Читать книгу Facing the Anthropocene - Ian Angus - Страница 11

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A Second Copernican Revolution

In terms of some key environmental parameters, the Earth System has moved well outside the range of the natural variability exhibited over the last half million years at least. The nature of changes now occurring simultaneously in the Earth System, their magnitudes and rates of change, are unprecedented. The Earth is currently operating in a no-analog state.

—AMSTERDAM DECLARATION ON GLOBAL CHANGE¹

The word Anthropocene has been coined three times.

In 1922, the Soviet geologist Aleksei Petrovich Pavlov proposed Anthropocene or Anthropogene as a name for the time since the first humans evolved about 160,000 years ago. Both words were used by Soviet geologists for some time, but they were never accepted in the rest of the world.

In the 1980s, marine biologist Eugene Stoermer used the word in some published articles, but no one seems to have followed his lead.

The third time’s the charm. Atmospheric chemist Paul J. Crutzen reinvented the word in February 2000, at a meeting of the International Geosphere-Biosphere Program in Cuernavaca, Mexico. Will Steffen, then executive director of the IGBP, was a witness:

Scientists from IGBP’s paleoenvironment project were reporting on their latest research, often referring to the Holocene, the most recent geological epoch of earth history, to set the context for their work. Paul, a vice-chair of IGBP, was becoming visibly agitated at this usage, and after the term Holocene was mentioned yet again, he interrupted them: “Stop using the word Holocene. We’re not in the Holocene any more. We’re in the … the … the … (searching for the right word) … the Anthropocene!”²

Five years earlier, Crutzen had won a Nobel Prize for work that helped prove that widely used chemicals were destroying the ozone layer in Earth’s upper atmosphere, with potentially catastrophic effects for all life on Earth. In his acceptance speech, he said that his research on ozone had convinced him that the balance of forces on Earth had changed dramatically. It was now “utterly clear,” he said, “that human activities had grown so much that they could compete and interfere with natural processes.”³ His interjection at the IGBP meeting in 2000 crystallized that insight in a single word, Anthropocene. “I just made up the word on the spur of the moment,” he says. “Everyone was shocked. But it seems to have stuck.”⁴

Crutzen was something of a scientific superstar: according to the Institute for Scientific Information, between 1991 and 2001 he was the world’s most-cited author in the geosciences.⁵ There is no question that his high profile drew attention to his articles on the Anthropocene, and eventually helped win broad acceptance for the idea.

Steffen, Crutzen, and environmental historian John McNeill subsequently explained the need for a new word this way:

The term Anthropocene … suggests that the Earth has now left its natural geological epoch, the present interglacial state called the Holocene. Human activities have become so pervasive and profound that they rival the great forces of Nature and are pushing the Earth into planetary terra incognita. The Earth is rapidly moving into a less biologically diverse, less forested, much warmer, and probably wetter and stormier state.⁶

“A no-analog state,” “planetary terra incognita”—these phrases are not used lightly. Earth has entered a new epoch, one that is likely to continue changing in unpredictable and dangerous ways. That’s not an exaggeration or a guess: it’s the central conclusion of one of the largest scientific projects ever undertaken, one that requires us to think about our planet in an entirely new way.

Earth as an Integrated System

Though it has gone unnoticed by most people and unmentioned in mainstream media, scientific understanding of our planet has radically changed in the past three decades. Scientists have long studied various aspects of Earth, using the methods of geology, biology, ecology, physics, and other disciplines. Now many are studying Earth as an integrated planetary system—and discovering that human activity is rapidly changing that system in fundamental ways:

Crucial to the emergence of this perspective has been the dawning awareness of two fundamental aspects of the nature of the planet. The first is that the Earth itself is a single system, within which the biosphere is an active, essential component. In terms of a sporting analogy, life is a player, not a spectator. Second, human activities are now so pervasive and profound in their consequences that they affect the Earth at a global scale in complex, interactive, and accelerating ways; humans now have the capacity to alter the Earth System in ways that threaten the very processes and components, both biotic and abiotic, upon which humans depend.⁷

Studying Earth as a system became possible and necessary in the 1980s. It became possible when new scientific instruments became available—in particular, satellites designed to gather data about the state of the entire Earth and computer systems capable of collecting, transmitting, and analyzing vast quantities of scientific data. It became necessary when scientists and others realized that nuclear weapons, ozone-destroying chemicals, and greenhouse gases could radically remake the world: human activity was causing not just change but global change, with potentially disastrous consequences.

