Dispute over the Anthropocene. Lake Crawford failed to convince geologists

antropocen

The word Anthropocene has been appearing more and more in the public space in recent years, and slowly we are all getting used to it, like many other neologisms, signs of our times. The word has entered common parlance in politics, art or journalism. I also use it quite freely, basically without thinking more deeply about what its formal status is. Is this a widely accepted term in the scientific community? It turns out that not necessarily, as a group of more than a dozen geologists from the International Commission on Stratigraphy(ICS) has just decided. The decision was made this month not to recognize the Anthropocene as an epoch in Earth’s history.

Who decides the geological eras?

The main body regulating the geologic time scale is the International Commission on Stratigraphy(ICS, or International Commission on Stratigraphy) – the largest scientific body of the International Union of Geological Sciences. One of its primary tasks is to establish a worldwide standard stratigraphic table. It is a diagram of Earth’s history depicting successive geological periods and arrangements of rock layers. It spans nearly 4.6 billion years and divides our planet’s history into eras, periods and epochs.

According to the current calendar, our world is currently in the Holocene, which began 11,700 years ago. years ago, with the last retreat of the great glaciers. Changing the chronology to say that we have moved into the Anthropocene would mean recognizing that human-induced changes in geological conditions were profound enough to end the Holocene. Do we have enough justification to mark the transformation of the planet by mankind with a separate chapter in Earth’s history, the Anthropocene or the human era?

Golden nail, or milestone ending an era

The term Anthropocene has been adopted as the name for the period in Earth’s geological history when humanity became a driving force in changing the world. The proposal goes back to 2009, when the ICS established the Anropocene Working Group (AWG) to study whether recent planetary changes merit a distinct place on the geological timeline. The group includes more than thirty renowned scientists from centers around the world.

For more than a dozen years, the Group has studied whether and (possibly) when the world transitioned from the Holocene into a new era defined by the global impact of humanity. In 2016, it concluded in a vote that such a transition had indeed occurred and took place in the 1950s, with the post-war economic growth and rapid increase in fossil fuel consumption. It considered that the best date for the start of the new period would be 1950.

In order to solidify its thesis, the Group had to find an object, a physical place that would clearly indicate an epochal change. For example, such a geological deposit as the iridium layer between clays of the El Haria Formation in the Tunisian town of El Kef, left by an asteroid impact (which contributed to the extinction of the dinosaurs) and which marked the end of the Cretaceous period 66 million years ago. Such evidence in the English-language literature is expertly called GSSP (Global Boundary Stratotype Section and Point), and colloquially is called golden spike (golden nail ), which can be compared to our milestone.

And here, all in white (literally), enters the water thread

Over the past half decade, 12 sites from 5 continents and a variety of environments have competed for the title of golden nail for the Holocene and Anthropocene, although the vast majority represent aquatic environments. Among the GSSP candidates were three lakes (Searsville in the US, Canada’s Crawford and China’s Sihailongwan), two marine areas (the East Gotland Basin and Japan’s Beppu Bay), two coral reefs (Flinderska and West Flower Garden Bank), San Francisco Bay, an ice plain on the Antarctic Peninsula, Ernesto Cave in Northern Italy, the Sniezka peat bog in Poland’s Sudety Mountains (our national candidate!), and even an urban area – Karlsplatz in Vienna.

The final choice was Crawford Lake. It is a deep (24 m), meromictic reservoir located in a protected area in Ontario, Canada. Sediments have accumulated at its bottom for centuries in intact layers, and their geochemical analysis has made it possible to reconstruct the history of the area and the trends and sources of pollution over the past 150 years or so.

Lake sediments have revealed layers of white calcite crystals that precipitate in the lake during summer algal blooms, fed with nutrients from fertilizer runoff and other human activities. Around 1950. The sediment has seen a dramatic rapid increase in particles from coal combustion in industrial processes, including steel production at the nearby Hamilton Foundry. Plutonium has also been shown to increase as a result of nuclear testing, nitrogen isotopes as a result of fertilizer application, and changes in the chemical composition of precipitation, known as “plutonium. Acid rain. Interestingly, scientists question the reliability of dating the anthropopressure based on the presence of microplastic in the sediments, as its particles have proven to be so mobile that they have been found in layers dating as far back as the 18th century.

