Editor’s note: The article below, authored by Owen Gaffney of the Stockholm Resilience Centre, introduces the term Anthropocene, increasingly used by Earth scientists to describe a new epoch in geological history reflecting the profound changes humans are making to Earth’s natural systems.
At a recent academic meeting in Berlin, my mind wandered off during a long, complicated discussion of Middle Eastern geopolitics.
On impulse, I sent a tweet to my friend Paul Salopek, asking if he’d be willing to share his ground-level perspective with the meeting. He tweeted back, and the next day he addressed the meeting by mobile phone from a deserted house on the border between Syria and Turkey.
Dozens of academics listened in a darkened auditorium as Paul vividly described the flood of Syrian refugees crossing the border into Turkey. Tens of thousands of people were fleeing the Islamic State, an organization that did not even exist when Paul’s Out of Eden Walk began in January 2013.
As Paul recounts in his dispatches for National Geographic, human migration is a defining feature in our collective narrative, whether it be driven by threat of violence, desperation, hunger, environmental stress, or a search for better opportunities. The narrative is the same today as it was 70,000 years ago, when we left our African home.
The audience at the meeting, called the Anthropocene Campus, was receptive to that sort of thinking. For just as Paul practices “slow” journalism to piece together a grand narrative along the pathways of early human migration, the pace of science, too, can be painstakingly slow before a grand narrative emerges. Analyzing how the Earth operates as a system takes decades, drawing in strands from many diffuse fields examining the atmosphere, oceans, ecology, and geology. Increasingly, researchers studying the Earth system bring in additional strands from the fields of economics, political science and the psychology of behavioral change.
Looked at from another angle: If humanity were a ship sailing the ocean, these Earth-system scientists would be the lookouts sitting high up in the crow’s nest. Some of them peer forward off the bow and out to the farthest horizon. Others face back, tracing the ship’s wake through time until it becomes hazy and indistinct, then farther still to another distant horizon. More recently, others peer down through the fog and rigging and monitor the ship’s size and speed, its energy flows and its effluence.
Since 2000, these lookouts, piecing together how Earth maintains a delicate stability, have reached profound conclusions about our ship’s course and impact, of which, more later.
Throughout human history, major geological events have punctuated our journey. During the Pleistocene epoch around 74,000 years ago, the Toba super-volcano erupted on the island of Sumatra, ejecting a giant ash cloud that blocked out the sun and would have severely affected food supply. It has been suggested this contributed to the near collapse of the human population around that time.
On a more positive note, just 11,700 years ago a slight but predictable shift in Earth’s orbit around the sun brought our planet out of a deep ice age. Earth’s systems — ocean currents, ice sheets, biodiversity, and climate — settled into a new equilibrium, and we entered the epoch that geologists call the Holocene, Latin for “entirely recent.”
The Holocene was a “goldilocks” period for Homo sapiens: not too hot, not too cold. Preceded by a deep ice age, the Holocene’s climate allowed agriculture to arise and flourish independently in the Middle East, China, and elsewhere. More complex social structures such as towns and cities arose, followed much more recently by enormous population growth and development.
The Holocene is the only known epoch capable of supporting a global civilization of 7.2 billion people, a rapidly growing number that is expected to stabilize at 10-12 billion in the coming century.
But what if Earth, as a system, is now operating in a quantifiably new state? What if Earth has moved out of the Holocene and into a new geological period? What if the ship on which we sail has grown so large that its insatiable appetite and increasing effluence have radically altered all around it?
If true, such a revelation demands a seismic rethinking of our worldview on par with Copernicus’ conclusion that the Earth orbits the sun, or with Darwin’s theory of natural selection. It also demands that we acknowledge that our actions now will shape the future of Earth’s life support system for centuries, or even millennia, to come.
These were the questions being discussed in Berlin. For several years now the world’s top Earth-system scientists and geologists, and increasingly philosophers, theologians, urbanization researchers and other experts, have gathered to debate, discuss, and describe a new geological epoch in Earth’s history. This period is being called the Anthropocene, or the epoch shaped by man.
The term itself had been coined only recently — in February 2000 by the Dutch chemist and Nobel Prize-winner Paul Crutzen in a flash of insight* during a scientific meeting in Mexico. Crutzen’s historic intervention was supported by a growing mountain of evidence. As an idea, the Anthropocene stands on solid scientific ground; and the implications are as big as they come.