Following discussion of global change at meetings of the International Council of Scientific Unions (ICSU) in Warsaw in 1983 and Ottawa in 1985, a series of international symposia and reports recommended creation of a coordinated international research program on global change. As a member of the American Geographical Union wrote, the need went beyond scientific curiosity:

It was noted that stresses on the support systems that sustain life were building up at an ever-increasing pace as the result of increases in world population, industrial activity, waste products, pollution, and resource exploitation, as well as because of long-term trends in regional climatic change. To preserve or expand the life-support systems during the 21st century, governments of all nations would have to design long-term plans that, while addressing their own specific national goals, would have to be based on basic scientific knowledge of the global terrestrial environment and on anticipated natural and anthropogenic change. The required detailed and quantitative scientific knowledge simply does not yet exist.⁸

In 1986, the ICSU initiated the International Geosphere-Biosphere Program, “the largest, most complex, and most ambitious program of international scientific cooperation ever to be organized.”⁹ The IGBP’s objective was to “describe and understand the interactive physical, chemical, and biological processes that regulate the total Earth system, the unique environment it provides for life, the changes that are occurring in that system, and the manner in which these changes are influenced by human actions.”¹⁰

A secretariat was established in Stockholm in 1988, and some 500 scientists worldwide began planning initial projects. By the early 1990s, the IGBP was coordinating the work of thousands of scientists studying the Earth System, a term that has been well defined by Frank Oldfield and Will Steffen:

In the context of global change, the Earth System has come to mean the suite of interacting physical, chemical, and biological global-scale cycles (often called biogeochemical cycles) and energy fluxes which provide the conditions necessary for life on the planet. More specifically, this definition of the Earth System has the following features:

• It deals with a materially closed system that has a primary external energy source, the sun.

• The major dynamic components of the Earth System are a suite of interlinked physical, chemical, and biological processes that cycle (transport and transform) materials and energy in complex, dynamic ways within the System. The forcings and feedbacks within the System are at least as important to the functioning of the System as are the external drivers.

• Biological/ecological processes are an integral part of the functioning of the Earth System, and not just the recipients of changes in the dynamics of a physico-chemical system. Living organisms are active participants, not simply passive respondents.

• Human beings, their societies and their activities are an integral component of the Earth System, and are not an outside force perturbing an otherwise natural system. There are many modes of natural variability and instabilities within the System as well as anthropogenically driven changes. By definition, both types of variability are part of the dynamics of the Earth System. They are often impossible to separate completely and they interact in complex and sometimes mutually reinforcing ways.¹¹

As Hans Schellnhuber of the Potsdam Institute for Climate Impact Research wrote, this was a revolutionary shift in the scientific view of Earth, comparable to the sixteenth-century discovery by Copernicus that Earth orbits the Sun.

Optical magnification instruments once brought about the Copernican revolution that put the Earth in its correct astro-physical context. Sophisticated information-compression techniques including simulation modeling are now ushering in a second “Copernican” revolution….

This new revolution will be in a way a reversal of the first: it will enable us to look back on our planet to perceive one single, complex, dissipative, dynamic entity, far from thermodynamic equilibrium—the “Earth system.”¹²

Global Change and the Earth System

An overarching goal of the IGBP’s work was to develop “a substantive science of integration, putting the pieces together in innovative and incisive ways toward the goal of understanding the dynamics of the planetary life support system as a whole.” By early in the twenty-first century, they were confident that “an integrative Earth System science is already beginning to unfold.”¹³

In 2000, the IGBP was a decade old, and its various projects had begun preparing comprehensive reports on what had been learned in ten years of Earth System research. The extensive documents that resulted were subsequently published by the German publishing house Springer Verlag, as the IGBP Book Series.¹⁴

The meeting in Mexico in February 2000 was part of the summing-up process. Paul Crutzen’s outburst—“We’re in the Anthropocene!”—led to intense unscheduled discussions. For ten years, the participants had been immersed in detailed investigation of aspects of the Earth System; now they saw a theme that unified their work: the Earth System as a whole was being qualitatively transformed by human action. That realization confirmed the need for an overall synthesis of scientific knowledge about the past, present, and probable future of the Earth System:

The synthesis aimed to pull together a decade of research in IGBP’s core projects, and, importantly, generate a better understanding of the structure and functioning of the Earth System as a whole, more than just a description of the various parts of the Earth System around which IGBP’s core projects were structured. The increasing human pressure on the Earth System was a key component of the synthesis.¹⁵

Crutzen’s proposal crystallized a new perspective on the impact of global change. According to Steffen, “The concept of the Anthropocene became rapidly and widely used throughout the IGBP as its projects pulled together their main findings. The Anthropocene thus became a powerful concept for framing the ultimate significance of global change.”¹⁶

After the February 2000 IGBP meeting, a literature search found that Eugene Stoermer had previously used the word, so Crutzen invited him to co-sign a short article in the IGBP’s Global Change Newsletter:

Considering these and many other major and still growing impacts of human activities on earth and atmosphere, and at all, including global, scales, it seems to us more than appropriate to emphasize the central role of mankind in geology and ecology by proposing to use the term “anthropocene” for the current geological epoch.¹⁷

The article alerted scientists associated with the IGBP that a new synthesizing framework was emerging. A few months later, the message was reinforced by a peer-reviewed article in the prestigious journal Science, in which the members of the IGBP’s Carbon Cycle Working Group referred to humanity “rapidly enter[ing] a new Earth System domain, the ‘Anthropocene’ Era.”¹⁸

But the Anthropocene’s real coming-out party was in Amsterdam, in July 2001. “Challenges of a Changing Earth,” a conference organized jointly by the IGBP, the International Human Dimensions Program, the World Climate Research Program, and the biodiversity program DIVERSITAS, was a critical turning point in the development of Earth System science. About 1,400 people, including researchers from 105 countries, took part in four days of lectures and discussions, many of them focused on the IGBP’s research.

