If the biosphere really is a single coherent system, then it must have something like a physiology. It must have systems and processes that perform living functions. In Gaia's Body, Tyler Volk describes the environment that enables the biosphere to exist, various ways of looking at its "anatomy" and "physiology", the major biogeographical regions such as rainforests, deserts, and tundra, the major substances the biosphere is made of, and the chemical cycles that keep it in balance. He then looks at the question of whether there are any long-term trends in the earth's evolution, and examines the role of humanity in Gaia's past and future. Both adherents and sceptics have often been concerned that Gaia theory contains too much goddess and too few verifiable hypotheses. This is the book that describes, for scientists, students, and lay readers alike, the theory's firm basis in science.
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Tyler Volk is Associate Professor of Earth System Sciences at New York University and the author of Metapatterns: Across Space, Time, and Mind. He lives in New York and New Mexico.Excerpt. © Reprinted by permission. All rights reserved.:
PREFACE: FANTASTIC VOYAGERS
Before leaving New York for the year to write this book, I sought out an old film. Packing boxes and other preparations for the move to New Mexico had grown frantic. But I was driven to take the time to relive an adventure story I had seen as a teenager, with the hope of gleaning inspiration for this book. So, a few days before jetting west, I rented Fantastic Voyage.
The hero in the story is a government trouble-shooter. One night he is rushed to a briefing deep within a secret underground laboratory. An anxious clamor surrounds the body of an unconscious diplomat who has been critically injured by foreign agents. Fortunately, the laboratory possesses an astounding new invention, an all-purpose miniaturizer. The plan is to put the hero and four others--a driver, a helper, a surgeon, and Raquel Welch--inside a submarine, shrink all to the size of a blood cell, and then launch them into the diplomat's body. Once inside the blood stream, the crew will attempt to navigate the sub to the brain and there, using a laser, clear an otherwise inoperable blood clot.
The briefing ends. The team is asked, "Is there anything else you need?" The hero, who had been growing ever more dubious, says, "Yeah, a taxi to get me outta here." Too late for that, buddy. On the other hand, the surgeon's assistant, played by Ms. Welch, can hardly wait to climb aboard.
In their nanosubmarine, the nanovoyagers are injected by hypodermic needle into an artery in the diplomat's neck, headed for his head. Blood cells gyrate around them in an acid-rock light show (the film is vintage 1966). They stare slackjawed, like ecotourists on the Amazon River.
Things do not go as planned. A hair-raising detour forces them to navigate through the heart--temporarily halted for their safety. Eventually the intrepid explorers enter the left lung. The blood passageway narrows and narrows. Undulating blobs magically shimmy from blue to red. The voyagers have become the first in history to witness the revitalization of blood cells, as those cells release carbon dioxide and absorb oxygen across a supply capillary's thin membrane. Because the submarine is low on oxygen, the hero dons scuba gear, swims over to the membrane, and snakes an airhose across it.
Why, after more than thirty years, was I so keen on seeing this movie again? The idea of traveling inside a giant body resonates in my mind like an archetype. I am a voyager inside the biosphere.
We need not wait to be shrunk by some futuristic wizardry to witness an exchange of gases from an interior viewpoint. Just walk in the woods. Trees are taking in carbon dioxide and releasing oxygen across the membranes of their leaves. Each of us already has an airhose, the trachea, by which we tap into the atmosphere and inhale what the trees freely offer. Take a deep breath. Or swim amid the living colors of a reef. Lie down in a field of undulating grass. Let a hand bob in a river's eddies. Smell some pungent dirt. We are already fantastic voyagers. All of us are cells within the embracing physiology of what Jim Lovelock has called "Gaia."
Thinking of Earth's life-inhabited surface as a physiological system immediately conjures up an image of a giant volitional being, as does naming the system after a Greek goddess. We thus must exercise some care in applying this analogy. Organisms evolved; Gaia did not. Beyond alluding to such concepts, I will not weave detailed arguments for or against the idea that Earth is alive, that Gaia self-regulates, and that Gaia is a self-sustaining organism, or perhaps quasi-organism. Such notions depend on a slew of ambiguous words that, however carefully defined, either ready readers for an Earth-hug or raise their hackles. In either case, the reader's attention to the science of Gaia and its overarching principles may lapse. I will therefore try to work with a tricky binary. On the one hand, I experience a delightful sense of being inside a giant metabolism. This perception grows more acute the more I learn, but I am also convinced that Gaia is very different from any organism. Thus I can honestly apply the principles of science to study the global metabolism without postulating a global organism.
