‘This book … is about a search for life, and the quest for Gaia is an attempt to find the largest living creature on earth. Our journey may reveal no more than the almost infinite variety of living forms which have proliferated over the earth’s surface under the transparent case of the air and which constitute the biosphere. But if Gaia does exist, then we may find ourselves and all other living things to be parts and partners of a vast being who in her entirety has the power to maintain our planet as a fit and comfortable habitat for life.’
With these portentous words, the British independent scientist James Lovelock began, in 1979, his pioneering book Gaia: A New Look at Life on Earth. The search, which for him had started more than a decade earlier, faced formidable obstacles, most of them set in his path by his professional colleagues. At that time the prevailing view among scientists was that life on earth was in essence a vastly improbable accident; life was ‘a quiet passenger’ that had ‘hitched a ride on this rock ball in its journey through space and time’. It was this very improbability – the miniscule odds that exactly the right conditions for life should exist and continue to exist – that inspired Lovelock to develop the concept of Gaia: the idea that it is life itself that maintains the conditions necessary for its own survival.
In the decades following its first public appearance in 1979, the Gaia hypothesis was much refined, not least by Lovelock himself in a series of follow-up books. At the core of the thesis is the idea of self-regulation, or homeostasis, a property he believes belongs to the entire system that comprises ‘all life tightly coupled with the air, the oceans, and the surface rocks’. Through various feedback mechanisms, these components work together to regulate the climate, the gaseous balance of the atmosphere and the chemical composition of the ocean in such a way as to produce and maintain a physical environment that is optimally adjusted to life. At the suggestion of his friend and neighbour William Golding, the Nobel Prize-winning novelist, Lovelock named this complex entity ‘Gaia’, after the ancient Greek goddess of the earth.
A stable planet of unstable parts The seeds of what would eventually grow into Gaia were set in 1965, when Lovelock was working on the NASA space programme as a part of a team whose task was to detect whether there was life on Mars. A general characteristic of living organisms, he recognized, is to reverse or reduce entropy – in other words, to move their environment away from chemical equilibrium. Earth-based analysis of the atmospheres of Mars and Venus showed that both were close to equilibrium and hence that the planets themselves were probably lifeless. Once it became clear just how different our planet is from its two dead neighbours, Lovelock’s mind was ‘filled with wonderings about the nature of the Earth’.
The earth is in an extreme state of chemical disequilibrium. Unlike the atmospheres of Mars and Venus, which are made up almost entirely of carbon dioxide, the earth’s atmosphere is just over one-fifth oxygen, with a trace quantity (about 350 parts per million) of carbon dioxide. The oxygen level is optimal for supporting animal respiration, while the tiny percentage of carbon dioxide is essential to drive the life-supporting process of photosynthesis but not so much (human activity aside) to trigger a potentially catastrophic greenhouse effect. Again, in spite of solar output having risen by a quarter since the earth’s formation, the planet’s surface temperature has remained constant, close to a global average of around 15°C – an ideal level for terrestrial life. It was the remarkable constancy of these and other parameters, maintained against expectation over hundreds of millions of years, that led Lovelock to suggest that our ‘stable planet made of unstable parts’ might have been brought to such a state and kept there by the combined regulatory activity of the living and non-living components.
‘Our destiny is not dependent merely on what we do for ourselves but also on what we do for Gaia as a whole. If we endanger her, she will dispense with us in the interests of a higher value – life itself.’
Václav Havel, 1994
Beyond Daisyworld Much of the early criticism of Lovelock’s theory focused on its supposed teleological assumptions – on the way that Gaia seemed to have a capacity for foresight and future planning. What appeared to be lacking were plausible evolutionary paths that could explain how the necessary regulatory feedback mechanisms could have arisen in the first place. This criticism set much of the agenda for the development of the Gaia theory over the following decades.
The first product of these efforts was Daisyworld, a simulated ecosystem consisting initially of just two species of daisy, black and white. Each species has a different environment-modifying characteristic – white daisies reduce the ambient temperature, black daisies increase it; and each thereby determines its own relative abundance. In spite of the input of solar energy rising (as on earth), the model suggests that the surface temperature can be kept close to the optimal level merely by the interplay of the two kinds of daisy. The inference, then, is that modification of the environment can be achieved purely by means of competition and natural selection at the level of the individual.
Real-world feedback mechanisms supposedly analogous to those in Daisyworld have since been studied intensively. A notable example is a mechanism whereby marine phytoplankton is claimed to have a climate-cooling effect. These organisms produce a gas called dimethyl sulfide (DMS) which forms aerosol droplets in the atmosphere; these have the effect of making clouds more reflective and hence increase the amount of solar radiation scattered back into space. Growth of the phytoplankton (and hence DMS production) increases with temperature, so the system as a whole functions like a thermostat to keep the temperature constant.
The legacy of Gaia The message of Gaia has sometimes become obscured by the rhetoric and lobbying of both supporters and opponents. Some of the animosity towards the symbolism of Gaia, not least the name itself, remains, but the many serious implications of the theory itself have left their mark. In the past, earth scientists, climatologists and other experts within their own disciplines tended to approach the complexity of the environment as something to be analysed and reduced into simpler, more manageable parts.
Now, this complexity is widely recognized as fundamental to the system. In a new, more holistic approach, the focus of much research has moved to the earth as a unitary system – to the major feedback mechanisms within environmental systems and to their role in maintaining long-term global stability. Today, at a time when we are faced with the unprecedented threats of climate change and global warming, the deepest lesson of Gaia – that the health of our world depends on taking a planetary perspective – seems more relevant and pressing than ever.
the condensed idea
The quest for Mother Earth