The Sunday Times last weekend reported on a GP who discourages families from having more than two children. (See: Green GP refuses to help women have large families.) Dr Pippa Hayes is a member of the Optimum Population Trust whose motto is "stop at two". Essentially, the OPT believes that having more children is not eco friendly. This is an old idea dressed up in green language; human beings are seen as a kind of pollution.
The article does give space to an alternative assessment - that in fact large families often lead more environmentally friendly lives. To take one example, they certainly don't use air travel to the same degree because with a large family, package holidays in the sun are prohibitively expensive. The active outdoor alternatives are not only very beneficial for children but also, in fact, tend to waste fewer natural resources. The photo shows one family making the most of our current weather.
The large families I know also tend to make economies of scale at home, passing on clothes and other things, cooking with fresh ingredients, growing stuff in the garden, keeping chickens, enjoying games with things that have been made, not bought, and generally getting out into the environment rather than just talking about it.