The latest book by Australia’s foremost science intellectual, Tim Flannery, Here on Earth: A New Beginning*, should really be read with at least one other person in the room. That way you can look up and say: “Whow, did you know that continental drift ensures the saltiness of the ocean remains constant?” (Flannery explains that while water takes 30,000 to 40,000 years to recycle from evaporation in the ocean through precipitation and hence through soil and rock (picking up salt) and down rivers back to the sea, but over 10 million to 100 million years it passes through hydrothermal vents in the ocean crust, which remove the salt.)
“Or did you know that soils represent a huge carbon reserve, about 150 billion tonnes, roughly twice that in the atmosphere?” (Flannery explains that soil carbon is made up of humus (which makes it took black and is relatively stable, and can absorb its own weight in moisture), charcoal and roots and other underground parts of plants, which is the most prevalent form, but intensively used croplands have lost from 30 to 75% of their carbon content over the past two centuries. Lots more – though not enough is known to estimate a value – has been lost from poorly managed grazing lands and eroded soils.)
Or “did you know that the first agriculture in the world was probably in Papua New Guinea, 10,000 years ago – earlier than the Fertile Crescent or China?” (Flannery explains it was based on taro and banana, and probably the most productive, supporting the highest rural population densities on earth. And the two most widely planted varieties of sugar cane originated in PNG.)
As those examples suggest, Here on Earth is a wide-ranging book – in fact it attempts not just to tell the story of how life has developed on, and shaped, Earth, but how we as life’s conscious beings might ensure that our own and other life continues. It’s really a fleshing-out of James Lovelock’s Gaia hypothesis, with some added politics and sociology that consider us as an important part of the tapestry and history of life.
Flannery clearly accepts the idea that Gaia can be seen as a single living organism – but in what way? Flannery points out that we humans are made up of a number of independent or formerly independent elements – our cells are powered by mitochondira that were once independent living things “these partners must have started by forming a loose association, but after more than a billion years of evolution they have become indivisible parts of an organism”. And within a human are still independent organisms that make up part of what we think of as us – “Without many of these creatures – for example gut bacteria – we could not exist. These fellow travellers make up 10% of our weight, and are so pervasively distributed over our bodies that were we to take away all ‘human’ cells, a detailed body shadow consisting of them would remain.” If you look at an individual person that way, it is not so hard to look at the Earth as in some sense a single organism.
But of course the Earth lacks what Flannery calls a “command-and-control” system, but as he says, so do extreme complex ant colonies. They rely on pheronomes. And Flannery suggests potential substances in Gaia that act as “geo-pheronomes”, which act to help maintain conditions suitable to life, including ozone, which shields life from ultraviolet rays, the greenhouses hases, which play a critical role in controllling surface temperature, and dimethyl sulphide, produced by certain algae, which assists in cloud formation. There’s also atmospheric dust, much of which is organic in origin.