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Gaia by Lovelock James

Gaia by Lovelock James

Author:Lovelock, James
Language: eng
Format: epub
Publisher: OUP Oxford
Published: 2000-08-14T16:00:00+00:00


Fig. 6. The fluxes of oxygen and carbon between the major reservoirs of the Earth’s atmosphere, surface, and oceans. Quantities are shown in units of terramoles. A terramole of carbon is 12 megatons and of oxygen 32 megatons. Figures inside the circles are annual fluxes. Figures in the two reservoirs, the atmosphere and the sedimentary rocks, indicate their size. Note how the carbon, en route for burial in the sedimentary layers beneath the sea and the marshes and wet lands, is for the most part vented back to the atmosphere as ‘marsh gas’, methane.

The second possibly important activity of nitrous oxide concerns its behaviour in the stratosphere where it decomposes to give, among other products, nitric oxide, which has been claimed to be catalytically destructive of ozone. This may seem an alarming situation in view of the warnings of many environmentalists that the worst catastrophe at present threatening our world is the destruction of the ozone layer in the stratosphere by supersonic transport or the products of aerosol spray–cans. In fact, if oxides of nitrogen do deplete ozone, nature has been in the business of destroying the ozone layer for a long, long time. Too much ozone may be as bad as too little. Like everything else in the atmosphere, there are desirable optima. The ozone layer could increase possibly by as much as 15 per cent. For all we know, more ozone might be climatically undesirable. We certainly do know that ultra–violet light from the sun is useful and beneficial in some respects, and a thicker ozone layer might prevent it from reaching the Earth’s surface in sufficient quantity. In humans vitamin D is formed by exposure of the skin to ultra–violet radiation. Too much ultra–violet may mean skin cancer; too little most certainly means rickets. Although we cannot expect some particular global beneficence for us as a species from the microorganisms through their production of nitrous oxide, low–level ultra–violet may be valuable to other species in ways we do not yet know. A regulating device would at least seem helpful and nitrous oxide, together with that other recently discovered atmospheric gas of biological origin, methyl chloride, may serve this purpose. If so, the Gaian control system will include a means of sensing whether too much or too little ultra–violet radiation is getting through the ozone layer, and of regulating nitrous oxide production accordingly.

Another nitrogenous gas made in large volumes in the soil and the sea and released to the air is ammonia. It is a difficult gas to measure, but its estimated rate of production is not less than 1,000 megatons a year. As with methane, the biosphere uses a great deal of energy in producing ammonia, which is now entirely of biological origin. Its function is almost certainly to control the acidity of the environment. When the total production of acids by the oxidation of nitrogen and sulphur is taken into account, the ammonia produced by the biosphere is found to be just sufficient to sustain a rainfall pH near 8, the optimum for life.



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