That is not to say there is no debate. One of the biggest questions is, when did this new geological epoch begin? Some argue that the Neolithic revolution — the dawn of agriculture around 10-8,000 years ago — fundamentally changed the Holocene. As we cleared land, burned forests, and dug irrigation channels to grow food, we undoubtedly altered landscapes and watersheds. But did we begin to alter the planet on a global scale? Evidence for that conclusion is slight.
In 2002 Crutzen proposed in the journal Nature that the Anthropocene could have begun around 1800, with the industrial revolution in Britain. Two decades earlier, in 1776, Scottish engineer James Watt installed the first steam engines to pump water out of mines. In the same year, economist Adam Smith, another Scot, published The Wealth of Nations, a blueprint for generating economic growth based on rapid industrialization. These innovations sparked a raft of others, leading to the first flexing of industrial muscle in Great Britain and elsewhere at the dawn of the 19th century. Perhaps 1800, Crutzen offered, is the boundary between the Holocene and the Anthropocene?
The Dawn of the Anthropocene
Two years after Crutzen’s proposal, in 2004, after almost two decades of research, the International Geosphere-Biosphere Programme (IGBP) published its first synthesis of the Earth as a system. Led by Earth-system scientist Will Steffen, and including Crutzen, the report focused heavily on the concept of the Anthropocene, reiterating that the industrial revolution looked the likely candidate as the boundary. But it also contained an intriguing series of 24 graphs, which pointed to a significant event that occurred around 1950.
The most striking conclusion from the graphs is that in the mid-20th century, humanity’s effect on the Earth crossed a tipping point. This is when post-World War II production and consumption slipped into overdrive, and we, the producers and consumers, moved onto a new, almost exponential trajectory fueled by use of Earth’s natural resources. Incredibly, in a single human lifetime, changes in major planetary indicators started moving almost in synchronicity with social and economic indicators of change, one force seemingly driving the other. Now, we are in a whole new world.
From this perspective, the most significant event in the 20th century was not the Great Depression, the World Wars, or the Cold War — but rather the moment that a single species, ours, came to dominate Earth’s natural cycles.
Today we use an area the size of South America to grow our crops and an area the size of Africa to graze our livestock. We move more sediment and rock annually than all natural processes combined. And we are in the midst of Earth’s sixth mass extinction, a result of human activity.
So will future geologists regard 1950 as the boundary between Holocene and Anthropocene? Crutzen has changed his mind about 1800 and now favors around 1950. So too have many other researchers.
The International Commission on Stratigraphy, the scientific body that decides what “time” it is, geologically, has set up a working group to sift the evidence for the Anthropocene. The group met for the first time in Berlin a few weeks before the Anthropocene Campus, and is due to report its conclusions in 2016. Yet several members of the working group have already published academic papers indicating that Earth-system evidence points towards around 1950 as the beginning of a new geological epoch.
Geologists assessing claims of new eras, ages, and epochs search out unmistakable signatures to inform their decisions. Rock created at the time of the extinction of the dinosaurs 65 million years ago contains an extraordinary spike in the amount of the metal iridium, for example, indicating that an asteroid rich in that very rare element struck the Earth and sent a cloud of iridium dust all over the world. Geologists call these signatures “golden spikes” and sometimes even erect a plaque to mark a spot.
The Anthropocene will have many such markers. The imprint of our concrete and steel cities will be forever embedded in the rocks. So too will the record of mass extinctions and the altered chemistry of Earth’s atmosphere and oceans. But there might be an even more compelling marker in the strata.
On July 16, 1945, the Manhattan Project reached its goal when U.S scientists detonated the first atomic bomb in the desert of New Mexico. On that exact date, radioactive isotopes entered the atmosphere and will now forever remain in the sedimentary record — like the layer of iridium, an unmistakable marker for future geologists.
But only recently, this date has been challenged. A new research paper published in Nature, “Defining the Anthropocene,” proposes nine possible dates and argues strongly for two: 1610 and 1964.
The authors say the arrival of Europeans in the Americas in the 1500s sparked a global upheaval of species such as maize, corn, rice and potatoes jumping between continents. Diseases brought by Europeans killed as many as 50 million people in the Americas. Tropical forests then replaced abandoned agricultural land, drawing in more carbon dioxide from the atmosphere. Carbon dioxide reached a low in 1610 — clearly visible in ice core records.
The year 1964, marks the peak in radioactive carbon due to nuclear testing, which had been building since 1945. After this date, the Nuclear Test Ban Treaty, signed in 1963, caused levels to decline sharply.
