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Standing Committee on the Environment and Energy
13/02/2019
Inquiry into controlling the spread of cane toads

CAPON, Professor Robert, Private capacity

LETNIC, Professor Mike, Private capacity

PHILLIPS, Associate Professor Ben, Private capacity

SHINE, Professor Richard, Professor, Macquarie University

Evidence was taken via teleconference—

Committee met at 09:58

ACTING CHAIR ( Mr Conroy ): I declare open this public hearing of the House of Representatives Standing Committee on Environment and Energy for the inquiry into controlling the spread of cane toads. In accordance with the committee's resolution of Thursday, 13 October 2016, this hearing will be broadcast on the parliament's website, and the proof and official transcripts of proceedings will be published on the parliament's website. Those present here today are advised that filming and recording are permitted during the hearing. I remind members of the media who may be present or listening online of the need to fairly and accurately report the proceedings of the committee. I now welcome the participants in our roundtable session with academics and researchers. Do you have any comments to make on the capacity in which you appear?

Prof. Shine : I'm a professor in biology at Macquarie University. I'm here because I've conducted extensive research on cane toad ecology and control over many years.

Prof. Phillips : I'm an associate professor at the University of Melbourne. My expertise lies in ecology and evolution, particularly in invasive species, and modelling invasions. Like Rick, I've conducted extensive research on cane toads over about 18 years. I thank the committee for the opportunity to speak to that.

Prof. Letnic : I'm from the University of New South Wales. I've been working on cane toads and their ecology for a long time and invasive species more generally.

Prof. Capon : I'm a group leader and professorial research fellow at the University of Queensland Institute for Molecular Bioscience. I've had a long-term interest in cane toad control.

ACTING CHAIR: Excellent. Although the committee does not require you to give evidence under oath, I should advise you that this hearing is a legal proceeding of the parliament and therefore has the same standing as a proceeding of the House. The giving of false or misleading evidence is a serious matter and may be regarded as a contempt of parliament. The evidence given today will be recorded by Hansard and attracts parliamentary privilege. I now invite each of you to make a very brief statement before we proceed to discussion.

Prof. Shine : The main point that I tried to make in my submission was that we actually know a great deal about cane toad invasion now. Much of the expenditure of effort and resources in the early days had to be based on guesswork. People just had to do the best they could. But we now have very extensive information about what the impact of toads is and what methods are effective in controlling them and which ones aren't. I fear that the people involved in this particular roundtable are all researchers and they are all very familiar with that literature—and, indeed, they're the people who've written it—but there has been a disconnect between the researchers and the general community. There are still resources being put into methods that we know are not effective. I just think we need to somehow get the message out and to base continuing expenditure of effort on the methods that can be shown, with evidence, to be effective.

Prof. Phillips : I would reiterate what Rick has said, largely. I would add to that that I've worked on toads a long time and I probably spent the first 12 years of that convinced that nothing could be done to stop their spread, but all sorts of encouraging things have happened over the last six years. One of those, I think, is this idea of a waterless barrier. I've gone from being sceptical that anything could be done to stop toads to actually completely convinced that we can do very useful things to stop them.

Prof. Letnic : I've got a long background in invasive animals ecology and I've worked in government agencies previously. One of the things that I think are really missing from the approach to cane toads is an integrated approach. I think there's been a great deal of emphasis over the years on finding a silver bullet, a biological control or something, and people have been sort of ignoring other techniques—for example, constructing waterless barriers in arid regions. I think what we really need for cane toad control is to develop integrated approaches where, ideally, we do strive to find a biological control or something, but we look at other techniques as well and we have a strategy that takes into account the strengths and weakness of different methods in different locations—basically, an integrated approach that involves multiple methods to control them.

ACTING CHAIR: Thank you. Professor Capon?

