problems. This inefficient hopping from one single-species crisis to the next is, we argue, a waste of money and time. It lacks a long-term vision.

We need to recognise that species interact along complex pathways, and so the entire system should be managed as a whole (indeed, integrated pest management is advocated in many areas by our own government biosecurity experts). Worldwide, the release of mesopredators after the persecution of higher-order predators is now demonstrating many adverse consequences for biodiversity and economics, from sharks, rays and scallops in the Gulf of Mexico, from lynx, foxes and hares in Finland, from coyotes, cats and birds in America, to our own dingo-cat-fox-marsupial problem.

So with too many herbivores, too many mesopredator foxes and cats, and costly management, why don’t we let the dingoes do the work for us? If we focus on ecological function, then dubious labels of good/bad or native/feral become irrelevant. The loss of mainland predators such as devils, thylacines and marsupial lions means that the dingo is our one last hope to restore some ecological balance to our country’s highly disrupted ecosystem. Indeed, the solution is readily available and staring us in the face, if only we had the courage to employ it.

It is interesting that the Weekly Times held a poll asking readers to vote “yes” or “no” to the reintroduction of devils and dingoes to manage pest species; just before the poll closed, nearly 80 % had said “yes”. Clearly, sectors of the Australian community are receptive, including many pastoralists.

Of course, stock losses will always remain a concern, because sheep and dingoes will never co-exist in harmony. However, advances in trialling guardian dogs show immense promise in this regard, even for remote and large stock populations. Indeed, guardian dogs have even been successful in Namibia to protect stock from leopards.

We should shift our investment in pest control: let’s help graziers trial new and more effective solutions. The process will be slow and guarded, but we should be focussing on long-term solutions, instead of costly, questionably effective and ecologically myopic single-species interventions. In light of these arguments, each Australian should ask the question: is the dingo fence worth it?

This article was originally published at The Conversation.
Read the original article.

CJA Bradshaw & Euan Ritchie

Let me explain.

As a person who cut his teeth in field ecology (with all the associated dirt, dangers, bites, stings, discomfort, thrills, headaches and disasters), I’ve had my fair share of fun and excitement collecting ecological data. There’s something quaintly Victorian (no, I am not referring to the state next door) about the romantic and obsessive naturalist collecting data to the exclusion of nearly all other aspects of civilised life; the intrepid adventurer in some of us takes over (likely influenced by the likes of David Attenborough) and we convince ourselves that our quest for the lonely datum will heal all of the Earth’s ailments.

Bollocks.

As I’ve matured in ecology and embraced its mathematical complexity and beauty, the recurring dilemma is that there are never enough data to answer the really big questions. We have sampled only a fraction of extant species, we know embarrassingly little about how ecosystems respond to disturbance, and we know next to nothing about the complexities of ecosystem services. And let’s not forget our infancy in understanding the synergies of extinctions in the past and projections into the future. Multiply this uncertainty by several orders of magnitude for ocean ecosystems.

The upshot is that ecologists have been searching for proxies and indicators of biodiversity patterns and processes, with the ultimate aim of being able to predict dynamics (at least at broad spatial scales) from decidedly non-biological features. A case in point is one that I’m most familiar with – the use of ‘surrogates’ in marine ecology – that is, using a species/taxon to predict the distribution of many more species. We have also done some work to predict coral reef fish diversity using little more than the position of the reef (latitude and distance to shore), and we have inferred inherent susceptibility to extinction using nothing more than the shape and isolation of reefs.

I even remember once that Hugh Possingham wished out loud at a conference that he hoped we’d never have to collect a species again if we got our maths right. That might be a little far-fetched, but it gets at my main point.

So the theme of this post introduces a new-ish paper that my productive post-doc, Dr. Camille Mellin, has recently written in Ecological Applications entitled Multi-scale marine biodiversity patterns inferred efficiently from habitat image processing. Here the idea is fairly simple – by taking a photo of an area where animals hang out, you can estimate how many different types there are (diversity).

