On Gaia

A Critical Investigation of the Relationship between Life and Earth

Toby Tyrrell

• Publisher: Princeton University Press
• Year: 2013
• ISBN:
  9781400847914
• Topic: Ciencias físicas
• Subtopic: Geología y ciencias de la Tierra

A critical examination of James Lovelock's controversial Gaia hypothesis One of the enduring questions about our planet is how it has remained continuously habitable over vast stretches of geological time despite the fact that its atmosphere and climate are potentially unstable. James Lovelock's Gaia hypothesis posits that life itself has intervened in the regulation of the planetary environment in order to keep it stable and favorable for life. First proposed in the 1970s, Lovelock's hypothesis remains highly controversial and continues to provoke fierce debate. On Gaia undertakes the first in-depth investigation of the arguments put forward by Lovelock and others—and concludes that the evidence doesn't stack up in support of Gaia.Toby Tyrrell draws on the latest findings in fields as diverse as climate science, oceanography, atmospheric science, geology, ecology, and evolutionary biology. He takes readers to obscure corners of the natural world, from southern Africa where ancient rocks reveal that icebergs were once present near the equator, to mimics of cleaner fish on Indonesian reefs, to blind fish deep in Mexican caves. Tyrrell weaves these and many other intriguing observations into a comprehensive analysis of the major assertions and lines of argument underpinning Gaia, and finds that it is not a credible picture of how life and Earth interact. On Gaia reflects on the scientific evidence indicating that life and environment mutually affect each other, and proposes that feedbacks on Earth do not provide robust protection against the environment becoming uninhabitable—or against poor stewardship by us.

Chapter 1

GAIA, THE GRAND IDEA

THIS FIRST CHAPTER introduces the Gaia hypothesis and two competing hypotheses.

1.1. A BRIEF HISTORY

Gaia, the idea that life moderates the global environment to make it more favorable for life, was first introduced in 1972 in an academic paper titled “Gaia as Seen through the Atmosphere” in the journal Atmospheric Environment, followed rapidly by two other papers both in 1974: “Atmospheric Homeostasis by and for the Biosphere” in the journal Tellus, and “Biological Modulation of the Earth’s Atmosphere” in the journal Icarus.¹ James Lovelock was sole author of the first paper and coauthor with Lynn Margulis of the latter two. Both were already scientists of some note. Lovelock had already pursued a successful career inventing chemical instruments, including, most famously, the electron capture detector. This device, when coupled to a gas chromatograph, allows for the detection of trace chemical substances even at extremely low concentrations. Before that, Lovelock had worked for twenty years at the United Kingdom’s National Institute for Medical Research in Mill Hill, London, carrying out research in biomedical science.

Use of the electron capture detector started to become widespread due to its great utility, and through his consultancy work with it Lovelock was invited to participate in a NASA project to work out how to ascertain if Mars contained life. The two Viking spacecraft, now revered in history as the first spacecraft ever to land on the surface of another planet, were just then being designed, and a major priority was to decide which instruments to put on board. Reflection on this problem of how to detect the presence of life stimulated Lovelock’s first thoughts on the Gaia hypothesis.

Lynn Margulis was a groundbreaking microbiologist at Boston University. She had long been championing her own (separate) revolutionary idea, one that is now widely accepted. It proposed that in the evolutionary distant past one primitive cell managed to “enslave” another (engulf it without killing it) and in the process benefited from the new capabilities of the enslaved cell. She proposed that such “endosymbiosis” had occurred a number of times. Mitochondria, chloroplasts, and flagella are all part of the machinery of individual cells; they are subcomponents of many single-celled creatures and of individual cells in multicellular organisms. According to the endosymbiosis theory they are all suggested to be relics of long-ago-assimilated single cells.² Each cell of every animal and plant, including those making up human bodies, is from this perspective seen as an evolutionary amalgam of several different ancient lineages. This theory, initially treated with some considerable skepticism (an early Margulis paper on it was rejected by as many as fifteen different scientific journals before being accepted), is now the consensus view. Although she was not the first to conceive of the idea, Margulis was the first to support it with direct microbiological observations, and it was in large part thanks to her continued championing of it, against strong opposition, that it came to be widely accepted. It has considerable implications. For example, it requires some modification of the idea that evolution proceeds solely by selection among organisms, each of which is a slightly modified descendant of the previous generation. Among the unicellular microbes at least, evolution has at times created a radically new species in a single jump, as a novel intracellular symbiont has been acquired.