Prof. Capon : I'd like to make three very quick points. The first point is that the control of cane toads is a national problem and it operates at the invasion front to the west, in Western Australia and the Northern Territory, but it's also a major concern in the east, particularly in Queensland and northern New South Wales. So there's a need to recognise the problem in both locations. The second point—and I think it probably fits with what others have said—is that, where we have good approaches that look promising, we need to invest in a more coordinated approach and a validation and to basically get them out there and get them being used in the most appropriate fashion. The third point I would make is that one of the areas that has been less well developed is the area of chemical ecology—that is, understanding some of the key uses of the cane toad that the cane toad makes in controlling its survival, and the cane toad tadpole trapping technology that is being rolled out at the moment is a good illustration of how you can use cane toad chemical ecology to control it.

ACTING CHAIR: Thank you very much. I might start off with a couple of questions and then throw to Mr Evans. If we take a step back for a second and look at the impact of cane toads, are any of the witnesses familiar with any studies of the economic impacts of cane toads?

Prof. Shine : There are certainly accounts in the media of people who are trying, for example, to grow salad materials and so on having difficulties with very large numbers of small toads in there; if they use mechanised methods of harvest then they end up with bits of cane toad, and that's a substantial cost to them. I think tourism operators also complain that people who come to the wilderness hoping for an experience of 'real Australia' are very frustrated and disappointed to discover that the most common form of wildlife they see hopping around the bungalows is a cane toad.

Prof. Letnic : I don't know of any explicit literature about the economic impacts, but there is research showing that cane toads are major predators of dung beetles. Dung beetles were introduced to improve nutrient cycling and disrupt parasite lifecycles of cattle. Certainly it shows that cane toads suppress dung beetle numbers and interfere with dung breakdown. So there's a potential impact there.

Another impact is with Indigenous people. A lot of Aboriginal people in northern Australia and parts of central Australia consume a lot of bush tucker, and goanna is one of the major bush tucker foods. Certainly in the areas where I do research, in the Northern Territory, goanna is not on the menu anymore and hasn't been on the menu for a long time. That's an economic impact that hasn't been documented.

Prof. Phillips : I'd agree. I don't think there have been any formal studies of the economic impacts, but I think they're out there, and I agree with everything that Mike and Rick have said so far. The only other thing I could think of to add to that is that apiarists often complain bitterly about toads coming and sitting at the opening of their beehives and eating them all.

Prof. Capon : I think one of the points I would make is that we established the Cane Toad Challenge here in Queensland as a community engagement and citizen science project initially to roll out tadpole trapping, and, very shortly after we set that up, we received quite substantial donations from players in the market garden industry, as Rick said, with lettuce, but also pastoralists who were in the cattle industry, precisely because of the effect on the dung beetles.

ACTING CHAIR: I've got one more question and then I'll throw to Mr Evans. In a couple of your opening statements you talked about some of the control measures that are known not to work but are still being pursued. I'm wondering if people could identify some of the control methods still being used that aren't effective—that are a waste of time and money.

Prof. Shine : I think it would be harsh to say 'a waste of time and money', but an enormous amount of effort has primarily gone into collecting adult toads, which you can do fairly easily and effectively by walking around at night with a flashlight. Unfortunately, the reality of toad biology is that a single female can have 40,000 eggs, so, even if you massively decrease the abundance of local adult toads, the few survivors—because you cannot possibly get them all—will end up repopulating the area very quickly. So that only has a very short term effect on toad abundances, except if you're at the fringe of the invasion or you're in a satellite population that perhaps was established by some toads that jumped off the back of a truck. If the animals can't recolonise an area, then certainly picking up toads can have a big effect, but on its own it's not going to be effective.

The key is to stop reproduction, and that's why the tadpole trapping that Rob Capon and I have been involved with worked, and so on. I think that is a critical key. We need to simultaneously stop the toads from reproducing, and then we can focus on the survival of adults and try to decrease that to have an effect. Simply going out and picking up adult toads may have a role, particularly on the fringes, particularly in the southern areas, but I don't think it's sensible to put a lot of effort into it over most of the range of the cane toad.