Using a multi-scale dataset of images taken of the Great Barrier Reef – from the scale of a single transect to satellite images of multiple reefs – we measured the amount of ‘complexity’ in the photo using something called the ‘mean information gain’. After accounting for spatial non-independence, it turns out that we could explain up to 29 % of the variance in fish species richness, 33 % in total fish abundance, and 25 % in fish community structure at multiple scales.

Now, this might not seem like a lot to some, but take it from me, it is a remarkably high predictive ability for most ecological studies. And all from merely taking a photograph? I’m not suggesting (as the title of this post implies) that we need to abandon all ecological sampling studies, but we should be constructing ever-more-efficient ways to estimate biodiversity patterns and processes using such short-cuts. They’re less time-consuming, more cost-effective and potentially cover areas that are difficult or impossible to sample directly.

Oh, and before I leave this one – I’m foreshadowing a great example of data proxies for inferring the effectiveness of tropical nature reserves; this is a manuscript currently in review in a very high-profile journal (lead by Bill Laurance), and I hope to have some good news about it soon.

CJA Bradshaw

Today’s post comes from Salvador Herrando-Pérez (who, incidentally, recently submitted his excellent PhD thesis).

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Three species co-occurring in the Gulf of Mexico and involved in the trophic cascade examined by Myers et al. (8). [1] Black-tips (Carcharhinus limbatus) are pelagic sharks in warm and tropical waters worldwide; they reach < 3 m in length, 125 kg in weight, with a maximum longevity in the wild of ~ 12 years; a viviparous species, with females delivering up to 10 offspring per parturition. [2] The cownose ray (Rhinoptera bonasus) is a tropical species from the western Atlantic (USA to Brazil); up to 2 m wide, 50 kg in weight, and 18 years of age; gregarious, migratory and viviparous, with one single offspring per litter. [3] The bay scallop (Agropecten irradians) is a protandric (hermaphrodite) mollusc, with sperm being released a few days before the (> 1 million) eggs; commonly associated with seagrasses in the north-western Atlantic; shells can reach up to 10 cm and individuals live for < 2 years. In the photos, a black-tip angled in a bottom long-line off Alabama (USA), a school of cownose rays swimming along Fort Walton Beach (Florida, USA), and a bay scallop among fronds of turtle grass (Thalassia testudinum) off Hernando County (Florida, USA). Photos by Marcus Drymon, Dorothy Birch and Janessa Cobb, respectively.

The hips of John Travolta, the sword of Luke Skywalker, and the teeth of Jaws marked an era. I still get goose pimples with the movie soundtrack (bass, tuba, orchestra… silence) solemnizing each of the big shark’s attacks. The media and cinema have created the myth of man’s worst friend. This partly explains why shark fishing does not trigger the same societal rejection as the hunting of other colossuses such as whales or elephants. Some authors contend that we currently live in the sixth massive extinction event of planet Earth (1) 75 % of which is strongly driven by one species, humans, and characterized by the systematic disappearance of mega-animals in general (e.g., mammoths, Steller’s seacow), and predators in particular, e.g., sharks (2, 3).

The selective extirpation of apex predators, recently coined as ‘trophic downgrading’, is transforming habitat structure and species composition of many ecosystems worldwide (4). In the marine realm, over the last half a century, the main target of the world’s fisheries has turned from (oft-large body-sized) piscivorous to planctivorous fish and invertebrates, indicating that fishery fleets are exploiting a trophic level down to collapse, then harvesting the next lower trophic level (5-7).

Myers et al. (8) illustrate the problem with the fisheries of apex-predator sharks in the northeastern coast of the USA. Those Atlantic waters are rife with many species of shark (> 2 m), whose main prey are smaller chondrichthyans (skates, rays, catsharks, sharks), which in turn prey on bottom fishes and bivalves. Myers et al. (8) found that, over the last three decades, the abundance of seven species of large sharks declined by ~ 90 %, coinciding with the crash of a centenary fishery of bay scallops (Agropecten irradians). Conversely, the abundance of 12 smaller chondrichthyes increased dramatically over the same period of time. In particular, the cownose ray (Rhinoptera bonasus), the principal predator of bay scallops, might today exceed > 40 million individuals in some bays, and consume up to ~ 840,000 tonnes of scallops annually. The obvious hypothesis is that the reduction of apex sharks triggers the boom of small chondrichthyans, hence leading to the break-down of scallop stocks.

