–

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

–

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

© Y. Sugiura

Just a quick post this week about something I’ve been contemplating for a while.

What if every Australian pledged to eat a feral animal a week?

Yes, I know that it’s a bit out of the pitch, and I’m sure not everyone would do it. Nor would it be physically possible for one person to eat an entire camel, buffalo or deer in a week – but hopefully you get the picture.

Why propose this? Australia is quite over-run with feral animals. Some quick stats:

• We have well over 1,000,000 camels (Camelus dromedarius), possibly closer to 1.5 to 2.0 million
• There are in excess of 150,000 swamp buffalo (Bubalus bubalis), most of which are found in the Top End
• Although estimates are rather imprecise, there are possibly up to 23 million feral pigs (Sus scrofa) across the country
• As equally variable, there are an estimated 2.6 million feral goats (Capra hircus) in Australia
• There are around 5000 to 7000 banteng restricted to the Cobourg Peninsula
• I’m not aware of any population size estimates, but Australia hosts six species of feral deer: fallow (Dama dama), red (Cervus elaphus), chital (Axis axis), hog (Hyelaphus porcinus), rusa (Cervus timorensis) and sambar (Rusa unicolor) in 1000s of subpopulations spread around the continent’s fringe

Now we have, of course, many other ferals (cats, rats, foxes, mice), but I don’t think too many people would want to eat them. I have personally eaten feral pigs, camels, buffalo, goats, and red, fallow and sambar deer, mostly from my own research trips or from friends who hunt.

Camel is delicious, if not a little tough (nothing a good marinade and tenderiser won’t fix), buffalo is fantastic, any sort of venison is wonderful, and pig, well, pig is divine with almost anything.

Feral animals cost Australia billions in damage each year, wreak havoc on our native ecosystems and cost millions more to control (largely unsuccessfully).

Sure, many small-scale industries exist to provide meat to commercial markets, but remoteness, hygiene and transport issues have meant that they’re largely specialised industries with little impact on our nation’s meat-consumption patterns.

Nonetheless, if we instilled the notion in your average Australian that it was his/her duty to eat more feral animals to do some environmental good, perhaps the increased demand would fuel more culling. A corollary would be that we’d need to eat fewer sheep and cattle, which would improve our rangelands.

So, be a proud Australian and eat a feral a week!

CJA Bradshaw

By weird coincidence, Salvador Herrando-Pérez (student blogger extra-ordinaire – see his previous posts on evolution, pollination, bird losses, taxonomic inflation, niche conservatism, historical biogeography, ecological traps and ocean giants) has produced a post this week expanding on the problem of roads. Also weirdly coincidental is that both Salva and I are in his home country of Spain this week.

–

Australia’s > 800,000-km road network would go 60 times around the equator of our planet. Confined to the boundaries of any one country, roads are a conspicuous component of the landscape, and shape the dispersion, survival and reproduction of many plants and animals in urban and remote areas.

Those who drive (or are driven by) will be familiar with the image of a crushed kangaroo on the roadside (a hedgehog in Europe), or the sticky mosaic of insects smashed against the windscreen after a high-speed run. Mortality by collision is one of the many effects that roads can have on the demography of organisms – including humans. Those effects encompass

• physical alteration of terrestrial and aquatic habitats,
• chemical pollution leakage during road construction and maintenance, and from asphalt compounds during storms,
• alteration of animal behaviour (e.g., change in home range, or in patterns of flight or vocalisation),
• access to remote areas by hunters, fishermen and gatherers in general, and
• intense habitat fragmentation^1-3.

However, some species get around those negative impacts by using the roads as pathways to new territories, thereby eluding barriers like seas, mountains, rivers, dense vegetation, or competition for vital resources with other species.

Figure 1: Road use by cane toads in the Northern Territory, Australia (2). Top panel: frequency of radio-tracked individuals recorded at different distances to the nearest dirt road (25 to 975 m in 50 m intervals). Bottom panel: frequency of toads with body axis aligned at different angles with the main axis of the Arnhem Highway (0º for toads facing the main axis of the road, to |90|º for toads facing perpendicular to the right or left of the road). Most toads were found within 25 m of dirt roads, and facing -10º to 10º to the highway axis.