ACTING CHAIR: Does anyone have anything else to add on less-effective control techniques? If not, I'll throw to Mr Evans.

Mr EVANS: I think that, to paraphrase, it seems like there's a bit of a consensus among the experts here today that the most efficient way that we should be approaching this, the best use of funds, is probably to target things at the tadpoles and eggs stages rather than adults. For the purposes of people out there in the public listening—

Prof. Letnic : Just to hang on with that point: it depends on the circumstance. Targeting the adults by preventing them from accessing water in arid areas is effective. It's really tailoring the method and possibly having multiple methods in different circumstances.

Mr EVANS: Okay.

Prof. Letnic : Targeting the adults, as Rick pointed out, can be effective, particularly if you're applying the pheromone traps, but in arid areas targeting adults is very effective because you can have massive knockdown of the populations. It depends on the circumstance. When we talk about toads, we're often thinking about the populated areas in the wet tropics or on the east coast, but there's more than one area or habitat where they live, and we need different approaches in the different areas.

Mr EVANS: Thank you, that's useful evidence.

Prof. Phillips : I'll just add to that. Perhaps the focus should in fact be on controlling critical resources for them, which is water in dry parts of the world, and of course water is a key moment in their life cycle for tadpoles and eggs. So the focus on tadpoles and eggs is, I think, probably a focus on that moment in space and time when the toads are all in one place.

Mr EVANS: For the purposes of members of the public who might be listening in, can you please tell us a little bit more about the tadpole trapping, which is clearly where some of the most recent innovation has been. Where's it up to? How's it funded? How is it being rolled out? Can you tell us a little bit more about the current state of play?

Prof. Capon : I can give a quick summary of what we're doing in Queensland. Some years ago, with Rick and his team, we developed a tadpole-trapping approach which uses a pheromone that we can harvest from dead adult toads and make into an artificial attractant mate. When this is placed in a funnel trap, which is a simple plastic box with a couple of funnels glued into the side, you can catch hundreds, thousands, even tens of thousands, of tadpoles in relatively short periods of time. Even though we discovered that, patented it and published it almost eight years ago now—seven or eight years ago—it has proved to be very difficult to get it commercialised.

So, some years ago here in Queensland I set up an organisation called the Cane Toad Challenge. It runs out of the University of Queensland. It's a citizens science and community engagement initiative. We invited organisations to become affiliate members for free. We found that if we offered to charge them something they didn't want to join, so we made it free. We have over 50 organisations signed up now and a further 40 pending sign-off on their forms. They include most of the city and regional councils up the east coast of Australia and many companies and other organisations. We provide them with free baits, which they use their resources, their land and their facilities for. They make their own traps and do the trapping, and they report back to us what they got. That is fully funded at the moment by public donations. There is no funding source from any granting agency. It's a shoestring operation, yet it has already galvanised many thousands of members of the public to get involved.

Prof. Shine : I will chime in with some of the earlier history of that. The Australian Research Council has been the primary funder for my research on cane toads. It was very much a result of that ARC funding that enabled us to discover this cannibalistic response in cane toad tadpoles. A chemical coming out of toad eggs was attractive to toad tadpoles and not to the tadpoles of native frogs. We then worked with Rob to identify the nature of that chemical. The tadpole trap is a good example of a very serendipitous discovery that came out of fundamental research. We were actually trying to look at the impact of cane toads on native frogs. We were worried that some native frog tadpoles might be attracted to toad eggs and eat them and be poisoned, so we started looking at trials. We put out cane toad eggs in funnel traps expecting to catch native tadpoles, and, to our shock and horror, thousands of cane toad tadpoles tried to get into those traps. It really is a discovery that came out of fundamental science supported by the Australian Research Council and then developed by that foundation.