Trophic cascade linked to overfishing of large sharks in the Northeastern coast of USA (8). Graphs show catches of blacktip shark (blue, Carcharhinus limbatus) and bay scallop (red, Agropecten irradians), and censuses of cownose ray (grey, Rhinoptera bonasus) between 1970 and 2004. Relative abundances are standardized to a maximum of 1. In this trophic chain, sharks eat rays, and rays eat scallops. As can be seen, extirpation of sharks has occurred gradually as rays thrived and scallop catches plummeted. Those trends are supported across the assemblage of chondrichthyans in the region (8), while heavy ray predation on scallops has been demonstrated experimentally (17).

Eating and being eaten

Trophic downgrading is an example of a trophic cascade. In simple terms, a trophic cascade represents a predator-prey (or parasite-host) relationship, the balance of which affects the abundance, biomass or productivity of a third species (9). Thus, fish species in a freshwater lake might enhance local pollination of  terrestrial plants if, by feeding on aquatic larvae of dragonfly, diminish the abundance of adults of dragonfly that forage on pollinating bees (10).

Trophic cascades can originate from human action (e.g., trophic downgrading), natural factors, or both. Thus, at the beginning of last century, overhunting of Alaskan sea otters (Enhydra lutris) brought the species to the brink of extinction, but provoked the explosion of their preferred prey, sea urchins, which devoured kelp forests. Subsequently, kelp forests recovered after several decades of otter protection (11). Now some authors suggest that killer whale (Orcinus orca) predation on sea otters might jeopardize kelp forests again (12-14).

Most importantly, trophic cascades result not only from direct mortality of prey species, but due to change in prey behaviour avoiding their enemies (15). In Australia, tiger sharks (Galeocerdo cuvier) can shape local distribution and abundance of seagrass beds, because dugongs (Dugong dugon) avoid the lush shallow-water seagrass, in favour of deeper waters with less food, yet lower risk of shark encounters (16).

Globally, trophic cascades brought about by extirpation or introduction of predators or megaherbivores promote or exacerbate a range of severe, long-term environmental impacts such as wild fires, invasion of foreign species, disease bouts, CO₂ emissions, water hypoxia or impoverishment of species richness (4). Those outcomes manifest the complexity of trophic chains, and the need to account for species’ ecological functions in our (largely failed) endeavour of regulating our encroachments on nature and ecosystem services.

References

1. D. B. Wake, V. T. Vredenburg, Proc. Natl. Acad. Sci. USA 105, 11466 (2008)
2. J. K. Baum et al., Science 299, 389 (2003)
3. F. Ferretti, R. A. Myers, F. Serena, H. K. Lotze, Conserv. Biol. 22, 952 (2008)
4. J. A. Estes et al., Science 333, 301 (2011)
5. B. Bhathal, D. Pauly, Fish. Res. 91, 26 (2008)
6. D. Pauly, V. Christensen, J. Dalsgaard, R. Froese, F. Torres, Science 279, 860 (1998)
7. T. E. Essington, A. H. Beaudreau, J. Wiedenmann, Proc. Natl. Acad. Sci. USA 103, 3171 (2006)
8. R. A. Myers, J. K. Baum, T. D. Shepherd, S. P. Powers, C. H. Peterson, Science 315, 1846 (2007)
9. M. L. Pace, J. J. Cole, S. R. Carpenter, J. F. Kitchell, Trends Ecol. Evol. 14, 483 (1999)
10. T. M. Knight, M. W. McCoy, J. M. Chase, K. A. McCoy, R. D. Holt, Nature 437, 880 (2005)
11. J. A. Estes, D. O. Duggins, Ecol. Monog. 65, 75 (1995)
12. M. Schrope, Nature 445, 703 (2007)
13. A. M. Springer et al., Proc. Natl. Acad. Sci. USA 100, 12223 (2003)
14. A. M. Springer et al., Mar. Mamm. Sci. 24, 414 (2008)
15. M. R. Heithaus, A. Frid, A. J. Wirsing, B. Worm, Trends Ecol. Evol. 23, 202 (2008)
16. A. J. Wirsing, M. R. Heithaus, L. M. Dill, Oecologia 153, 1031 (2007)
17. C. Peterson, J. Fodrie, H. Summerson, S. Powers, Oecologia 129, 349 (2001)

