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Love it or hate it, the Anthropocene is here to stay

The Holocene as we knew it is over and there is no going back, contend Elizabeth Hadly and Anthony Barnosky

2 September 2024

We can no longer depend on what tomorrow will bring because we’ve never been here before. The rules of the Holocene no longer apply (© Shutterstock)

It doesn’t matter that the high courts of geology recently denied the existence of the Anthropocene Epoch.

It’s here, and it gets more real every day.

The Holocene includes the last eleven millennia, when tomorrow looked pretty much like yesterday, when predictability ruled, when we knew what crops to plant when and where, which flowers bloomed on spring’s long-established schedule, and what week of what month birdsong would fill the air. Those were the days when we had to stop frequently to clear our windshields of the swarms of insects that we drove through. Back then snowmelt would flow into our dams, and fish would swim upstream to spawn on schedule. Storms and heatwaves were less intense, and summers were not filled with wild-fire smoke. Few roads penetrated the Amazon. We could rest assured that the home we lived in today would still fit the climate of tomorrow.

We can no longer depend on what tomorrow will bring because we’ve never been here before. The rules of the Holocene no longer apply.

The Great Acceleration

This is what the Anthropocene Working Group (AWG), an international panel of 33 experts in relevant disciplines, documented to the Subcommission on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), the gate-keepers of the geological time scale. The AWG report (Waters et al., 2024), which relies upon and summarises peer-reviewed research carried out over the past 15 years, shows that geological evidence agrees with a host of other data in unequivocally verifying the end of the Holocene and the beginning of the Anthropocene.

Geologically, the functional beginning of the Anthropocene starkly shows in lake deposits, coral reefs, glacial ice, ocean sediments, cave deposits, landscape formation, and archaeological materials from around the world (Waters et al., 2023; 2024). It took off suddenly in the mid-20th century, in what has become known as the Great Acceleration, when human impacts, largely produced by industrialized societies, became so pervasive that the planet began working in a new way. That’s because, almost overnight, there were just so many of us with needs and wants: some 90% of the eight billion people now living on Earth were born since 1952 (Bump, 2022).

The functional beginning of the Anthropocene starkly shows in lake deposits, coral reefs, glacial ice, ocean sediments, cave deposits, landscape formation, and archaeological materials

Our exponential growth coincided with accelerating use of fossil fuels that changed the climate and the atmosphere (IPCC, 2023) and resulted in killing or burning vast tracts of the world’s forests, even rain forests, rapidly melting glaciers worldwide, and changing ocean chemistry. Over the same time, we built dams on most major rivers, rerouted water to our rapidly growing acres of farm fields and cities, and choked the flow of sediment to the oceans.

The 2024 Rio Grande do Sul floods, Brazil. Since the mid-20th century, exponential population growth globally coincided with accelerating use of fossil fuels (© Shutterstock)

Geological deposits began to take on a new character with many human-produced signatures (Waters et al., 2024), which are growing more evident every day. The geochemical signals of burning fossil fuels turned sharply upwards, and soils and sediments destined to become rocks began to preserve the detritus of our activities: human-made minerals, compounds, even actual rocks like concrete and asphalt; “forever chemicals” and other pollutants derived from our attempt to control life (i.e., pesticides, algaecides and herbicides) or to enhance growth and reproduction (i.e., hormones, genetically modified organisms, and synthetic fertilizers); so-called “technofossils,” made of everything from microplastics to scrap metal; and new assemblages of nascent plant and animal fossils that reflected how we’ve replaced most of Earth’s terrestrial life with ourselves and our domestic species (Smil, 2011; Britton-Purdy, 2021). On land and in the sea worldwide we’ve created brand-new ecological communities, now diverging ever more from what used to be, through moving thousands of species from where they evolved (Williams et al., 2022), and by decimating other living beings at lightning speed, increasing extinction rates of species some 10-fold from the 19th century (Ceballos et al., 2015), and wiping out nearly 70% of wild animals in just the past 70 years (WWF, 2022). All of these ways we’ve tinkered with life have had the cumulative effect of re-sculpting the biosphere into an Anthropocene rather than Holocene form.

As the American Environmentalist and author Bill McKibben once said: it’s a whole new Earth, we may as well give it new name.

Line in the sand

So too with the Anthropocene Epoch. The technical rules of stratigraphy demand that, to define a new epoch, one clear marker evident in geological deposits around the world must be specified, ideally a marker that shows up across the planet at pretty much exactly the same time everywhere. Importantly, the marker is not the cause of the epochal shift, it simply is the line in the geological sand that is easy to trace across the globe.

The Holy Grail of markers is something like the asteroid strike 66 million years ago that ended the Cretaceous world and ushered in that of the Paleogene, an instant in time recorded geochemically in rocks around the world by the iridium spike.  The AWG chose a geochemical signal analogous to the iridium spike to draw a line between Holocene and Anthropocene: the uptick in radioactive fallout, notably plutonium, that resulted from a sharp increase in thermonuclear bomb tests. From painstaking studies of geological deposits around the world involving nearly one hundred stratigraphers (Waters et al., 2023; 2024), the plutonium uptick was shown to be most evident in 1952, plus or minus two years, coincidentally at about the same time hundreds of other geological signals of the Anthropocene began to appear and/or increase.  Hence, 1952 became the date the AWG settled on to mark the beginning of the scientifically defined Anthropocene.