Mr HOWARTH: Professor Capon, you were talking before about the pheromone trap. Does that attract any native frogs or anything, or is it that when you put this in a freshwater lake or environment it specifically attracts cane toad tadpoles?

Prof. Capon : Our experience is that it's unique to cane toad tadpoles, not the frog tadpoles. Some of our trappers have reported that they get occasional bycatch in the form of certain types of fish. One of the advantages of the tadpole trapping is that it's non-lethal. They go into the trap and then they just look at the trap. If there's something there that they don't want, they release it.

Mr HOWARTH: What sorts of native fish are attracted to it?

Prof. Capon : I couldn't give you the precise species, but it has been documented. Brisbane City Council signed on as one of our affiliates and contracted an independent environmental company, Ecosure, to do a three-month study to independently validate the method. That study documented the nature of the bycatch quite thoroughly.

Mr HOWARTH: Did you say the trap is made out of plastic?

Prof. Capon : It's just a plastic box that you would get from Officeworks, Bunnings, Coles or something like that. It's nothing too fancy. It has a couple of holes drilled in the side and plastic funnels put into it. We don't make any of the traps for any of our affiliates. We just tell them how to do it.

Mr HOWARTH: What I'm interested in is the federal government or state governments funding something like this. I think a lot more money needs to be poured into combating the cane toad. What I'm wondering is: if these were made commercially funded by the government and put in every freshwater lake or dam throughout Queensland, Northern Territory and Western Australia, how effective do you think that would be at reducing cane toad numbers?

Prof. Capon : At the moment there doesn't seem to be a bottleneck in people making traps. They're perfectly happy to do so. That doesn't mean to say that everybody's traps are ideal. The value of a preprepared or predesigned trap would be that you could optimise their configuration and make them better. There would be value in having a supply of traps. The real limiting factor is the baits. We're the only ones that are making the baits at the moment and, as I said, we are doing it voluntarily.

Mr HOWARTH: And, when you say, 'we'—sorry, I missed it on the way in—which organisation are you with, Professor?

Prof. Capon : I'm with the University of Queensland, and 'we' is me and my postdoc working after hours.

Mr HOWARTH: I just wondered if there was a federal environment grant or something to fund the making of these baits as well—how much you'd need for that and what it would cost.

Prof. Capon : I think the picture of funding cane toad research is probably bigger than just the making of the baits. It's about coordinating the various processes, whether it's toad busting, trapping or fencing off areas and stuff. It's doing it in a coordinated fashion and in an informed fashion. Where the public gets involved, it's about making sure that they—and even government agencies—are properly advised on best practice.

Mr HOWARTH: Have you made a submission to the inquiry? Sorry, I haven't seen yours—have you put all that in there?

Prof. Capon : Yes, I have.

Mr HOWARTH: Okay. You might be interested too—I recently got a small grant for cane toad sniffer dog on Moreton Island up in South-East Queensland. Moreton Island is the only island, that I'm aware of, in South-East Queensland that is cane toad free. One of the benefits there is that on the western side of the island, where most of the campers, go there's not a lot of freshwater lakes, and I'm assuming they don’t breed in saltwater. I'm interested too in making sure that they never get a foothold there as well. If some of those bait traps could be put into freshwater on Moreton Island, that would be something I would be interested in as well.

Prof. Capon : Yes.

Prof. Phillips : Can I just chime in quickly. The idea of trapping tadpoles is wonderful and it will presumably remove a large number of tadpoles from breeding sites. The reality, however, is that it's not possible to achieve sustained control across a large landscape by trapping at water bodies. I think you're completely right to focus on an island. In places where toads aren't really going to immigrate in from and places where there's a set small number of water bodies that can be managed, you may well achieve considerable success. But, certainly on the mainland, and particularly in mesic parts of the country, where lots of rain happens, it is actually infeasible to put traps in every single pond. You'll find that animals move in from very large distances away and you only need to miss a few of them for there to be toads around. So I think we need to be clear that the tadpole trapping is only going to be effective—complete population suppression—in places where dispersal of toads from other places is strongly restricted.

