WHILE I would not go as far as Heather Causnett in compulsorily castrating young men in an attempt to prevent teenage pregnancies (End the handouts, Letters, September 22), her letter highlights an important point: over-population is detrimental to society, a drain on the economy and damaging to the environment.

Research by the Optimum Population Trust (see www.optimumpopulation.org) suggests the UK population needs to be reduced by about half, from 60 million to 30 million, to be economically and environmentally sustainable in the long term.

At the moment we are doing precisely the opposite, by allowing virtually unregulated immigration and by encouraging a positive rate of reproduction among the indigenous population.

To start addressing this problem we need to end net immigration (ie only allow immigrants in to directly replace emigrants out) and put in place strong disincentives to prevent irresponsible childbearing.

As an alternative to Ms. Causnett's "treatment" for the male perpetrators of teenage pregnancies, I propose a new criminal offence of conceiving a child without planning adequate provision to support its upbringing.

This would apply equally to the male and female parties, irrespective of age, and carry a stiff, deterrent sentence (ie several years behind bars) for both.

Over-population is the environmental and economic crisis that dare not speak its name, because politicians are too scared to address it.

Cars and power stations don't cause global warming in themselves - the people who use them do. But politicians feel they're less likely to lose votes by telling us to drive less than if they tell us to have fewer babies.

The Chinese realised this and grasped the nettle in the 1970s, when they developed and implemented the Planned Birth Policy. Three decades later, China has one of the fastest growing economies and standards of living in the world.

Leo Enticknap, Bootham, York.