Delingpole puts it so well: Biodiversity, "a noble-seeming concept has been subverted by the watermelons of the green movement in exactly the same way as “Climate change” has and with precisely the same aims: to extend the powers of government; to raise taxes; to weaken the capitalist system; to curtail personal freedom; to redistribute income; to bring ever-closer the advent of an eco-fascist New World Order."
Precisely. Just as we hear shouts of "terrorism" and "paedophiles" each time there's a new attack on personal freedom, so "biodiversity" is invoked by those who really mean "we're taking over your land". Folks like the RSPB start by saying wildlife belongs to "the nation", and five minutes later are claiming it for themselves - they're the experts after all? - and demanding wider and wider powers from government to help them do it. Wake up people, there's a revolution going on!
Update: Taking the argument to its logical conclusion, the League Against Cruel Sports are now arguing that shooters are getting a "free lunch" out of the nation's wildlife, and should be stopped.