The Gaia thing is another example of how pervasive magical and religious thinking is, and how it generally rots the brain. The notion of considering the Earth as if it were a single organism, and thus able to cope, as we are, with a spot of indigestion or a minor stab wound to the leg, is an interesting and potentially useful metaphor, but it is just that, a metaphor. Once you start touting it as your actual science then you need to be a lot more specific about what claims you are making, and answer awkward questions like:
- so are you saying that the Earth has some sort of guiding intelligence that's intervening to keep things in order? If you are, what exactly are its properties? Where is the physical seat of this intelligence? How would we test for its existence or non-existence? How would you know if you were wrong?
- if you're not saying that, then what you're really saying is whoah, dude, we breathe oxygen, right, and there's, like, just the right amount of oxygen in the air, yeah? Isn't that all just A Little Bit Too Convenient (significant look to camera, raised eyebrow), eh? That's really just a small-scale Earth-centric version of the anthropic principle, which, apart from being very silly, is also really just a restatement of the "guiding intelligence" option above with some of the details hidden to make it less obviously goddy.
- if you're not even saying that, then you're really just saying that a lot of the earth's systems (biological, meteorological, seismological, systematic, hydromatic, ultramatic, etc.) have, via various interactive feedback mechanisms that we perhaps don't fully understand, fallen into a sort of equilibrium with each other. To which the answer is: well, yeah. And?
One of the ways in which the Gaia thing closely resembles religion is the insistence on it all being real when talking to an uncritically accepting audience, but backtracking into "well, that bit's just a metaphor" when subjected to pointed questioning about any of it. That's exactly what, for instance, Christian types do when pinned down on any of the specifics in the Bible.
One of the other problems with this sort of hippyish Mother Earth thing is a kind of blithe assumption that It'll All Be All Right no matter what we do - plainly this has not been the case in the past (without any need for human intervention) so it's potentially a recipe for dangerous apathy and inaction in regard to things like man-made climate change. To his credit Lovelock is pretty solid about the reality of climate change, though his ideas on what to do about it are more controversial - he's a big proponent of nuclear power as the solution to the fossil fuel crisis and climate change. Now there's nothing especially cranky about that per se, though there's plenty of room for disagreement, but his blithe lack of concern about the dangers is a bit odd. Anyone who can handwave away the Fukushima disaster but insist that wind-farms are potentially lethal because if there was an earthquake the turbines might fall on someone and squash them needs to stop and have a bit of a think about what they're saying.
Oddly, one of Lovelock's big supporters during the 1970s was the late Lynn Margulis, another scientist who combined great work in some spheres with utter crackpottery in others. It's a very salutary lesson that no-one is immune from blind spots and irrationality, even those who do great things in other areas. Further examples include Isaac Newton's enthusiasm for alchemy and Linus Pauling's nuttery regarding vitamin megadoses.