Surely, if you were genuinely concerned about the environment, or it was a big factor when considering the size and shape of your family, you'd have no children or possibly just one?!
Saying you're not having more than two children for environmental reasons really grates me. Given the total fertility rate for women in the UK is 1.9, it's not like they're doing anything fucking special! They're just the average!
People who say this, get down from your high horse!
(P.s. Prolific name changer)