Microplastics, remnants of oil combustion and fallout from nuclear bomb explosions. This is what lines the bottom of Lake Crawford, near Toronto in Canada, chosen Tuesday as the world reference site for the beginning of the Anthropocene. The stratified sediments at the bottom of this small body of water of one square kilometer are the best evidence that a new chapter in the history of the Earth has opened, the members of the task force on this new time conclude. geological characterized by the impact of humanity on the Earth that scientists are trying to have officially recognized.
But the official approval by the world’s geological authorities that the Earth has left the Holocene, the period that began around 12,000 years ago at the end of the last glaciation, to enter the Anthropocene, “the time of the ‘Human’, remains very uncertain. “This vote in the working group is a routine step from the lowest level,” commented Stanley Finney, the secretary general of the powerful International Commission on Stratigraphy (ICS) to which the Anthropocene working group has yet to go. submit the conclusions of its work begun in 2009.
Eight other candidates
“Only then can they be subject to peer review and the evidence and arguments can be truly assessed,” added the scientist who leads the commission responsible for developing the frieze methodically dividing the 4.6 billion years of the Earth’s history into eras, periods, epochs and geological ages. The general opinion is that an approval will be very difficult. Renowned geologists believe that the technical criteria are not met to qualify the Anthropocene as a new “epoch”, even if they recognize that a rupture occurred in the last century.
If the bar of two-thirds majority voting by the ICS and another committee were passed, however, Anthropocene proponents would still have to convince the reputable guardians of the International Union of Geological Sciences (IUGS) intransigent on the modifications of the International Chronostratigraphic Charter. There is still a long way to go, but a major step has been taken with the choice of this Canadian lake as the physical embodiment of the Anthropocene, from a final list of nine candidates, including the sediments of a bay in Japan, the mud of a crater in China, the traces in an ice core or those on coral reefs.
Plutonium as justice of the peace?
“The data show a clear shift from the mid-20th century, taking the Earth system beyond normal Holocene boundaries,” said Andy Cundy, a professor at Britain’s University of Southampton and a member of the task force. . The sediments of Lake Crawford “provide exceptional testimony to environmental changes over the last millennia”, summarizes the chairman of the working group Simon Turner, of University College London.
And these changes are playing out in dramatic fashion: the first week of July was the hottest on record globally, wildfires out of control have been ravaging Canada for months, while the United States and China are facing to unprecedented heat, flooding and drought. The traces of human activity (microplastics, eternal chemical pollutants, invasive species, greenhouse gases) are everywhere, from mountain tops to the bottom of the oceans, and the disorders they cause are numerous (climate change, pollution, loss of biodiversity) to the point of breaking the natural balance of the globe.
International Commission on Stratigraphy (ICU) rules, however, require identifying a synchronous “primary marker” to mark the change in period that is detectable in geologic records almost anywhere on the planet. For the Anthropocene, the plutonium released by hydrogen bomb tests provides this “global footprint”, because there is very little in the natural state, defends Andy Cundy. This means that 1952, when the United States first detonated a huge hydrogen bomb in the Marshall Islands as a test, could become the starting point of the Anthropocene, he believes.