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Almost everything we own – our houses and cars and our very health – is insured. It works on a simple principal: the higher the risk, the higher the premium. It’s an age-old concept that ecological modelers have decided to apply to a new area: forest preservation.

A new proposal, published in the journal Conservation Letters, would create forest insurance to make the U.N. forest preservation program Reduced Emissions from Deforestation and forest Degradation, or REDD, more effective. REDD is generally supposed to function by paying developing countries to protect their forests in exchange for carbon pollution credits. Currently the program has 42 partner countries across the globe. The program is crucial to the fight against climate change since deforestation and forest degradation accounts for about 20 percent of global greenhouse gas emissions and threatens biodiversity.

“REDD is a fantastic idea,” said Corey Bradshaw, director of ecological modeling at the University of Adelaide and co-author of the study. “You get a carbon advantage and biodiversity doesn’t get wiped out at the same time, it seems perfect.”

But it has a few major flaws that the insurance scheme, called iREDD, seeks to remedy.

REDD only works if the parties are honest and stick to the agreement. Bradshaw doesn’t have much faith that will happen. “If there’s a way to cheat, people will cheat. That’s the nature of all life, not just humans, but we excel at it,” he said. If, for example, a country is paid to conserve one forest but moves its deforestation efforts to an adjacent forest in order to get both money and timber, in terms of carbon offsets, that transaction was a failure. This phenomenon is called “leakage.”

Carbon-capture also only works if it’s maintained indefinitely. If a country accepts money for ten years and then cuts its forest the day after the agreement expires, then all of that conservation was for naught. This issue is called “permanence,” usually translated into an arbitrarily defined period of time set by countries in terms of decades or centuries.

Finally, there is the concept of additionality: there is no point in paying to protect forests that aren’t in danger of being cut. Bradshaw calls leakage, permanence and additionality, the “unholy trinity” of REDD.

In order to stifle the temptation to cheat, Bradshaw and his colleagues proposed translating ecosystem services (hard-to-quantify but impossible-to-live-without benefits like the water cycle, pollination and forest carbon capture and storage) into a format that the market could understand: the insurance industry. “This polices the system through a financial mechanism,” Bradshaw explained. “People have an incentive to do the right thing because they get more money at the end.”

How would such a system work?

Individual contractual agreements must be drafted between the buyer, or the party interested in carbon credits, and the seller, or the forest manager. The researchers propose setting a premium based on an assessment of risk. To quantify this, an outside broker would use a Likert scale to assess an area’s governmental reputation, management capabilities, monetary resources, community endorsement, and political buy-in. Once the risk ranking has been made, then a certain amount of the invested cash – generally no more than one-third – is used to purchase an insurance policy that scales to that agreed-upon risk, Bradshaw explains in his blog, Conservation Bytes. The amount is put into an insurance account, which collects interest over the project’s duration.

If the forest managers meet the agreed upon conservation goal — including monitoring to make sure there is no leakage and maintaining the project over the agreed upon permanence scale—at the end of the contract, the seller gets all the money from the insurance premium plus the interest gathered. (Even if a contract was set for 100 years, a decadal pay scheme could be set).

If, on the other hand, the forest managers violate the contract and clear-cut parts of the forest anyway, the sellers could be charged or the buyers could pull out and get all of their money back plus the premium.

