Current immigration rates into Australia, and associated projected population growth, will make greenhouse gas emissions targets even more difficult to achieve in the future, a University of Adelaide-led study has found.

Published in the journal Asia and the Pacific Policy Forum, Professor Corey Bradshaw (University of Adelaide) in collaboration with Professor Barry Brook (University of Tasmania), examined the relative contribution of different immigration policies to Australia's future population size and trajectory. Australia's natural is below replacement, so both its recent past and future increases in total population size result from net immigration.

The researchers investigated how much Australia needs to reduce its per capita emissions to achieve future under six different immigration scenarios: zero net immigration; 'business-as-usual' net intake of 215,000 people/year; constant proportional immigration of 1 percent of the total population; total net intake of 20,000 and 100,000 a year; and doubling the net total immigration.

"Australians are among the highest per capita greenhouse gas emitters on the planet, exuding a whopping 25-27 tonnes of greenhouse gases (carbon dioxide equivalents) per person per year," says Professor Bradshaw, Sir Hubert Wilkins Chair of Climate Change at the University of Adelaide's Environment Institute. "By way of comparison, the French emit 5.2 tonnes, the Chinese 6.7 tonnes, the Canadians 14.1 tonnes and the Americans 17.0 tonnes – our emissions record is appalling."

The researchers looked at the current national targets of 5 percent reduction on year 2000 emissions by 2020, and 26-28 percent reduction on year 2005 emissions by 2030, as well as an earlier, no longer in place, target of 80 percent reduction on year 2000 emissions by 2050.

They found that achieving the 2030 target of 27 percent reduction (the median of 26-28 percent) would require a drop in per capita yearly emissions to between 12.5 and 17.4 tonnes by 2030, depending on the immigration scenario.

"We'll need to achieve massive reductions in our per capita emissions, regardless of which immigration policy we follow," says Professor Brook, Professor of Environmental Sustainability at the University of Tasmania.

"If we maintain constant proportional net immigration of 1 percent, we would have roughly 10 percent more emissions by 2030 than if our population remained stable. To meet the 2030 target we would need to get down to 15 tonnes of emissions per person by 2030 and, even at zero net immigration, that figure would be 12.5 tonnes. That's under 14 years from now.

"We need a rapid energy revolution if we want any chance of stemming emissions to meet our targets."

The 80 percent reduction by 2050 would require a drop to 3-5 tonnes emissions per person, equivalent to reducing per capita output by 6 to 10 times relative to today's emissions.

"Australia has no credible mechanisms in place to achieve these goals," says Professor Bradshaw. "That will require substantial policy changes across , energy, agriculture and the environmental sectors."

More information: Corey J. A. Bradshaw et al. Implications of Australia's Population Policy for Future Greenhouse Gas Emissions Targets, Asia & the Pacific Policy Studies (2016). DOI: 10.1002/app5.135