The Great Acceleration
As we leave the Holocene behind, our impact on the planet is growing, in what a team of Earth-system scientists has described as the Great Acceleration. To continue on this trajectory unchecked is an uncontrolled experiment that risks the stability of the Earth’s natural systems.
In 2009, Johan Rockström from the Stockholm Resilience Centre, with Will Steffen, led a group of scientists who analyzed the conditions that keep the Earth system stable enough for a global population. They identified nine planetary boundaries that would be unwise to cross. More worryingly, they announced that we’d already overstepped three: climate, biodiversity and biogeochemical flows, or fertilizers. We have entered a zone of high risk.
Intrigued to see if the trajectory of the Great Acceleration had changed in the decade since their first publication, Steffen and co-authors (including myself) recently updated the indicators to 2010, in The Anthropocene Review (1/16/15).
While most indicators (above) are on an alarming trajectory, two provide some reason for hope.
Following a worldwide ban on the manmade chemicals called chlorofluorocarbons (CFCs) that destroy ozone, there’s now a visible stabilization of the Antarctic ozone hole. This is a result of the most successful international environmental policy change in history.
We are also on track for Earth’s human population to start stabilizing soon. After a truly astounding period of growth, the number of children in the world has stopped growing.
Other indicators are more worrying. Marine fish captures are leveling off — not because we have stopped overfishing, but because we are running out of fish to catch. Consumption and production in wealthy nations continues to rise, and is now a greater concern than population growth. From deforestation to fossil-fuel use, consumption is driving the most significant changes.
On the same day that their “Great Acceleration” update was published, Steffen, Rockström, and their colleagues also updated the Planetary Boundaries research in the journal Science (see illustration, below). In their article, they announced that a fourth red line — deforestation — has now been crossed. The news made headlines around the world, and for good reason: With every passing year, we humans are degrading the only known safe operating space for our species.
Welcome to the Anthropocene
Formal acceptance of the Anthropocene concept by geologists could have far-reaching cultural, political, economic, and legal implications.
Artists and musicians are already using the concept to frame their work. The Berlin Campus last November was designed to develop a university curriculum on the Anthropocene that stretches beyond the narrow field of stratigraphy and into the social sciences and humanities, including law, political science, architecture, urban planning, and history.
Politically, resource distribution is the foundation of both dominant political ideologies, left (share) and right (hoard). But this divide was built on an assumption that the Earth’s resources are unlimited. The Anthropocene challenges these assumptions.
Economically, consumption and production without thought for the stability of Earth’s life support system now seems foolish, given our new knowledge. Moreover, economists calculate how goods are valued in the future by assuming a steady decrease in value as time passes. This model is deeply flawed: the cost to future generations of destabilizing the Earth system will be monumental.
If the Anthropocene is recognized internationally, say by the United Nations, the golden spike may become a legal battleground because it sets a marker for accountability. If the Neolithic period is chosen as the boundary, responsibility for adverse consequences would be assigned more broadly than if 1964 is the start date. But it is worth remembering the “Great Acceleration” has brought benefits to many, not least in education, health, and poverty alleviation.
As we wait for the Geological Time Scale to be amended, the current year, 2015, is important for the future narrative of humanity.
In September the United Nations General Assembly will agree on a set of universal Sustainable Development Goals — applying to all nations — to supersede the Millennium Development Goals that were established in 2000. And in December, nations of the world will meet in Paris to seal a new global agreement on climate change. These new agreements must reflect the responsibility we all share in the Anthropocene — for the direction that life on Earth will now take.
At the global level, these meetings offer a once-in-a-generation opportunity to change course. But to succeed, the global narrative must translate on the ground, in the world of ordinary people that Paul Salopek is describing, one step at a time, in his Out of Eden Walk.
As Paul works his way across the globe, he is in a unique position to report on how our species is coping with this new age, the Anthropocene.
While we — Homo sapiens, the sometimes-wise ape — have traveled far, we did not travel together, nor take the same route. But we’re all in the same boat now.
*Crutzen concluded that Earth had now entered the Anthropocene at a scientific meeting in 2000. US biologist Eugene Stoermer had been using the term informally in lectures since the 1980s. Crutzen and Stoermer co-authored the first article on the subject later in 2000.
Owen Gaffney is a writer for Future Earth and director of international media and strategy at the Stockholm Resilience Centre. He is a journalist with a background in astronautic engineering and has spent a decade writing about global change, the Earth system, and international policy.