Brown and colleagues⁴ illustrate the latter scenario with cane toads (formerly Bufo marinus; now Rhinella marina) in Australia. This species was introduced to Queensland in the 1930s to control (unsuccessfully) insect pests in sugar cane fields⁵. Nowadays, Aussie cane toads outnumber the human population in China, occupy a surface equivalent to 100 million soccer stadia, and only in 2009 crossed the border of Western Australia, > 2,500 km from the release point⁶ [see Rick Shine’s cane toad lab research]. For over 300 nights, Brown et al. radio-tracked 49 adult toads in farmland and eucalyptus forest in the Northern Territory. They found that these animals adjusted their movements to the local network of roads. In half of the records, toads were seen on or near dirt roads, mainly following those portions of the roads in the Northwest direction of progression of the invading front (Figure 1).

With an independent sample, they observed that the body axis of most individuals found near a highway was aligned with the principal axis of the road (Figure 1), giving evidence that the animals were moving relative to the trajectory of the highway. Undoubtedly, roads confer demographic benefits that compensate the > 200 tonnes of toads killed on the roads in (only) Queensland every year.

The invader’s backpack

Among the panoply of exotic species that are detrimental globally outside their native ranges⁷, the fungus Phytophthora lateralis is another self-explanatory example of road-loving biological invasion⁸. Rivers disperse the spores of this fungus. The spores then parasitise the roots of tree species along riverbanks and beyond (i.e., during floods), resulting in fulminating rot of the entire root system. In Oregon and California, spores have spread in most rivers in the mud stuck to vehicles and people’s shoes walking along local dirt roads. The disease was first recorded in the 1920s in Seattle in a plantation of Port Orford cedars (Chamaecyparis lawsoniana). It has since caused massive mortality of juvenile to centenary cedars in the conifer forests of Western USA, and has ruined a multi-million-dollar export of wood and ornamental trees (by means of which the fungus has already reached, at least, Asia and Europe).

Roads also contribute to the spread of insect and plant pests and human diseases^1,3. In the case of cane toads, dirt roads in the Northern Territory might be assisting in the dispersal of their toxicity (arguably the toad’s worst ecological impact⁶), present in all developmental stages (egg, tadpole, toadlet, and adult), especially for adults because toxicity increases with size. Up to 27 species of vertebrates have been reported to die from ingestion of cane toads⁵ – thus, at a population level, it is predictable that the worst ravages will occur in apex predators able to catch larger (and more toxic) toads, such as elapid snakes, varanid lizards, the freshwater crocodile (Crocodylus johnstoni) and quolls (Dasyurus spp.)⁶.

Surely we all want roads that are safe and (as much as possible) benign for biodiversity. Taylor and Goldingay² have recently reviewed the state of the art of published research into roads and wildlife worldwide, with the following highlights:

• studies on large ungulates and carnivores predominate, partly due to rocketing insurance and medical costs after collisions;
• road-crossing structures for wild animals are being widely applied, although population benefits remain poorly understood;
• behavioural avoidance with genetic and metapopulation implications occurs in some species, calling for landscape road planning;
• focused management actions are needed for globally threatened species like amphibians (surely not cane toads),
• poor experimental designs across the board.

It caught my eye that the three reviews I cite^1-3 did not encompass road impacts on subterranean ecosystems⁹ – a dark oasis of living wonders¹⁰ and reservoir of > 30 % (98 % along with glaciers) of available freshwater globally¹¹. Clearly, to those who build roads (from the politician to the engineer), environmental impact assessment should take into account their multiple ecological impacts, and not only along the route itself^2,3.

Next time you hit the road, be aware; you are never alone.