What is Gaia? Following Lovelock, I consider Gaia the interacting system of life, soil, atmosphere, and ocean. It is the largest level in the nesting of parts within wholes that encompassesand thus transcendsliving beings, a nesting that ranges from the molecules within cells all the way outward to the gaian system itself. Like the interiors of organisms, Gaia contains complex cycles and material transformations driven by biological energy. Indeed, Gaia's inclusion of life means that from some perspectives, it much resembles life. But how Gaia differs from organisms turns out to be its glory.
Consider: Although Gaia has changed through time, it does not evolve in a Darwinian sense. Nevertheless, it both contains and is built from evolving organisms. Furthermore, organisms are open, flow-through systems, whereas Gaia is relatively closed to material transfer across its borders. Gaia exists on its own unique level of operating rules, a level surely as complex as that of organisms and therefore worthy of its own science--which Jim Lovelock calls geophysiology.
Gaia is an entity whose properties we are just beginning to understand. How can that be? Oxygen and carbon dioxide, after all, have been known as a functional pair since 1779, when Jan Ingen-housz found that plants made "vital" air that would sustain animal life, during the day, and "vitiated" air, dangerous to animals, at night. The scientific question for our own time is why the "vital" component of air holds at 21 percent. On such a fundamental mystery alone I could rest my case that our voyage of discovery has barely begun. But consider further: Only since 1958 have measurements of carbon dioxide enabled us to witness the seasonal breathing of the biosphere. And only recently has it become possible to monitor the riverine transport of dissolved ions and particles to the ocean, revealing what flows from land to life at sea. Daily we hear announced the discovery of new microbes deep in rock, or underwater, or even in backyard soil. Data for the big picture--the gain picture--are just now pouring in.
For many years my professional work has been involved with Earth's carbon cycle, with crop growth for NASA's closed systems, and with evolutionary innovations that affected climate. Throughout, the focus has been on the role life plays in chemical cycles and on the complex interaction between life and the environment. This research led me naturally to the Gaia hypothesis of James Lovelock and Lynn Margulis, and I consider myself privileged to have personal and professional friendships with many scientists and nonscientists alike in what might be called the gaian community. We are all intrigued by the magnificent mysteries that loom before us as we ponder how this planet works.
It is from such a background that I offer this book. I believe that new insights will derive from contemplating the long known and newly known from fresh angles and that such re-visioning will invariably take us to the edge of the unknown. In articulating my personal vision of Gaia as a symphony of material flows and cycles, I have neglected some classic topics in the gaian literature, such as the Daisyworld model of climate regulation, debates about the theory of Gaia, and the history of gaian ideas and research. Readers will find these topics beautifully presented in Lovelock's own books and in the writings of others.
My focus is on the molecular transformations between life and the global environment. Atmospheric carbon dioxide, for example, seasonally rises and falls with the shifting dominance of respiration and photosynthesis in the Northern Hemisphere. This "breathing of the biosphere" leads, in chapter 1, to a number of directives for studying Gaia: We should follow the cycles of matter. We should attend to the cycles of causes, in other wordsto the feedback loops of influence that control the cycles of matter. We should look for key fluxes and agents. And in accordance with the prime directive for gaian inquiry, we should look to the profound difference that life works upon a planetary surface.
The second chapter, "A Global Holarchy," develops some conceptual underpinning for treating Gaia as a whole made up of parts. Parts influence their wholes by outward causation. Our exploration starts among the denitrifying microbes in the ocean. Then we follow the released molecules as they travel upward into the atmosphere and downward again by the efforts of nitrogen-fixing bacteria. Wholes, in turn, influence their parts by inward causation. How does Gaia influence its parts? I suggest that the fundamental effect results from the huge difference in magnitude between the flows and cycles rumbling inside Gaia and the relatively small leaks of molecules across Gaia's borders. Gaia's border frames the creativity of life within.
The next three chapters trace a path through the holarchy from large to small. "Outer Light, Inner Fire" examines the consequences for Gaia of the immense presences above and below, whimsically called Helios and Vulcan. Sunlight falling as parallel rays on a spherical surface endows various regions unequally with energy, and this inequality drives the whirls of atmosphere and ocean that freely provide Gaia with a circulatory system uniting life. Below Gaia churns the deep Earth with its heat. A minor source of raw energy, Vulcan nonetheless powers key transfers of material across gaian borders at ocean ridges, through volcanoes, and by subduction.
