Centre for Plant Bidiversity Research
Centre for Plant Bidiversity Research
CSIRO Discovery Lecture Theatre, Wednesday 27 September 2000 at 4 pm
Speaker:
Richard Hobbs,
of Murdoch University.
Chair: Denis Saunders, CSIRO Wildlife and Ecology (CSIRO Sustainable Ecosystems from 3 October)
Panel:
Summary of talk and discussion by Roger Beckmann
Richard Hobbs started with an interesting comparison: introduced species, he asserted, pose a threat far more real and probably far more pervasive than the alien invaders of science fiction imagination. However, the ‘triffids’, of John Wyndham’s book, were perhaps a closer representation of what biologists fighting introduced species have to deal with. (The Day of the Triffids tells the story of large, human-slaying plants that successfully take over the world.)
It’s no exaggeration to say that introduced plants can be catastrophic for humans. In South Africa, recent bush fires near Table Mountain spread to suburban houses because of the opportunities provided by thick growths of invasive introduced species.
Just how much an introduced species can dominate all else was graphically portrayed in two photos: one of Australian rainforest smothered by Thunbergia vine; the other of a shopping trolley dredged from the American Great Lakes, totally encrusted with the zebra mussel, an introduced pest that is responsible for considerable damage because of marine fouling.
It is not just plants that are a problem. In Hawaii, introduced mosquitoes have successfully spread avian malaria, devastating the native bird populations in many lowland areas.
A changing world
The fact that the world is undergoing big changes in land use, fire regimes, atmospheric composition and climate can affect the balance between introduced and native species. There is no doubt that human activities can benefit invaders. Added to this is the huge volume of global commerce and transport, and the deliberate movement of crops, livestock, pets and ornamental species. Inadvertent movement - for example in the ballast water of tankers and in small species present on imported objects - is another factor.
We cannot simply study invasive species in a static system; they operate in a changing world. Invasion is a global issue, but one with important local impacts.
Money
Invasions are also expensive. A recent estimate from Pimental et al suggests that the cost in the USA is about US$137 billion, which comes from lost production and the expenses of attempted controls.
The irony here is that the cost would be considerably less if action were taken before the problem became excessive. Most invasions follow a standard pattern [see graph]: invader abundance is very low for some time (the lag phase), followed by a period of exponential growth; there is then a levelling-off as the new species fills the area that is suitable for its survival.
Total eradication is feasible during the slow lag phase. As the exponential phase progresses and abundance increases, only control measures - that slow the problem - are possible. The more abundant the invader, the more expensive (and the less cost-effective) are the controls. Crucially, the best control is prevention; quarantine, by stopping an invasion, is the most cost-effective method of dealing with the problem.
Sleeping giants
Because the lag phase can be decades, it’s considered likely that in Australia we have many species that are waiting before they break out into a problem. These ‘sleeping giants’ will be expensive to control in the future, unless we take action now.
Identifying a likely troublemaker before it hits its exponential growth is not always easy. Should we - could we - bother to control everything?
What constitutes a problem?
Are Fresias (originally from South Africa) a problem in Perth’s Kings Park? People appreciate the flowers and therefore the species is not considered a weed. This is an example of how perceptions can affect our priorities. If the plants are not harming or excluding natives, do they constitute a real problem - or should we be spending our time on tackling other, more important, invaders?
Biodiversity is about local uniqueness. We can’t hope to eradicate or even control all the invasive species that we have in Australia. Do we have to learn to live with invasives and accept new species assemblages? Unfortunately, Richard said he did not have an answer.
However, he did offer an example from South Africa, which he had recently been visiting. There are huge weed problems in that country - ironically, many are caused by Australian species. The introduced pines, hakeas and acacias use more water than many of the native species. The consequent reduction in available soil water and in run-off volumes is an issue that many people can relate to. As a result, the government has now set up a ‘Working for Water’ program in which local people take action to remove the plants. Given the high unemployment rate, the program successfully addresses two social concerns in rural areas - the availability of work and of water.
Connecting invasive species to broader issues like this, Richard felt, would enable biological invasions to receive the attention they required.
Priorities
Richard concluded with a brief mention of our priorities, including the $7 billion price tag of a Collins submarine. Perhaps similar quantities of money should be spent on the very real biological invasions that are taking place, rather than the less likely military ones.
He exhorted the audience to talk to people other than scientists, so as to get the message across to all of society.
Denis Saunders then questioned the panel. He started by mentioning Phytophthora cinnamomi in W.A (which may or may not have been introduced) and pointed out that we tend not to think of the smaller organisms that have been introduced and of their potential for harm. He asked Mike Wingfield, a mycologist, to enlarge on this.