If this system worked, it would provide a means to sequester more carbon to offset increasing anthropogenic emissions. The potential interested parties are extensive, including companies, countries, forest ministries, governmental departments, individuals and agencies like USAID. “This won’t completely solve the problem, but it would put dent in the way emissions are tracking,” Bradshaw said. “It’s just one of the many things we have to do to get our heads around climate change and do something about it.”

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Rachel Nuwer is a science journalist who writes for venues including the New York Times, ScienceNOW and Audubon Magazine. She lives in Brooklyn, New York. She tweets @RachelNuwer

Here’s a little video production The Environment Institute put together that explains some of our lab‘s work and future directions.

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CJA Bradshaw

Some of you might be aware that the Australian Commonwealth Government has just released its Draft National Wildlife Corridors Plan for public comment, but many of you might not really know what a ‘corridor’ constitutes.

Wildlife or biodiversity ‘corridors’ have been around for a long time, at least in terms of proposals. The idea is fairly simple to conceive, but very difficult to implement in practice.

At least for as long as I’ve been in the conservation biology biz, ‘corridors’ have been proffered as one really good way to make broad-scale landscape restoration plausible and effective for (mainly) forest-dwelling species which have copped the worst of deforestation trends around Australia and the world. The idea is that because of intense habitat fragmentation, isolated patches of primary (or at least, reasonably intact secondary) forest can be linked by planting some sort of long corridor of similar habitat between them. Then, all the little creatures can merrily make their way back and forth between the patches, thus rescuing each other from extinction via migration.

This appeals to a lot of people because it doesn’t necessarily require vast tracks of public or private land (makes the farmers happy, makes the urban sprawlers happy, keeps the greenies happy because it looks good for conservation, keeps the politicians happy because they don’t have to wade in and make unpopular decisions). Or at least, that’s the idea.

As it turns out, ‘connectivity’ per se between habitat patches is probably not quite as important as we once believed for population persistence. I’ve blogged before about several papers that have over-turned the ‘connectivity paradigm’ through experimental manipulation of microcosms (mini ecosystems), and coincidentally, I found another by Mike Bull & colleagues that just came out today in Austral Ecology showing that roadside vegetation corridors did little to explain variation in reptile abundance.

Why might this be the case? Many, many papers (including many of my own) now identify that population size and habitat quality are far more important for population persistence than connectivity per se. While we have also identified that isolated and small populations are more temporally variable (and hence, more prone to extinction), it seems like the evidence is mounting that just ensuring some degree of connectivity doesn’t really do what many think it should do in terms of reducing extinction risk.

So, what are the alternatives? Well, I still think connectivity needs to be endorsed to reduce overall fragmentation, but it must be done smartly and guided by the evidence-based principles of extinction biology. As mentioned above, the most important driver of extinction risk is population size, and as overall habitat area is increased, so too does population size. Thus, a thin thread of a corridor attaching fragments is insufficient – we should view these ‘corridors’ instead as patches themselves, with the aim to maximise their size (i.e., total area) instead of their connectivity enhancement per se. Think a big, fat chunk of restored habitat rather than a thin line of vegetation.

I’ve more or less indicated this to the Corridors Plan people in my submission, and I had the opportunity to meet with the committee a few weeks ago in Adelaide to reiterate my recommendations. Despite all the uncertainty about the true conservation effectiveness of wildlife corridors, we do know for certain that more area is better. Let’s at least follow this one principle.

CJA Bradshaw

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

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

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

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

Thus, there are three unquestionable facts regarding species conservation:

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

One of the modern debates among conservationists pivots around how to use resources efficiently^3-6. Schneider and colleagues⁷ have dealt with this question for woodland caribou (Rangifer tarandus) in Canada. A total of 18 populations of this ungulate persist in the Canadian province of Alberta, all undergoing demographic declines due to mining extractions (oil, gas and bitumen), logging and wolf predation. The species is listed as ‘threatened’ regionally and nationally. The Alberta Caribou Recovery Plan (2004-2014) is attempting to protect all herds. Under such a framework, Schneider et al.⁷ predicted that woodland caribou would be regionally extirpated in less than a century.

