Climate change linked to increased military threats

Defence Force chiefs were told last night they could be called on to defend ''Fortress Australia'' from starving outsiders under the worst-case scenarios for global warming.

The security implications of climate change were delivered to the military's top brass at the Australian Defence Force Academy by former director of The Australia Institute Professor Clive Hamilton.

The Chief of the Defence Force, Air Chief Marshal Angus Houston, was present for the speech, along with leading figures from the army, navy and air force.

Professor Hamilton told his high-profile audience a leaked Pentagon report four years ago canvassed scenarios in which Australia and the United States were ''likely to build defensive fortresses'' around their countries to protect their resources from desperate outsiders and aggressive states caused by rapid climate change.

''It analysed the prospects for aggression 'if carrying capacities everywhere were suddenly lowered drastically by abrupt climate change','' he said.

''Humanity would revert to the norm of constant battles for diminishing resources ... Once again warfare would define human life.

Professor Hamilton said the world had only 12 months to decide on combined action or risk ''runaway'' climate change . ''We have one last chance to avoid the worst, and it comes at the Copenhagen conference at the end of 2009,'' he said.