Australasian Science Magazine

By Don Driscoll

Is the suggestion of introducing elephants to control gamba grass in Australia such a ridiculous idea?

Professor David Bowman of the University of Tasmania really set the cat amongst the pigeons when he published an opinion piece in Nature suggesting that we should introduce elephants to Australia to control an invasive grass. There was a loud and ferocious response ridiculing the idea, yet much in what he suggests warrants reflection.

Bowman makes two critical points with which most conservationists would agree: Australian ecosystems are in a severe state of degradation due to invasive plants and animals, and we need to put all of the management options on the table to try to find ways of reducing the rate at which our biodiversity succumbs to the impacts of invasive alien species and other land management dilemmas.

He’s right. We should consider introducing elephants and rhinoceros to Australia. However, this should be weighed up alongside alternative approaches for dealing with the problem.

Let’s first consider the elephants and the objective of gamba grass control. The problem here is that gamba grass, introduced by the cattle industry, forms dense monocultures in tropical woodlands. Gamba grass can carry fires up to 25 times hotter than native grasslands.This cooks woody shrubs, trees, and everything that lived in them, thus completely changing the ecosystem. So exterminating gamba grass is a good idea – although many in the cattle industry disagree.

In assessing the value of elephant introduction, we need to establish how effectively elephants would control the target weed. But elephants also eat leaves from woody plants and love to push over trees, so once again the wider ecosystem is affected. Furthermore, elephants have a tendency to roam, requiring expensive fences to protect local communities.

However, the real question is whether all of those problems are worse and more expensive than other control methods. Gamba grass control is not without its limitations: the control methods are labour-intensive, machinery and chemicals are expensive, and the herbicides will have impacts on non-target species. And, as with the elephants, we need some data on how effectively spraying and slashing controls gamba grass.

While a knee-jerk reaction to Bowman’s out-of-the-box suggestion is that it is completely mad, to decide if we should reject this idea we have to discard our prejudices and look very carefully at the costs, the effectiveness, and the impacts on other societal objectives compared with the other options.

The same discarding of preconceptions and reconsidering all of the options using evidence is now needed in many of the land management decisions that we make. Bowman raises one of these: dingo culling.

Through the dogged research of Professor Chris Johnson, we now know that culling dingos in our rangelands is counter-productive as it leads to an increase in foxes and kangaroos. More foxes mean fewer native Australian mammals (goodbye Easter Bilby), and more kangaroos mean less grass for cattle and sheep producers.

Dingo culling is the elephant-in-the-room in Australian rangelands. If dingo packs are allowed to establish, they keep away foxes to the benefit of bilbies, and they control kangaroo numbers to the benefit of other native plant species (and commercial productivity).

Another area where elephants are called for (metaphorically speaking) is in bushfire management in southern Australia. Here, the standard practice has been to burn extensive areas of bush with the expectation that such burning will help to prevent house loss during bushfires. Recently the Victorian Government set the arbitrary goal of annually burning 5% of the forest estate as a response to the Black Saturday bushfires of February 2009. However, when you start gathering the evidence on the effectiveness of different management approaches, it quickly becomes apparent that widespread forest burning is not the solution to the protection of houses and lives during bushfires.

Using data from the Victorian 2009 bushfires, Dr Phillip Gibbons showed that burning forest at large distances from a house had only a relatively small protective effect (AS, April 2012, p.46). In contrast, the type of vegetation within 40 metres had a much larger influence on the risk of house loss. And this didn’t even consider the full range of out-of-the-box ideas, such as sprinkler systems, fire-resistant building designs or letting houses burn and then rebuilding them.

The 5% target of the Baillieu Government won’t protect houses, it costs a lot of money to implement and it has adverse impacts on biodiversity. This is the approach of a dinosaur when what we really need is an elephant!