Mike agreed that the invisible often went unnoticed. Phytophthora was perhaps an exception because its effects (jarrah dieback) were so obvious. Other pathogens in woody ecosystems (such as Chestnut blight in the UK and USA) also entered people’s consciousness. But many other transplanted fungal or bacterial organisms were less obvious: for example, the introduced soil fungi that that were brought in to help form mycorrhizae for pine trees to flourish. What effect do they have on soil ecosystems? Work in New Zealand has shown that some of these are moving into native ecosystems. But are they changing them?
Denis then focussed on the idea of priorities that Richard Hobbs had raised. He asked Gerry Maynes, of Environment Australia, whether the environment was a core priority for government, and if not, why not?
Gerry replied that programs for national feral animal control and weed eradication were split between EA and AFFA. In contrast to matters related to primary production (where money can be more forthcoming), biodiversity is everybody’s problem but also nobody’s problem. There was also the issue of differing values. A weed could be a valuable pasture plant. However, things have improved slightly. Ten years ago there was not much government interest. Now it is small, but growing.
Denis asked Henry Nix about native species being moved to another part of the country - for example rainbow lorikeets in Perth. Does it matter?
Henry declared that it did. He also pointed out that in Australia we tend to have a gap in our institutional arrangements. While there is some money and effort for quarantine, there is then a hiatus. The next level happens only once something has been declared a weed or noxious pest. We are thus unable to nip growing invasions in the bud.
He gave an example. Many years ago he had foreseen that the garden plant Bryophyllum (known as ‘mother of millions’) could be a problem in Queensland. Despite pleading with the authorities, nothing was done while the plant was restricted to cities and suburbs. Now it has spread out and will move even faster, as it has reached roadsides way beyond the town. It has just been declared noxious, but it is too late. It is beyond eradication.
In response to a question about developing the existing ‘well-oiled’ system for responding to invasions that threaten agriculture and forestry, Gerry Maynes pointed out that a new Environment Protection and Biodiversity Conservation Act would help deal with the gap that Henry Nix had mentioned.
The idea of predicting which species would be troublesome before they arrived was also suggested from the floor. Richard Hobbs felt that the best sign was if a species had been a problem somewhere else. However, changes in land use may spark off a problem with a species where there had not been one before.
Denis also pointed out that this could be complicated by species that could change their tolerance or range. For example, it could not have been predicted that the Arum lily would be able to grow so close to the sea on Garden Island, and tolerate saline water.
Mike posed the questions of Eucalyptus rust pathogens - of which there are none in Australia. However, if one arrives from South America, what effect would that have?
Richard mentioned the example of Cactoblastis, the moth used in Australia to control Opuntia, the prickly pear cactus. Also used on Caribbean islands as biocontrol agent, the moth had recently arrived in the southern USA, where it threatened the native Opuntia species.
Legal controls
Citing the visible invasion of pines into the eucalyptus forest near the Brindabellas, one questioner asked what is the legal onus on planters of crops to control them?
Gerry Maynes said that there was none, unless the species was on a State or Territory noxious plant list.
A better solution, another audience member suggested, was therefore to declare everything noxious and have people prove otherwise if they wanted to.
Gerry said that the Wildlife Protection Act since 1984 has worked from a similar premise, which is that new non-natives should not be introduced if there is evidence that they could pose an environmental problem. But often, of course, we don’t know. The newer Act, with its Alert List, should help with this.
Money and priorities
A questioner said that money given to communities to help fix local problems (such as Greening Australia dealing with willows in the upper Murrumbidgee catchment) was helpful but was not enough money to help win the war against invaders.
Gerry said that the National Heritage Trust was set up for specific purposes, which didn’t include weeds because they were seen as a landowner responsibility. Willows, however were one of 20 weeds of national significance. The best way of progressing was to look at how best to ameliorate the problem, not just count the numbers of dead of the invading species (rapid population increase can follow the killing).
Richard Hobbs stressed again how the South Africans had linked invasive issues to social ones. If we could do that, we wouldn’t have problems with funding.
An audience member confirmed that bitou bush along the Great Ocean Road in Victoria had been targeted by informing the local community. This society-based effort had been very effective.
Mike Wingfield commented, however, that many small organisms were simply not apparent. That made this approach harder. They might not even be known about by professionals. For example, it seemed that all the powdery mildews in Australia were non-native. But we need money for good basic biology to actually discover, name and study the vast unknowns of the microbial world.
Henry Nix continued with the theme of community by pointing out there was a resident population of indigenous people in northern Australia who were very alert to new species. He had proposed that they be organised into the Australian Biomonitoring Organisation - the acronym of which was not approved by governments.
Seminar summary by Roger Beckmann
