Australasian Science Magazine

By Stephen Luntz

As climate change makes existing habitat unsuitable for many species, conservation managers will increasingly be faced with the decision over whether to relocate their charges to cooler locations. An Australian–New Zealand collaboration has provided a mechanism to assist such judgements.

“With the climate changing more rapidly than species can move or adapt, our only chance of saving some species may be to move them to more climatically suitable areas,” says lead author Dr Tracy Rout of the ARC Centre of Excellence for Environmental Decisions. “But introducing species to areas outside their historical range is a controversial strategy – and we have to be sure it will work, both for the animals themselves and for other species in their ‘new’ habitat.”

Rout was able to draw on pre-existing tools. “Australia has a risk assessment process for importing species to decide whether they have the characteristics to become invasive,” she says. The same methodology can be used to decide whether a species threatened in its old territory might become a threat to others in the new.

Other important factors to consider are how likely a species is to become extinct if efforts are not made to relocate representatives, and how much it is valued.

Rout admits that no model can decide for us how important species are. “Some are valued for their iconic status. Others have an important role in the ecology, but of course that may not be the case when moved to a new ecosystem. There will always be some kind of value judgement, but we are trying to separate that judgement out from the science.”

To test the model, Rout and New Zealand colleagues explored the possibility of moving the tuatara from the islands it inhabits off the coast of New Zealand to a hypothetical South Island location.

Tuatara look like lizards but occupy a distinct branch on the evolutionary tree, being closer to dinosaurs than anything alive. Like many reptiles they use temperature-dependent sex selection. Living in climates that are unusually cold for reptiles, the tuatara adults thrive in the warmth, but hatchlings are increasingly skewed male. This may eventually occur to such an extent that the species becomes unable to breed within its existing range.

“We explored how different value judgements for the importance of the species would affect what the model said about the decisions,” Rout says.