Guardian: Ken Livingstone put the environment at the centre of his campaign to be re-elected as London mayor today, claiming a victory for his Tory rival, Boris Johnson, would be “a disaster” for the fight against climate change. Speaking at the launch of his environment manifesto in Richmond, south-west London, Livingstone said that voters faced a clear choice between a pro-environment coalition of Labour and the Green party, and Johnson when they go to the polls on May …