It's true that in places where birthrates remain high, e.g. sub-Saharan Africa, per-capita emissions are quite low. Joseph Chamie and Betsy Hartmann see this as reason not to pursue a population policy to reduce emissions. We argue that full access to contraception in such regions can help with emissions reduction because per capita emissions must rise in order for people to be lifted out of poverty. The environmental impact of development can be reduced if there are fewer poor people needing to make the transition.
Relentless population growth means eventually reaching a limit of environmental collapse where the supply of crucial, irreplaceable resources (e.g., water and land) is grossly exceeded. If one doesn't have the purchasing power to acquire such resources from others, the only options are to migrate as environmental refugees; accept international handouts forever; or die by starvation, disease, or slaughter. This is demographic entrapment. It's a highly inconvenient truth. Thus, we use the terminology but reject unambiguously the dreadful baggage (e.g. "lifeboat ethics") added by Maurice King, Garrett Hardin, or anyone else.
John Guillebaud was brought up in Rwanda, preferring Kinyarwanda to English until age six. He has visited the Genocide Museum in Kigali and wept for his boyhood friend, Husi Kajuga, and his family, who lie there in a mass grave. There were fewer than 2 million Rwandans when John played with Husi during the 1940s, but 8 million by the 1994 genocide. Resource-poor Rwanda had grown no larger in that time. James Gasana, Rwanda's minister of agriculture and environment from 1990-1992, asserts unequivocally the relevance of population growth to the genocide, though Betsy should note we accept in addition the major roles of inequity and longstanding ethnic divisions fomented by outsiders--the United Nations also shares some culpability. (See Linda Melvern's "Conspiracy to Murder: The Rwandan Genocide.")
For the whole planet to avoid the fate of Rwanda, we say "Malthusian thinking" needs rehabilitation. Since Malthus first highlighted population in 1798, humans have multiplied sevenfold. Economists thought we'd disproved Malthus with Norman Borlaug's green revolution, which ushered in a spectacular increase in food production. Yet that improved technology is wholly dependent upon fossil fuels for fertilizers, tractors, and transport. When our fossil fuels are gone, there will be a vast surplus population whose energy needs Earth will no longer be able to supply, and it will be too late for family planning. But if properly resourced now, family planning can still help by minimizing the number of new arrivals who will produce additional greenhouse gases as they rise from poverty.
Contraception is a remarkable invention, uniquely available to our species. A common myth is that large families among poor couples are a calculated choice, based on high child mortality and the social security factor. These factors have some relevance, but our experience is that large families happen chiefly because couples aren't empowered to prevent them. Frequent sex is human nature, which makes avoiding conception difficult--for everyone. The difficulty increases in the many settings where women's rights are abused, where contraceptives are in short supply, where the extent and range of barriers to their use aren't well understood, and where misinformation stifles demand.
We agree that we must also pursue everything in Betsy's penultimate paragraph. What would it mean to us as individuals to sufficiently reduce per-capita emissions in the high-consuming countries (mainly North American and Europe)? To reach the maximum sustainable global biocapacity--given our current population--of 1.83 global hectares (gha) per person, we would need to reduce our mean footprint from 6.4 gha to 3.7 gha per person, or further if the small ecological footprints of low-consuming countries increase. But we won't achieve that 42-percent reduction through minor gestures such as unplugging electronics and recycling. We need to fly half as much; shift massively from cars to bicycles and public transportation; eat half as much meat; buy half the amount of goods; tolerate less air conditioning in hot weather and less heating in cold weather; and if all that doesn't work, institute rationing, as in time of war--all of which entails reducing consumer appetites and fully implementing a "reduce, reuse, and recycle" culture.
The current unrest in Haiti and elsewhere over food prices underlines the real conflict between growing population pressure and the limited biocapacity of a warming planet. We urgently need to balance the equation by reducing population, but not by population control--Betsy's word, never ours. Rather, we should wisely and compassionately demonstrate the necessity through education, through the media, by example, and above all, by meeting women's needs and everyone's right to have fewer children by choice, not chance.