The Ages of Gaia

"Lovelock has written five or six books. I chose his second book, Ages of Gaia . Gaia is the Greek goddess of Mother Earth and Lovelock’s Gaia hypothesis is the idea that life itself stabilises a planet’s environment. He would say that the reason the Earth is habitable is precisely because it is inhabited. It’s an interesting theory but I don’t think you have to have an inhabited planet in order to have a habitable planet. He came to that view thinking about the faint young sun problem. This is a problem which is near and dear to my heart, because I have worked on it for a long time. We know that the solar system – the Earth and the sun – are about four and a half billion years old, and the sun, we think, was about 30 per cent less bright early in solar system history. This means that if the Earth was no different from how it is today and we have the same atmosphere and the same greenhouse effect, then the Earth would have been frozen over during the first half of its history. Lovelock was aware of this. CO2, along with water vapour, is our main greenhouse gas so Lovelock suggested that there was more CO2 in the early atmosphere, and then organisms took CO2 out of the atmosphere by using photosynthesis. And that counteracted the increase in solar luminosity. That is really how he came up with the Gaia hypothesis."

"Yes, James Lovelock wrote The Ages of Gaia, I think, in 1988. It wasn’t his first Gaia book, but it is probably the best written one. I have just been re-reading it recently and certain themes that he picked up on are ones that are still considered novel today. Not just the whole idea of the way the earth works, almost as a living organism. But also looking at the way humanity is going to have to reconcile itself with the constraints and the limits of the planet. The Gaia hypothesis was something which sprung from Lovelock’s work for NASA when he was trying to figure out ways to see whether Mars and other planets had life on them. He realised that having lots of reactive gases altogether in an atmosphere indicated that something must be there constantly producing them, which is life. Mars is obviously a dead planet because there’s nothing in the atmosphere which hasn’t been there for millions of years. Whereas if you look at Earth it’s a churning mixture of dynamically unstable gases. It was that insight which made him think about why these very dynamic systems have been stable for so long. Why levels of oxygen haven’t been below 15 per cent or above 30 per cent for probably close to a billion years. Yes, I mean I don’t buy the Gaia theory completely. I can see all sorts of criticisms. He thinks of life as a sort of self-regulating mechanism keeping the planet habitable with life, and I don’t actually see many ways of how that operates in the real world. It’s a great theory and it seems to be what happens, but I don’t think many scientists can point to the ways in which it supposedly operates. Lovelock is one of the most important thinkers on the environment and science generally in the last 50 years. One of the things that always impress me about people who are interdisciplinary is that he is quite happy to range across different areas. I mean there is a chapter in the book called God and Gaia, talking about theology and whether he can reconcile faith in God with what he sees in terms of biology and so on. So his ability and breadth of knowledge I always find really striking."