Although Margulis jointly authored some of the early papers and remained a champion of Gaia, the hypothesis has always been first and foremost the brainchild of James Lovelock. Following the Lovelock and Margulis papers and some other papers in academic journals, none of which generated large amounts of interest or attention, Lovelock brought out a book called Gaia: A New Look at Life on Earth.³ When this book came out, in 1979, it brought Gaia to scientific prominence at last. The book stimulated a mixture of admiration and opposition among scientists. Many evolutionary biologists, in particular, were very critical, for reasons that will be explained in the next chapter. Some of the biologists’ objections were subsequently countered by modifying the hypothesis and also by the production of a now-famous model, Daisyworld. This model demonstrated the theoretical possibility of stable regulation of planetary temperature by organisms that are still adhering to biologically plausible rules of behavior and reproduction.⁴ The Daisyworld paper, by Andrew Watson and James Lovelock, came out in 1983 in the academic journal Tellus. In the ensuing years Lovelock produced two more books: The Ages of Gaia: A Biography of Our Living Earth, in 1988, and Gaia: The Practical Science of Planetary Medicine, in 1991.⁵

In the 1980s the Gaia hypothesis was considered both interesting and controversial and continued to attract a mixture of agreement, interest, doubt, and rejection. By the mid-1980s it was decided that there was sufficient interest to merit organizing an international conference. In 1988 a prestigious Chapman Conference of the American Geophysical Union brought together advocates and interested skeptics in a wide-ranging scientific discussion of the hypothesis.⁶ Further international conferences on Gaia were convened at Oxford University in 1994, 1996, and 1999, with membership primarily by invitation. In 2000 a second open Scientists on Gaia Chapman Conference was held in Valencia, Spain.⁷

As Lovelock, now in his nineties, has become less active, others have taken up the torch. Tim Lenton, for instance, an Earth system scientist at the University of Exeter, has written many papers on Gaia, including a review article in Nature in 1998.⁸ The Gaia hypothesis had achieved a degree of scientific respectability.⁹ However, a brief review of its reception in books published since 2007 shows that while it is now accepted gladly by some, it also continues to stimulate intense debate.¹⁰ This was also revealed in back-and-forth exchanges in the pages of the journal Climatic Change in 2002 and 2003.¹¹ Nevertheless, when interviewed for a biography published in 2009, Lovelock claimed that Gaia has made the transition from being just a hypothesis to being solid science.¹²

The degree to which Gaia has been accepted by a large part of the scientific community, including those in its higher echelons, was highlighted by the Amsterdam Declaration on Global Change.¹³ This document is a synthesis of the work of four international research umbrella organizations, including the International Geosphere-Biosphere Programme (IGBP) and the World Climate Research Programme (WCRP) and was discussed at a conference attended by more than one thousand scientific delegates. The second paragraph of the declaration asserts: “Research carried out over the past decade under the auspices of the four programmes to address these concerns has shown that: The Earth System behaves as a single, self-regulating system comprised of physical, chemical, biological and human components.” The wording could almost have been lifted from one of Lovelock’s books. A Nature editor, reporting on the second Chapman Conference in 2000, judged that “James Lovelock’s theory of the biotic regulation of Earth has now emerged with some respectability following close scrutiny by the biogeochemical community.”¹⁴

Is the scientific respectability and the continuing prominence justified? Read the rest of this book if you want to find out.

1.2. THE HYPOTHESIS

The Gaia hypothesis is nothing if not daring and provocative. It proposes planetary regulation by and for the biota, where the “biota” is the collection of all life. It suggests that life has conspired in the regulation of the global environment so as to keep conditions comfortable. During the more than two (probably more than three) billion years that life has existed as a continuous presence on Earth, Lovelock suggests that life has had a hand on the tiller of environmental control. And the intervention of life in the regulation of the planet has been such as to promote stability and keep conditions favorable for life.

That, in a nutshell, is the hypothesis. Providing a more precise definition is, however, made difficult by a couple of factors: (1) the hypothesis has not stayed constant but instead has been modified over time in response to criticisms; and (2) Lovelock’s publications do not provide a completely clear definition, although others have tried subsequently to clarify it for him, as described below.

