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Photo Gallery: Has a New Epoch Begun?

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The Anthropocene Debate Do Humans Deserve Their Own Geological Era?

With climate change, concrete deserts and agriculture, human beings have fundamentally altered the face of the Earth. But have we really ushered in a new geological era, the so-called Anthropocene?
Von Christian Schwägerl und Axel Bojanowski

Paul Crutzen, winner of the Nobel Prize in chemistry, finds it hard to believe. "It's incredible to see what a single word changes," he says. Crutzen coined the word "Anthropocene," Greek for the "recent age of man," 12 years ago at a scientific conference in Mexico. He used the term as a way of describing radical change in nature, saying that man's influence on the environment was now so overwhelming that a new epoch -- the "Anthropocene" -- had begun.

For some geologists, the proposal has been nothing less than revolutionary, and an unwelcome challenge. Indeed, it has unleashed a heated debate that has now spilled over from the scientific world into the public realm. Newspapers and magazines are proclaiming the advent of the "age of man" on their cover pages, artists are invoking the Anthropocene and even German governmental advisers have adopted the term.

Indeed, there are many who are enthusiastic about the defining of a human epoch. As an editorial from late February in the New York Times put it, the "true meaning of the Anthropocene is that we have affected nearly every aspect of our environment -- from a warming atmosphere to the bottom of an acidifying ocean." According to the British news magazine The Economist, humans "have become a force of nature reshaping the planet on a geological scale." Indeed, a recent edition of the magazine bore the title "Welcome to the Anthropocene" on its cover page above a picture of a globe being constructed by humans from within.

Still, there is strong opposition to the proposal among the geologists who have final say over whether a new geological epoch is officially proclaimed, and the issue has ignited a heated debate in their ranks.

The 'Golden Spike'

The earth's official calendar is kept by the International Commission on Stratigraphy (ICS), the world's principal authority on stratigraphy, the study of Earth's history through the analysis of rock layers and layering. The ICS uses sediment data to determine whether a new epoch has begun. Since the boundaries between geological epochs mark radical turning points in the planet's history, each period must be clearly discernable on the basis of a stratum -- or "boundary layer" -- that remains uniform across the globe.

It is precisely this piece of evidence pointing to the existence of the Anthropocene that geologists are trying to locate. "We are searching for the 'golden spike,' so to speak, " says geologist Jan Zalasiewicz of the University of Leicester -- in other words, a stratum that clearly demonstrates man's global influence on the planet.

At a recent meeting of the Geological Society of London, scientists compiled a large number of indicators that make the "age of man" seem plausible:

  • Erle Ellis, a geographer at the University of Maryland, explained that humans have already reshaped more than three-quarters of the Earth's surface. Only 23 percent is still wilderness, and only 11 percent of photosynthesis on land happens in wilderness areas, Ellis said. The rest consists of farmland, settlements and industrial areas.
  • Australian climatologist Will Steffens argued that climate change caused by human activity will fundamentally alter the air, land and oceans for tens of thousands of years. In his view, this also entails the long-term acidification of the oceans by carbon dioxide, which will have a lasting impact on rock formation on the ocean floor.
  • American geologist James Syvitski of the University of Colorado at Boulder spoke of how dams, mining, erosion and urban development have already changed soils in fundamental ways. For example, he discussed how having huge amounts of sediment build up behind dams has resulted in a lack of sediment in coastal areas.
  • Massive biological changes are also taking place. Although man contributes to the extinction of species by cutting down rainforests, he simultaneously creates new life forms through cultivation and biotechnology -- including, most recently, artificial chromosomes. In addition, trade, transportation and agriculture are spreading organisms, that previously only existed in niche environments, around the world. "Future geologists will also see this in fossils left over from our age," Zalasiewicz says.

Zalasiewicz heads the Anthropocene Working Group, which the ICS has commissioned to examine whether the changes attributed to human activity satisfy the criteria for formalizing a new geological epoch. "We have to be able to demonstrate convincingly that global environmental changes are sufficiently profound to leave behind clearly discernable signals in soil layers forming today and in the future," Zalasiewicz says.

'Not Familiar with the Rules'

However, since their profession primarily deals with the past, many geologists have little use for statements about the future. According to Stanley Finney, a geology professor at California State University in Long Beach and chairman of the International Commission on Stratigraphy (ICS), it is wrong to define a geological epoch on the basis of mere predictions. The ICS has the last word when it comes to decisions on geological periods.

Other geologists put it even more succinctly. "From a scientific perspective, the introduction of the Anthropocene into the Geologic Time Scale would create more problems than benefits," says Manfred Menning of the German Stratigraphic Commission (DSK). Menning notes that it would force geologists to re-examine their criteria for defining geological eras.

