Toby's book On Gaia: A Critical Investigation of the Relationship between Life and Earth is the culmination of more than ten years of research into the subject. Professor Toby Tyrell was interviewed especially for Ocean and Earth research news.

Why did you become interested in Gaia?

When I read Lovelock’s book Gaia: a new look at life on earth, I became intrigued by the idea that the planet could regulate itself. It is a very attractive theory but it seemed too good to be true; could things really be as simple as he suggested?

How did you become a sceptic?

Lovelock put forward three main arguments for why Gaia is correct: that Earth is extremely favourable for life, that life has greatly altered our environment and that the environment has remained fairly stable over the last three billion years. Surprisingly, these claims have not been comprehensively challenged since they were made in the 1970s. After testing these assertions against the latest scientific evidence, I found some serious problems with the theory.

What did you find?

The suggestion that Earth has always been a hospitable and stable planet is at odds with what happened during the ice ages, as environmental scientist Stephen Schneider previously argued. During these periods, around half of the vegetation died away and shallow seas, which teem with life, were mostly lost due to the fall in sea level. Ice ages are paced by periodic variations in our planet’s orbit about the sun, not by life, although life, through its influence on the carbon cycle, is partly responsible for the low CO2 levels which allow ice ages to occur.

Lovelock claims there is the ‘right amount’ of nitrogen in the seas to support life. However, most of this element is found as inert molecules made of two nitrogen atoms which only a few specialised organisms can make use of. Unfortunately, powerful microbial processes in the nitrogen cycle ensure that nearly all of the vast stores of nitrogen on Earth are kept as the ‘wrong sort’, and nitrogen starvation is, as a result, widespread. His assertion that life has greatly altered the environment can be supported, but the alterations over geological time have not always been helpful. An alternative hypothesis, ‘coevolution of life and planet’, which I support, argues that life and the environment do influence each other but not necessarily in a beneficial manner.

Does this have implications for climate change?

Belief in Gaia can potentially make people dangerously complacent about the impact of human activity on our planet, although Lovelock himself was in fact sometimes overly alarmist. In my view natural systems are not as robust as Gaia can lead one to believe. Rather than assuming a Gaian network of stabilising and protective mechanisms, we should instead be vigilant for Achilles’ heels in the climate system, as previously found for CFCs and the ozone layer.

How did you become an oceanographer at Southampton?

I was always interested in the natural world, growing up in the countryside in North Wales, helping my father with his forestry business at weekends, and walking in Snowdonia. After degrees in other subjects I was stimulated to convert to oceanography partly through reading Lovelock’s books. I now research ocean acidification and marine biogeochemistry and am also interested in how life, in particular phytoplankton, interacts and has interacted with the environment.

Professor Tyrrell's book is published by Princeton University Press and is available here.

Professor Tyrrell specialises in Ocean acidification and his primary research group is Marine Biogeochemistry