Strictly speaking the Gaia hypothesis is that ecosystems have built-in negative feedback loops to maintain conditions favorable to the organisms that comprise them.
The personification of Earth is a philosophical overlay more along the lines of religion, much as people interpreted Newton's "clockwork universe" as evidence of divine precision. It was not part of Lovelock's hypothesis, though it can be useful as a metaphor as long as one doesn't go overboard.
In its strictly scientific form, the Gaia hypothesis has become the dominant paradigm in the earth sciences.
So let's cut to the chase:
Lovelock's scientific credentials are impeccable.
He says there is a reasonably high probability that we will soon enough see a > 5 degree Celsius rise in average global temperatures, and that this will produce radical changes that render most of the Earth inhospitable to humans.
He says that the few regions that will remain hospitable include the polar regions and the coastal regions far from the equator: in the northern hemisphere, the northern coastal regions, and in the southern hemisphere, the southern coastal regions.
According to a close friend who's read the book (I haven't yet): in the US this means northern New Hampshire and Maine (lucky you, Revi) and the region from northern California up through the border with Canada (so our group (URL below) will be in a viable region also).
Now comes the scary part:
What happens to the rest of the world's current 6.5 billion heading toward 8 or 9...?
Logically, the answer is, a tsunami of migration toward the viable regions. Far beyond the population levels they can sustain.
Work out the implications of that for yourself.
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www.thefosl.org The Foundation Of Sustainable Living: building community, education, and R&D, for a sustainable northern California.