Welcome to the Anthropocene: Humankind's layer on the Earth


TokyoWelcome to the Anthropocene. Man’s impact on the planet is now believed to be so great geologist are considering creating a new geological epoch. What factors are driving such a substantial impact on the planet? What will cause the geological record to mark our presence? If we are in the Anthropocene, when did it begin?

According to Elizabeth Kolbert writing in the March issue of National Geographic, Paul Crutzen coined the term “anthropocene” while attending a scientific conference. When the chairman kept using the term Holocene to describe the current epoch, Crutzen exclaimed “'Let's stop it, we are no longer in the Holocene. We are in the Anthropocene.' Well, it was quiet in the room for a while." That quiet has since led to a lot of thinking and scientists now considering the possibility that a new geological epoch has begun.

Stratigraphers are geologists that study the Earth's strata, the layers you can see at a roadside cut. Kolbert observes:

Stratigraphers … take the long view—the extremely long view—of events, only the most violent of which are likely to leave behind clear, lasting signals. It's those events that mark the crucial episodes in the planet's 4.5-billion-year story, the turning points that divide it into comprehensible chapters.

So it's disconcerting to learn that many stratigraphers have come to believe that we are such an event—that human beings have so altered the planet in just the past century or two that we've ushered in a new epoch: the Anthropocene. The record of our impact leaving “may look as sudden and profound as that of an asteroid”

If we are depositing Earth’s latest layer, what will the layer consist of when studied in the future? A number of possibilities have been suggested:

  • Cities - Not likely. These may only leave “transient” marks on the geological record.
  • Farming - Agriculture now covers about “38 percent of the planet's ice-free land.” However, its impact may be hard to detect and is more likely to come “from the pollen record—from the monochrome stretches of corn, wheat, and soy pollen that will have replaced the varied record left behind by rain forests or prairies.”
  • “Massive” soil erosion - May be hard to detect since dams “are holding back sediment that would otherwise be washed to sea.”
  • Destruction of forests - “Loss of forest habitat is a major cause of extinctions, which are now happening at a rate hundreds or even thousands of times higher than during most of the past half billion years.”
  • Alteration of the atmosphere - Kolbert notes that alteration in the composition of the atmosphere is “probably the most significant change, from a geologic perspective” and “could push global temperatures to levels that have not been seen for millions of years.” "The consequences of burning billions of tons' worth of coal and oil are likely to be clearly discernible." As our oceans are acidified, coral reefs will disappear.  This “reef gap” will be visible as are the ones that “marked each of the past five major mass extinctions.”

When did the proposed Anthropocene begin? Was it during the agricultural revolution when Homo sapiens began to increase the CO2 content of the atmosphere? Or, during the late 18th century when “carbon dioxide levels began what has since proved to be an uninterrupted rise.” Or, in “the middle of the 20th century, when the rates of both population growth and consumption accelerated rapidly.” Kolbert also notes:

Some scientists argue that we've not yet reached the start of the Anthropocene—not because we haven't had a dramatic impact on the planet, but because the next several decades are likely to prove even more stratigraphically significant than the past few centuries.

Over the next few years, the International Commission on Stratigraphy (ICS) will be debating whether to officially name our current epoch the Anthropocene, and if so, when it began. Whether it started 10,000 years ago, or is just about to start, humankind is changing the planet dramatically and in a short geological timeframe. Future geologists will see our mark in those stripes of stone we see in roadside cuts or in the mountains as we travel our fair planet. 

Source: Enter the Anthropocene—Age of Man. Elizabeth Kolbert, National Geographic, March 2011.