Colonise or Perish


Colonise or Perish

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Professor Stephen Garnett

Assisted colonisation of new species to Australia has always cut two ways. On the one hand it is the basis of Australian agriculture – without sheep, cattle and wheat we would be far poorer. But cane toads, gamba grass and a plethora of weeds and feral animals wreak havoc on the environment and cost a fortune to control.

It is against this background that RIEL’s Professor Stephen Garnett is part of a group exploring the pros and cons of assisted colonisation as a viable conservation strategy in the face of climate change.

“Assisted colonisation has been happening throughout human history,” Stephen explains. “Even for conservation the idea has been around a while. As a way of adapting to climate change, however, it is new and needs a lot of thought”.

The idea is that, if the climate is predicted to be unsuitable for a species, you move them to a new site where the climate should be better suited."

Since running a four-day workshop for the National Climate Change Adaptation Research Facility (NCCARF) called “Preparing for climate change – move who, when, where, how and why?” in Western Australia in 2010, Stephen and his colleagues have co-authored five peer-reviewed articles on the topic. Each article has taken one angle from the polygon of issues arising from assisted colonisation, and several authors to identify and discuss its contours. One piece published in 2011 looks at current legislative barriers to implementing such a conservation strategy. Another article released last year navigates some of the moral topography associated with assisted colonisation.

Three articles published this year address the idea from yet other angles. One explores two separate conservational functions of assisted colonisation, colloquially termed ‘push’ and ‘pull’ respectively. The ‘push’ kind of assisted colonisation works to revive the dwindling numbers of a certain species by moving it to an area where it is more likely to survive and prosper. Meanwhile, the ‘pull’ approach looks at ecosystems that will be hampered from functioning by the decline of a particular species. ‘Pulling’ in a substitute species could replace the missing species’ role in the functioning of the ecosystem – providing tree hollows for nests and shelter for example. Sometimes ‘push’ and ‘pull’ functions could be filled by the same species.

A second article, just published, looks at the guidelines for choosing sites for assisted colonisation. “It is all about risk management,” says Stephen, “the best sites are those from which the assisted species are least likely to escape should they prove weedy. Some sites, though, should be left alone.”

This year’s third article, ‘Making decisions to conserve species under climate change’, presents a potential decision framework for implementing assisted colonisation. The framework outlines a question and answer adaptation pathway that decision-makers can follow before settling on assisted colonisation as the answer to protecting a threatened species. Assisted colonisation is near the end of the path as a last resort if other, potentially less compromising conservation alternatives are unlikely to succeed.

Despite the diversity of minds and ideas churning over assisted colonisation as a viable conservation strategy, there remains vigorous debate both in and outside of the scientific community about whether to consider it at all.

“There are a group of people who are afraid of any sort of new introductions,” Stephen says. “There’s the worry that they will become pests of one sort or another, as has happened so often. But the other side of the debate is that invasive species are going to arrive anyway unless we manage the environment to help less mobile species.”

Apart from acknowledging that people are ultimately responsible for the climate change that will send many species to and over the brink of extinction, Stephen refrains from offering his own opinion on whether assisted colonisation is the right thing to do.

“It is our duty as scientists to communicate climate change scenarios and alternatives to the community,” he says. “The decision to implement assisted colonisation shouldn’t be decided by scientists and technical experts- they will bring their own personal philosophies into it which won’t necessarily reflect those of the wider community. Ultimately we’re part of a democratic system and we need to work with the view of the community about which choices we should be making with regard to climate change.”

Stephen declines to recommend any moral road here, although he does dish out the following, rather sobering, food for thought:

“While there are some species that will probably adapt to new climates, many we must assist or they will be lost. We, as a community, have decided to change the climate through our actions. We now have to consider the extent of ethical responsibilities for the consequences.”