With the world risking ecological disaster at every turn-climate change, water stress, habitat destruction, over-hunting and over-fishing, pollution-sustainability of the world economy will require action on several fronts. We will have to economize on our use of scarce and depleting resources, especially fossil fuels and natural habitats vital to other species. We will have to foster resource-saving technologies, such as environmentally sound fish-farming to substitute for over-harvesting of ocean fisheries. And we will have to help the poor regions of the world to complete the demographic transition to achieve stable populations, a process that is underway but by far not fast enough. True, rapid population growth is not the main driver today of environmental threats. Pride of place goes to the high and rising rates of resource use per person, rather than to the rise in the sheer number of people. Even if the world's population were to stabilize at today's level of 6.5 billion people, the pressures of rising per capita resource use would continue to mount, as today's poor and middle-income societies increase their resource use to live like the rich countries, while today's rich countries continue their seemingly insatiable quest for still greater consumption levels. With the rich countries living at roughly $30,000 per person and the world's average income at around $10,000 per person, simply having the poor catch up with the incomes levels of the rich would triple global economic throughput, with all of the attendant environmental consequences.

The continued rapid population growth in many poor countries will markedly exacerbate the environmental stresses. Under current demographic trends, the U.N. forecasts a rise in the world's population to around 9 billion as of 2050, another 2.5 billion people. They will arrive in the poor regions, but aspire to income and consumption levels of the rest of the world. Those 2.5 billion people eventually living at the income standards of today's rich would have an income level more than today's entire world GNP. If the economic aspirations of the newly added population are fulfilled, the environmental pressures would be mind-boggling. If those aspirations are not fulfilled, the political pressures will be similarly mind-boggling. All the better, therefore, to slow population growth while there is still the chance.

The case for spurring rapid and voluntary reductions in fertility rates in the poorest countries is overwhelming. It would be among the smartest investments that the rich countries can make today for their own future welfare. Oddly, though, under the thrall of the religious right, the Bush Administration has turned its back on fertility control in poor countries, to the detriment of America's own national security and economic wellbeing in the decades ahead.

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