The Revenge of Gaia is not a book to read should you be feeling a bit down, a bit uncertain about the future, worried about the grandkids. Should, however, you be seeking a scientific foundation for an apocalyptic, end-of-the-human-race novel, it would be just the ticket.
But this is far from fiction, which is what makes it so scary; it is the considered, quite probably final, view of the likely future from the now 80-plus James Lovelock, the man who 40 years ago conceived the theory of Gaia – in his words:
A view of the Earth that sees it as a self-regulating system made up from the totality of organisms, the surface rocks, the ocean and the atmosphere tightly coupled as an evolving system. The theory sees this system as having a goal – the regulation of surface conditions so as always to be as favourable as possible for contemporary life.Then it was a way-out, radical theory that caused shock and drew derision (in part because it did get taken up by the mystical crowd in ways that Lovelock had never intended.) Now it is broadly accepted.
The problem that Lovelock identifies in The Revenge of Gaia is that she’s getting hotter. (Why the gender? Well the name comes from an ancient Greek goddess, so it seems fair enough.) In part that’s an extremely long-term trend – the sun at the earth’s birth was probably about 25 per cent less luminous than it is now. It was only in a window about two billion years ago that the temperature was just right for life to start (before that it was too cold), and in about one billion years the heat will be unbearable for Gaia, Lovelock says, and the Earth will be lifeless. But that’s a process we could hurry along, by both destroying the natural systems such as forests that help to cool, while also pumping heating gases into the atmosphere.
We think of warmth as enhancing growth, being more productive, but in the great photosynthetic powerhouse of the oceans, that isn’t the case. It was during the great glacial periods, with comparatively little warm water, and great expanses of chilled ocean water, teeming with life, that Gaia was at her richest, plus with all of that water locked up in ice, an extra spread of land, at its greatest extent equal to the area of Africa.
But there’s more. When the sun is able to warm the top layer of the ocean - between 30 and 100m deep - into a single layer, it forms a stable layer that fails to mix with the denser cold water beneath. Lovelock explains what happens then:
The formation of the surface layer exerts a powerful constraint on ocean life; primary producers that seed the newly formed warm layer in early spring soon go through a succession that uses up nearly all the nutrients of the layer. The dead bodies of this spring bloom sink to the ocean floor, and soon the suface layer is empty of all but a limited and starving population of algae. This is why warm and tropical waters are so clear and blue; they are the deserts of the ovean, and just now they occupy 80 per cent of the world’s water surface. In the Arctic and Antarctic, the surface waters remain below 10C and so are well mixed from the bottom to the surface and nutrients are available anywhere.Similarly on land, once the temperature gets above about 25C the rate of evaporation is so great that without almost continuous rain the soil dries out and you have a desert. Rainforests to some extent overcome this by creating their own microclimate of cloud above the trees, but Lovelock quotes a study in the Amazon suggesting that a 4C increase in temperature would disable this system and reduce the great forest to scrub or desert.
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