Anthropocene not yet – we’re still in the Holocene

In the fall of 2022. The AWG has submitted its Anthropocene proposal to the next ICS bodies for a vote. This is because recognition of an application requires approval by three consecutive committees of the International Union of Geological Sciences by a number of at least 60 percent. votes. Geologists, however, were deeply divided from the beginning of the discussion over the recognition of the Anthropocene as a separate epoch, and acceptance of the proposal was not at all obvious. And in fact, in early March of this year, an article appeared in the journal Science, which confirmed that a panel of geologists from the Subcommittee on Geosciences and the Committee on Mining and Metallurgy had been able to determine whether the project was a good idea. The ICS Quaternary Stratigraphy Committee voted down a proposal to end the Holocene and inaugurate the Anthropocene (by 12 votes to the contrary out of 18 voting members, with 2 abstentions).

While even opponents of the proposal to recognize the Anthropocene have no doubt that the human impact on the planet, including climate change, has been enormous, some felt that the proposed determinant of the epoch – about 10 cm of sediment from Canada’s Lake Crawford – was insufficient to define it. They also questioned the possibility of setting a specific date as the beginning of humanity’s multifaceted impact on the planet.

Even if geologists do not deny that our era stands out from other periods in Earth’s history, qualifying the Anthropocene as a distinct epoch on the geological time scale requires a more detailed and unambiguous definition. The organization applies very strict criteria to ensure that it maintains common global standards for describing the planet’s history. First of all, according to the principles of stratigraphy, each Earth time interval requires the definition of a clear, objective starting point, valid throughout the world. Proposed as a starting point by the AWG, the mid-20th century. for several committee members proved inadequate and too limited. And why not consider it the beginnings of agriculture? What about the industrial revolution? Colonization of the Americas and Australia?

Among opponents of recognizing the Anthropocene as a new epoch, there were also claims that the whole process was unnecessarily political and publicized in the media. During the period when geologists were pondering the definition of the Anthropocene, other scientists, as well as artists, writers or politicians, adopted the term without waiting for its formal recognition. Some use it to describe the beginning of any human impact on Earth, starting with the beginnings of agriculture 12,000 years ago. years ago, others to identify changes that began several thousand years ago, when humans developed the ability to cut down forests and build structures. Everyone uses the concept of the Anthropocene for their own purposes, not really caring about the lack of a formal definition of it.

If not the era, then perhaps the event

Proponents of the Anthropocene will now have to wait at least a decade before the AWG’s proposal can be revisited. That’s how long the grace period established by the ICS is. Admittedly, the Anthropocene has not been formally recognized by geologists, but it will remain with us. It has already entered common use, daily communication, functions in art, journalism and even science. There are claims that perhaps it should be recognized as an event. In the language of geology, it’s an informal term that doesn’t require an exact global starting point, doesn’t appear on an official timeline, and no committee has to approve its start date.

Many of the planet’s major events are of the order of magnitude, including earthquakes, volcanic eruptions, mountain movements, the Great Oxidation Event (GOE) caused by the massive production of oxygen by cyanobacteria that occurred 2.4-2.1 billion years ago, or the Great Ordovician Biodiversity Event (GOBE), an explosion of biodiversity some 466 million years back.

Despite voices questioning the 10 cm of Craword Lake sediments as the golden nail of the Anthropocene, the traces of human activity recorded in them are clear and indisputable. There is no going back to the state the planet was in 100 years ago. The changes in its systems are irreversible. Our impact on the planet will remain visible and there is no doubt that it will be recognizable in the geological record in the future. How to classify it will already be decided by future generations.


Photo. main: James St. John/flicker

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