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Scientists believe they are on the brink of proving the Earth has entered a new era for the first time in 11,700 years with the advent of the Anthropocene epoch, or the point when humanity’s influence on the planet’s geology became irreversible.
A small lake in an area outside Toronto has been identified as the site to provide the formal reference point for the new era, after extensive research by the international Anthropocene Working Group, made up of geologists and historical scientists.
The group was formed in 2009 and set itself the challenge of defining and establishing the Anthropocene era in relation to Earth’s 4.6bn-year timeline. The current Holocene epoch began at the end of the last ice age.
The scientists involved say changes to the planet can no longer be explained without taking into account human activity and interventions, the effects of which have been evident since the 1950s.
“We can see that humans have basically created a new Earth sphere beyond the biosphere,” said Jürgen Renn, a scientific member at the Max Planck Institute for the History of Science, referring to the areas of the Earth where life exists.
“If we really want to understand the system, we have to not only take into account the traditional Earth spheres, like hydrosphere, the atmosphere and the biosphere, but also the human technosphere,” he said.
The concept of the Anthropocene was first introduced by the Nobel Prize-winning atmospheric chemist Paul Crutzen in 2000, and has slowly gained interest and acceptance in the scientific community.
Over the past three years, the working group has sought to find a “golden spike” location, or point that defines the start of a new ecological era.
To test whether signs of the Anthropocene are present across the planet, the team assessed and voted on 12 potential sites, including the Antarctic peninsula, Beppu Bay in Japan, Ernesto Cave in Italy, Flinders Reef in Australia and Crawford Lake in Ontario, Canada.
In all of the sites, the researchers looked for signs of human-made markers such as artificial radionuclides, combustion particles, neobiota — or organisms that appear in areas where they are not native — and organic pollutants, which point to human-caused planetary change.
Crawford Lake displayed the most evidence of changes in species and human activity in fossils over time, since its depth of almost 24 metres means matter that sinks to the bottom is well preserved.
“The record at Crawford Lake is representative of the changes that make the time since  geologically different from before and worthy of, we think, a golden spike,” said AWG member Francine McCarthy.
Plutonium markers in the rocks allowed scientists to identify the start of the cold war, since the radioactive material fell out of the atmosphere during nuclear-weapon testing.
They also observed evidence of rapid geological change owing to fossil fuels, nitrogen fertilisers and new species, indicating that the Anthropocene may have begun in the 1950s.
As well as identifying Crawford Lake in conjunction with the fourth International Congress on Stratigraphy in Lille this week, researchers will lodge submissions on why an Anthropocene epoch should be considered and the date it began. A final vote is planned for the International Geological Congress in Busan, South Korea, next year.
However, the researchers stressed that the vote may herald a new age of the Holocene epoch, instead of an Anthropocene era.
They added that declaring the Anthropocene could spur political action to limit humanity’s impact on the Earth.
“There was nothing inevitable about this, even a century ago, that we would move into a new epoch. It shows that the combined impacts of humanity can be changed rapidly for the good and for the bad,” said AWG chair Colin Waters, from the University of Leicester. “There’s hope in that respect.”