James Lovelock

I made a point of listening to James Lovelock on the Today programme this morning, as he has spent most of his 90 years studying environmental issues.
Is his Gaia theory right or wrong? Has our planet's bio-system been altered beyond repair by human activity?
He is very gloomy about the future for the human race, but is right about one thing, which has been left out of the clip, our planet is a wondrous place to live!