Gill co-authors report arguing Anthropocene should be a geological event, not an epoch

Scientists studying how human activity alters the Earth use the term “Anthropocene” to describe a generalized period of time in which humanity has impacted the planet through landform and ecosystem alteration, species eradication, climate change and more. Yet Anthropocene has no concrete scientific definition, resulting in it being given several conflicting meanings that cause confusion among researchers and the general public.  

To help alleviate the ambiguity, some experts suggest that the Anthropocene should be defined as a formal epoch within the Geologic Time Scale. Jacquelyn Gill, however, contends that the Anthropocene should be considered a geological event, or significant transformation of the Earth marked in its geology. 

Gill, an associate professor of paleoecology and plant ecology at the University of Maine, and other researchers advocated for this argument in a Cambridge University-led paper published in the journal Episodes

Identifying the Anthropocene as an epoch could hinder scientists’ ability to understand, investigate and discuss how humans have altered the planet, according to Gill and her colleagues. Human action has altered the Earth for thousands of years at different scales and across numerous cultural practices, so restricting the Anthropocene to a specific period in time could limit the amount of activity to research and explore. 

As a geological event, however, the Anthropocene would encompass a broader variety of anthropogenic effects throughout human history. The label also more accurately reflects the diachronous and variable nature of human-influenced global change, according to researchers. A geological event would make the Anthropocene more useful across different disciplines as well, while still grounding its understanding in the geological record.

“No one disputes that people are a significant shaping force on our planet — but exactly how those impacts will be incorporated into the geologic record has been trickier to define, in part because the ‘how’ and ‘when’ of those impacts has varied across the globe,” says Gill, an NSF CAREER researcher who was named a 2020 Friend of the Planet by the National Center for Science Education. “We hope our proposed framework gets us out of the quagmire of debating when the Anthropocene started, allowing us to instead focus on understanding what it means to be living in the Age of Humans.”

Defining the Anthropocene as either an epoch or geologic event will connect it to the global geological record. Many scientists study the inorganic and organic deposits within the rock layers on the Earth’s surface to investigate the global environmental impacts of human actions. Linking the Anthropocene to the geological record would lay the groundwork for a scholarly framework to help guide future investigations into and discussions about how humans alter environmental systems across the planet. 

One coalition of scientists, the Anthropocene Working Group of the Subcommission on Quaternary Stratigraphy of the International Commission on Stratigraphy, is proposing to establish the Anthropocene as an epoch that begins in the 1950s with the “Great Acceleration” that occurred after World War II. 

That designation would exclude events that occured before the mid-20th century and ongoing human activities that are changing the global environment systems, according to Gill and other report co-authors. They also say that instituting another start would be “neither accurate nor practical.” 

A geological event, by contrast, can be defined by any range of time, from seconds to millions of years, and at any scale, from local to global, according to researchers. Therefore, an Anthropocene geological event could be vast enough to account for multiple small and large-scale events across different times, places and cultures in human history, all of which cumulatively cause planetary change.  

Identifying the Anthropocene as a geological event better reflects the existing time-transgressive stratigraphic evidence of human-influenced alterations to Earth’s environmental systems, according to researchers. 

As a geological event, the Anthropocene also would stand alongside other significant transformations of the planet, such as the Great Oxidation Event and Great Ordovician Biodiversification Event.

“What may seem like a nerdy semantic argument actually has implications for how geologists, archaeologists and others think about the relationship between people and the Earth. The public is honestly ahead of us; the common usage of ‘the Anthropocene’ is already in line with it being a geological event, and not some bright line that we crossed at some still-as-yet-undecided moment,” Gill says. “And at the end of the day, isn’t the point of all this to come to a better understanding of how to be better planetary stewards?”

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