Geoscience Reference
In-Depth Information
As mentioned previously, a number of authors have chosen to highlight Love-
lock's Gaia theory as a principle way of linking biosphere and whole-Earth behav-
iour. Given that it was fi rst defi ned in 1972, it clearly pre-dates the initiative of the
ESS Advisory Panel. Equally, however, it was infl uenced by the work of NASA - in
this case, Lovelock's work to defi ne methods for detecting life on Mars by looking
at atmospheric chemistry. In its fi rst formulation, the theory is defi ned by
suggesting:
that life at an early stage of its evolution acquired the capacity to control the global
environment to suit its needs and that this capacity has persisted and is still in active
use. In this view the sum total of species is more than just a catalogue, 'The Biosphere',
and like other associations in biology is an entity with properties than the simple sum
of its parts. Such a large creature, even if only hypothetical, with the powerful capacity
to homeostat the planetary environment needs a name; I am endebted to Mr. William
Golding [the novelist] for suggesting the use of the Greek personifi cation of mother
Earth, 'Gaia'.
As yet there exists no formal physical statement of life from which an exclusive test
designed to prove [sic] the presence of 'Gaia' as a living entity. Fortunately such rigour
is not usually expected in biology and it may be that the statistical nature of life
processes would render such an approach a sterile one. At present most biologists
can be convinced that a creature is alive by arguments drawn from phenomenological
evidence. The persistent ability to maintain a constant temperature and a com-
patible chemical composition in an environment which is changing or is perturbed if
shown by a biological system would usually be accepted as evidence that it was alive.
(Lovelock 1972, p. 579)
The article goes on to produce such statistical evidence, and two further papers
(Lovelock and Margulis, 1974; Margulis and Lovelock, 1974) developed the idea
in much more detail. A series of topics (e.g. Lovelock, 1979; 2000; 2006) did much
to popularise the idea.
Kirchner (1991; 2002) has provided some of the strongest critiques of Gaia
theory and the slipperiness of its central homeostatic principle. In particular, he
differentiates a 'weak Gaia' hypothesis, in which life is said to create a more suitable
environment for itself, from a 'strong Gaia' hypothesis in which the entire planet is
considered as a single organism. Kirchner (2002) believes that such approaches 'may
be useful as metaphors but are unfalsifi able, and therefore misleading, as hypothe-
ses' (p. 393). Lovelock (2000, p. 271) has dismissed the arguments of Kirchner's
fi rst paper as 'sophistry, not science' but fails to refute the claims directly. Others
have taken on the mantle in trying to test the weak form of Gaia (notably Lenton,
2002; Lenton and Van Oijen, 2002; Lenton and Wilkinson, 2003), although both
Volk (2003) and Kirchner (2003) have suggested that they have tended to be selec-
tive with the evidence and to focus only on cases where biological activity has tended
to stabilise the Earth system.
For present purposes, two important issues arise from this debate. First, propo-
nents of strong Gaia present an argument that is non-scientifi c - at least in strictly
Popperian terms. Given that the ESS blueprint was essentially underpinned by criti-
cal rationalist thinking, often with explicit aims of future prediction, the two
approaches are incompatible. Weak Gaia, on the other hand, is testable and indeed
has rarely been challenged in that it is not too distant from ideas of Humboldt,
Huxley and many others since. This form is not incompatible with ESS, but has