"The prospects for the introduction of the Anthropocene are unrealistic," says his colleague Stefan Wansa, chairman of the DSK's Quaternary Subcommittee, which focuses on the most recent period in geological history. "The proponents of the Anthropocene must confront the charge that they are not sufficiently familiar with the rules of stratigraphy," Wansa adds.

Traces Everywhere

Finney also doesn't believe that the crucial geological layer can be found. He argues that human activity has not been reflected in the simultaneous formation of sediments worldwide. Likewise, he points out that some areas, such as the Americas, were cultivated later than places like China and the Middle East.

Still, there are also geologists who are convinced that the Anthropocene could be justified under the existing rules of the discipline. The Geological Society of America (GSA), for example, apparently has no compunction about labeling its annual meeting in October "Archean to Anthropocene."

One of these supporters is Susan Trumbore, a geologist who directs the Max Planck Institute for Biogeochemistry in the eastern German city of Jena. "The Anthropocene is an obvious reality," Trumbore says. "Mankind is leaving traces almost everywhere."

What's more, according to Zalasiewicz, a few years ago, 21 of 22 scientists on the Stratigraphy Commission of the Geological Society of London said that the idea of formalizing the Anthropocene epoch merited further examination. "The society is a cross-section of stratigraphers chosen for technical expertise, not environmental radicalism" he stressed in a May interview with SPIEGEL ONLINE .

In Search of the Elusive Boundary Layer

The first proposals for describing the boundary layer marking the beginning of the Anthropocene are already being discussed. The rise in the level of greenhouse gases, which can be demonstrated on the basis of air bubbles trapped in glaciers, has been proposed as evidence of the beginning of the "age of man." The problem is that since the increase in the gas content did not occur abruptly, there is no clearly discernible boundary layer.

Zalasiewicz notes that the current favorites are strata from roughly 1800, during the Industrial Revolution, and from around 1945, when the first atomic weapons were tested. Both events can be recognized in sediments worldwide in the form of exhaust gas particles and radioactive fallout, respectively.

Zalasiewicz concedes that a determination would first have to be made on whether these deposits satisfy the criteria of stratigraphers. For example, the layers containing radioactive particles apparently arrived late in the game because supporters of the Anthropocene theory believe that the period had already begun by the time the first atom bombs were exploded. And, at this point, traces of industrialization can only be found in sediments in Europe.

Indeed, determining how to establish a sharp, worldwide boundary is "not clear at present and may never be unambiguously established," says Philip Gibbard, an expert on the Quaternary epoch, the period which began some 2.6 million years ago and extends to the present, at the University of Cambridge.

A Matter for History Rather than Geology

Margot Böse, a geologist at Berlin's Free University, also rejects the idea of the sudden onset of a new epoch. The soil contains evidence of the influence of man since the Stone Age, Böse explains, and this age has already been treated as an independent geological era for a long time.

The ICS's Brian Pitt adds that since the Holocene epoch -- a part of the Quaternary Period stretching back roughly 12,000 years -- already recognizes the influence of man, no additional designation is needed.

Still, the scientific journal Nature does not believe that such designations have to be set in stone. In an editorial published in May, the respected publication argued that the Holocene could simply be renamed the Anthropocene. Doing so would eliminate the need to find a boundary layer, it continued, because the Holocene has already been defined scientifically.

Even critics like Finney concede that the new concept of the Anthropocene is "useful." Nevertheless, he believes that it is really a subject for historians rather than geologists. As he explains, the Geologic Time Scale is largely based on the stratigraphic record. But he doesn't see any significance evidence in the geological record on which to base this new epoch; instead, he sees it in the "voluminous" and "more-or-less continuous" human records of the last 200 years. For this reason, he posits that it would be "more appropriate" to view the Anthropocene as an epoch of human rather than geological history.

A New 'Era of Responsibility'

The impact of the term Anthropocene has already been felt outside the scientific community. In fact, many people concerned with the interaction between man and the environment are now using the term as if it had already been officially recognized. They find the concept helpful because it brings together a wide range of phenomena that are normally discussed separately; it represents the sum of all man-made environmental changes, both positive and negative.

Zalasiewicz and his colleagues believe that adopting the concept of the Anthropocene could do away with the old antithesis between man and nature. As they see it, in the future, we would have to concede that man shapes nature.

Nature sees the relatively new concept as presenting an opportunity to improve the role of human beings on Earth. Adopting it, the journal writes, "would encourage a mindset that will be important not only to fully understand the transformation now occurring but to take action to control it."

The German Advisory Council on Global Change (WBGU) begins its most recent report with Crutzen's idea, noting that the concept of the Anthropocene describes "not only the impact brought about by humans on the Earth system, but also the cognitive shift in global civilization, which is becoming increasingly aware of its importance as a shaping force."

Indeed, according to the WBGU, we are entering an "era of responsibility."

Translated from the German by Christopher Sultan
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