The Anthropocene: The search for the best representative site of humans’ impact on the planet | Science and Technology

On Thursday, November 17, 2022, a select group of geologists, climatologists, and paleontologists began the final process of selecting the place on the planet that best represents human-made changes to Earth. For the next month, they will analyze the nine sites with the best records for the impact of our actions. The main indicator of this effect is the presence of radioactive material from nuclear tests. But they will also consider the clear, persistent, and countable year-by-year footprint left in the deposits of other human creations, including particles from burning gasoline, microplastics, technical fossils, carbon dioxide, and so on. Scientists should have a candidate for an exact start date for the Anthropocene – a new geological epoch marking the beginning of major human impact on the planet – in a month’s time.

Although time passes continuously, humans divide it into seconds, days, years, decades, millennia … The geological time scale, which refers to the history of the Earth, is so large that other terms are used: chron, age, epoch, period, era and eon. Ages and epochs are the largest units of time; It spans hundreds of millions or billions of years. In general, the separation of each of the main stages is punctuated by a catastrophe, such as the meteor that wiped out the dinosaurs, marking the end of the Cretaceous period and the beginning of the Paleogene period. Usually, shorter time periods are marked by more periodic events, such as glaciation/decay ages or changes in the planet’s magnetic polarity. Earth is currently in the Holocene, an era that began about 11,000 years ago with the end of the last great ice age. This group of scientists, which makes up the Anthropocene Working Group (AWG), debates whether the Holocene era ended and humans began their own era, the Anthropocene, and where this change is most evident.

University of the Basque Country paleontologist Alejandro Cearita, an expert in human footprinting and environmental change, is one of 23 members of the ad hoc working group. All geological time divisions have it [own] stratotype, the place where changes are best represented,” he says. The group has been seeking and receiving proposals for stratotypes — the places that would define the beginning of the Anthropocene — for years. Man-made sites, such as the Fresh Kills landfill in the US, have reached out to Pre-selection stage The site opened in 1948 and served as New York’s landfill for more than half a century Nearly 30,000 tons of waste arrived daily until its closure in 2002, following the disposal of the rubble of the Twin Towers that collapsed in a terrorist attack the previous year The Fresh Kills landfill is 70 meters high and covers an area of ​​about eight million square meters;it contains 150 million tons of garbage, which could be the largest human being ever created.But the landfill did not meet all the requirements to be considered a stratigraphy and was rejected.

Plutonium from nuclear bombs has reached Antarctica.  The ice of the Palmer Archipelago on the Antarctic Peninsula is a candidate for the site with the clearest signs of the beginning of the Anthropocene.
Plutonium from nuclear bombs has reached Antarctica. The ice of the Palmer Archipelago on the Antarctic Peninsula is a candidate for the site with the clearest signs of the beginning of the Anthropocene. GT

“Looking for stratification is complicated,” says Cearreta. To qualify, it must indicate the first change, which is an indication of one of the signs chosen by the scholars. The primary sign is the presence of plutonium-239, the material used in the bomb dropped on Nagasaki, which was also the fuel for most nuclear testing and powering today’s atomic-laden missiles. Plutonium-239 and other radioactive isotopes, such as americium-241 and cesium-137, all of which are man-made, are found in soil, peat bogs, lakes, and the sea floor, as well as trapped in ice plumes and tree rings. Plutonium-239 is the primary indicator [because] It is artificial, its presence is global and we can follow it year after year, ”explains the Basque scientist.

The nine sites (designated Global Boundary Layer Sections and Points, abbreviated by GSSP) that made it to the final round of the selection process have recorded plutonium-239 since the 1950s. As stated in an article recently published in the Scientific Journal SciencesAnd the The options include two marine deposits, one in the Baltic Sea and one in the Beppu Gulf in Japan. Both consist of layers of carbon-rich clay and silt and have picked up many signs of the Anthropocene, such as spherical carbonaceous particles that could only have come from soot from fossil fuels, microplastics, or pesticides. Two reefs, one in the Gulf of Mexico and one in Australia, are also in operation. Coral reefs can pick up geochemical changes from year to year and over centuries. Three other filters are also aquatic, but they are at the bottom of three lakes; the first in Canada, the second in China, and the third in the United States; The last one is an American dam reservoir built in the late 19th century. Ice cores, one extracted from Antarctica and the other from a peat bog in Poland, complete the list of candidates.

Geologist Colin Waters, Emeritus Professor of Geography at the University of Leicester (UK), is also a member of the AWG and a co-author on research recently published in Sciences. An ideal GSSP, the boundary between an era or time period, Waters explains, should be “the best possible record of relevant marker events, such as the plutonium fallout.” In addition, the GSSP “must have no interruptions in the accumulation of layers, and the rate of their accumulation should generate sufficient thickness to distinguish time units,” he says in an email. The location must not be altered by the actions of living beings or human activities, and must allow for dating from year to year. Finally, Waters adds, the candidate site “must have been extensively studied, be available for future research and be protected from degradation.”

Cearreta, Waters, and other AWG members have 30 days to select finalists. If a site wins 60% of the vote, the AWG’s proposal is to the International Union of Geosciences (IUGS; the organization to which the working group belongs) to mark the beginning of the Anthropocene. If not, the members will continue to vote until they choose one of the three. The final decision could come in March at the IUGS summit in Berlin.

Votes are secret and confidential. In addition to choosing the site with the clearest record of the Anthropocene, voters must also determine whether the changes that occur are significant enough to merit the Holocene replacement. “We have to vote by the scale,” says Cearreta. The Holocene is an epoch, and more recently the subdivisions (age or chron) are named (Gronlandian, Norgrebian, and Megalian). “[The AWG] It can determine that it is a subsection of the Holocene [epoch]… But the scale of the changes we humans are making to the planet is unprecedented. We’ve seen other extinctions and geochemical changes, but the speed, quantity and intensity of the current changes are unparalleled,” adds Ciaretta.

Waters notes in his email that the Anthropocene would not be classified as a new period (we are now in the Quaternary), let alone a new era (the current era is the Cenozoic). Such a change would require a catastrophe, such as the extinction of the human race. But by the time that happens, Cearreta concludes, “it wouldn’t make sense to call it the Anthropocene, and there would be no one to call it.”

signed for Weekly newsletter For more English-language news coverage from EL PAÍS USA Edition

Leave a Comment