Here is the anguished cry of another distinguished scientist distressed by our collective incapacity to grasp the enormity of the earth’s looming environmental crisis. It has been obvious for a long time—many decades—to legions of individual scientists, and to prestigious scientific organizations like the Union of Concerned Scientists and the National Academy of Sciences, that the global human enterprise is on a collision course with the physical and biological limits of the earth.
Estimates of how bad the situation is, of course, differ, but various assessments agree that the global economy is consuming resources at a rate equivalent to 1.3 to 1.5 times the earth’s capacity to supply them sustainably. The only way this can happen is for us to be consuming the resource capital from which we should be harvesting only the interest. The consumption of resource capital is evident in the sluicing of millions of tons of topsoil into the oceans, the drawing down of underground aquifers, the salinization and desertification of erstwhile croplands, the depletion of fisheries stocks, the overharvest of forests, and on and on. We, the prodigal sons of the modern era, collectively seem powerless to stop any of this. Efforts to date, such as international fisheries commissions, the Rio biodiversity treaty, and the Kyoto Protocol have been feeble and ineffective. The much-anticipated Copenhagen summit on climate change of December 2009 flopped.
On top of this already dire situation we face the added stress of climate warming, which promises heat waves, droughts, torrential flooding, forest fires, Class-5 hurricanes, coastal inundation, and the melting of the glaciers that serve as the vital water supply for millions of people. Can it get any worse, one wonders? It can, and worse will be our reward for disregarding the warnings of a generation of scientists.
In Here on Earth, Tim Flannery softens the frightening reality of these inconvenient truths by resorting to an overzealous use of metaphors to engage the reader and create a sense of the individual’s connection to nature. The subtitle, “A Natural History of the Planet,” would have been apt for one of his earlier books, The Eternal Frontier (2001), but fails to suggest that this new book is a galloping history of man’s relationship to the environment with chapters on overpopulation, financial discounting, the role of markets, global governance, and other topics far afield from natural history.
Flannery is a consummate storyteller who has written a series of fascinating books on human prehistory and the history of life. His earlier works, including The Future Eaters (1994), Throwim Way Leg (1998), and others are rich in detail and drama, and leave a lasting impression. I wish I could say as much of Here on Earth. Flannery describes the book as “an investigation of sustainability—not how to achieve it, but what it is.” The subject matter is wide-ranging, encompassing human history from the out-of-Africa diaspora to exploring the dimensions of our “War against Nature.” The presentation is consequently fast-paced, almost breathless, as Flannery attempts to cover the history of man’s interactions with the environment from Homo erectus to the future in 281 pages. Many topics are necessarily skipped over lightly in a work designed more to impress than to grapple with intricacies. Trying to cover too much too quickly, he fails to achieve coherence and momentum.
By the end, one doesn’t know quite what to make of it. Does the book have a clear message other than that we humans have to cooperate with one another better than we have in the past? As the brief chapters fly by, punctuated with anecdotes and biographical snapshots, the answer to the question is not clear. Many books concerned with the earth’s future thunder doom and gloom on every page. Flannery handles the material with a lighter touch, buoyed by the soothing principle of Gaia, the earth’s propensity to maintain a stable environment congenial to life.
The concept of Gaia as a metaphor for how the earth maintains conditions congenial to life appears to captivate Flannery. James Lovelock, the originator of the Gaia hypothesis,* is a chemist who marveled at the composition and stability of the atmosphere, necessary conditions for the evolution and continuity of life on earth. Lovelock was bemused by “the image of the Earth as a living organism able to regulate its temperature and chemistry at a comfortable steady state.” His musing has found enthusiastic reception among those of a mystical persuasion, but the reality is much less ethereal and better explained by the laws of chemistry. Gaia is woolly romanticism; it is not science because it is not subject to refutation.
In a formal sense, the Gaia concept rests on a circularity. Modern multicellular life evolved under conditions we regard as benign and conducive to life because life is adapted to precisely these conditions. An essential feature of the earth’s atmosphere is that 20 percent of it is oxygen, a fact that could be regarded as mysterious because oxygen is a reactive element, readily forming oxides, compounds of oxygen with the most abundant elements in the earth’s crust, including silicon, iron, and aluminum. For roughly half of the earth’s history, the atmosphere lacked oxygen and was replete with noxious gases: carbon dioxide, ammonia, and methane. Still, life originated under these alien conditions. Oxygen appeared much later with the ascendancy of photosynthesis as the dominant process by which the energy of sunlight converts carbon dioxide into organic compounds. The oxygen in the atmosphere today was derived through the photochemical splitting of water into its components hydrogen and oxygen through photosynthesis. The hydrogen combines with carbon dioxide to form carbohydrates and the oxygen is released into the atmosphere as a byproduct. The atmosphere contains oxygen because plants produce it faster than it is lost to the oxidation of iron and other minerals.
