Lead author Dr. Simon Lewis said, “In a hundred thousand years scientists will look at the environmental record and know something remarkable happened in the second half of the second millennium. They will be in no doubt that these global changes to Earth were caused by their own species. Today we can say when those changes began and why. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right – as Earth-changing as a meteorite strike.”
In the past, geological epochs began and ended through factors such as meteor strikes, shifting land masses or prolonged volcanic eruptions.
In order for an epoch to be defined, two criteria must be met. First, long-lasting changes to our planet must be documented. Second, scientists need to find and date a global environmental change in a natural material (think rocks, ice cores, etc). This is called a ‘golden spike.’
Scientists found two dates that meet these criteria. The above mentioned 1610, and 1964. Radioactive fallout from nuclear weapons testing peaked in the mid 1960s. While fallout could be detected geological deposits, nuclear weapons testing wasn’t seen as a geologically Earth-changing event.
Let’s go back to 1610. When the Old World and New World collided, globalization formed. Granted, it was no where near what it is today, but global trade started.
Ok, so what were the long-lasting changes to our planet? Scientists cite maize from Latin America. The first fossil pollen of maize appears in marine sediment in Europe in 1600. Maize became commonplace in Europe after being imported from the Americas.
That meets the first requirement.
Lewis adds, “Historically, the collision of the Old and New Worlds marks the beginning of the modern world. Many historians regard agricultural imports into Europe from the vast new lands of the Americas, alongside the availability of coal, as the two essential precursors of the Industrial Revolution, which in turn unleashed further waves of global environmental changes. Geologically, this boundary also marks Earth’s last globally synchronous cool moment before the onset of the long-term global warmth of the Anthropocene.”
Now, scientists just needed to find a ‘golden spike.’ They found it in a noticeable dip in carbon dioxide around 1610. This dip was captured in Antarctic ice-core records and was the direct result of Europeans coming to the Americas. When European smallpox killed about 50 million indigenous people, farming came to a grinding halt across the continent.
With no one farming, forests quickly returned. These forests and other vegetation absorbed enough carbon dioxide from the atmosphere to cause the dip (a temporary drop between 7 and 10 parts per million). Scientists’ golden spike.
Co-author Professor Mark Maslin had this to say about the meaning behind defining the Anthropocene. “A more wide-spread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth will have implications for our philosophical, social, economic and political views of our environment. But we should not despair, because the power that humans wield is unlike any other force of nature, it is reflexive and therefore can be used, withdrawn or modified. The first stage of solving our damaging relationship with our environment is recognizing it.”
Next year, a decision on whether to formally recognize the Anthropocene and its start date will be initiated by a recommendation of the Anthropocene Working Group of the Subcommission of Quaternary Stratigraphy.