—

1. S. C. Trombulak and C. A. Frissell, Conserv Biol 14 (1), 18 (2000) doi:10.1046/j.1523-1739.2000.99084.x
2. B. D. Taylor and R. L. Goldingay, Wildl Res 37 (4), 320 (2010) doi:10.1071/WR09171
3. W. F. Laurance, M. Goosem, and S. G. W. Laurance, Trends Ecol Evol 24 (12), 659 (2009) doi:10.1016/j.tree.2009.06.009
4. G. P. Brown, B. L. Phillips, J. K. Webb et al., Biol Conserv 133 (1), 88 (2006) doi:10.1016/j.biocon.2006.05.020
5. C. Lever, The Cane Toad. The History and Ecology of a Successful Colonist. (Westbury Academic and Scientific Publishing, Otley, UK, 2001)
6. R. Shine, Quart Rev Biol 85 (3), 253 (2010) doi:10.1086/655116
7. S. Lowe, M. Browne, and S. Boudjelas, Aliens 12, S1 (2000)
8. E. M. Hansen, Boreal Environ Res 13, 33 (2008); E. M. Hansen, D. J. Goheen, E. S. Jules et al., Plant Disease 84 (1), 4 (2000) doi:10.1094/PDIS.2000.84.1.4; E. S. Jules, M. J. Kauffman, W. D. Ritts et al., Ecology 83 (11), 3167 (2002)
9. M. Knez and T. Slabe, in Encyclopedia of Caves and Karst Science, edited by J. Gunn (Palgrave Macmillan, London, UK, 2004), pp. 419
10. J. Gibert and L. Deharveng, BioScience 52 (6), 473 (2002) doi:10.1641/0006-3568(2002)052[0473:SEATFB]2.0.CO;2; D. C. Culver and B. Sket, J Cave Karst Stud 62 (1), 11 (2000)
11. D. L. Danielopol, C. Griebler, A. Gunatilaka et al., Environmental Conservation 30 (2), 104 (2003) doi:10.1017/S0376892903000109
12. B. L. Phillips, G. P. Brown, J. K. Webb et al., Nature 439 (7078), 803 (2006) doi:10.1038/439803a
13. N. Sallam, Aust J Entomol 50 (3), 300 (2011) doi:10.1111/j.1440-6055.2010.00807.x

© 2008-2011 ~Hiuki http://fav.me/d1j3ns9

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

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

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

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

His latest regurgitation of spectacularly uninformed and politically motivated, anti-environmental vomit couldn’t have missed the point more on the Macquarie Island feral eradication programme. Most would agree that despite our general failing of biodiversity conservation, conservation biologists have had a fair share of major wins with island pest eradications; indeed, at times it seems the only thing we can get right is killing the baddies we were originally responsible for introducing.

Now, I’m no fan of the Tasmanian legislators and government drones who for years delayed or severely under-appreciated science to inform sound environmental policy when it came to Macquarie Island (indeed, I would go so far as to say that the established environmental autocracy in the Tasmanian government is one of the principal enemies of conservation because of their entrenched anti-science stance), but for once, they finally got around to doing something good with this ~ million-dollar programme.

And I have some history there too – I was stationed on Macquarie Island over 4 years from 1999-2004 during my postdoctoral fellowship, during which time I worked on many aspects of elephant seal population and behavioural ecology (see associated publications here). In my last year there, I was shocked upon my return to the island after an 18-month stint back in mainland Australia about just how much damage the rabbits had done after the last cat had been shot a few years before. I was so moved that I wrote a popular article on the matter to bring it to the public’s attention – you can read that article (published in Australasian Science) here for more background information.

For the ultra-right wing Senator Abetz to turn this success into his own political poisoned arrow is, to be perfectly honest, an environmental crime in its own right. Using the weak argument that some protected species have suffered as a consequence is the classic tool of the so-called ‘environmentalists’ who would rather focus on a single species (or even individual) while the rest of biodiversity melts into extinction (see related post here). We just don’t have time for this nonsense, and this is why we have to consider uncomfortable choices such as triage and controversial energy-generation technology.

I’m not for a moment insinuating that Senator Abetz truly feels for the poor seabirds who had the misfortune of swallowing a bit of poisoned bait in the quest to return their island to its former pristine biodiversity greatness; rather, I think he used the weak and uninformed argument for his own political gains (a double travesty). We have to move past this double-dipped bullshit if we want to make some real gains for biodiversity in Australia.

