The views expressed here are the author's own and do not reflect those of the Department of Defence or the Australian Government.

There is considerable evidence that plants and animals are changing their ranges in response to climate change. Species are moving to higher altitudes and latitudes in order to remain in temperature zones best suited to their needs. In the past, humans exhibited similar patters of behaviour. For example, the Central Asian steppe and the Sahara Desert have been described as lungs, pulling in and expelling out migrants as climatic conditions change.

Like all species, the human species requires resources to meets its needs. In the past, as the availability of resources waxed and waned, ancient humans often moved to balance need with availability. Now however, there exist man-made barriers to movement that were not as evident in earlier eras.

National boundaries serve to obstruct migration, while cultural and ethnic constraints further impede free access. Humans have also filled up most of the spaces in which they can survive, and with a global population now in excess of 7.2 billion, few unpopulated but habitable areas remain. Moreover, the world's resources are already heavily taxed; there is little opportunity for their further exploitation. 

As of 2012 the world had 45 million refugees. It is not possible to specify how many of these were climate refugees, because decisions to migrate have multiple causes including conflict, persecution and hunger. Climate-based motivations are more subtle than these, and, as it has been argued elsewhere, are often overlooked by researchers.

While physical barriers and societal boundaries provide disincentives to migrate, there is another even more important factor that militates against migration: the international order.

Wealthy states, international organisations and aid agencies provide direct grants, fund infrastructure improvements and offer educational and professional development assistance, all of which aims to improve the wellbeing of the world's less fortunate. Some states are virtual dependencies on the world's beneficence. For example, the Egyptian Government uses much of its foreign aid to subsidise domestic food prices so that its poor can afford to eat. 

As the effects of climate change continue to be felt they will reduce the resources available to meet human needs in many parts of the world. Humans have maximised their access to resources by harmonising production methods with their environment. Changes to rainfall patterns, the melting of glaciers, and the warming of coastal waters will affect the environmental systems on which humanity depends. Barring rapid adaptation, the risk is an uncoupling of production from its synchronisation with the environment. The effect of this in many parts of the world will be a widening of the gap between resource requirement and availability.

In the past, when deficits occurred the international community responded by shifting resources to regions in need. This acted as a safety valve that helped to provide stability and reduce conflict and social unrest. However, two developing challenges threaten to overwhelm the international system. The first is climate change, whose effect will reduce the availability of the resources that humanity requires. The second is that the existing international system is under threat from rising challenges to the dominance of the US and the superpower's own perception of its place in the world.

A world system in which there is a single international order has the ability to respond to crises when it chooses to do so. It is not a perfect system, but the US-led order has maintained the safety valve that has successfully reduced international tensions while improving the wellbeing of many peoples. If a new world order emerges, perhaps a multipolar one dominated by different values, the safety valve may no longer offer the same protection.

The replacement of the existing world order will have implications for a planet affected by climate change. Without a functioning safety valve, conflict between and within states will become more frequent and more vicious. As the deficit between resource requirement and availability widens, peoples who see their futures in terms of survival will be more prone to move in order to provide for their needs. As the support of the international community lessens, the destabilisation of weak states will become more prevalent and some areas of the world will sink into turmoil and chaos.

Humanity must adapt to climate change if it is to maintain its resource base and meet its needs. To do so, many dependent parts of the world will need a functioning international system that has a vested interest in the fate of weaker states. A failure to sustain such a system will lead to a world dominated by a fight for survival for all. 

Photo by Flickr user Balazs Gardi.