A group of scientists has chosen a small lake near the U.S.-Canada border as the site that best represents the Anthropocene Epoch—a proposed period of geologic time marked by humans’ drastic impact on the Earth. They say sediment at the bottom of the lake has well-preserved evidence of human activities, including microplastics, fallout from fossil fuel burning and even traces of radioactive plutonium from nuclear bomb testing.
“[W]e are living in a new geological period, one in which the scale and power of human activities match or even exceed the scale and power of natural processes,” Naomi Oreskes, a historian of science at Harvard University, tells Alison Snyder of Axios.
Researchers divide the Earth’s geologic history into units approved by the International Commission on Stratigraphy called eons, eras, periods, epochs and ages. Our current age, the Meghalayan, began with a drought about 4,200 years ago, while our current epoch, the Holocene, started about 11,700 years ago at the end of the last ice age. The Holocene has witnessed all of humans’ recorded history and the rise and fall of many civilizations.
But in 2000, Nobel Prize-winning chemist Paul Crutzen suggested that humans had so drastically altered the Earth that a new epoch was needed: the Anthropocene, or the new age of humans. Crutzen proposed that the epoch should begin in 1784, shortly after the beginning of the Industrial Revolution. Yet, while evidence of the Industrial Revolution can be seen in lake sediments in North America and the U.K., its impact is not ubiquitous around the globe, writes Belinda Smith for the Australian Broadcasting Corporation.
After years of intense debate in the scientific community, a group of geologists called the Anthropocene Working Group suggested in 2016 that the new epoch should start in the 1950s, coinciding with geological signals “resulting from the ‘Great Acceleration’ of population growth, industrialization and globalization,” per the group. In the past few years, the team has been deliberating between 12 sites as the Anthropocene’s “golden spike”—a geologic deposit that best shows the boundary between geologic stages.
On July 11, 2023, Crawford Lake in Milton, Ontario was voted by the Anthropocene Working Group to be the most suitable location for the proposed “golden spike,” a global reference point in the Earth’s stratigraphic record that indicates the start of a new geological unit of time. pic.twitter.com/yZPiuD2nnS— Royal Ontario Museum (@ROMtoronto) July 12, 2023
Crawford Lake, located about 37 miles west of Toronto, is a rare type of lake in which the layers of water don’t mix. This means sediments have settled to the bottom, nearly 80 feet beneath the surface, and sat in undisturbed layers for centuries. Every summer, calcium carbonate precipitates from the lake’s warming water and falls to the lakebed, creating a visible barrier between each year of sediment.
“Crawford is just brilliant for this,” Simon Turner, a geologist from University College London tells BBC News’ Jonathan Amos. “A core from its bottom muds looks like a massive dirty lollipop, but it contains these beautiful, annually laminated sediments.”
And in these sediments, scientists have found immense evidence of human activity. An increase in a lighter form of nitrogen signaled humans were burning more fossil fuels. Radioactive plutonium pointed to tests of nuclear weapons. And preserved grains of pollen show how the surrounding forest shifted to more heat-loving tree species over time, writes the Washington Post’s Sarah Kaplan.
Still, not all researchers agree with the AWG’s epoch proposal, saying it misses the fact that humans have been altering the environment since long before the mid-20th century. Others say that since only 70 years have passed since the proposed start of the Anthropocene, it’s simply too short to designate its own epoch.
“European scientists seem to be quite captivated that this time period starts very recently,” Zoe Todd, an anthropologist with Red River Métis ancestry at Simon Fraser University in Burnaby, Canada, tells Nature News’ Alexandra Witze. “For Indigenous and other displaced and dispossessed peoples who were impacted by massive forms of violence that characterize the last 600 years, everything that leads up to what makes this global shift possible starts much earlier.”
AWG’s proposal still has several hurdles to pass before it’s approved. The group must come up with an auxiliary golden spike, then it must pass three more votes—including one at the International Commission on Stratigraphy and one from the International Union of Geological Sciences—and earn a supermajority of more than 60 percent at each one, per CBC News’ Emily Chung.
“It’s a very conservative process, you know,” Colin Waters, chair of the Anthropocene Working Group, tells the publication. “And probably there’s good reason for that, because you don’t want to establish the formalization of the unit if it’s not grounded on very strong evidence.”
But regardless of the outcome, many researchers agree that human actions have had a profound impact on the planet.
“There are so many changes that have been committed already—the glaciers melting, the entire cryosphere,” Jurgen Renn, who directs the Max Planck Institute for the History of Science in Berlin, tells the Independent’s Louise Boyle. “These changes that we have induced will only unfold in the next decades and centuries. And there is no way that we can that we can stop this for the time being.”