CJA Bradshaw

The Genesis

A few years ago, a few of us (Bob Lacy, Phil Miller and JP Pollak of Vortex fame, Barry Brook, and a few others) got together in a little room at the Brookfield Zoo in the suburban sprawl of Chicago to have a crack at some new modelling approaches the Vortex crew had recently designed. The original results were pleasing, so we had a follow-up meeting last year (thanks to a few generous Zoo benefactors) and added a few post-docs and students to the mix (Damien Fordham, Clive McMahon, Tom Prowse, Mike Watts, Michelle Verant). The great population modeller Resit Akçakaya also came along to assist and talk about linkages with RAMAS.

Out of that particular meeting a series of projects was spawned, and one of those has now been published online: Novel coupling of individual-based epidemiological and demographic models predicts realistic dynamics of tuberculosis in alien buffalo.

The Coupling

So what’s so novel about modelling disease in buffalo, and why would one care? Well, here’s the interesting part. The buffalo-tuberculosis example was a great way to examine just how well a new suite of models – and their command-centre module – predicted disease dynamics in a wild population. The individual-based population modelling software Vortex has been around for some time, and is now particularly powerful for predicting the extinction risk of small populations; the newest addition to the Vortex family, called Outbreak, is also an individual-based epidemiological model that allows a population of individuals exposed to a pathogen to progress over time (e.g., from susceptible, exposed, infectious, recovered/dead).

The problem was that Vortex and Outbreak generally operated at different time scales, such that you really couldn’t model disease dynamics well within the Vortex population framework, nor could you incorporate the complexities of population dynamics very well in Outbreak. That clever Lacy-Miller-Pollak trio figured out a way of coupling the two via something they called MetaModel Manager (MMM – about which I blogged last year) which could allow the daily step of Outbreak to run effectively within the annual step of Vortex (other breeding cycles are possible within Vortex, of course).

Buffalo-Tuberculosis

Now for the example in question, we wanted to see if we could effectively model the dynamics of tuberculosis in feral swamp buffalo (Bubalus bubalis) in northern Australia. A little background is required here.

Buffalo were introduced to northern Australia in 1826, 1827 and 1843 from Timor-Leste, and subsequently spread rapidly throughout the Northern Territory, growing to ~ 350,000 by the 1970s. Unfortunately, buffalo harboured bovine tuberculosis, which also crossed over readily to commercial cattle livestock. So the government at the time initiated a broad-scale culling programme called the ‘Brucellosis-Tuberculosis Eradication Campaign’ (BTEC) in the 1980s and 1990s. The cull successfully reduced or eradicated buffalo from major pastoral lands in the Northern Territory (taking tuberculosis with it), but since then, no follow-up culling has occurred and the population is re-invading the formerly culled areas. Although Australia now trades its livestock under the ‘TB-free’ banner, the disease is prevalent throughout Africa, southern Europe, the Middle East and parts of Asia, so in many ways, it’s only a matter of time before it rears its ugly head again here. And if it does, it could cost our cattle industry over $10 billion to fix.

The bottom line is that we need tools like Vortex-MMM-Outbreak to plan the optimal culling regimes should TB (or other, nastier diseases like foot-and-mouth) (re-)enter Australia.

The Implications

I won’t go into too many of the finer details of the paper here, although we did find that the population dynamics (especially age at first breeding) most dictated the prevalence of TB in the population – not the characteristics of the disease itself (e.g., transmission probability, incubation time, contact rate, etc.). This has HUGE implications for wildlife disease modelling in general; if one fails to incorporate the dynamics of the population in gory detail, chances are the predictions relating to the disease itself will be erroneous.

Second, we found that the probability of detecting a disease as well-known as TB was vanishingly small, such that current monitoring programmes in northern Australia done by the Northern Australia Quarantine Strategy (NAQS), a division of the Australian Quarantine and Inspection Service (AQIS), are woefully inadequate for monitoring wildlife disease in our vast northern regions.

Third, we found that if the goal was to reduce prevalence to near-zero, somewhere between 30 and 50 % of the population would have to be culled each year for about 15 years. That’s a lot of buffalo.

Now, those are really the ‘meat’ results of the paper, but I do want to re-iterate that it’s the software coupling itself that’s the most novel. In fact, part of the review process required us to model our system using ‘analogous’ software for comparison. The problem is, there just simply isn’t any customisable software out there that can do what Vortex-MMM-Outbreak can. And the best part is, it’s all free.

