The highest governing body in geology has upheld a contested vote by scientists against adding the Anthropocene, or human age, to the official timeline of Earth’s history.

The vote, which a committee of around two dozen scholars held in February, brought an end to nearly 15 years of debate about whether to declare that our species had transformed the natural world so thoroughly since the 1950s as to have sent the planet into a new epoch of geologic time.

Shortly after voting ended this month, however, the committee’s chair, Jan A. Zalasiewicz, and vice chair, Martin J. Head, called for the results to be annulled. They said the members had voted prematurely, before evaluating all the evidence.

Dr. Zalasiewicz and Dr. Head also asserted that many members shouldn’t have been allowed to vote in the first place because they had exceeded their term limits.

After considering the matter, the committee’s parent body, the International Union of Geological Sciences, has decided the results will stand, the union’s executive committee said in a statement on Wednesday.

That means it’s official. Our planet, at least for the time being, is still in the Holocene epoch, which began 11,700 years ago with the most recent melting of the ice sheets.

Even if the Anthropocene does not yet have an official place on the geologic time scale, the term will “continue to be used not only by earth and environmental scientists, but also by social scientists, politicians and economists, as well as by the public at large,” the statement from the geological union said. “It will remain an invaluable descriptor of human impact on the earth system.”

The statement did not directly address Dr. Zalasiewicz’s and Dr. Head’s concerns about the voting process. It said only that the committee members had acted with integrity and had wide expertise as geologists. “The scientific decision is clear, and the specialists do not see any value in adding a new epoch in the geological record,” the union’s president, John Ludden, said by email.

Even though the voting results have been declared valid, Dr. Head, an earth scientist at Brock University in St. Catharines, Ontario, said he expected the Anthropocene episode to prompt geologists to change their procedures for deciding on future updates to the time scale.

“I feel this has been a missed opportunity to recognize and endorse a simple reality, that our planet left its natural functioning state in the mid-20th century,” Dr. Head said by email. “A myriad of geological signals reflect this fact.”

The Anthropocene issue has polarized scientists in a way that few issues in the history of the geological time scale ever have.

The scale divides Earth’s past into chapters that encapsulate planet-spanning changes. There’s no question our time is full of such changes. Pollution, urbanization, rapid greenhouse warming and other disruptions to ecosystems and natural processes have left traces that will linger in the rocks for long to come.

But to merit inclusion on the geological scale, any time interval needs to meet certain criteria, such as having a clear, objective starting point.

Last month, the first of three scientific committees began voting on whether the decades since World War II fit the bill. The results, which were first reported by The New York Times, showed that most committee members weren’t ready to ratify an epoch that is still so young, at least by the standards of Earth’s 4.6-billion-year history. The rejection means the Anthropocene question will not advance to the next round of voting.

The results are “a sign that the system is not equipped to deal with looking at the present, nor with the rate of change currently occurring on our planet,” said Brad E. Rosenheim, chair of the Geological Society of America’s Geochronology Division, in a statement.

“Although it is unclear whether the Anthropocene will ever become a geological division, it is an important question for every one of us to ponder: What exactly are we doing to this planet that supports our civilization?” said Dr. Rosenheim, a geological oceanographer at the University of South Florida.

With the Anthropocene issue behind them, the keepers of the geologic timeline can now turn to other matters. Next on their agenda, among other things, is deciding precisely when the late Pleistocene epoch began.

That would be the time, something like 130,000 years ago, when the planet was warmer than it is today. As time went on, the world grew cold again. The ice sheets returned. Neanderthals and other prehistoric ancestors were either wiped out or assimilated, leaving only modern humans.

Geologists say this period deserves an official start date, but they still need to figure out how and where to define it. The question has been on their minds for a long time, longer than the Anthropocene has been. Much longer, in fact. The first time scientists officially put forth a potential starting point for the late Pleistocene was in 1932.


Source link

Credit: NYTimes.com

Leave a Reply