The guardians of the world’s official geological time scale have strongly rejected a proposal to declare an Anthropocene epoch, after an epic academic tussle.
The proposal would have designated the period from 1952 as the Anthropocene to reflect the planet-changing impact of humanity. This would have ended the Holocene epoch, the 11,700 years of stable climate since the last ice age and during which human civilization arose.
The International Union of Geological Sciences (IUGS) has announced, however, that geologists rejected the idea in a series of votes. Those who objected noted a much longer history of human impact on Earth, including the dawn of agriculture and the industrial revolution, and unease about including a new unit in the geological time scale with a span of less than a single human lifetime, it said. Most units span thousands or millions of years.
It also acknowledged: “The Anthropocene as a concept will continue to be widely used, not only by Earth and environmental scientists, but also by social scientists, politicians and economists, as well as by the public at large. As such, it remains a valuable descriptor in human-environment interactions.”
The Anthropocene Working Group (AWG), formed by the Subcommission on Quaternary Stratigraphy (SQS), in turn part of the IUGS, took 15 years to develop the proposal. It concluded that the radioactive isotopes spread worldwide by hydrogen bomb tests was the best marker of humanity’s transformation of the planet. Geological units of time also need a specific location to typify the unit and the Crawford Sinkhole Lake in Canada has been selected.
An SQS vote in February rejected the proposal by 12 to four, but its chair, Prof Jan Zalasiewicz of the University of Leicester, who supported it, said the vote did not follow the rules. However, the IUGS has now announced that in the next phase of the process the chairs of its 17 sub-commissions have almost unanimously endorsed the negative SQS vote, with 15 votes, one abstention and one person not voting. This final decision cannot be appealed.
“Although the proposal was decisively rejected, the AWG has provided an important service to the scientific community by compiling a wide body of data on human impacts on global systems, and this database will be an essential source of reference well into the future,” said the IUGS.
Zalasiewicz said: “The IUGS decision means that the Anthropocene will continue to confusingly represent widely different concepts. It was a missed opportunity to recognize and endorse a clear and simple reality, that our planet left its natural functioning state, sharply and irrevocably, in the middle of the 20th century. A host of geological signals reflect this fact.”
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The row is likely to continue. Zalasiewicz said the AWG is preparing a detailed response to “major inconsistencies” in the IUGS statement that “sets the factual record straight”. He also said it will continue its work outside the IUGS to “stabilize the meaning of the term and concept so that it will be of use to the wider community”.
One possibility is that the Anthropocene could be called an event, an informal term that geologists already use for major changes to the planet, such as the flooding its atmosphere with oxygen by photosynthesizing cyanobacteria 2 billion years ago, and the explosion of complex life at the beginning of the Cambrian period 540 million years ago.
