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Jon Turney¡¯s review of Toby Tyrrell¡¯s On?Gaia: A?Critical Investigation of the Relationship between Life and Earth (Books, 8?August) refers to Tyrrell¡¯s proposal that the Gaia hypothesis is not a reasonable view of how the Earth and life interact.

Tyrrell¡¯s investigation is hugely valuable and makes a considerable contribution to current understanding. On Gaia, however, makes a?category error conflating Gaia theory as the new field of holistic science with the very human desire for explanations and mechanisms. Gaia theory has made the Earth, its rocks, oceans and atmosphere and all of life upon it the ultimate system of ecological study. In Revolutions that Made the Earth (2011), Tim Lenton and Andrew Watson write: ¡°Gaia Theory and the Earth system are for us close to being synonymous.¡±

Tyrrell considers ¡°there is a lack of any clinching fact or argument that points exclusively to Gaia as the only plausible hypothesis for how Earth and life influence each other¡±. This is a young science, and the lack of an explanatory mechanism is no reason for rejection or for acceptance.

Tyrrell writes that ¡°a complacent belief in the comforting power of Earth to self-heal, which can come as unwanted baggage with the Gaia hypothesis, is neither merited nor helpful¡±. James Lovelock in his writings and broadcasts agrees as he continually argues that our actions are likely to perturb the Earth system.

Lovelock¡¯s genius sets out the new world-view that Earth system science is taking forward. His fruitful questions are guiding scientists, non-governmental organisations and politicians to imagine to what extent we can mess with the planetary system before it bites back. Gaia science¡¯s new paradigm is specifying for engineers, entrepreneurs and investors the challenge to develop solutions to adaptation and mitigation as the Earth system approaches tipping points.

John Gilbert
Friends of the Lovelock Archive at the Science Museum