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The Ages of Gaia

A Biography of Our Living Earth

by James Lovelock

255 pages, paperback , W. W. Norton, 1995

The Ages of Gaia explains Lovelock's theory that the earth is a living organism. The book describes how the living earth may work, today, and in ages past, based on the latest research of Lovelock and others.

Praise for The Ages of Gaia

"This book describes a set of observations about the life of our planet which may, one day, be recognized as one of the major discontinuities in human thought. If Lovelock turns out to be as right in his view of things as I believe he is, we will be viewing the Earth as a coherent system of life, self-regulating and self-changing, a sort of immense living organism."--Lewis Thomas, from the Foreword

Quotes from The Ages of Gaia

"Earth is indeed the best of all worlds for those who are adapted to it. But the excellence of our planet takes on a different significance in the light of the evidence that geochemists themselves have gathered. Evidence that shows the Earth's crust, oceans, and air to be either directly the product of living things or else massively modified by their presence. Consider how the oxygen and nitrogen of the air come directly from plants and microorganisms, and how the chalk and limestone rocks are the shells of living things once floating in the sea. Life has not adapted to an inert world determined by the dead hand of chemistry and physics. We live in a world that has been built by our ancestors, ancient and modern, and which is continuously maintained by all things alive today. Organisms are adapting in a world whose material state is determined by the activities of their neighbors; this means that changing the environment is part of the game. . . . If, in the real world, the activity of an organism changes its material environment to a more favorable state, and as a consequence it leaves more progeny, then both the species, and the change will increase until a new stable state is reached. On a local scale adaptation is a means by which organisms can come to terms with unfavorable environments, but on a planetary scale the coupling between life and its environment is so tight that the tautologous notion of 'adaptation' is squeezed from existence. The evolution of the rocks and the air and the evolution of the biota are not to be separated."

"The simple model Daisyworld illustrated how Gaia might work. It pictured an imaginary world that spun like the Earth as it circled and was warmed by a star that was the identical twin of our own Sun. On this world, the competition for territory between two species of daisies, one dark and one light in color, led to the accurate regulation of planetary temperature close to that comfortable for plants like daisies. No foresight, planning, or purpose was invoked. Daisyworld is a theoretical view of a planet in homeostasis. We can now begin to think of Gaia as a theory, something rather more than the mere 'let's suppose' of an hypothesis.

"There is much more to Daisyworld than just the answer to a criticism. I first made it for that purpose, but as it has developed I have found it to be a source of insight and an answer to questions about theoretical ecology and Darwinism, as well as to questions about Gaia. An important property of the model is its docility and stability in mathematical terms. As I continue to work with these models I find that the number of species, and trophic levels, that can be accommodated appears to be limited only by the speed and capacity of the computer used and by my patience. Whatever the details, the inclusion of feedback from the environment appears to stabilize the system of differential equations used to model the growth and competition of the species."

"There is no way for us to survive without agriculture, but there seems to be a vast difference between good and bad farming. Bad farming is probably the greatest threat to Gaia's health. We use close to 75 percent of the fertile land of the temperate and tropical regions for agriculture. To my mind this is the largest and most irreversible geophysiological change that we have made. Could we use this land to feed us and yet sustain its climatic and chemical geophysiological roles? Could trees provide us with our needs and still serve to keep the tropics wet with rain? Could our crops serve to pump carbon dioxide as well as the natural ecosystems they replace? It should be possible but not without a drastic change of heart and habits."

"There is as yet no answer as to what proportion of the land of a region can be developed as open farmland or forest without significantly perturbing either the local or the global environment. It is like asking what proportion of the skin can be burnt without causing death."

"The forests of the humid tropics act on a global scale by pumping vast volumes of water back into the air (evapotranspiration); this has the potential to affect climate locally by causing the condensation of clouds. The white tops of the clouds reflect away the sunlight that otherwise would heat and dry the region. The evaporation of water from the liquid state absorbs a great deal of heat, and the climate of distant regions outside the tropics is considerably warmed when damp tropical air masses release their latent heat in the condensation of rain. The transfer of nutrients and the products of weathering by the tropical rivers are obviously part of their interconnection and must also have a global significance.

" If evapotranspiration, or the additions of the tropical rivers to the oceans, is vital to the maintenance of the present planetary homeostasis, then this suggests that its replacement with an agricultural surrogate or a desert not only would deny these regions to their surviving inhabitants but would threaten the rest of the system as well. We do not yet know; we can only guess that tropical forest systems are vital for the world ecology. It may be that they are like the temperate forests that seem to be expendable without serious harm to the system was a whole; temperate forests have suffered extensive destruction during glaciations as well as during the recent expansion of agriculture."

"Gaia theory provokes a view of the Earth where:

1. Life is a planetary-scale phenomenon. On this scale it is near immortal and has no need to reproduce.
2. There can be no partial occupation of a planet by living organisms. It would be as impermanent as half an animal. The presence of sufficient living organisms on a planet is needed for the regulation of the environment. Where there is incomplete occupation, the ineluctable forces of physical and chemical evolution would soon render it uninhabitable.
3. Our interpretation of Darwin's great vision is altered. Gaia draws attention to the fallibility of the concept of adaptation. It is no longer sufficient to say that 'organisms better adapted than others are more likely to leave offspring.' It is necessary to add that the growth of an organism affects its physical and chemical environment; the evolution of the species and the evolution of the rocks, therefore, are tightly coupled as a single, indivisible process.
4. Theoretical ecology is enlarged. By taking the species and their physical environment together as a single system, we can, for the first time, build ecological models that are mathematically stable and yet include large numbers of competing species. In these models increased diversity among the species leads to better regulation.

"We have at last a reason for our instinctive anger over the heedless deletion of species; an answer to those who say it is mere sentimentality. No longer do we have to justify the preservation of the rich variety of species in natural ecosystems, like those of the humid tropical forests, on the feeble humanist grounds that they might, for example, carry plants with drugs that could cure human disease. Gaia theory makes us wonder if they offer much more than this. Through their capacity to evaporate vast volumes of water vapor through the surface of their leaves, trees may serve to keep the ecosystems of the humid tropics and the planet cool by providing a sunshade of white reflecting clouds. Their replacement by cropland could precipitate a regional disaster with global consequences."

Table of Contents of The Ages of Gaia

1. Introductory
2. What is Gaia?
3. Exploring Daisyworld
4. The Archean
5. The Middle Ages
6. Modern Times
7. The Contemporary Environment
8. The Second Home
9. God and Gaia
10. Gaia Since 1988

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