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

–Figure 1. Estimated budgets to protect 12 of the 18 woodland caribou herds in Alberta (Canada)7. In the graph, herds are ordered (left to right) from (current) increasing threat (estimated as time until herd size is < 10 individuals given current population size and decline rates). Bar height is proportional to the magnitude of investment needed to avoid population extirpation (bar tops show investment amounts in millions of Canadians dollars [M$], and investment periods in years). Conservation measures include forest restoration (bar subsection = M$), habitat protection with zero exploitation of natural resources (100xM$), and wolf control (M$). For instance, Cold Lake (CL) and Athabasca River East (ESAR) herds are among the most threatened populations and require considerable costs for 36 years; Richardson (RICH) and Athabasca River West (WSAR) herds could be recovered in 25-27 years at a relatively high price; and A la Peche (ALP) and Redrock-Prairie Creek (RRPC) herds would be viable in 7-21 years with minimal cost. The observed differences reflect contrasting fertility/survival rates, spatial distributions, and industrial developments across herds and habitat ranges. By applying principles of triage, managers would establish a sequence of herd-by-herd investment to maximize the total number of viable herds in the future. This is not to say that triage is infallibly objective, because it relies on heavy computation, numerous assumptions, and multiple predictors. Thus, Wasser et al.19 have used resource-selection models to show that wolves might target mainly deer to the east of Athabasca River where Schneider et al.7 considered wolf culling to alleviate predation on caribou; further caveats address assumptions and methods to calculate population growth rates20-22.–

‘Triage’ means to classify cases by order of treatment given finite resources⁹. This French concept originated in emergency medicine (e.g., during wars, environmental catastrophes, etc.), in situations where shortage of resources prevents everybody’s treatment, each wounded individual requires immediate care, and the probability of survival (according to lesion severity and therapy complexity) varies among individuals.

Let’s imagine that the war-wounded soldiers and civilians are caribou populations, or species sharing forests and savannas with rhinos, or habitats and countries for which WWF scrutinises its funding. Triage in medicine and conservation biology are similar in that both aim to maximise the number of survivors. Nevertheless, in a situation of emergency, medical triage would mean not treating a moribund individual in the first place if the resources at hand could compromise the survival of other individuals, whereas in conservation biology moribund populations/species/habitats often attract the majority of funding^10,11.

Those who defend the application of triage schemes in conservation biology argue that to protect all biodiversity is impossible, that prediction of management costs and protection success rates should determine what to conserve (e.g., ^12,13), and that relative evidence for different extinction/viability scenarios could motivate further funding from governments and sponsors¹⁴. Those who object to triage qualify it as defeatist and immoral because the sacrifice of some components of biodiversity is proposed as a conservation strategy, which could arm unscrupulous politicians and business people against investment to prevent extinctions (e.g., allowing eradication of large predators blamed for cattle kills), and because it ignores the science underlying conservation efforts that make the most progress (arguably) when confronted with imminent extinctions^15,16.

The ongoing controversy juggles ethical and financial matters. An alien visiting the Earth (and equipped with more common sense [“sound and prudent judgment based on a simple perception of the situation or facts”] than the human race) would find it astonishing that the countries which rule the world’s economy invest less on protecting the planet than on destroying it (armament), or searching for new planets (astronautics). Let alone the surmounting evidence that biodiversity and habitat losses ruin ecosystem services (pollination, fisheries, carbon sequestration, etc.) that are vital for human survival, and that well-planned conservation programs can yield nothing but outstanding revenues¹⁷

So the protection of (perhaps most of) all biodiversity is technically possible at a reasonable price (e.g., ¹⁸), but certainly sounds chimerical given the dominating political status quo of indefinite economic growth which, in practice, still externalizes the monetary value of biodiversity. In the short-term, environmental managers faced with limited resources already do practice triage routinely, even if implicitly and intuitively (like protecting what is most threatened). Therefore, the explicit incorporation of triage strategies in environmental policy  and management has the valuable virtue of converting conservation planning to a quantifiable (and potentially more objective) process.

