Concluding remarks

A system's view of nature, replete with feedbacks, is a remarkably recent way of viewing the world. In European thought the dominant technological metaphor of many centuries was clockwork: something that should run perfectly, without the need for feedback, once it had been set going. During the eighteenth century, especially in Britain, it became increasingly common to find ideas of 'checks and balances' and self regulation; especially in political and economic theory (Mayr, 1986; Henry, 2002). Technology utilizing feedback had been known from at least the world do not have to cause mass extinctions, however, such low-Intensity use probably requires a much lower population size than currently found on Earth, if it is to be widespread. (a) Forest Meadow at Rashult (the birth place of Linnaeus) in southern Sweden. Pollen analysis has shown that this meadow system was created, from woodland, about 900 years ago (Lindbladh and Bradshaw, 1995). It is still managed by traditional methods, with the aid of subsidies, as this is no longer an economic way to farm in Sweden. It is rich in plant species, as is appropriate for the birthplace of one of the greatest names in plant taxonomy! (b) Traditional, species rich, alpine meadow in the Italian Dolomites. Because of the steep terrain it is still managed by traditional methods (the mechanical harvester in the picture being little larger than a domestic lawn-mowing machine).

the first century ad, however these were 'toys' rather than devices of practical use. Feedback starts to become technologically important in eighteenth-century England: first for devices for regulating windmills and later for regulating steam engines—for example the famous Boulton-Watt centrifugal governor of 1788 (Mayr, 1986). These ideas of feedback and checks and balances moved from economics and technology to medicine during the nineteenth century, most importantly in the work of Claude Bernard in France on the idea which would later become known as homeostasis (Porter, 1997). Almost 100 years later, during the Second World War, physiologists studying the aiming of anti-aircraft guns came to appreciate the crucial importance of feedback processes in the interaction of muscles and brain, an insight they took back to postwar medical research (Miller, 1978). It is possible that our understanding of such complex feedback-rich systems is still in need of new concepts and approaches before we can develop good quantitative theory. For example, Joel Cohen (2004), in a recent essay on Mathematics and Biology, suggested that understanding coupled atmospheric, terrestrial, and aquatic biospheres in the context of global biogeochemical processes may require major mathematical innovations and that research in this area may encourage such developments in much the same way that attempts to study the dynamics of interacting species stimulated Alfred Lotka's mathematical ideas in the early twentieth century.

In the context of Gaia it is probably relevant that James Lovelock spent the first part of his scientific career working in medical research—for example playing a crucial role in elucidating the mechanism by which cells are damaged by freezing, a result with huge implications for reproductive medicine and the storage of eggs, sperm, and embryos (Pegg, 2002). Ideas of feedback already existed in the environmental sciences, such as the 'systems ecology' of Hutchinson and the Odum brothers during the mid-twentieth century (for an Earth Science example see the 'flow diagrams' in Holmes, 1944). However, Gaia was marked out by a particular emphasis on feedback and regulation, which was unusual in the environmental sciences in the 1970s, indeed the interest in ecosystem processes in ecology was about to suffer a decline (Fig. 11.1). As John Lawton (2001) has pointed out in an editorial on Earth Systems Science in Science 'James Lovelock's penetrating insights that a planet with abundant life will have an atmosphere shifted into extreme thermodynamic disequilibrium, and that the Earth is habitable because of complex linkages and feedbacks between atmosphere, oceans, land and biosphere were major stepping-stones in the emergence of this new science.' As far as I have been able to discover, the term Earth System Science was coined at NASA during the mid-1980s. At least no one working in the area who I have spoken to can remember the term used prior to this.

The Earth System is obviously very complex and we are currently altering it in many ways. A Gaian approach is a way of trying to organize a lot of information in a way that allows one to ask interesting, and hopefully useful, questions. In particular, it forces us to think hard about feedbacks and gives microbes the central place they deserve in ecology. In the context of the processes described in this book the ecologically most important group (Kingdom sensu Margulis and Schwartz, 1998) are the prokaryotes followed by the single-celled eukaryotes and then the fungi and plants (perhaps of equal importance). The least important group is the animals. The striking thing about this ranking is it is almost exactly opposite to the amount of attention given to these groups by ecologists!

In the terminology of Vespsalainen and Spence (2000) Gaia is not really a scientific theory (a relatively constrained statement about the world susceptible to a single test which could find it wanting), but an 'explanatory framework'. Such frameworks are 'road maps to solutions, rather than solutions themselves... so that an investigator can pick and choose what is required to effectively understand a specific event or situation' (Vepsalainen and Spence, 2000, p. 211). It is now clear to many scientists that it is impossible to understand a planet such as the Earth without considering multiple feedbacks between life and the abiotic environment. It is also clear to many that the Earth exhibits a certain amount of regulatory behaviour, in which life is intimately involved. Key questions for the future are about the strength of these regulatory processes and the mechanisms underlying them, and how the fundamental ecological processes contribute to the working of the Earth System.

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