H-bombs or chicken bones: the race to determine the start of the Anthropocene | Environment

HExactly where and when did the Anthropocene begin? Scientists are trying to answer this historical question in the coming months by choosing a place and time to represent the moment when humanity became a “geological superpower”, overcoming the natural processes that have ruled the earth for billions of years.

They could decide that the beginning was marked by an explosion, thanks to plutonium isotopes quickly spread around the planet by hydrogen bomb tests beginning in late 1952, or with a barrage of soot particles from the surge in fossil-fuel power plants after World War II.

Or they may opt for the post-war explosion in industrial fertilizer use and its profound effect on the Earth’s natural nitrogen cycle. Microplastics, chicken bones, and pesticide residues may also be among the selective markers used to enhance the definition of the Anthropocene. Other potential markers include lake bottoms in the US and China, Australian coral reefs, a Polish peat bog, black sediments under the Baltic Sea and even human debris piling up under Vienna.

An international team of about 40 scientists, commissioned by the official guardians of the geological time scale, must choose a place where layered sediments show the clear transition from the previous era to the new one. The team has come up with a shortlist of 12 sites that have now begun a series of votes – but there can only be one winner. Humanity has undoubtedly changed the Earth far beyond the Holocene settlement, the 11,700-year period during which all civilization arose, and which will end with the advent of the Anthropocene. The atmosphere, lakes, oceans and the living world have been altered by greenhouse gas emissions, pollution and the destruction of wildlife and ecosystems. Humans now have more influence in shaping the Earth’s surface than natural processes of transformation 24 times more material What rivers move.

Defining the Anthropocene is vital, the researchers say, as it brings together all of humans’ impacts on the world, providing a platform for comprehensive understanding and, hopefully, work to repair the damage. From a scientific perspective, a precise definition is essential to a clear basis for debate.

Tractor spraying crops in the field.
Tractor spraying crops in the field. Photo: Cretas/Alami/Alami

The first stage of voting is already underway. The site will need to show “specific physical properties in the sediment layers or strata, which capture the effects of recent increases in human population; unprecedented industrialization and globalization; and imposed changes to the landscape, climate, and biosphere,” according to a Recent research in Science Written by Professor Colin Waters of the University of Leicester and Dr Simon Turner of University College London, President and Secretary of the College respectively Anthropocene Working Group (og).

But creating a new time unit is a big decision in geological circles, and in parallel, the ad hoc working group also has to accomplish a larger task—convincing geologists that a new era is justified after all.

Both tasks are to identify the obvious signs of change, and hundreds of scientists are doing just that. Broad signs of anthropogenic transformation include rising levels of atmospheric carbon dioxide, recorded in air bubbles trapped in ice cores, and a massive change in populations and locations of species, with High numbers of people and livestock And it spreads while wild animals drown and disappear.

But other markers provide the “golden height” needed for precise definition and to enable layers to register a sharp, clear rise. Chief among them is the distinctive signature of radioactive isotopes, particularly plutonium, produced by Cold War hydrogen bomb tests, conducted by the United States on November 1, 1952 at Eniwetok Atoll in the Marshall Pacific Islands.

Dozens of above-ground tests soon followed, some even launching into the stratosphere. The ramifications of the tests were rapid and global, circling the planet in about 18 months, until atmospheric testing was banned in 1962.

“For a short period of time, they tested their new arsenal a lot,” Turner said. “That’s why you have this very unique global time-bound indicator that’s very useful to our business.”

Another small useful sign spherical carbon particles (SCPs), a type of hard fly ash produced only by the high-temperature combustion of coal or heavy oil. “They took off with the sudden increase in the number of thermal power plants after World War II,” Turner said. “They’re good at traveling on a continental scale and you find them globally because so many continents spawned them.” Work done for the AWG revealed for the first time the presence of SCPs in ice cores in Antarctica.

Climbers near the summit of Mount Everest.
Polyester, acrylic, nylon and polypropylene fibers have been found in samples collected on Mount Everest. Photo: Baker Perry/National Geographic/Penn

Scientists said plastic pollution is also a sign of the Anthropocene. “The 1950s began to see the majority of polymers that were familiar to the invention start to appear in products,” Waters said, with nylon replacing silk in World War II for example.