Salvador Herrando-Pérez

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References

1. Butchart, S. H. M. et al. Global biodiversity: indicators of recent declines. Science 328, 1164-1168, doi:10.1126/science.1187512 (2010)
2. Stokstad, E. Despite progress, biodiversity declines. Science 329, 1272-1273, doi:10.1126/science.329.5997.1272 (2010)
3. Parr, M. J. et al. Why we should aim for zero extinction. Trends Ecol Evol 24, 181-181, doi:10.1016/j.tree.2009.01.001 (2009)
4. Marris, E. What to let go. Nature 450, 152-155, doi:10.1038/450152a (2007)
5. Jachowski, D. S. & Kesler, D. C. Allowing extinction: should we let species go? Trends Ecol Evol 24, 180-180, doi:10.1016/j.tree.2008.11.006 (2009)
6. Bottrill, M. C. et al. Finite conservation funds mean triage is unavoidable. Trends Ecol Evol 24, 183-184, doi:10.1016/j.tree.2008.11.007 (2009)
7. Schneider, R. R., Hauer, G., Adarnowicz, W. L. & Boutin, S. Triage for conserving populations of threatened species: The case of woodland caribou in Alberta. Biol Conserv 143, 1603-1611, doi:10.1016/j.biocon.2010.04.002 (2010)
8. McDonald-Madden, E. V. E., Baxter, P. W. J. & Possingham, H. P. Subpopulation triage: how to allocate conservation effort among Populations. Conserv Biol 22, 656-665, doi:10.1111/j.1523-1739.2008.00918.x (2008)
9. Kennedy, K., Aghababian, R. V., Gans, L. & Lewis, C. P. Triage: Techniques and applications in decisionmaking. Ann Emerg Med 28, 136-144, doi:10.1016/s0196-0644(96)70053-7 (1996)
10. McIntyre, S., Barrett, G. W., Kitching, R. L. & Recher, H. F. Species triage – seeing beyond wounded rhinos. Conserv Biol 6, 604-606, doi:10.1046/j.1523-1739.1992.06040604.x (1992)
11. Wilson, H. B., Joseph, L. N., Moore, A. L. & Possingham, H. P. When should we save the most endangered species? Ecol Lett 14, 886-890, doi:10.1111/j.1461-0248.2011.01652.x (2011)
12. Ferraro, P. J. & Pattanayak, S. K. Money for nothing? A call for empirical evaluation of biodiversity conservation investments. PLoS Biol 4, 482-488, dpi:E105, doi:10.1371/journal.pbio.0040105 (2006)
13. Wilson, K. A. et al. Conserving biodiversity efficiently: What to do, where, and when. PLoS Biol 5, 1850-1861, dpi:e223, doi:10.1371/journal.pbio.0050223 (2007)
14. Bottrill, M. C. et al. Is conservation triage just smart decision making? Trends Ecol Evol 23, 649-654, doi:10.1016/j.tree.2008.07.007 (2008)
15. Noss, R. F. Conservation or convenience? Conserv Biol 10, 921-922, doi:10.1046/j.1523-1739.1996.10040921.x (1996)
16. Pimm, S. L. Against triage. Science 289, 2289, doi:10.1126/science.289.5488.2289 (2000)
17. Balmford, A. et al. Economic reasons for conserving wild nature. Science 297, 950-953, doi:10.1126/science.1073947 (2002)
18. James, A., Gaston, K. J. & Balmford, A. Can we afford to conserve biodiversity? BioScience 51, 43-52, doi:10.1641/0006-3568(2001)051[0043:cwatcb]2.0.co;2 (2001)
19. Wasser, S. K., Keim, J. L., Taper, M. L. & Lele, S. R. The influences of wolf predation, habitat loss, and human activity on caribou and moose in the Alberta oil sands. Front Ecol Environ 9, 546-551, doi:10.1890/100071 (2011)
20. Boutin, S. et al. Why are caribou declining in the oil sands? Front Ecol Environ 10, 65-67, doi:10.1890/12.wb.005 (2012)
21. Wasser, S. K., Keim, J. L., Taper, M. L. & Lele, S. R. To kill or not to kill – that is the question. Front Ecol Environ 10, 67-68, doi:10.1890/12.wb.006 (2012)
22. Sorensen, T. et al. Determining sustainable levels of cumulative effects for boreal caribou. J Wildl Manage 72, 900-905, doi:10.2193/2007-079 (2008)

