A couple of weeks ago a body calling itself the Optimum Population Trust called for families in the UK to limit themselves to a single child. The Times had this to say:

Britain’s birthrate, growing at its fastest for nearly 30 years – at 1.87 children per couple – is, says the author of its report, Professor John Guillebaud, an environmental liability. “Each new UK birth, through the inevitable resource consumption and pollution that UK affluence generates, is responsible for about 160 times as much climate-related environmental damage as a new birth in Ethiopia.”

Professor Guillebaud has three children.  As does Sir Crispin Tickell, a patron of the Trust. The majority of the other patrons, and Prof Guillebaud's co-chair, Val Stevens, have two children each.