Mr HOWARTH: Obviously it would be very labour intensive—people checking the traps—and unless there's funding for people to do that, you're relying on volunteers. Can I just ask one more thing. I missed the beginning. Biological control: what sort of money is currently available for scientists to research and develop biological controls to wipe out cane toads. If there's nothing, what would be needed? Obviously it wouldn't be as labour intensive if you had something released that would just knock out cane toads. Is anything like that possible?

Prof. Capon : Just to be clear, the reason we have cane toads is because of a failed biological control. There is tremendous—while there is the possibility, the hope, that you could come up with a voluntary control, there is also the challenge of how you do that scientifically. Then, even if you think you've got something, there is the question of whether there is the public enthusiasm or even legislative enthusiasm to release another control agent into the environment.

Mr HOWARTH: Just because it's failed once before—they're now a massive problem, aren't they? They're poisonous; they kill our dogs; they kill snakes; they kill lizards; they kill a whole lot of native animals. Just because they’ve stuffed up in the past doesn't mean we shouldn’t look at it in the future, surely?

Prof. Capon : There was funding; several millions of dollars were spent looking for a biological control with CSIRO, and that came to nothing.

Prof. Letnic : Just to add a couple of points, to provide some context on the chemical traps. Cane toads have sort of occupied approximately half of Queensland and half of the Northern Territory at the moment. So, if we were to try to get rid of them by deploying traps across all of that area, it is just physically not possible, especially as we can't get there when the cane toads are breeding as there is no access; it is all under water.

There is great potential if we can find a biological control, but a biological control isn't entirely a silver bullet. We know this from myxomatosis and calicivirus. They have been enormously successful at reducing rabbit numbers, but evolution is always in process. So the rabbits have actually evolved to have a resistance to the viruses and the viruses have actually evolved to be less deadly. So the effectiveness of the viruses has actually waned over time. They still work but we need other methods; we need a multitude of methods. With rabbits we don't just rely on the control. So it is important to realise that there is no silver bullet for cane toads. We are going to have to use multiple approaches in different contexts.

Prof. Shine : I might weigh in briefly on the biological control story. I can certainly endorse Mike's comments about the need for adjusting the approach to the local situation. Cane toads are over such a vast array of habitats and in proximity to people in some places and not others. I guess the question I would like to pose is: suppose we came up with a terrific silver bullet that really did kill toads and had no effect on native frogs and didn't jump across to native frogs—which of course is always a real danger—I think that that wonderful bullet would very rapidly spread. There are a lot of backpackers going to Indonesia from Darwin with mud on their boots. There are plenty of native toads in Indonesia. I suspect that somebody would probably get back to Brazil pretty quickly. Do we really want to have a cane toad killing virus that wipes out cane toads across their native range? That would be an international wildlife catastrophe, far greater than anything that cane toads have done in Australia. So I think we have to be exceedingly careful when talking about biological control. We wouldn't want to repeat the errors of 1935.

Mr HOWARTH: Wouldn't that be a responsibility for the country where cane toads are native? As an Australian member of parliament, I am interested in what is happening in Australia and the damage being done to our reptiles. I am assuming that it does kill some fish and perhaps turtles if they eat tadpoles. I am not sure about that. We have strong customs and border protection here, and people aren't allowed to come into our country with mud on their boots. Maybe other countries need to adopt that as well.

Prof. Shine : I think people try very hard, but it is very difficult to stop things like viruses moving from one place to another. History tells us how difficult that is.

The ecological impact of cane toads is actually a lot different than most people think. Many Australian native species can eat cane toads without problems—like rats, birds, insects and so on. They generally don't seem to have any impact on native fish or turtles. They kill occasional individuals, but they don’t impact population viability. The primary impact of cane toads occurs at the invasion front, when they first arrive. Predators like goannas, quolls, freshwater crocodiles, snakes and bluetongue lizards eat a toad and die of a heart attack. So it is a catastrophic impact at the invasion front, but, as far as we know, there's actually not all that much of a continuing impact from cane toads after they've been around for a few years. Indeed, those vulnerable species do tend to recover.

