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
