The competition to determine the onset of the Anthropocene: H-bombs or chicken bones

 

Scientists claim that humanity has become a "geological superpower" and that in order to address the effects of this, a new epoch must be declared.

Fri Jan 06 2023 11.54 GMT

Where and when did the Anthropocene start exactly? In the following months, scientists will try to provide an answer to this historic issue by identifying a location and time that best exemplify the point in Earth's history when humans overpowered the natural forces that have shaped the planet for billions of years.

They may determine that the beginning is marked by a boom, caused by the plutonium isotopes that the hydrogen bomb testing that started in late 1952 swiftly shot across the earth, or by a shower of soot particles brought on by the increase in fossil-fuel power plants after World War II.

Alternately, they might opt for the postwar rise in the use of chemical fertilisers and their significant effects on the Earth's natural nitrogen cycle. Microplastics, chicken bones, and pesticide residues might potentially be considered among the eclectic indications supporting the Anthropocene theory. Additional clues may be found in Chinese and American lake bottoms, Australian corals, a Polish peat bog, the dark sediments beneath the Baltic Sea, or even the human waste that has collected beneath Vienna.

The official keepers of the geological timescale have asked an international committee of roughly 40 experts to choose a location where layered deposits clearly illustrate the change from one age to the next. There can only be one winner after the group selected a shortlist of 12 locations, and voting has started. The Holocene, the 11,700-year period during which all civilisation originated and which will end with the announcement of the Anthropocene, has definitely been significantly altered by humanity. Greenhouse gas emissions, pollution, and the extinction of animals and ecosystems have all changed the atmosphere, lakes and seas, and the living world. By moving around 24 times more material than rivers do, humans are currently changing the Earth's surface more than natural processes.

Researchers claim that defining the Anthropocene is important because it combines all of the effects that people have had on the planet, providing a framework for a comprehensive knowledge and, ideally, remedial action. A specific definition is necessary from a scientific standpoint in order to provide a solid foundation for discussion.

Field of crops being sprayed by a tractor.

The voting process has already started. According to a recent paper in the journal Science by Prof. Colin Waters of Leicester University and Dr. Simon Turner of University College London, the chair and secretary, respectively, of the Anthropocene Working Group, the site will need to demonstrate "specific physical properties in sediment layers, or strata, that capture the effects of recent increases in human population; unprecedented industrialization and globalisation; and changes imposed on the landscape, climate, and biosphere" (AWG).

But in geological circles, defining a new era is a significant choice, and the AWG must simultaneously accomplish a more difficult task: convincing geologists that a new epoch is even warranted.

Both activities rely on finding distinct indicators of change, and hundreds of scientists are engaged in this work. The broad indicators of anthropogenic transformation include increasing atmospheric carbon dioxide concentrations, as seen in air bubbles trapped in ice cores, and the dramatic shift in species populations and distributions, with human and livestock numbers soar and spread while those of wild animals plummet and disappear.

The "golden spike" required for a precise characterization, however, is provided by additional markers, which also allow strata to record a sudden, obvious elevation. The first H-bomb test, conducted by the US on November 1, 1952, on the Eniwetok atoll in the Pacific Marshall Islands, left behind a distinctive fingerprint of radioactive isotopes, mainly plutonium.

Numerous above-ground experiments quickly followed, some of which were even sent into space. The effects of the experiments were swift and widespread, covering the globe in little over 18 months before atmospheric testing was outlawed in 1962.

They extensively tested their new weapons for a brief time, according to Turner. Because of this, you have a highly special, time-specific global identifier that is really helpful for our work.

Tiny spheroidal carbonaceous particles (SCPs), a form of hard fly ash exclusively created by the high-temperature burning of coal or heavy oil, are another helpful marker. After World War II, there was a significant rise in thermoelectric plant construction, according to Turner. They can move quickly between continents, and since many different continents gave birth to them, you may find them anywhere. SCPs have been discovered for the first time in Antarctic ice cores thanks to work done for the AWG.

Samples that were taken at the summit of Mount Everest contained polyester, acrylic, nylon, and polypropylene fibres.

According to the experts, plastic pollution is another indicator of the Anthropocene. According to Waters, the majority of the polymers that people are familiar with were developed in the 1950s and began to be used in products. For instance, around the time of the Second World War, nylon essentially replaced silk.