The earth’s environment has not always been so benign. Early earth history includes a massive collision that liquefied the earth’s core and spun off the moon, a long period when the atmosphere was replete with greenhouse gases but lacked oxygen, and a time about a billion years ago when the entire earth froze over. Where was Gaia then? On a time scale of millions of years the earth’s geological processes can attain a dynamic quasi equilibrium that permits life to flourish and diversify; but on a scale of billions of years, the story becomes, from a human perspective, one of forbidding strangeness and intolerable conditions.
Life evolved in the absence of oxygen. The legacy of that early time is an extraordinary array of organisms known as extremophiles. Principally bacteria, extremophiles live in unimaginably hostile environments, such as superheated hot springs, sulphurous vents in the ocean floor, anaerobic muck, and Antarctic deserts. If catastrophe were to befall the earth, another meteorite impact, for example, such as the one that ended the age of dinosaurs, extremophiles would inherit the earth and perhaps launch a new experiment in evolution. The existence of extremophiles lends credence to the notion that life has evolved many times, perhaps millions of times in an essentially infinite universe. But how often has life evolved into sentient beings capable of achieving self-awareness through science? That is certainly a much smaller number. Perhaps we’re not far from obtaining an estimate as previously unknown planets are being discovered at an accelerating rate and means are being developed of gathering information about their atmospheres.
Whether one regards Gaia as merely a convenient rhetorical device or a manifestation of supernatural guidance, it doesn’t really matter in a practical sense. What matters is the delicate checks and balances that make the earth habitable, even congenial to human well-being. The earth maintains a stable environment because it is a dynamic system and dynamic systems possess stable equilibriums. Less widely recognized is that the earth is a complex dynamic system. A cardinal feature of complex dynamic systems is that they can attain multiple forms of equilibrium. One such alternative equilibrium would be an ice-free Northern Hemisphere: this appears inevitable unless greenhouse gas emissions are sharply curtailed. Once the Northern Hemisphere has shifted to an ice-free state, a new stable equilibrium would prevail. Most of the solar energy that falls on the top of the world now is reflected back to space by snow and ice, but in the absence of ice, most of the energy would be retained, creating a warmer climate that would no longer accumulate ice.
The self-regulating qualities of the earth that led James Lovelock to conceive of the Gaia hypothesis fall into the domain of biogeochemistry, a multidisciplinary field that, as the name implies, combines elements of biology, geology, and chemistry. Whereas Gaia holds the Earth’s physical homeostasis in awe, biogeochemistry endeavors to understand it by picking it apart, measuring its component processes, and putting them back together in the form of global balance sheets. Often the balance sheets don’t balance, as in the case of both carbon dioxide and methane, the two greenhouse gases that are contributing most to the increasing heat-trapping capacity of the atmosphere.
Uncertainties in rectifying the balance sheet for carbon dioxide, for example, contribute to uncertainties in the projections of climate change. The problem is immensely complicated because carbon dioxide has many sources in addition to the burning of fossil fuels. Plants consume carbon dioxide while animals and microbes produce it. Volcanoes contribute to the atmospheric pool. Huge reservoirs of carbon reside in standing forests, peat deposits, and permafrost, and underground in the soil and buried sediments, in amounts dwarfing that in the atmosphere. Human activities, from clearing forests to plowing the ground to overgrazing grasslands to making cement, often disturb nature’s equilibrium and complicate the task of quantifying fluxes of carbon dioxide.
On the other side of the balance sheet are processes that consume carbon dioxide: the growth of forests and other vegetation, absorption by the sea, formation of coral reefs, and losses to sedimentation. Human activities disturb all of these processes and by different amounts in different parts of the world. When one realizes this (and a lot more), it can be appreciated why it took more than two thousand experts to compile the latest (2007) report of the Intergovernmental Panel on Climate Change. To trivialize a collaborative global effort of this magnitude as “the biggest hoax ever perpetrated on the American people,” as Oklahoma senator James Inhofe recently claimed, would be farcical if attitudes such as this weren’t driving our public policy on an issue that threatens the well-being of billions of people. It should not be difficult to understand why we scientists are exasperated.
Flannery rightly warns that any notion of a sustainable world economy is ultimately constrained by the earth’s biogeochemical cycles. Water, carbon, nitrogen, trace gases in the atmosphere (e.g., methane, ozone), and mineral elements essential to plant growth are all involved. Human activities are altering the equilibriums of nearly all biogeochemical cycles as well as releasing huge amounts of fertilizers, herbicides, pesticides, and heavy metals that are poisoning surface waters and underground aquifers throughout all the densely settled portions of the planet. Many of the chemicals being released into the environment are new and their effects on organisms or ecosystems are poorly known. Here is another case where we seem blind to history. Several classes of compounds, notably chlorinated diphenyls (DDT and related compounds), polychlorinated biphenyls (PCBs), and chlorofluorocarbons (CFCs) were banned only after it was discovered—decades after they had been in widespread use—that they impose unacceptable burdens on the environment, other species, and ourselves. Many more will surely follow, but after how much damage has been done?