The Environment Agency has an interesting page on the sustainability of London and what needs to be done to fix the unsustainable growth and put a stop to environmental degredation.
See here for what they have to say.
To see the condition of the environment in your area, click here.
The Earthbound Report 
This caught my eye: “Every Londoner is using an area the size of five-and-a-half football pitches to support their way of life, which amounts to an area 250 times the city itself.”