Challenging convictions

When they received the AWG data that showed the Anthropocene merited its own epoch that started in 1952, a majority of members of the SQS voted against the proposal (Zhong, 2024) – a decision that was quickly upheld by the ICS and then the governing body for all of geology, the International Union of Geological Sciences (IUGS), although some questioned the voting procedure (Witze, 2024a,b; Barnosky & Hannibal, 2024).

Based on the statement released by the IUGS (IUGS, 2024), it is difficult to conclude that the decision was based on the details of the science: the vote against the AWG recommendation stopped short of articulating competing facts that would outweigh the evidence presented by the AWG. Instead, the report states only three ideological convictions: that the Anthropocene has deeper roots in geological time, that 70 years was too short for an epoch, and that human impacts on Earth cannot be adequately marked by a single point in time. But this outcome implies that, despite the voluminous evidence presented to the contrary, the way humans have recently changed the working of Earth and its geology is nothing out of the ordinary in human history.

Besides going against the scientific evidence presented by the AWG, those convictions go against the findings of many other branches of science, including climatology (www.ipcc.ch), ecology (WWF, 2022), physics (Prăvălie, 2014), complex systems theory (Barnosky et al., 2012; Steffen et al., 2018), and even medicine (Gluckman et al., 2020).

The vote outcome implies that the way humans have recently changed the working of Earth is nothing out of the ordinary in human history (© iStock)

This leads us to question whether those convictions simply reflect that formalising the Anthropocene Epoch challenges the traditions and the practice of geology more than the discipline is yet ready to accept. As geologists, we are taught to deal in millions of years. That a new geological epoch could have started within the lifetimes of senior members of the profession—well, perhaps for some that is a hard pill to swallow.

Second, whether or not it was the intention, the outcome of the vote leads to the perception that geoscience as a discipline somehow doubts human influence on Earth’s systems. Indeed, most geologists are and traditionally have been employed in energy, mining, construction, and manufacturing industries; in government or consulting agencies set up to both support and monitor those activities; and in universities and colleges that train students for those jobs (e.g., Gonzales & Keane, 2021; EFG, 2019; Australian Government, 2024)—training that itself is substantially funded by energy companies (e.g., Westervelt, 2023; Colbert, 2023). In that light, it would not be unreasonable to question whether long-established geological institutions might be reticent to broadcast the message that the Holocene died from the very activities that traditionally employ most geologists.

An undeniable reality

Of course, the outcome of the vote does not mean what we see around us and rapidly accumulating in geological deposits is not real, nor does it mean that all geologists deny the Anthropocene as an epoch. The members of the AWG (who overwhelmingly backed their proposal prior to submission to the ICS; http://quaternary.stratigraphy.org/working-groups/anthropocene/), for example, were largely classical stratigraphers, palaeontologists, and geochemists who followed the evidence the geological record revealed to teams of scientists working around the world.

Ultimately, it was an interdisciplinary collaboration of scientists in the atmospheric, geological, biological, and social sciences, that showed how the sheer numbers of humans on the planet and their collective impacts had so profoundly changed Earth’s systems (Steffen et al., 2020). They determined that humanity, from the mid-1950s, precipitated a change in how Earth worked, that went far beyond the mere presence of humans and their long history of local and regional impacts. Suddenly, and for the first time in our planet’s history, we were influencing all parts of the globe simultaneously by the dramatic changes we accelerated in the atmosphere, biosphere, hydrosphere (oceans, rivers, and lakes), cryosphere (glaciers), and lithosphere (geology) and how all those “spheres” interacted. And that began to push our planet out of a safe operating space for our species (Rockström et al., 2009; Richardson et al., 2023).

Humanity, from the mid-1950s, precipitated a change in how Earth worked, that went far beyond the mere presence of humans and their long history of local and regional impacts

If that does not herald the end of the Holocene, what does?  Only in the last 70 years has the magnitude of what we’ve wrought become apparent, not only in scientific studies, but in our everyday lives. That is the Anthropocene we have to grapple with, nested within the many other ways the name is already widely used in thousands of scholarly publications and millions of mentions in the popular media. And its reality is now as undeniable as that of plate tectonics – another transformative concept that was originally fiercely opposed by many.

Mourn it or celebrate it, but let’s see the Anthropocene for what it is—a new time on Earth, defined by our power to influence the workings of our planet’s fundamental processes. In the end, the resistance to denote the Anthropocene as an official epoch does not change the profound, recent impacts of humanity, the scientific evidence under our feet, and the power that acknowledging reality gives us to guide our future.

Prof Elizabeth Hadly

Professor in the Departments of Earth System Science and Biological Sciences, and Director of the Life in the Anthropocene Lab, Stanford University, USA. A global change scientist whose research in Quaternary geology focuses on the biological impacts of humanity on planet Earth, and who joined the reconstituted Anthropocene Working Group after the vote took place.

Prof Anthony Barnosky

Emeritus Professor at the University of California-Berkeley, USA. A paleobiologist who has worked as a geologist in industry, government, and academia, and has been a long-time member of the Anthropocene Working Group.

They are co-authors of the popular book Tipping Point for Planet Earth, How Close Are We To The Edge? (Thomas Dunne Books, 2016, 264 pp.)

Further Reading

 

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