SETH BOHRENSTEIN (AP Science Writer)
From climate change to species extinction and environmental pollution, since the mid-20th century, humans have had such an impact on the Earth with such force and persistence that, according to a special team of scientists, a new geological era has begun.
This era, called the Anthropocene and derived from the Greek words for “human” and “new,” scientists believe began sometime between 1950 and 1954. While there is evidence around the world showing the impacts of burning fossil fuels, exploding nuclear weapons, and dumping fertilizer and plastic on land and waterways, scientists suggest a small but deep lake outside of Toronto, Canada – Lake Crawford – for placement of historical marker.
“It is very clear that the scale of change has increased incredibly, and it must be a human impact,” said University of Leicester geologist Colin Waters, who led the Anthropocene Task Force.
This puts human power in a somewhat similar class to the meteorite that crashed into the Earth 66 million years ago, wiping out the dinosaurs and starting the Cenozoic era, or what is colloquially referred to as the Age of Mammals. But not really. While this meteorite ushered in an entirely new era, the task force suggests that humans have just begun a new era, which is a much smaller geologic time period.
The group aims to determine a specific date for the start of the Anthropocene by measuring plutonium levels at the bottom of Lake Crawford.
The Anthropocene idea was proposed at a scientific conference over 20 years ago by the late Nobel Prize-winning chemist Paul Crutzen. Since then, groups of scientists have been debating the issue and finally set up a working group to look into whether this is necessary, and if so, when the era will begin and where it will be celebrated.
With a depth of 79 feet (29 meters) and an area of 258,333 square feet (24,000 square meters), Lake Crawford was chosen from 11 other locations because the annual impact of human activity on terrestrial soil, atmosphere, and biology is so clearly preserved in its sediment layers. This includes everything from radioactive fallout to species-threatening pollution and steadily rising temperatures.
There are clear and multiple signals from around 1950 at Crawford Lake showing that “human influence is overpowering the Earth system,” said Francine McCarthy, a committee member who specializes in the site as a professor of earth sciences at Brock University in Canada.
“The remarkably well-preserved annual report on Crawford Lake sedimentation is truly amazing,” said U.S. National Academy of Sciences President Marcia McNutt, who was not on the committee.
According to several scientists, the Anthropocene demonstrates the strength and arrogance of mankind.
“The arrogance is that we imagine we are in control,” said former US White House science adviser John Holdren, who was not part of the scientists’ working group and disagrees with the proposed start date, wishing it started much earlier. “The reality is that our ability to transform the environment far exceeds our understanding of the consequences and our ability to change course.”
Geologists measure time in eons, eras, periods, epochs and centuries. The Science Working Group suggests that the Anthropocene epoch followed the Holocene epoch, which began about 11,700 years ago at the end of the Ice Age.
They also propose to start a new era, named Crawford, after the lake chosen as the starting point.
The proposal has yet to be approved by three different groups of geologists and could be approved at a major conference next year.
The reason geologists have not declared the Anthropocene to be the beginning of a larger and more important dimension of time, such as the period, is because the current Quaternary, which began almost 2.6 million years ago, is based on permanent ice at the Earth’s poles, which is still exists. But in a few hundred years, if climate change continues and they disappear, it might be time to change that, Waters said.
“If you know your Greek tragedies, you know that power, arrogance and tragedy go hand in hand,” said Harvard historian of science Naomi Oreskes, a member of the task force. “Unless we address the harmful aspects of human activity, the most obvious of which is destructive climate change, tragedy awaits us.”
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