Chapter 4 moves from these outer agents to the "parts of Gaia." What are its parts? Are they perhaps the biomes? The genetic divisions of kingdoms or domains? The cycles of elements? All these viewpoints combined? One perspective focuses on the biochemical guilds: groupings of organisms that perform similar chemical functions (photosynthesis, for instance). Such guilds may be the closest analog in gaian physiology to living organs. Another potent approach to Gaia's parts emphasizes the four primary pools: life, soil, atmosphere, and ocean. Life, a minor pool in terms of its store of crucial elements, exhibits its strength as a major player in the Earth system by generating surface areas of leaves, algae, fungi, and bacteria that sum to the nearly astronomical in size.
The living surfaces only hint at how organisms are interlaced with the gaian matrixes of soil, atmosphere, and ocean. Chapter 5 continues the inward journey, to the little molecules that run the world, the "worldwide metabolisms." For example, the green chlorophyll of plants, algae, and cyanobacteria unites these disparate kingdoms into a single biochemical guild of water-splitting photosynthesizers. Another universal is the enzyme Rubisco, which ushers carbon dioxide into the biological molecules of plants and algae. More worldwide molecules directing the cycles of nitrogen and phosphorus indicate that, overall, the key processes of Gaia are best seen by looking right through the borders of organisms.
All these fluxes of matter between life and the gaian matrixes are driven by energy. How much of the sun's energy is bound into biochemical energy by photosynthesis? When we apply an analysis called the energy cascade, the theoretically possible number turns out to be surprisingly small, and the real number is only a tenth of that. How, then, can life have any impact on the planet? The answer, explored in Chapter 6, is in how that "embodied energy" is used: to drive chemical transformations that would be either absent or rare without life--for example, mining water molecules for precious hydrogen and thus freeing oxygen as waste. Further, life embodies not just energy but also a mix of elements that is amazingly uniform in proportions across the organic spectrum. The feeding of life on its own productions amplifies the availability of crucial elements such as terrestrial phosphorus to high values, a boost that life gives to itself by tightening the cycles of matter with! ! in Gaia.
Chapter 7, "The Music of This Sphere," continues the theme of the cycling ratios after elements travel down river to the sea. There, for example, the cycling ratio of phosphorus is even higher than on land. There too we encounter a duet between phosphorus and nitrogen played on the grandest of scales: in their steady ratios as dissolved nutrients at all depths of the global ocean. What brings about this chemical regulation? For an answer, we revisit the microbial activities of denitrifiers and nitrogen fixers. Other interactions include iron, sulfur, and then clouds, climate, atmospheric carbon dioxide, and the biotic enhancement of weathering.
Finally, in Chapter 8, we contemplate "Gaia in time." Gaia's story involves the emergence of many of the biochemical guilds in life's earliest days (geologically speaking). But there was plenty of room left for the evolution of new guilds between that distant then and now, as the environment altered by previous forms of life opened opportunities for new guilds. Gaia owes its continuity during its long tenure to the nearly closed network of life and life's wastes, both organic and inorganic, held within the gaian matrixes. This is the physiology of Earth. How, in the end, should we regard ourselves in this story?
The crew in Fantastic Voyage do reach their goal. They blast away the blood clot; the diplomat survives. Moreover, my idiosyncratic craving to watch this film during the domestic madness of a major move was well rewarded. "Fantastic voyage" is an apt metaphor for the scientific quest to understand Gaia. To repair damage caused by humans, the crew travels through the passageways of a body made by nature. Isn't that our current situation? We inhabit a global metabolism with a four-billion-year pedigree. In just the past few decades, we have awakened to an awareness of damage we ourselves are inflicting on this metabolism with our blind urges to procreate and appropriate. Perhaps in the fantasies of many, the "taxi outta here" would be a time machine. Just tell the time taxi to stop at nature a thousand or more years ago. But because most of us would want to keep the postal service, the Internet, MRI scans, and an abundance of items in stock at a local supermarket, we m! ! ust proceed with the world as it is, and that requires knowing how the foundational processes of nature work. I am convinced that such knowledge, if widely held, will contribute to shaping the future of Gaiaa future in which we, as a new biochemical guild, will necessarily be integrated into the global metabolism, for better or for worse. We can make it for the better by promoting an informed reverence for Gaia's body.
That said, let the journey begin.
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