| We are becoming increasingly aware of our dependence on the rest of nature and of the interdependencies that exist between different forms of life, between living systems and the physical and chemical environment that surrounds life on the Earth — and indeed between ourselves and the rest of the universe. The scientific theory named Gaia after the Greek Earth Goddess and publicised particularly by James Lovelock emphasises these interdependencies. Lovelock points out that the chemical composition of the Earth's atmosphere is very different from that of our nearest planetary neighbours, Mars and Venus. Their atmospheres, apart from some water vapour, are almost pure carbon dioxide. The Earth's atmosphere, by contrast, is seventy-eight per cent nitrogen, twenty-one per cent oxygen and only 0.03% carbon dioxide. So far as the major constituents are concerned, this composition has remained substantially unchanged over many millions of years — a fact that is very surprising when it is realised that it is a composition that is very far from chemical equilibrium. This very different atmosphere on the Earth has come about because of the emergence of life. Early in the history of life, plants appeared which photosynthesise, taking in carbon dioxide and giving out oxygen. There followed other living systems which 'breathe', taking in oxygen and giving out carbon dioxide. The presence of life therefore influences and effectively controls the environment to which living systems in turn adapt. It is the close match of the environment to the needs of life and its development which seems so remarkable and which Lovelock has emphasised. He gives many examples; I will quote one concerned with oxygen in the atmosphere. There is a critical connection between the oxygen concentration and the frequency of forest fires. Below an oxygen concentration of fifteen per cent, fires cannot be started even in dry twigs. At concentrations above twenty-five per cent fires burn extremely fiercely even in the damp wood of a tropical rain forest. Some species are dependent on fires for their survival; for instance, some conifers require the heat of fire to release their seeds from the seed pods. Above twenty-five per cent concentration of oxygen there would be no forests; below fifteen per cent, the regeneration that fires provide in the world's forests would be absent. The oxygen concentration of twenty-one per cent is ideal. It is this sort of connection that has driven Lovelock to propose that there is tight coupling between the organisms that make up the world of living systems and their environment... Lovelock's first statement in 1972 of the hypothesis was that 'Life, or biosphere, regulates or maintains the climate and the atmospheric composition at an optimum for itself.' In his later writings he introduced the analogy between the Earth and a living organism, introducing a new science which he calls geophysiology — a more recent book is entitled Gaia, the Practical Science of Planetary Medicine. An advanced organism such as human being has many built-in mechanisms for controlling the interactions between different parts of the organism and for self-regulation. In a similar way, Lovelock argues, the ecosystems on the Earth are so tightly coupled to their physical and chemical environments that the ecosystems and their environment could be considered as one organism with an integrated 'physiology'. In this sense he believes that the Earth is 'alive'. That elaborate feedback mechanisms exist in nature for control and for adaptation to the environment is not in dispute. But many scientists feel that Lovelock has gone too far in suggesting that ecosystems and their environment can be considered as a single organism. Although Gaia has stimulated much scientific comment and research, it remains a hypothesis. What the debate has done, however, is to emphasise the interdependencies that connect all living systems to their environment — the biosphere is a system in which is incorporated a large measure of self-control. There is the hint of a suggestion in the Gaia hypothesis that the Earth's feedbacks and self-regulation are so strong that we humans need not be concerned about the pollution we produce — Gaia has enough control to take care of anything we might do. Such a view fails to recognise the effect on the Earth's system of substantial disturbances, in particular vulnerability of the environment with respect to its suitability for humans. To quote Lovelock, "Gaia, as I see her, is no doting mother tolerant of misdemeanours, nor is she some fragile and delicate damsel in danger from brutal mankind. She is stern and tough, always keeping the world warm and comfortable for those who obey the rules, but ruthless in her destruction of those who transgress. Her unconscious goal is a planet fit for life. If humans stand in the way of this, we shall be eliminated with as little pity as would be shown by the micro-brain of an intercontinental ballistic nuclear missile in full flight to its target.' | — John Houghton, Global Warming: The Complete Briefing, Chapter 8 – Why Should We Be Concerned | Indexes/18 |
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Lovelock's first statement of the 1972's hypothesis' life, or the biosphere, or maintain regulatory climate and atmospheric composition optimization itself. He also describes his later life and the earth gave biological analogy, the introduction of new technology, new knowledge, as he is dissatisfied with the geophysiology - and the book is entitled, more recently one of Guyana is a practical scientific medicine planet.
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