There is now a worldwide signal of plastic garbage from the summit of Mount Everest to the deepest ocean trench. Other researchers discovered plastic was being deposited into layers in 2019, which indicated the plastic era was replacing the stone and iron ages. However, the greatest increase in plastic pollution occurs a few decades after the H-bomb tests' plutonium isotopes, despite the fact that both have the benefit of being completely new to the geological record.

Since the output of broiler chicken bones increased dramatically after World War II, some scientists have proposed that they are a sign of the Anthropocene. Additionally, due to agricultural breeding, their DNA and skeletons are obviously distinct from those of their wild forebears.

The largest number of birds on the globe now, according to Waters, is chickens. "But additionally, domesticated animals like cows, sheep, pigs, and others make up two-thirds of the total mass of big mammals on the earth. Given the decline of native species, there has certainly been a significant shift in species populations. According to WWF, the number of wild animal populations has decreased by an average of 70%. According to Waters, these biological changes are significant yet occur more gradually than other indicators.

Chickens for broiling on a farm in the UK.

According to the researchers, invasive species that humans have introduced to new areas can also serve as indicators. The bay was altered by the unintentional introduction of alien species carried in the ballast water of ships coming into San Francisco from Asia. According to Waters, there was a time when 98% of the animal species in the area were genuinely invasive. Pollen from alien plant species, as those found in commercial forestry, can also serve as a change-recording tool.

According to Turner, sediments also contain chemical and metal pollution. "The Green Revolution was based on artificial fertilisers and pesticides, so you see that in sediment cores," he said. Following the war, the entire cocktail of industrial chemicals suddenly erupted. It remains to be seen if the compounds last in the environment long enough to serve as Anthropocene markers.

All of the 12 probable sites for the site that will signify the new era share some of the indicators, yet they are all highly different. We're still working to persuade people that the Anthropocene is not something localised, but rather something you discover and correlate in a huge variety of various ecosystems since the Anthropocene has not yet been legally recognised, according to Waters.

"They all do a great job of capturing this stunning Anthropocene shift. But the sites that really stand out are those, like some of the lake, coral, and polar ice sites, where you can truly see a yearly resolution of strata, according to Turner. The yearly resolution at which these sites describe planetary changes is absolutely astounding.

In the Baltic Sea, algae grows.

Each has advantages and disadvantages. The longest record of the Anthropocene is the 32-meter-long Palmer ice core from the Antarctic Peninsula, however due to its distant position, some of the markers' traces are sometimes weak. As the Anthropocene begins, the pale Baltic Sea sediments become black. Algal blooms fueled by pollutants that suck up all the oxygen in the water are what produce this. However, there are no yearly laminations in the sediments. Artifacts from the archaeological site in central Vienna provide a 200-year record, however there are gaps in the record due to redevelopments.

The 23 voting members of the AWG will choose the location, which will serve as the official time and location for the onset of the Anthropocene, but it must first be approved by the Subcommission on Quaternary Stratigraphy, the International Commission on Stratigraphy, and the International Union of Geological Sciences. There is a limit as well: the AWG's authority ends in 2024 at the international geological congress in South Korea. We essentially have till then to do this, according to what has been mentioned, added Waters.

The Harvard University professor and non-voting member of the AWG, Prof. Naomi Oreskes, stated: "As geologists, we were raised to consider that people were negligible. That used to be accurate, but it is no longer. The AWG's collection of data proves beyond a shadow of a doubt that the human imprint is now discernible in rocks and sediments. Though essentially a scientific term, the Anthropocene also emphasises the cultural, political, and economic ramifications of human behaviour.

"I think the Anthropocene is a key philosophical phrase, because it allows you to think about what influence we are having, and what impact we want to have in the future," said Prof. Mark Maslin of UCL, co-author of The Human Planet with Prof. Simon Lewis.

Maslin and Lewis once claimed that the Anthropocene began in 1610 to reflect the enormous and fatal influence that European colonists had on the Americas and, by extension, the rest of the globe. Maslin countered that agreement on a term is more crucial than its exact placement.

He said that before, "we have discussed issues like climate change, the biodiversity catastrophe, and the pollution crisis as different things." "The central idea of the Anthropocene is to bring all of this together and assert that people have a significant influence on the world and are the planet's new geological superpower. The ability to ask: "What do we do about it?' results from that comprehensive perspective.