A remote lake in Canada could be the birthplace of a new era for the planet
Scientists are a step closer to officially declaring a new geological time segment that marks the beginning of humanity’s irreversible impact on Earth after choosing a remote lake in Canada as its starting point.
An international team of experts, who have been gathering evidence of human-induced changes beneath the planet’s surface, have put forward Crawford Lake in Ontario as the official birthplace of the Anthropocene epoch.
The Anthropocene, or the time of humans, describes the time in the planet’s history when human activities began to have a significant influence on the global systems, from icy mountains to the deep ocean.
The scientists said the formal start date of this epoch is the 1950s, coinciding with the appearance of plutonium, a man-made radioactive element used in nuclear weapons, as well as the start of ‘the great acceleration’, which refers to the dramatic surge of human activity across the planet.
Professor Andrew Cundy, chair in environmental radiochemistry at the University of Southampton and an AWG member, said: ‘Recognition of the Anthropocene as a geological epoch I think is important, because it really evidences to wider society the true extent of our impacts on the Earth.’
The Crawford Lake was among 12 other sites: including a peat bog in Poland; an ice sheet in Antarctica; and a coral reef in Australia; that were investigated by the Anthropocene Working Group (AWG).
The AWG was set up by a scientific body responsible for defining the phases of Earth’s past known as the International Commission on Stratigraphy (ICS).
Professor Francine McCarthy, a micropaleontologist at Brock University in Canada and an AWG member, said that Crawford Lake was chosen because it is ‘completely isolated from the rest of the planet except for what gently sinks to the bottom and accumulates as sediment’.
For a thousand years, this lake has been absorbing the signs of changes from the world above – which is now permanently preserved in layers of mud.
Digging into these layers, scientists found markers of the profound changes caused by humans to the planet’s climate and chemistry.
Geologists said these markers are the ‘golden spike’ – or, more formally, the Global Boundary Stratotype Section and Point (GSSP) – heralding the start of the Anthropocene.
Dr Simon Turner, from University College London, who is also the AWG secretary, said: ‘The sediments found at the bottom of Crawford Lake provide an exquisite record of recent environmental change over the last millennia.’
He added: ‘It is this ability to precisely record and store this information as a geological archive that can be matched to historical global environmental changes which make sites such as Crawford Lake so important.’
Samples from the lake and other sites have also revealed traces of plutonium, a result of nuclear bombs being tested in the atmosphere.
Professor Cundy said: ‘The presence of plutonium gives us a stark indicator of when humanity became such a dominant force that it could leave a unique global fingerprint on our planet.
‘In nature, plutonium is only present in trace amounts.
‘But in the early 1950s, when the first hydrogen bomb tests took place, we see an unprecedented increase and then spike in the levels of plutonium in core samples from around the world.
‘We then see a decline in plutonium from the mid 1960s onwards when the Nuclear Test-Ban Treaty came into effect.’
Other indicators of human activity found in sediments include microplastics, ash from coal-fired power stations, concrete, and high concentrations of heavy metals such as lead.
Some have suggested the Anthropocene should begin at the start of Britain’s Industrial Revolution in the 18th century, which created the world’s first fossil fuel economy.
But Colin Waters, honorary professor at University of Leicester and chair of the AWG, said that while there is evidence of the Industrial Revolution’s impact in the UK and Europe, countries in Asia and other parts of the southern hemisphere were largely unaffected by it during that time.
He added: ‘So the more we looked into this, and it was not until probably about 2014, that we actually came to this conclusion that, really, the point across the planet where you start to see a synchronous change is the middle of the 20th century.’
Officially, humanity and all the other inhabitants of Earth are still living in the Holocene epoch, which began about 11,700 years ago when the climate became more stable.
The Anthropocene has been debated by experts since the phrase was coined by atmospheric chemist Paul Crutzen more than two decades ago but is yet to be formally recognised as a unit of geologic time.
However, Prof Waters believes it is unlikely the planet will ever return to its Holocene state, due to irreversible human-induced changes which ‘has caused greenhouse gas emissions into the atmosphere, which will take thousands of years to return back to what might be considered to a Holocene level’.
Meanwhile, Prof McCarthy added: ‘I can think of one other species that has affected the planet more (than humans) and those are the cyanobacteria who, (about) two billion years ago, oxygenated the atmosphere.’
The AWG scientists presented their findings at the 4th International Congress on Stratigraphy in Lille, France.
As part of the next steps, the Crawford Lake site selected by the AWG will need to pass through three more voting stages for it to be officially ratified as the golden spike for Anthropocene.
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