Gaia is not a hard-and-fast, well-defined concept. It is not a “set menu.” Rather it is more like a loosely defined smörgåsbord, from which “diners” can take their pick from a collection of several related hypotheses, often couched in rather vague terms. The lack of clarity presents a problem for those of us who want to analyze and evaluate Gaia. It may even seem a poor basis for a book such as this one. However, fortunately, there are central components of Gaia that are fundamental to all definitions, and it is these that I examine in this book. These concepts are at the heart of the hypothesis and are present regardless of which variant is chosen:

A. Earth is a favorable habitat for life.

B. It has been so over geologic time as the environment has remained fairly stable.

C. This is partly due to life’s role in shaping the environment. For instance, life has influenced the chemical composition of the atmosphere and the sea.

In Lovelock’s own words, the hypothesis has been defined in various different ways over the years:

We have since defined Gaia as a complex entity involving the Earth’s biosphere, atmosphere, oceans and soil; the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet. The maintenance of relatively constant conditions by active control may be conveniently described by the term “homeostasis.” (Lovelock 1979)

The main part of the book … is about a new theory of evolution, one that does not deny Darwin’s great vision but adds to it by observing that the evolution of the species of organisms is not independent of the evolution of their material environment. Indeed the species and their environment are tightly coupled and evolve as a single system. What I shall be describing is the evolution of the largest living organism, Gaia. (Lovelock 1988)

The concept that the Earth is actively maintained and regulated by life on its surface. (Ibid.)

Gaia theory predicts that the climate and chemical composition of the Earth are kept in homeostasis for long periods until some internal contradiction or external force causes a jump to a new stable state. (Ibid.)

Gaia is the Earth seen as a single physiological system, an entity that is alive at least to the extent that, like other living organisms, its chemistry and temperature are self-regulated at a state favourable for life. (Lovelock 1991)

The top-down view of the Earth as a single system, one that I call Gaia, is essentially physiological. It is concerned with the working of the whole system, not with the separated parts of a planet divided arbitrarily into the biosphere, the atmosphere, the lithosphere, and the hydrosphere. (Ibid.)

Organisms and their environment evolve as a single, self-regulating system. (Lovelock 2003b)

The hypothesis that living organisms regulate the atmosphere in their own interest. (Ibid.)

By the end of the 1980s there was sufficient evidence, models and mechanisms, to justify a provisional Gaia theory. Briefly, it states that organisms and their material environment evolve as a single coupled system, from which emerges the sustained self-regulation of climate and chemistry at a habitable state for whatever is the current biota. (Ibid.)

In Gaia theory, organisms change their material environment as well as adapt to it. (Ibid.)

And from Tim Lenton:

The Gaia theory proposes that organisms contribute to self-regulating feedback mechanisms that have kept the Earth’s surface environment stable and habitable for life. (Lenton 1998)

Some changes have been made to the hypothesis over time. A first correction was to alter the proposed life effect on the environment, from one of making it optimal to one of making it comfortable:

The first edition of this book used the terms optimum and optimize too freely; Gaia does not optimize the environment for life. I should have said that it keeps the environment constant and close to a state comfortable for life. (Lovelock 1979, in the preface to a 1987 revised edition)

A second clarification was to renounce any ascribing of purpose or intent to the biota. It was made clear that any biotic regulation of the environment must be automatic and unconscious. The reason for their impacts on the environment is not because the organisms responsible consciously want to help out their brothers in life:

At first we explained the Gaia hypothesis in words such as “Life, or the biosphere, regulates or maintains the climate and the atmospheric composition at an optimum for itself.” This definition was imprecise, it is true; but neither Lynn Margulis nor I have ever proposed that the planetary regulation is purposeful. (Lovelock 1991)

This topic is returned to in the next chapter.

An attempt to seek greater clarity of definition came from James Kirchner, an Earth scientist at the University of California, Berkeley. The first Scientists on Gaia conference, in 1988, was the first time that large numbers of both proponents and interested skeptics got together in open debate. As might be expected, the...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Table of Contents
• Dedication Page
• Preface
• 1. Gaia, the Grand Idea
• 2. Good Citizens or Selfish Genes?
• 3. Life at the Edge: Lessons from Extremophiles
• 4. Temperature Paces Life
• 5. Icehouse Earth
• 6. Given Enough Time . . .
• 7. Evolutionary Innovations and Environmental Change
• 8. A Stable or an Unstable World?
• 9. The Puzzle of Life’s Long Persistence
• 10. Conclusions
• Notes
• Further Reading
• References
• Acknowledgments
• Index