Prof. Letnic : I don't entirely agree with that point, Rick. They turn the ecology upside down. I haven't seen a goanna on the Victoria River or the Daly River—where I work—for more than 10 years, and certainly Aboriginal people haven't either. So things don't go extinct, but the ecosystem is completely shifted. So things do change in the long term.

ACTING CHAIR: We are going to move on and give Dr Gillespie an opportunity to ask a question.

Dr GILLESPIE: Reading your submissions, the pheromone and the amoeba, to me, look like the best spreadable thing that won't have implications for the international situation—namely, a virus to kill them. If all of you were Prime Minister for the day and you could set up a program to control and aim to eradicate or minimise to a negligible population, what would be in your various wish lists? You've outlined lots of things, but what should we do?

Prof. Letnic : I think we look at the different parts of the country and we see what we can do. There are some easy things we can do, and Ben will have a lot more to say about this. Most of the country that cane toads will invade in Australia is arid and sparsely settled. In those areas we can keep the toads out by simply keeping them out of water. I would like to invest money in keeping them out of the water in those areas. That would be a huge area of the country. There are many other circumstances where I think the pheromone traps have got great potential, but we need to look at the circumstances in each situation. With those two approaches, I think we could go forward a long way, but they both need investment. Excluding cane toads from water has had almost no investment at all, even though we've shown it to be very effective. So I think developing integrated approaches for cane toad control that are regionally appropriate, and not forgetting regions, is the most important thing. There's no way that the pheromone traps can be used in the more arid or remote parts of the country.

Prof. Phillips : If I could have my wish list I would invest in setting up a waterless barrier to stop them getting into the Pilbara. The primary reason for that is that, if you manage a small bit of country and you keep them out of 270,000 square kilometres of Australia, the biodiversity benefits of that are huge. And, as Rick has mentioned, most of those diversity impacts happen in the first few years that the toads get there. In terms of bang for buck, stopping them from getting to somewhere is a huge win. A lot of the control options that happen after toads have invaded are useful in reducing their numbers. But, as Rick has pointed out, many of the impacts have already happened by that stage. So, bang for buck: keep them out of places where they haven't got to yet.

Dr GILLESPIE: I gather you mean water barriers around bores or putting water barriers around dams or creeks?

Prof. Phillips : The submission we put together pointed out that we have this incredible opportunity before us at the moment. Cane toads are about to spread through the Kimberley. They will get to Broome. To go any further than that they need to move through a very narrow corridor along the coast, between the Great Sandy Desert and the ocean, where there is water that's been brought up by pastoralists. If we manage a section of those water bodies such that we upgrade the infrastructure for the pastoralists—so they don't leak—the toad invasion stops at that spot; the toad invasion does not continue down into the Pilbara and it doesn't take up another 268,000 square kilometres of the country. So, as I said, were I to have my wish list that is what I would see done. I would also say that the science behind that idea is very well developed, to the point that we're pretty much sitting here saying, 'It's done, largely.' It's a very well developed idea. It can work. It just requires some political leadership and some capital.

ACTING CHAIR: Other people have mentioned the waterless barrier there. Does anyone have an idea about the quantum of the costs to make those infrastructure investments?

Prof. Phillips : For the waterless barrier, we have actually gone through the entire process of modelling the costs. In terms of the maintenance and upgrade of infrastructure, it works out to be about $100,000 a year to keep toads out of the Pilbara. There are obviously some monitoring costs that haven't been factored into that, in terms of salaries and effort there, but it's astonishingly cheap for a very large impact.

