I give fair warning that some of you may be offended by this post. I am pretty sanctimonious about over-population.
When I was 12 - in 1965 - I realised that the last thing the planet needed was extra mouths to feed, especially from me. Even at that age, I knew I wasn't maternal, so I decided not to breed. At the age of 23 I made a permanent commitment by undergoing a sterilisation operation.
Not only am I the youngest of my generation of the family by far, being the late child of two late children, but from the 1930s, my very poor relatives (dockers, bakers) had obviously known how to control the size of their families. No one had more than 2 children. Several had one or none. I wasn't used to being surrounded by babies and young children, and they played no part in my life.
So when I see people in the developed world having large families, I am in despair. In the Third World, with such high rates of infant mortality, I can understand that people need to breed to make sure that any child survives them. When mortality rates decrease and access to contraception increases, birth rates decline. There is no such excuse in the west.
And let's not forget the influence of the Roman Catholic ban on contraception, which affects poorer countries in places like South America out of all proportion to Europe, whence the senseless edict comes, and where it is largely ignored.
Meanwhile, having destroyed our own wild land (in the UK, over 2,000 years ago) we expect poor countries to protect their rainforest and fragile habitats on our say-so.
Captive breeding of endangered species is pointless if there is no habitat to return them to. But humans will use up that habitat to feed themselves, just because they think that an ever-increasing population is OK, or "nothing to do with me".
The worst response, in my opinion, is from the wealthy, when they say, "Oh, but we can afford X number of children." THE PLANET CAN'T! The wondrous leaders of our "greenest ever" government (as they call themselves, oblivious of the irony) Cameron and Clegg, have 3 children each. That represents a 50% population increase. And each child of theirs will have a far greater impact on climate change than any child of a Third World country, bar those of the corrupt dictators who pocket aid meant for their citizens.