Over the past two decades, the term Anthropocene has appeared in multiple headlines, documentaries, podcasts, and research journals, both in the natural sciences and in the humanities and social sciences. It has often been used informally as a new “geological epoch” where humans are the main agent of transformation of the planet. Anthropogenic climate change, ocean acidification and loss of biodiversity are some symptoms that illustrate this.
However, it was never clear when and where these effects on the planet began from a stratigraphic point of view, that is, what their imprint was in the sediments. Hence, after 15 years of research not without criticism, the Working Group on the Anthropocene proposed to formally set its beginning in 1952. The choice of this specific date was based on the possibility of identifying the radionuclides scattered by the hydrogen bombs detonated at that time as a reliable chemostratigraphic marker.
Well, this proposal was rejected on March 4, 2024. Twelve of the eighteen members of the Quaternary Stratigraphy Subcommittee, the committee in charge of accepting modifications in the organization of the most recent period of the Earth, voted against, as reported the New York Times. Their conclusion has been clear: with the standards used to define units of geological time, the Holocene cannot be considered over and considered to be living in a different era.
As a philosopher and historian of science, I have closely researched the work of the Anthropocene Working Group from its establishment in 2009 to the present. In my studies, I have shown how this project has generated tensions in the stratigraphic community. Many maintain that the proposal to formalize an era that covers only 75 years would have a negative impact both in the scientific and social, political and cultural spheres.
One of the aspects that has caused the greatest controversy is the fact that the Anthropocene was not proposed from geology, as one might imagine, but was spontaneously mentioned by the atmospheric chemist Paul Crutzen in the year 2000.
From that moment on, the term began to become popular, encapsulating a disruptive idea: the Earth system had entered a state of operation not analogous to any previous time, including events such as the alteration of biogeochemical cycles, the increase in pollution by plastic and other waste. solids and air, water and soil pollution due to industrial and urban activity, among others. Everything was summarized in the Amsterdam Declaration in 2001 on the newly established science of the Earth system.
Meanwhile, for geology – a discipline that is traditionally responsible for ordering the history of the Earth – human beings have been living in the Holocene since the last ice age ended, that is, around the year 9700 BC. and. c. This era has been characterized by a relatively stable climate and an environment conducive to the development of human civilization as we know it today.
Crutzen proposed, however, that a new human time had begun with the Industrial Revolution at the end of the 18th century – a fact evidenced under the paradigm of Earth system science – and whose beginning could perhaps be set with events such as the invention of the machine. steamer in 1769 by James Watt.
The proposal became so popular that a few years later, in 2008, it attracted enough attention from the stratigraphic community to begin a project to convert the Anthropocene from an informal term to a fully formal geological epoch.
Since its formation, the group has investigated different options to determine the exact beginning of the Anthropocene, with around 1950 being the most supported alternative, an idea that was initially promoted with the publication of the graphs of the so-called “great acceleration of the 20th century.” .
These graphs reflected the overwhelming evidence of the tipping point following the end of World War II, where the human impact on the Earth system increased exponentially in multiple variables.
This Dutch scientist was awarded the Nobel Prize in Chemistry for his contributions to understanding the destruction of the stratospheric ozone layer and was also one of the scientific leaders of the new science of the Earth system.
This new paradigm brought about the understanding of the Earth as a single self-regulating system, integrating the different subsystems that had been studied separately – the atmosphere, hydrosphere, biosphere, etc. – and studying the phenomena that emerge in their interactions.
At this historical moment, radioisotopes such as plutonium-239, cesium-137 or strontium-90 were dispersed throughout the planet due to thermonuclear bomb tests carried out in the early 1950s. These radioactive isotopes were deposited in sediments marine, soil, plants and other geological records.
In fact, the plutonium spike in the sediments of Lake Crawford near Toronto, Canada, was selected as the “golden nail” to mark the beginning of the Anthropocene, initially providing fairly clear evidence to formalize an epochal shift.
Although the Anthropocene Working Group has argued that there are irreversible changes on a geological scale caused by human activity on the Earth's surface, outside the range of natural variability of the Holocene, several experts on the subcommittee in charge of evaluating the proposition affirm that its definition is too limited.
According to Philip Gibbard, a geologist at the University of Cambridge, the proposition “suggests that, in my own lifetime, the changes that are affecting the planet appeared suddenly.” In an internal meeting, he stated that it was rejected because “in fact, humans have been influencing the natural environment for 40,000 years.”
The same is implied by Jan A. Piotrowski, a member of the committee, for whom the suggestion “limits, confines and narrows the entire importance of the Anthropocene.” Specifically, he asks: “What was happening during the beginning of agriculture? What about the Industrial Revolution? What happens with the colonization of America, of Australia?”
Furthermore, assuming that this first evaluation had been passed, there would still have been obstacles that were difficult to overcome. Stanley C. Finney, secretary general of the International Union of Geological Sciences and who had already described the proposal as more political than scientific, criticizes that from the beginning a categorization as “epoch” was ensured and proposals for a less designation were ignored or counteracted. formal of the Anthropocene.
If they had made their formal proposal sooner, they could have avoided a lot of wasted time, Finney adds: “It would have been rejected 10 years earlier if they had not avoided presenting it to the stratigraphic community for careful consideration.”
In short, some of the main reasons for the rejection are related to trying to establish a beginning at such a recent date and with samples that are too superficial to broadly represent the human impact on the strata and equate it to the great epochal changes that the region has experienced. Earth in millions of years.
In any case, discussions about a possible geological time of human imprinting are not yet over, although Anthropocene advocates will now have to wait a decade before their proposal can be considered again. The term is likely to continue to be used informally. It is also possible that the concept is accepted in the category of “geological event”, as has been suggested lately as it is a less compromised option.
But what is quite unlikely is that in the near future it will be officially declared that we live in the geological epoch of the Anthropocene.
This article was previously published on The Conversation. José Luis Granados Mateo is a researcher at the University of Cambridge.