Yes, you can download all the software here:

1. Vortex
2. Outbreak
3. MetaModel Manager (64-bit here)

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The reasons for the decline of Australia’s unique biodiversity are many, and most are well known. Clearing of vegetation for urban and agricultural land uses, introduced species and changed fire patterns are regularly cited in State of the Environment reports, recovery plans and published studies as major threats to biodiversity. But, while these threats are widely acknowledged, little has been done to quantify them in terms of the proportion of species affected, or their spatial extent at a national, state or local scale. To understand why such information on threats may be useful, consider for instance how resources are allocated in public health care¹.

Threat knowledge

Conditions such as cancer, heart disease and mental health are regarded as National Health Priority Areas in Australia, and have been given special attention when prioritising funds since the late 1980s. The burden of disease in these priority areas are quantified according to the incidence or prevalence of disease or condition, and its social and economic costs. Estimates of burden of disease and their geographic distribution (often according to local government areas) can assist in communicating broad trends in disease burden, but also in prioritising efforts to achieve the best outcomes for public health. An approach similar to that used in healthcare could help to identify priorities for biodiversity conservation – using information on the species which are impacted by key threats, the spatial distributions of species and threats, and the costs of implementing specific management actions to address these threats.

In a study recently published in BioScience¹, we examined in detail the threats reported for threatened species listed under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act). We first calculated the percentage of threatened species affected by eight key threats:

• habitat loss
• introduced species
• inappropriate fire regimes
• disease
• pollution
• overexploitation
• native species interactions, and
• natural causes.

Figure 1. Relative impacts of major threatening processes expressed as the % of extant species threatened, the % of mapped species threatened (subset of extant threatened species for which spatial data were available), and the % of continental area of Australia across which the threat occurs within sub-catchments.

From this we were able to confirm that habitat loss is the most important threat to Australian biodiversity, affecting 81% of threatened species (Figure 1). However, we also found that changes to the natural fire patterns and introduced species threaten proportionally more species in Australia than in other countries including the United States of America, Canada and China.

Reporting on statistics such as these can be useful for making broad comparisons in the relative importance of threats, or to communicate better the dire situation facing Australia’s biodiversity – but the value of such analyses in informing practical efforts to conserve threatened species can be limited. One important reason for this is that the distribution of threats and species vary across the landscape. To become useful in conservation planning, we need to quantify threats spatially.

Which species, where?

To do this, we used species distribution models from the Species of National Environmental Significance database, and matched the listed threats for each species to their corresponding spatial models. From this we determined which of the 62,629 sub-catchments across the Australian continent contained species affected by each threat.

Figure 2. Distribution of the predominant threats to biodiversity across Australia. The ‘predominant threat’ is the threat affecting the greatest number of species in each sub-catchment. Where 2 or more threats affect an equivalent number of species, we assume no predominant threat occurring in these sub-catchments (shades of grey). Darker colours indicate a larger overall number of threats occurring in the sub-catchment. White indicates areas where no threatened species occur.

Our first effort revealed important connections between the distributions of species and threats. For instance, changed fire patterns are a threat to species across almost 90 % of the Australian landscape, but affect less than half of the threatened species. We then calculated the proportion of species affected by each threat contained within each sub-catchment, and subsequently determined the predominant threat in each sub-catchment. From this it became clear that multiple stressors are impacting native biodiversity over much of the continent (Figure 2) – even in regions sparsely populated by humans such as northern Australia.

This means that effective conservation management is critical even in areas considered to be wilderness. Our study has shown that the majority of Australia’s threatened species are affected by multiple pressures (over 75% of species), and these threats are distributed across most of the continent – many of which cannot be eased through the protection of habitat alone⁴. This is an important result – as it means that getting the best outcomes for biodiversity requires a broad understanding of factors to decide best direct conservation efforts: what threats exist, what are the potential benefits of conservation management, what are the most suitable management actions and how much will they cost?

What’s the priority?

The next step in this research is to understand how we can effectively prioritise resources to maximise conservation outcomes where a range of threats to biodiversity exist. We pursued this by developing a multiple-action, return-on-investment framework³. Similar approaches have been used to determine what conservation management actions to do, where and when – but so far, a lack of information on the threats to species and their spatial distributions means that the additional complexity of how to address the impacts of multiple threats on species has not yet been considered.