The materials that participants were given included a 32-page pamphlet, signed by all four sponsors but obviously prepared by the IGBP. Titled Global Change and the Earth System: A Planet Under Pressure, it would later be expanded, using the same title, into the IGBP’s 350-page synthesis report. The pamphlet, which is in effect a high-level outline of the later book, included a chapter, “The Anthropocene Era,” that expanded on the arguments presented in the Crutzen-Stoermer newsletter article:

Until very recently in the history of Earth, humans and their activities have been an insignificant force in the dynamics of the Earth System. Today, humankind has begun to match and even exceed nature in terms of changing the biosphere and impacting other facets of Earth System functioning. The magnitude, spatial scale, and pace of human-induced change are unprecedented. Human activity now equals or surpasses nature in several biogeochemical cycles. The spatial reach of the impacts is global, either through the flows of the Earth’s cycles or the cumulative changes in its states. The speed of these changes is on the order of decades to centuries, not the centuries to millennia pace of comparable change in the natural dynamics of the Earth System.

The extent to which human activities are influencing or even dominating many aspects of Earth’s environment and its functioning has led to suggestions that another geological epoch, the Anthropocene Era … has begun:

• in a few generations humankind is in the process of exhausting fossil fuel reserves that were generated over several hundred million years,

• nearly 50% of the land surface has been transformed by direct human action, with significant consequences for biodiversity, nutrient cycling, soil structure and biology, and climate,

• more nitrogen is now fixed synthetically and applied as fertilizers in agriculture than is fixed naturally in all terrestrial ecosystems,

• more than half of all accessible freshwater is used directly or indirectly by humankind, and underground water resources are being depleted rapidly in many areas,

• the concentrations of several climatically important greenhouse gases, in addition to CO₂ and CH₄, have substantially increased in the atmosphere,

• coastal and marine habitats are being dramatically altered; 50% of mangroves have been removed and wetlands have shrunk by one-half,

• About 22% of recognized marine fisheries are overexploited or already depleted, and 44% more are at their limit of exploitation,

• Extinction rates are increasing sharply in marine and terrestrial ecosystems around the world; the Earth is now in the midst of its first great extinction event caused by the activities of a single biological species (humankind).¹⁹

The pamphlet presented the Anthropocene concept tentatively—it said the changes have “led to suggestions,” not that a new geological period had definitely begun. This likely reflected unwillingness by the other three sponsors to endorse a concept that was new to them.

This caution extended to the Declaration on Global Change the conference adopted. Although it said that “the Earth System has moved well outside the range of the natural variability exhibited over the last half million years at least,” and that “Earth is currently operating in a no-analog state,” the Declaration did not mention a new geological epoch or use the word Anthropocene.²⁰

After the Amsterdam conference, Paul Crutzen submitted a more strongly worded article to Nature, one of the world’s most widely read scientific journals. The oddly titled “Geology of Mankind,” published in January 2002, was the first peer-reviewed paper to specifically argue that a new geological epoch had begun.

Again Crutzen listed ways in which human activity was changing the face of Earth, including:

• A tenfold human population growth in three centuries.

• Maintaining 1.4 billion methane-producing cattle.

• Exploiting 20–50 percent of Earth’s land surface.

• Destruction of tropical rainforests.

• Widespread dam building and river diversion.

• Exploitation of more than half of all accessible fresh water.

• A 25 percent decline of fish in upwelling ocean regions and 35 percent in the continental shelf.

• A 16-fold increase in energy use in the twentieth century, raising sulphur dioxide emissions to over twice natural levels.

• Use of more than twice as much nitrogen fertilizer in agriculture as is used naturally in all terrestrial ecosystems combined.

• Increasing atmospheric concentrations of greenhouse gases to their highest levels in over 400,000 years.

He pointed to global consequences, including acid precipitation, photochemical smog and global warming of 1.4 to 5.8 degrees Celsius during this century. He was careful to add that “these effects have largely been caused by only 25% of the world population.”

Barring a global catastrophe such as a meteorite impact, world war, or pandemic, Crutzen wrote, “mankind will remain a major environmental force for many millennia,” and so “it seems appropriate to assign the term ‘Anthropocene’ to the present, in many ways human-dominated, geological epoch.”²¹

A New Synthesis

Meanwhile, an eleven-person team headed by Will Steffen had begun the complex and time-consuming task of synthesizing a decade’s work by thousands of scientists into a single volume that would be largely accessible to a non-expert audience. Steffen says the main text was “a true synthesis, as we did not assign chapters to individual authors but rather wrote the whole book as a single, integrated narrative with all authors contributing to the whole book.”²² The team also commissioned and included short essays by individual experts to highlight important aspects of the subject.

Completed early in 2003 and published in 2004, Global Change and the Earth System: A Planet Under Pressure (not to be confused with the earlier pamphlet of the same name) was an invaluable contribution to broad understanding of the Earth System—and despite the many scientific advances that have been made since, it remains essential reading for anyone who wants to understand the scientific basis for declaring a new epoch, the Anthropocene.²³