Prof. Letnic : On that point, if there's anywhere that we could achieve a win against cane toads it is in that Pilbara barrier. We know from the fieldwork and various experiments that we've done that we can successfully keep the toads out by using those approaches. While I would love to invest in lots of other areas of the country to keep cane toads out, that's an area where we're most likely to succeed, and we've got a great deal to lose if we let them through.

Mr HOWARTH: That sounds like a fantastic idea, and for not a lot of money. Would a cane toad barrier only need to be very low? It would need to be only a foot or less, and native frogs could still crawl over it. Is that right?

Prof. Letnic : No. In that seasonally dry country, where it is either permanently arid—even in the southern parts of the wet-dry tropics, it rains for only a short amount of time and then most of the year it is dry and there is no natural surface water. In those areas the only natural surface water is the dams that are provided for cattle. The cane toads use those dams as refuges during the dry season. You might get a thousand toads living in one dam and when it rains the toads jump out of the dam and hop out into the landscape and some of them find the next dam. So, they are using the dams as stepping stones to get across the landscape. The idea of the fences or the barriers isn't to create a fence. It is to make the dams toadproof. You actually only build a fence, say, it might be a 100-metre long fence, around a dam or you install a different type of reservoir. You can have alternative types of reservoirs, like flat tanks made of steel or plastic to provide the water. They just need to keep the toads out of the water, not create a fence.

Mr HOWARTH: I understand that, but doesn't keeping them out of the water require a fence around the current dams. The fence would be low so that kangaroos or whatever can jump over it but toads can't. I understand they can't jump very high. And in the future, why couldn't the government invest in little toadproof fences around a whole lot of freshwater places throughout Australia to stop them getting into those areas and breeding?

Prof. Phillips : The issue there is cost. What we are talking about with this idea of stopping the toads from getting down in the Pilbara is that almost all of the water that is coming up onto the surface is pastoral infrastructure. It can just go into a tank or a cattle trough and the toads can't get to it, because, as you pointed out, they can't actually jump very high. They can't get into cattle troughs if the cattle troughs are set up correctly. That's actually a very cheap thing to do. In fact, many of the pastoralists have already moved over to that type of infrastructure, because it is more efficient for them that way. Putting fences around water bodies is a larger undertaking. With the kind of turkey nest dams that people build in arid parts of the country it is reasonably easy to do that. But once you start to look at a natural water body and you start to have very large rainfalls, like we have seen in Townsville, for example, the cost of that rapidly becomes incredibly prohibitive.

Mr EVANS: I have a couple of questions on the waterless barrier idea in Western Australia between the Kimberley and the Pilbara. Give us an idea of the scale of this. How far inland would it have to go?

Prof. Phillips : Most of the pastoral infrastructure is within 15 or 20 kilometres of the coast. So, what we're talking about is managing around about 70 to 100 water bodies, depending on where you put it. When I say water bodies I mean artificial water points. You manage about that many artificial water points and that sets you up an area that's about 70 kilometres deep and about 20 or 30 kilometres wide that contains all of the available water in that area. It's an area that the toads have to move through. You effectively deny them access to the water that they need in the dry season to survive. During the wet season the toads move into that area if it rains a lot. But when it dries out and gets very hot, they have no water resource to survive and they all perish, so the invasion gets pushed back to the edge of the barrier.

Mr EVANS: That's a very modest and manageable size and scale. Who owns the land? Are there private property interests to navigate here? Is it just different levels of government working together? What are the possible regulatory hurdles?

Prof. Phillips : The land is owned by the Karajarri and Nyangumarta people. They had their native title declarations in 2014, I believe. There are numerous pastoral leases over that stretch of country; I think there are 11 of them. As to effecting that barrier, there are several properties that could do it all on their own. So a single pastoral lease could do that, in some circumstances. In other circumstances, a couple of pastoral leaseholders could get together and make it work. So really it would require a reasonably small consensus of stakeholders to make it happen.

Mr EVANS: Fantastic. Thank you.