There are two possible consequences of ignoring the issue of multiple threats: first, the benefits of abating a single threat may be overestimated because species might be threatened by multiple processes; second, the cost of abating two threats in one place might be cheaper than the sum of the costs of abating each threat alone.

We tested our approach by considering two key threats to Australian biodiversity: the red fox and the European rabbit. Some species are threatened only by foxes, some only by rabbits, but some are affected by both – and so require management actions directed at both threats in order to persist. Using spatial data on the distributions of threatened species, and of the two introduced species, we calculated the area within each of Australia’s bioregions requiring management for foxes rabbits, or both. We then tested four return-on-investment frameworks (Figure 3).

Figure 3. Investment into conservation actions at a continental scale for all 72 bioregions, according to our 4 return-on-investment (ROI) frameworks: (a) Two-action-independent ROI, (b) three-action-independent ROI, (c) action-dependent ROI and (d) action-dependent ROI with spatial targeting. Map shows the priority bioregions for investment as indicated by the total percentage of funding for a bioregion summed over all actions, which is shown as low (up to 1%), medium (up to 2%) or high (up to 6%).

The first ignored the presence of more than one threat on threatened species. In this case, it was best to spend the majority of funds over all bioregions (68 %) on rabbit control – as many more species are threatened by rabbits than foxes. Our second method considered species impacted simultaneously by both foxes and rabbits, but ignored the benefits of integrated fox and rabbit control to species affected by only one of the threats. In this case, rabbit control was still the best option (receiving 62 % funds overall).

But when we fully considered the management requirements of species affected by multiple threats, as well as the benefits of integrated management for species only affected by one threat, we found that 96 % of the total funds were allocated to integrated management of foxes and rabbits. In short, fully accounting for the potential to implement integrated management actions that address more than one threat to biodiversity resulted in improved cost efficiencies and better conservation outcomes.

Our final analysis investigated whether detailed information on the spatial overlap of species’ distributions within each bioregion influenced the timing or amount of investment directed to management. For example, a bioregion where species are more densely concentrated than others might provide a greater return with targeted investment in conservation. However, we found that accounting for spatial overlap in the distributions of threatened species did not alter the prioritisation of funds to alternative management actions or locations (Figure 3d).

This suggests that refined data on distributions of threatened species might not improve our ability to determine where and when funding should be directed to conservation actions to mitigate specific threats to biodiversity. Our research suggests that efforts to prioritise conservation investments would be improved by gaining better information on the specific threats impacting on species, the distribution of these threats and the costs of management actions.

In a time when getting conservation outcomes through wise investments is crucial, we should also focus on gaining a greater understanding of the efficiencies gained through integrated management, and the institutional structures that facilitate this.

Megan Evans

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References

¹Mitchell, R. J., R. J. McClure, J. Olivier, and W. L. Watson. 2009. Rational allocation of Australia’s research dollars: does the distribution of NHMRC funding by National Health Priority Area reflect actual disease burden? The Medical Journal of Australia 191:648-652

²Evans, M. C., J. E. M. Watson, R. A. Fuller, O. Venter, S. C. Bennett, P. R. Marsack, and H. P. Possingham. 2011a. The spatial distribution of threats to species in Australia. BioScience 61:281-289. doi:10.1525/bio.2011.61.4.8

³Evans, M. C., H. P. Possingham, and K. A. Wilson. 2011b. What to do in the face of multiple threats? Incorporating dependencies within a return on investment framework for conservation. Diversity and Distributions 17: 437-450. doi:10.1111/j.1472-4642.2011.00747.x

⁴Watson J.E.M., Evans M.C., Carwardine J, Fuller R.A., Joseph L.N., Segan D.B., Taylor M.F.J., Fensham R.J., Possingham H.P. 2011. The capacity of Australia’s protected-area system to represent threatened species. Conservation Biology 25: 324-332. doi:10.1111/j.1523-1739.2010.01587.x

Megan C. Evans, James E. M. Watson, Richard A. Fuller, Oscar Venter, Simon C. Bennett, Peter R. Marsack, & Hugh P. Possingham (2011). The spatial distribution of threats to species in Australia BioScience, 61 (4), 281-289 : 10.1525/bio.2011.61.4.8

This post doubles as a Conservation Classic and a new take on an old concept. It’s new in the sense that it updates what we believe is an advance on a major milestone in conservation biology, even though some of the add-on concepts themselves have been around for a while.