Plastic waste can now be found from Mount Everest summit to me The deepest ocean trench, gives a global signal. Other scientists discovered in 2019 that plastic was deposited in layers and suggested that the Stone Age and Iron Age followed. The age of plastic. However, the biggest spike in plastic pollution comes two decades after the plutonium isotope was tested from the hydrogen bomb, although both have the advantage of never appearing in the geological record before.

Some scholars suggested Broiler chicken bones as a sign of the Anthropocene, with their production rising from World War II onwards. Furthermore, agricultural breeding means that their skeletons and genetics are distinctly different from those of their wild ancestors.

“Chickens are now the largest number of birds on earth,” Waters said. “but also Two-thirds of the mass of large mammals On the planet there are domesticated species – cows, sheep, pigs etc. This is obviously a huge change in species numbers, especially given the decline of natural species.” The WWF estimates that Average 70% reduction in wildebeest population size. These biological changes are significant, Waters said, but they are more gradual than other signs.

Broiler chickens on a farm in the UK.
Broiler chickens on a farm in the UK. Photo: Room with Views/Alami

Scientists said invasive species introduced by humans to new areas could also be markers. The unintentional importation of exotic species in the ballast water of ships coming to San Francisco from Asia has transformed the bay. “There was a point where, in fact, 98% of the mass of every animal species in the Gulf was invasive,” Waters said. Pollen from introduced plant species, such as trees used in commercial forests, can also register change.

“Chemical and mineral contamination shows up in the sediment as well,” Turner said Green Revolution It was based on synthetic fertilizers and pesticides, and that’s how you see that in sediment cores. The whole mix of industrial chemicals exploded in the postwar period.” Whether the chemicals have been present in the environment long enough to be signs of the Anthropocene remains to be determined.

The 12 potential sites for the site that will define the new era show some signs, but they are very diverse. “Because the Anthropocene has not been formally accepted, we’re still trying to prove to people that this isn’t something local, it’s something you find and associate with in a whole bunch of different environments,” Waters said.

“They all illustrate this dramatic shift in the Anthropocene very well. But the really standout sites are the ones where you can actually see annual dissolution of layers,” including some of the lake, coral and polar ice sites. “It’s quite surprising that These sites detail planetary changes in annual resolutions.”

Algae blooms in the Baltic Sea.
Algae blooms in the Baltic Sea. Photo: European Space Agency

Each has its pros and cons. The 32-meter Palmer ice core off the Antarctic Peninsula is the longest record in the Anthropocene, but its remote location means the trail of some marks is often faint. Baltic sediments turn from pale to black with the onset of the Anthropocene. This is caused by pollution-fed algal blooms that suck all the oxygen out of the water. But the sediment does not have an annual lamination. The archaeological site in central Vienna gives a 200-year history, dated by artifacts, but has gaps in the record due to redevelopments.

The choice of the site, and thus the official time and place for the dawn of the Anthropocene, is in the hands of the 23 voting members of the AWG, but will then have to be passed by Subcommittee on Quaternary Layersthen International Stratigraphy Commission Finally it is validated by International Union of Geosciences. There is also a deadline:International Geological Conference In South Korea in 2024, when the mandate of the AWG expires. “It’s been pretty much said we have until then to get it done,” Waters said.

Professor Naomi Oreskes, of Harvard University and non-voting AWG member, said: “As geologists, we’ve been trained to believe that humans aren’t important. That was once true, but it isn’t anymore. There is no doubt that the human footprint is now present in rocks and sediments. The Anthropocene is primarily a scientific concept, but it also sheds light on the cultural, political and economic implications of our actions.”

Professor Mark Maslin of the University of California, who co-authored it human planet With Professor Simon Lewis, he said: “I think the Anthropocene is a critical philosophical term, because it allows you to think about the impact we’re having, the impact we want in the future.”

Formerly Maslin & Lewis Proposal 1610 As the beginning of the Anthropocene, it marks the huge and deadly impact that European colonizers had on the Americas and thus the world. But Maslin said agreeing on a definition was more important than where it was located.

“Until now, we’ve talked about things like climate change, the biodiversity crisis, and the pollution crisis, as separate things,” he said. “The basic concept of the Anthropocene is to put it all together and say that humans have such an enormous impact on Earth, we are the new geological superpower. This comprehensive approach then allows you to say, ‘What do we do about it?’”

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