James Lovelock (b. 1919) is an independent scientist whose work has inspired a whole new way of thinking about the world. Of his many important contributions to science, probably the greatest has been the message that earth's environment is to a large extent controlled by life itself. Much of this book is about the ways that living organisms have seized control of climate and atmosphere. Although there have always been scientists who worked on the effects of life at the broad scale, in the last 35 years there has been an enormous expansion in this way of looking at the world. Many of the scientists who nowadays work on the effects of plants on climate or the carbon cycle attribute much of their inspiration to Lovelock's view that life has an integral role in controlling the global environment.
Lovelock honored the global system—with life at its center—with the name "Gaia" after the ancient Greek earth goddess. This choice of a label has proven controversial, and some scientists have even accused Lovelock of venturing into religious mysticism. Lovelock himself has said that the name Gaia was merely intended as an inspiring metaphor, but there is no doubt that his view of the earth system has gained a lot more attention because of his choice of this name.
Daisyworld is a hypothetical example that demonstrates a general principle: that living organisms acting in their own short-term interest on a local microclimatic scale (both responding to and changing their microclimate) might add up to very big global changes. The overall result can be a control mechanism that regulates the earth's climate. Although daisies have never changed the world, it is possible that things rather like this have actually happened in the past. Three or four billion years ago in the Precambrian, the first life on land was probably dark-colored layers and mats of algae and perhaps lichens. By altering the amount of sunlight absorbed at the earth's surface (the albedo), these plants may have brought about rather similar changes in heat balance of the world. It is thought that at that time the sun would have been fainter, and the earth in continual danger of freezing up. However, despite their possible stabilizing influence, gathering sunlight, there are signs of very severe and long-lasting ice ages before about 700 million years ago. In some of these cold phases the ice sheets spread down close to the equator, suggesting that almost the whole planet was iced up. The appearance of more complex land plants (with leaves, roots and suchlike) may have helped to impart more long-term stability on climate, keeping the earth within the band of temperatures suitable for maintaining life. However, such plants did not appear until around 400 million years ago, so they cannot be the reason in themselves why the great global ice ages ended. Nevertheless, from what we understand about the role of plant life in making climate (see Chapters 5 and 6) they may well have prevented such severe glaciations from occurring again since then.
So, in the more recent geological past, since large plants with leaves and roots first evolved, it is likely that the influence of plant microclimates in regulating broad-scale climates has become even more important. In the next couple of chapters (Chapters 5 and 6) we will explore some of these possible effects of plants on both regional and global climate.
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