It’s clear that life has evolved with the atmosphere, oceans and rocks of the Earth, with each affecting the other. Despite all the radical changes in the air since life arose, adjustments and feedback arrangements have contrived to keep the surface of the Earth within a narrow range of temperatures over hundreds of millions of years. This range was just the one needed to keep water liquid, and therefore to keep life alive.
If life on Earth ended tomorrow, oxygen would vanish from the air in a few million years, sucked out by inorganic chemical reactions, while carbon dioxide would be dissolved in water and be gone into rock in a few thousand. These gases have to be continually maintained by biological activity and geological processes, which seem to cooperate in maintaining reasonably constant levels over vast periods of time.
A similar constancy is seen in the composition of the oceans, which has remained the same during geological time at a salinity of 3.5%, with the proportions of various salts held in exquisite balance. This precise composition should have changed drastically with the erosion of salts from the land, but it hasn’t. Looking at this overall, long-term pattern of dynamic balance in the Earth’s systems, in the early 1970s James Lovelock introduced the idea of Gaia, named for the ancient Greek goddess who personified the Earth.
This he described as a complex entity involving the biosphere, atmosphere, oceans and soil, all of them parts of a feedback system that maintains conditions exactly favourable to life. His collaborator, Lynne Margulis, described Gaia as the single huge ecosystem at the Earth’s surface, which is made up of all the connected ecosystems there, and which behaves in some ways as a kind of physiological system.
To an ecologist equipped with hindsight and a Gaian education, all this seems quite reasonable. There’s no particular reason to see Gaia as either a real goddess or a real super-organism, but in practical terms you wouldn’t be far off track if you did. In any case, conscious or not, the capacity of Gaia to correct imbalances in the biosphere is clearly vast.
The planetary over-heating caused by our emissions of greenhouse gases is certainly on a scale likely to provoke such a correction. Quite what it might involve is not clear, but on past performance we’d expect the causative agent of instability – our own excessive numbers and impacts – to be especially affected.
The blunt responses of Gaia cannot be precisely targeted, and as the correction occurs we’d expect the present-day biosphere to be utterly transformed. But, alone amongst all the species that have ever existed, we have the capacity to anticipate this. We could, in theory, act to transform our own relationship with the biosphere, instead of letting it change under us.
The global water crisis described in the rest of this book amounts to a warning that transformation is inevitable, one way or the other. That is, transformation either of the biosphere, or of our attitudes, behaviours and economies.
Read on: The experience of water.