Gaia: The Practical Science of Planetary Medicine [ペーパーバック]

We are all well aware of the world-wide problems concerning humans harming the environment, such as ozone depletants and cars causing global warming. We are a great deal less aware, however, of the real damage done to the earth and whether or not the planet can recover.

In this revolutionary book Lovelock describes his profound new theory of planetary ecology. The Gaia theory views the earth as a living, self-regulatory organism in which the evolution of life is closely coupled with the evolution of the climate. The theory accounts for the remarkable ability of the biosphere to recover from planetary disasters such as the impact that killed the dinosaurs, and many other previously unexplained features of life on earth.

The book should be on the shelf of anyone interested in the planetary maladies mankind has inflicted upon the earth. In easy to understand language with the minimum of jargon. Lovelock eloquently explains his theory and suggests sensible and empirical remedies for an ailing Gaia.

The other review on this page was written by me (Lloyd) a few years ago. I am writing this review as a second look at the book now that I am older and (hopefully) more critical - i.e. less willing to be persuaded (!). Whilst I still think that the Gaia hypothesis is a fascinating idea and that Lovelock's book is well worth reading, I am now much more sceptical about the actual evidence for the hypothesis -- empirical evidence is, after all, the final and absolute test of a hypothesis in science.

Lovelock's writing can be very poetic. I don't think this is necessarily a bad thing, but in some cases -- such as the description of the earth as being an `organism' -- clarity and scientific precision seems to be sacrificed in favour of emotion. In the review `Reviewing Lovelock's second book on the Gaia Hypothesis' of `The Ages of Gaia' someone explains Lovelock's ideas about the earth as an organism more eloquently than I can. I find this view much less likely (and therefore not as good as a scientific hypothesis) than the more down to earth -- if you will forgive the pun! -- statement that living things sometimes modify their environment in a way that keeps conditions favourable for life.

Which brings me back to the all-important question of whether the earth is `self regulating'. It seems to me that this would be quite a difficult thing to demonstrate experimentally or by observation (although Lovelock does give examples of observations that support his hypothesis). I don't know what the current evidence amounts to (I am not a scientist!) but it seems to me that the current consensus is not with Lovelock.

In summary, I would recommend people to read the book but to bear in mind that Gaia is not a well-established theory. In particular, it might be good to also read some books about more mainstream evolutionary theory by authors such as Dawkins and Stephen Jay Gould (which are, in my opinion, brilliant books) first.

I read this book back in college. ~1998-99. It must have been republished with an updated forward or similar, given the publication date listed here. My memory is, admittedly, less that perfect but we did spend a lot of time on the book.

The big question for readers should be; exactly how strong a suggestion is Lovelock making here? How testable is it? "How does plant life impact its environment" is an interesting question, but this book is weak on supporting general rules from individual cases.

The book argues that life impacts its environment, that the earth's temperature stability in the face of vastly differing solar output was due to the presence of life, and that extra terrestrial bodies can be shown to have life based on the presence of unstable compounds which life produces.

Plant life emits tons of IR radiation, granted, so plant growth would cool hot regions. If you've ever done IR photography, the plants turn out as white because they're so radiant in the IR. Normal substances don't do that. Also, the earth seems to show a more stable temperature than would be expected given changes in solar output over earth's history.

Also, the notion that unstable compounds in the atmosphere are charicteristic of life seems interesting since the notion, combined with other work, would suggest life on Mars.

"What was obvious to him, after measuring reactive gases of biological origin such as ammonia, methane, and nitrogen and sulfur oxides, was that the air was loaded with exudates of life.

These gases were accompanied by many other detectable trace compounds such as terpenes (piny essences), volatile amines (garbage smells), and methyl bromide (seaweed odor). Yet, as every chemistry student knows, all of these reduced organic compounds react readily and easily with oxygen and, from the point of view of chemistry alone, they should not be present for long in air samples. This thinking led Lovelock to the unassailable conclusion that the search for life on Mars should mainly be a thorough gas analysis that not only identified every gaseous component of Martian air but also measured their fluxes: the rate at which each was produced and removed. He figured: because the Earth's air is made of highly reactive mixtures, it shows the unmistakable presence of life. He suggested looking for reactive mixtures, or at least changes in gas concentrations, in the atmospheres of Mars and other planets, to see if any explanation beyond chemistry and physics would be required for understanding them.

[...]"

But as for things like cloud formation, Lovelock writes on p. 140 that most dimethyl sulphide induced cloud formation is in the arctic and antarctic, and such cloud formation is cooling rather than warming. So we have life in the coldest parts of the earth making the area less temperate, not more. This suggests that sometimes life may make the environment less hospitable for other life. And we see something similar with the bacterial and fungal production of various toxins. Sometimes interactions are symbiotic, sometimes they are antagonistic.

It would be helpful for "Gaia theory", going forward, to draw on game theory, the problems with free riders, genetic relatedness of cooperating organisms, signaling and similar concepts used in studying the formation of bacterial colonies like cholera.

In any case, with the various toxins that living organisms produce we can see a force at work which is directly antagonistic to the "daisyworld" regulatory mechanism which Lovelock proposes. Under what conditions should the presence of life be regulator and under what conditions should it free-ride or be antagonistic? If Lovelock covers this in this later edition, I don't know. But he didn't seem to address it directly in the earlier edition which I read. (IIRC)

In short, the ideas in the book are very preliminary and undeveloped.