Before I had a good grasp of extinction dynamics, I wouldn’t have attributed much import to the role of roads in conservation. I mean, really, a little road here and there (ok, even a major motorway) couldn’t possibly be a problem? It’s mostly habitat destruction itself, right?

Not exactly. With our work on extinction synergies, I eventually came to realise that roads are some of the first portals to the devastation to come.

Figure 1. (A) A large population within unmodified, contiguous habitat fluctuates near full carrying capacity (K). (B) When habitat is reduced (e.g. 50% area loss), total abundance declines accordingly. (C) All remaining fragmented subpopulations have limited connectivity, implying much greater extinction risk than that predicted for the same habitat loss in less fragmented landscapes.

It sort of works like this (see Fig. 1 from our paper in Trends in Ecology and Evolution). Instead of destroying habitats (forests, reefs, grasslands, savannas, etc.) systematically (i.e., in large, contiguous blocks – Fig. 1B), we tend to fragment landscapes into many disconnected patches (Fig 1C). The vehicle by which we do this in terrestrial (especially forest) ecosystems is with roads connecting the matrix. As in turns out, instead of reducing biodiversity by the proportion of primary habitat lost (in this case, by 50 %), the multi-patch type of fragmentation leads to a much larger proportional biodiversity loss. This is because of the interactive effects of piecemeal fragmentation: roads between patches facilitate human and other predator access to areas previously isolated, micro-climatic changes resulting from a high proportion of ‘edge’ habitats can alter suitability, and invasive species have many more pathways by which they can spread.

But the role of roads in extinctions has long been recognised. I’m probably most familiar with Bill Laurance‘s work on Amazonian roads being responsible for massive fragmentation in the tropics. It also so happens that there’s an entire field of ‘road ecology research’ that probably didn’t even register on most conservation radars prior to the last few decades.

The reason I’m raising this topic now is that I’ve just stumbled across an interesting online paper in Trends in Ecology and Evolution by Lesbarrères¹ & Fahrig entitled Measures to reduce population fragmentation by roads: what has worked and how do we know? And these Canadians should know a thing or two about road-driven habitat fragmentation – Canada has now some of the most fragmented portions of the boreal forest, with < 40 % of its area considered ‘contiguous’ (i.e., not bisected by roads).

The authors talk about so-called ‘ecopassages’, which have been put in place in many road developments to mitigate wildlife ‘conflict’, such as crossing structures (bridges, underpasses, etc.) that are supposed to link habitats bisected by roads too difficult to cross safely for most species. Their main point is, however, that most of these lack any real scientific rigour in either testing their effects (do they actually work?), or even planning them from the outset. The authors go on to give a detailed description about how road developments should design transportation networks with wildlife connectivity in mind prior to building, and that rigorous scientific protocols should be developed to test their effectiveness. Fair cop.

However true these pleas and recommendations are, I still think the paper misses the main point (and it has a decidedly North American bias) – why do we need so many roads in the first place? Indeed, in most places in the world now, finding primary habitats is difficult enough, so surely we can be a bit cleverer about putting fewer roads in places where they are not strictly needed?

The point is that roads are generally very bad, not just because they impede connectivity, but because they open up a Pandora’s box of conservation nightmares still to come. Still, forcing road-network planners to consider these issues pre- and post-development can only do good.

CJA Bradshaw

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¹Interesting to note that this surname is remarkably close to ‘les barrières’ in French, meaning ‘barriers’ or ‘fences’. How appropriate!