I'm a member of the RSPB and several other wildlife protection societies. But when these bodies complain about destruction of existing habitats (eg the Thames Estuary) they conveniently forget to mention all the new wildlife habitat that is being created, eg old gravel pits, the Great Fen project in Cambridgeshire, coastal marshes.
Win some, lose some. I cannot accept that any wildlife objections should take precedence over building a new airport in the Thames. The corollary to a new airport there would be the downsizing of Heathrow over the next century which would release huge areas of potential habitat. Even with the inevitable building of housing, think of all that heathland that could be created for the benefit of wildlife.
Go for the Thames, ignore the views of the RSPB and other wildlife bodies. We "conservationists" do not always agree with everything our "leaders" say.
Heathrow is in a daft place (but a lot of fun for pilots - well I used to enjoy the views of London)
Jack