The birth of the earth's seven billionth citizen this week has focussed predictable attention on the optimum size for the population of our planet.
Commentators on population matters have long been divided into "Isle of Wight optimists" and the "Malthusian pessimists." The former point out that we must get the issue into proportion. Large as it is, if you stood us shoulder to shoulder you could still get the world's entire population on an the Isle of Wight, so there's nothing much to worry about. The pessimists predict starvation and doom, as did the Rev'd T R Malthus in the 18th century. (The church's penchant for bad PR is nothing new.)
I tend to side with the Isle of Wight optimists. First, we are far from starvation point. If the world's food supply were divided equally between the seven billion there would be enough for 3 000 calories per person per day. In other words, if we all consumed our fair share we should all need to be enrolling for Weight Watchers. If 1bn people are starving and another 3bn hungry, the problem is one of distribution rather than numbers or resources. The real problem is one of coping with "waste", both natural and chemical, and the side effects of our industrial processes (pollution, greenhouse gasses etc.)
The truth about population size is that there is no acceptable method of doing much about it in the short run. Yes, we can make contraceptive methods available worldwide, and, more expensively, expand the most effective contraceptive method of all, girls' education. But forced methods such as the Chinese "one child" policy and the sterilisation programmes tried in India in the 70s and 80s are neither effective not acceptable.
Happily the long term solution is inbuilt. As poorer countries develop and children become expensive the population will control itself, as has already happened in the rich world. So welcome, little seven billionth citizen: you have entered an environment furnished with enough for everyone's need. Now we all need to work hard to make sure that you get your fair share.