Trust the military to give it to me straight. Population comes up at virtually every talk I give - on climate change, development or just about anything else. But usually my questioners are a bit more circumspect than the man from the armed forces who asked what could be done about "women popping them out" in poor countries.
People cause climate change, therefore cut the number of people. Right? Not really. A closer look shows that the conventional view is wrong, or at least a gross over-simplification.
First, the numbers. The global population is about 6.8 billion and rising, but the rate of growth is slowing and the world population is expected to peak at about 9 billion in 2050. The growth rate is slowing fast, verging on collapse in some countries (South Korea is in a national panic about falling fertility rates and shrinking populations and is likely to look to immigration to fill the gap). The drivers for a far faster demographic transition than that seen in previous centuries in Europe or America are a combination of urbanisation, women's education, access to contraception and (one hopes) the spread of notions of women's rights and control over their own fertility.
So one response is that the "problem" is self-solving, and indeed, if the transition gets any faster, the world could be faced by a serious shortage of working age people to look after the rising numbers of elderly. If their arguments were based on logic alone, the population control lobby would probably be advocating compulsory euthanasia rather than birth control, but its preponderance of elderly white male members makes that pretty unlikely.
In what sense is population growth a "problem" (or "challenge", as the management-speak people like to say)? Certainly not on climate change mitigation - reducing emissions. Over the last 30 years, the countries with fastest population growth rates have the slowest emissions growth rate, and vice versa. But that hasn't stopped a bit of blatant opportunism by the Optimum Population Trust (OPT), launching an offset scheme where you can offset your carbon emissions by funding birth control programmes in developing countries. Guys, the problem is consumption, not population. A cull of rich Americans or Australians might have an impact; population growth in Africa is largely irrelevant.
Adapting to climate change is more of an issue. In dozens of developing countries, Oxfam has witnessed the hammering that poor communities are already taking from climate change. Overcrowding in rural areas can increase their vulnerability. But the OPT doesn't seem too bothered about that (wonder why?). Population is undoubtedly one among many factors in hunger and local environmental degradation, although often there is enough food, it's the distribution that goes wrong.
So if population growth is (sometimes) important, what is to be done? Listen to women, stupid. No coercion is required, just access to education and family planning services (not just contraception, but also proper abortion facilities to reduce the horrendous death toll from backstreet butchers). Amartya Sen famously showed that a combination of girl's education and access to contraception prompted a demographic transition in Kerala every bit as fast as China's coerceive one child policy.
I'm talking evidence and arguments thus far, but the choice of language also matters. As soon as the issue is framed as "population control", the problem becomes "them" - those women "popping them out". That, along with population control programmes' chequered history of coercing and tricking people into being sterilized in several poor countries, is why many people in developing countries find the term so offensive. Start with "women's rights" and the discussion becomes about "us", our shared rights and the solidarity to achieve them. Talk about the problem of over-consumption, and the debate revolves around equity, redistribution and low carbon development, not fewer babies.
That discomfort on language is, I think, why so many on what could loosely be described as the left tend to avoid the subject altogether. But in doing so, we unwittingly abdicate the ground to the bad guys. Time to go on the offensive?
The population debate matters, especially in these two Copenhagen weeks, because it risks becoming a massive distraction. We need to focus on curbing consumption and emissions, not babies and women's rights. Otherwise we risk blaming the victims and letting the climate villains off the hook.
Duncan Green is head of research at Oxfam. Visit his blog