The effect on the planet of having one child less is an order of magnitude greater than all these other things we might do, such as switching off lights. The greatest thing anyone in Britain could do to help the future of the planet would be to have one less child.

Having one less child is the biggest contribution anyone can make to leaving a habitable planet

We must not put pressure on people, but by providing information on the population and the environment, and appropriate contraception for everyone (and by their own example), doctors should help bring family size into the arena of environmental ethics, analogous to avoiding patio heaters and high carbon cars.

Should we now explain to UK couples who plan a family that stopping at two children, or at least having one less than first intended, is the simplest and biggest contribution anyone can make to leaving a habitable planet for our grandchildren?

The effect on the planet of having one child less is an order of magnitude greater than all these other things we might do, such as switching off lights. The greatest thing anyone in Britain could do to help the future of the planet would be to have one less child.

The greatest thing anyone in Britain could do to help the future of the planet would be to have one less child.