Mid-way through last year the United Nations published its latest biennial review of world population prospects. Despite it holding major long-term implications for human-kind, the release scarcely raised a ripple. Two years earlier it was the same with the previous report. Ditto for the several reports before that. World population growth is perceived, unfortunately, as being yesterday's problem. With the global growth rate down from the high levels of the 1960s and '70s and the apocalyptic demographic prognostications of Paul Ehrlich, the Club of Rome and other doomsayers not having come to pass, the population bomb is widely seen as having been defused. This view is dangerously wrong. Although global population growth has dropped by about 40 per cent in the past 40 years, there is still a considerable increase ahead before human numbers can realistically be anticipated to level off. According to the "medium" scenario in the UN report there will likely be 1.1 billion additions to the world's population between 2010 and 2025, and then about the same number again in the following quarter-century. With more growth after that. Yet these figures excite little interest. While the world would be better off without those additions, it is not so much the projected global increase that is the worry. The problem is that the great bulk of it will occur in countries least capable of handling it — where population pressures are already all too clearly present.

Some countries are projected have population growth of 40 per cent or more by 2025. All up, 24 countries are likely to add 10 million or more people to their populations in the blink of the decade and a half. With one exception (the United States), all are less developed countries. While significant falls have occurred in birth rates in most less developed countries, "wanted fertility" is still well above replacement level in many. Even where fertility has fallen close to, or below, replacement level, the age structures resulting from previous high birth rates mean substantial built-in momentum for further population growth. In absolute numbers, the two demographic billionaires, India and China, are, not surprisingly, likely to increase the most. India is projected to add more than 200 million people by 2025, and China about 100 million. Both countries are on established economic development paths and will probably be able to handle those numbers. However, India already has well over 200 million people who are undernourished and a quarter of its population lives under the global poverty line of $1 a day. There are greater concerns for other places. One has to wonder about Pakistan's capacity, for instance, to accommodate more than 60 million extra people by 2025, as the UN has projected. Or Nigeria gaining a further 52 million in the same period. Ethiopia, 35 million. Bangladesh, 31 million. The Democratic Republic of the Congo, 30 million. What prospects for Niger being able to comfortably absorb a 72 per cent increase? East Timor, 60 per cent? Afghanistan, a 54 per cent increase? The Gaza/West Bank Palestinian territories, 49 per cent? Somalia, 49 per cent? Yemen, 46 per cent?

What should also raise major concerns is the projected increase of 41 million to the US population in the next 15 years, and then perhaps 45 million or so more in the 25 years after that. The biggest worry is the ecological footprint that these likely heavy order consumers will place on the planet. Unless there are substantial changes to US production and consumption patterns, these additions will have a far greater impact on the global environment than those of Pakistan, Nigeria, Ethiopia, Bangladesh and the Democratic Republic of Congo combined. What does the future hold for Australia? Bob Birrell and Ernest Healy of Monash University have demonstrated that the projected population increase here will pose problems for the government's goal of cutting greenhouse emissions by 5 per cent by 2020. Over and above environmental and humanitarian concerns, these demographics have important national and international political and security ramifications through their lengthening of potentially volatile "youth bulges" in many less developed countries. Studies have shown that countries with large youth bulges (usually defined as where people aged 15-29 make up 40 per cent or more of the adult population) are especially prone to civil unrest and armed conflict.

A youth bulge in itself does not make unrest and conflict inevitable. If a nation's economy can meet the demographic pressure for productive job creation, a bulge of up to 30 years can be the foundation for sustained economic growth — a workforce "demographic dividend". But when mixed with high levels of young adult unemployment and frustration at the lack of opportunities for advancement, youth bulges be form a volatile recipe for political upheaval. Unfortunately, political troublespots Iraq, Afghanistan, Pakistan, the Palestinian territories and Somalia are all excellent examples. The conflicts in these countries are usually viewed through political, military, religious and ethnic lenses, but there will be no long-term stability in any of these countries until their underlying structural demographics and parallel economic development deficiencies are addressed. Nor are those countries an exhaustive list. Yemen, Egypt, Saudi Arabia and several other Arab states, along with Nigeria, the Democratic Republic of Congo, Kenya and other sub-Saharan nations are places where demographic youth bulges will almost certainly be powerful destabilising forces in the years ahead. In our own regional neighbourhood, East Timor, Papua New Guinea and several Pacific Island states are of concern. Not according these demographics their due importance will be costly.

Kevin McCracken is a former dean of environmental and life sciences and now an honorary senior research fellow at Macquarie University.