First, the classic.

The ‘evil quartet’, or ‘four horsemen of the ecological apocalypse’, was probably the first treatment of extinction dynamics as a biological discipline in its own right. Jarod Diamond (1984) took a sweeping historical and contemporary view of extinction, then simplified the problem to four principal mechanisms:

1. overhunting (or overexploitation),
2. introduced species,
3. habitat destruction and
4. chains of linked extinctions (trophic cascades, or co-extinctions).

Far from a mere review or list of unrelated mechanisms, Diamond’s evil quartet crystallized conservation biologists’ thinking about key mechanisms and, more importantly, directed attention towards those factors likely to drive extinctions in the future. The unique combination of prehistorical through to modern examples gave conservation biologists a holistic view of extinction dynamics and helped spawn many of the papers described hereafter.It would now appear prudent to add a fifth ghoul to the team - severe anthropogenic interference with the global climate system. The response of biodiversity to past global climate change characteristically unfolded over thousands to millions of years, whereas anthropogenic global warming is now occurring at a greatly accelerated rate. If carbon emissions are not reduced rapidly, the Intergovernmental Panel on Climate Change’s Fourth Assessment Report 2007 projects a rate and magnitude of 21^st Century planetary heating that is 5–9 times greater than that of the past century. This is comparable to the difference between now and the height of the last glacial maximum.

A clear lesson from the past is that the faster and more severe the rate of global change, the more devastating the biological consequences, and as I’ve covered before here on ConservationBytes.com in a separate Conservation Classic, this has seriously negative implications for biodiversity.

Now it’s time though to add a sixth rider – extinction synergies (Brook et al. 2008). For example, exacerbating the problems associated with recent climate change is that species trying to shift distribution must now contend with massively modified landscapes. Even in cases where global warming might allow species to expand their range, these benefits can be outweighed by other threats such as habitat change. The new conditions and altered communities might also allow more invasions by alien species that outcompete native species or act as predators to reduce their populations further. Harvest, habitat modification and changed fire regimes will also interact with and probably enhance the direct impacts of climate change.

In summary, we now appreciate that most extinctions involve a synergy of these factors (Brook et al. 2008), with individual causes being difficult or impossible to isolate. These synergies thus represent a situation where the combined effects are substantially more problematic for biodiversity than the mere sum of their individual effects.

To extend the apocalypse analogy further, it’s as though the horsemen’s orgy of species destruction has finally produced a bastard son far more evil then his vile parents.

We should no longer talk of the ‘evil quartet’ – it is now (at least) the ‘evil sextet’.

CJA Bradshaw (& Navjot Sodhi, William Laurance & Barry Brook)

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References

• Brook, B.W.; Sodhi, N.S. & Bradshaw, C.J.A. (2008). Synergies among extinction drivers under global change. Trends in Ecology and Evolution 25: 453-460
• Diamond, J.M. (1984). ‘Normal’ extinction of isolated populations In: Extinctions, M.H. Nitecki (Ed.), 191-246, Chicago University Press, Chicago, USA

Before I proceed to regale you with the salient details of the ‘International Symposium for Biodiversity and Theoretical Ecology‘, I am compelled to state publicly that I offer my sincerest condolences to Fangliang and his family; unfortunately Fangliang’s brother passed away while we were at the workshop and so Fangliang wasn’t able to spend much time reaping the fruits of his organisational labour. If you know Fangliang, please send him a supporting email.

That sad note aside, I am delighted to say that the workshop was compelling, challenging and also rather fortuitous. I was one of many overseas invitees, and I must say that I was at times overwhelmed by the size of the brains they managed to pack into the auditorium. Many colleagues I didn’t know attended, and I hope that many will become collaborators. The international invitees were:

• Rob Colwell
• Sean Connolly
• Rampal Etienne
• Alan Hastings
• Subhash Lele
• Brian McGill
• Annette Ostling
• John Spence
• Doug Wu
• Weini Huang

But it wasn’t just a show of us lǎo wài (老外) – there was an abundance of excellent talks by many fine Chinese ecologists (professors, post-docs and students). I am constantly amazed how the Chinese just give it a go in English even though it is an incredible challenge to present good science in a foreign tongue.