ACTING CHAIR: Without getting into a debate about climate change, all the experts have said that climate change is causing Australia to get hotter and rainfall to either fall in some places or increase in intensity in other parts of the country. So, from all your research, what impact do you think climate change will have on the spread of cane toads?

Prof. Letnic : If we're going to get bigger rain events up in the tropics then it could potentially increase their potential to spread, but it is very hard to say; it's very difficult. But we know already that there's a great deal of variability in climate and it's those really big years, the big wet years, that are the years when the toads spread the most. So, really, we'd be having more of those big year spreads. I guess, if we were thinking about waterless barriers, we would be modelling our scenarios and planning our scenarios on what we know as being big years for rainfall, to try and build an appropriately sized barrier.

ACTING CHAIR: On the temperature side, if the whole continent is getting warmer, does that extend the range for the cane toads into places like Canberra, for example?

Prof. Letnic : I don't know about Canberra, but they'll go a bit further south, into New South Wales especially. I couldn't see them going a huge lot further, but they'll go further for sure.

Prof. Phillips : I would agree with Mike that it's very difficult to work out what the effect of climate change would be on the possible range of the toad. I think there has been one exercise that has tried to model it, and that, in fact, surprisingly, came up with a slightly reduced range in northern Australia, I think because it's hot and dry at the wrong times of the year so the seasonality is changed very slightly. So the response of the animals is very complicated and difficult to predict. But I also agree with Mike that, if we were trying to set up a waterless barrier, we should be modelling the possibility that toads might be living in paradise, because that's a possibility, and in fact we have done that—we've said, 'Okay, let's throw out the current climate and let's just imagine toads are living in paradise for six months of the year,' and so some of the modelling we have done around this waterless barrier idea has already taken into account the possibility at least that things might become a lot better for cane toads.

ACTING CHAIR: We'll let Dr Gillespie have one final question and then we will have to wrap up.

Dr GILLESPIE: We've got the message: the Kimberley-Pilbara barrier is the way to go. That's prevention being better than a cure. But, for areas that are already infested, what do you think is the best thing we should be doing? Like I said, if you were king or Prime Minister for the day and you had to make a decision on what we're going to do as a nation to try and minimise or even eradicate the toads, what would you be doing?

Prof. Capon : My prediction is that the cure for cane toads hasn't yet been invented. All the things we're talking about are stopgap measures. We've found that the relatively modest investment in the basic research that Rick did in identifying the behaviour of cane toad tadpoles and eggs, and the subsequent translation of that into trapping technology, has shown that a chemical ecology approach at that intersection between ecology and the science of chemistry has revealed a very practical solution. I am of the view that there are other equally attractive and even better solutions that are yet to be discovered in that general area. So I would encourage the committee to consider that further investment in chemical ecology based research around cane toads has tremendous potential.

Dr GILLESPIE: Thanks very much. Any other suggestions, Professors?

Prof. Shine : I agree with Rob. I think that emerging wildlife diseases are also interesting. There are many, many reports of cane toads dying suddenly over quite large areas, and we don't really know the pathogens involved. We've done quite a lot of research on the lungworm that the toads brought with them from South America. It can be fatal, but it is not generally transferred to native frogs. We've recently discovered an amoeba that causes a fatal dysentery. I think there are all kinds of potential for organisms already within Australia. If we understood a bit more about how they affect toads, perhaps we'd end up with some useful weapons.

Dr GILLESPIE: Thanks very much.

ACTING CHAIR: Thank you for attendance here today via teleconference. If you've been asked to provide any additional information, could you please forward it to the secretariat. The committee may have additional questions for your response on notice which will be sent to you from the secretariat. You'll be sent a copy of the transcript of your evidence and will have an opportunity to request corrections to transcription errors. Can I thank you all for making the effort to put in submissions, to appear via teleconference today and, more broadly, for the work you do in a very important area to preserve Australia's ecological uniqueness and our native flora and fauna. So, thank you very much and have a great day.