by Adam Frank
About 12,000 years ago (give or take a thousand) the glaciers covering much of the northern hemisphere disappeared and an ice age gripping the Earth ended. The planet became warmer, wetter and entered the geological era scientists call the Holocene. Marked by a stable climate, the Holocene has been good to humans. The entire history of our civilization (agriculture, city building, writing etc.) is bound within the Holocene and its bounty of productive land and oceans.
Now, it appears, the Holocene is over.
Recently The Economist reported on a radical idea that has been floating around in the geological community for last few years: we are entering a new era in the history of the planet dominated by human “forcing.” As the article aptly puts it: “Welcome to the Anthropocene.”
I’ve been introducing the Anthropocene concept for the last few years in my “Astrophysics of Planets” course. It such a deep perspective-shift that it always soaks up an entire class-hour’s worth of discussion.
The first point to absorb is that there are no politics in the designation. It is neither a value judgment nor a critique. Instead, it is simply a recognition that human activity has now come to be the most significant “forcing” driving the various interlocking systems that define the current “state” of the planet.
Scientists digging through sediments millions of years from now should easily be able to identify the transition from the Holocene to the Anthropocene. From the fossilized remains of our cities to changes in the carbonate content in sea-floor sedimentation, the Anthropocene may appear as clearly to future scientists as the Cretaceous appears to us.
And before we begin the usual tired argument about climate change, it’s important to understand that climate is just one part of this transition. Along with unintentional changes in the carbon-cycle, humans have also intentionally altered the nitrogen-cycle as well. With the invention of the Haber process we figured out how to extract more nitrogen from the atmosphere and use it to create fertilizer to grow more plants. The dead zones increasingly common in costal regions where algae blooms feed off fertilizer-rich run-off are one result of an epic alteration of the planet’s nitrogen cycle. The presence of so many of us eating all that fertilized food is another.
To see how recognition of the Anthropocene is relatively free of politics, consider the responses various communities have had to the concept. For some the advent of the Anthropocene is recognition of our greed and ignorance. With the birth of industrialization we failed to recognize the forces we were unbalancing and now a planet “tipped” into another, perhaps harsher, regime relative to human habitation is the fate awaiting us. For others our entry into the Anthropocene is the ultimate acknowledgement of our privileged status in the hierarchy life. It was exactly through the intelligence that forged industry that this planet was shaped in our image. In response, it will be through intelligence that we will engineer our way through the Anthropocene to a planet that can handle our ever-growing numbers.
Thus one response sees the Anthropocene as the advent of an eco-apocalypse. It is a disaster that can only be averted through a draw down of the technologies that brought us here and the development of smaller scale human footprints on the planet.
The other response sees global-scale technological responses as the only effective solution. “Geo-engineering” projects — such as altering the chemistry of the oceans to increase carbon uptake — represent one proposed mechanism to a human friendly Anthropocene (with genetic engineering perhaps designing new forms of carbon eating algae).
Regardless of your philosophy, the recognition that we have entered a geologic age of humanity raises the obvious question of just how long such an age will last.
In the infamous KT boundary geologists can see evidence for a rather short-lived event that also reshaped the planet. Sixty five million years ago an asteroid struck the Earth, driving one of only five mass extinctions in the planet’s history. The loss of the dinosaurs turned out to be an opportunity for our mammal ancestors and led directly to our own age.
Since the Anthropocene appears to mark a sixth great extinction, one has to wonder what it will take for us to make it out of own era with civilization intact.