So, on to the content. I won’t cover everything, but here are some highlights:

• Alan Hastings, whose work I’ve highlighted before here on ConservationBytes.com, presented some of his work on how regime shifts can arise from apparently simple, relative ‘stable’ dynamics
• Rampal Etienne presented his work on speciation-extinction models from which phylogenies can be simulated. He talked a lot about ‘diversity dependence’, which is something I’d like to model within the Cronus framework
• Sean Connolly talked about lognormal patterns approximate coral and coral fish distributions
• Rob Colwell showed how tropical species wax and wane in response to deep-time climate changes, and the processes underlying the patterns
• Brian McGill presented a new way to model species distributions, something he calls the Gause Liebig biogeographic law
• John Spence talked about the biggest forestry experiment in history – EMEND. Amazing stuff.
• Doug Wu gave a two-part talk in two languages (Mandarin & English) on the theory of symbiosis (he claims most interactions are mutualistic, not competitive) and on the revolution in molecular markers for biodiversity assessment
• Annette Ostling gave a great talk on demographic complexity and neutral theory
• Subhash Lele contests that with some independent information on species detection covariates, multiple surveys are not needed to estimate measurement error in biodiversity surveys

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© 中國蜂

Over the last few weeks there has been much media attention given to the Asian honeybee (Apis cerana) incursion in far north Queensland. The Asian honeybee was first detected near Cairns in May 2007. Since then an effort to eradicate the bee has been made. This peaked during 2010, when over 40 bee eradication personnel were employed to hunt and destroy in areas around Cairns, the Atherton Tablelands, and other nearby locations.

In late January this year, the committee established to manage the eradication program (governments and industry), decided to pull the plug on eradication efforts (on money to pay for efforts that is). They decided it was no longer possible to achieve eradication (a majority decision, not a unanimous decision). The position to stop resources for eradication is not supported by industry, or ecological commentators. Arguments have been made that this is the only window of opportunity for eradication (for ever!), and that more resources need to be put towards it now, while there is still a chance of success.

A few points to be made about the Asian honeybee in Australia:

• Over 340 colonies have been found since the original incursion in 2007 (mostly after 2009).
• Based on the Asian honeybee’s native range, it has the potential to survive in most parts of Australia.
• Being a cavity nester, the Asian honeybee will compete for nesting sites with native stingless bees, birds, and mammals (much as the Western honeybee (Apis mellifera) does already).
• The bee is a little bit smaller, and behaves in a slightly different manner than the Western honeybee, so might compete with native fauna differently at floral resources.
• Asian bees are believed to be less efficient as crop pollinators than Western honeybees, and are also known to rob Western honeybee hives of honey.
• Industry is worried about the Asian honeybee competing with managed Western honeybee colonies.

There is also much concern about Asian honeybees being the natural carrier of the Varroa mite (which it is). However, some interesting points to be made on this are:

In early 2010 I was informed that all colonies that had been destroyed were genetic descendants from the first 2007 colony. Thus, this has all resulted from a single incursion. None of the nests found yet have been positive for Varroa, which is unsurprising because the original colony was not a carrier. I think the real Varroa worry comes if this Asian honeybee incursion does establish in Australia, as it will then be harder to detect subsequent incursions, which may carry Varroa. As I have stated on ConservationBytes.com previously, Varroa only affects Apis cerana and Apis mellifera. It is potentially fatal only to Apis mellifera.

There have been comments made about this being the next cane toad or rabbit for Australia. Who knows, but it will certainly have a major impact. It will certainly be very bad for biodiversity, and it will probably be bad for agriculture. ONLY $3 million has been spent on the Asian honeybee eradication program so far.

Listen to Tim Low talk about the politics surrounding the Asian bee eradication program being stopped, on ABC Radio National Breakfast here.

Those to make demands to about putting resources towards further eradication efforts are: Federal Agriculture Minister Joe Ludwig, as well as any local members, and State and Territory politicians, in all States and Territories.

Tobias Smith