When did the Anthropocene begin?

Image by Craig Mayhew and Robert Simmon (source NASA Goddard Photo and Video/Flickr)

The profound impact of human activity has motivated a concept that has been slowly emerging in science: human activities are a significant geological force.  In 1873,  Antonio Stoppani, an Italian Catholic priest and geologist, coined the “Anthropozoic era” to identify  the increasing power and impact of humanity on the Earth’s systems. Few years later, Joseph LeConte in 1879 proposed the term Psychozoic to describe the same phenomenon,  in 1922 Pavlov used the word Anthropogene, and Vernadsky in 1962 used  the term Noosphere. In 2000 Paul Crutzen – during a meeting of the International Geosphere-Biosphere Programme (IGBP) in Mexico – proposed use the term Anthropocene to designate the last two hundred years of human history and to mark the end of the current Holocene geological epoch. He and Stoermer placed the beginning of the Anthropocene at A.D. 1750–1800, when the Greenland ice cores registered a dramatic increase of carbon dioxide and methane.

Alternative temporal boundaries for the Holocene–Anthropocene boundary (calibrated in thousand of years before present) From Smith 2013

Ruddiman and Thomson (2001) argued that before the industrial revolution, human societies had a great influence on the earth’s atmosphere. They identified the inefficient wet rice agriculture as the most plausible source of increased anthropogenic methane input to the atmosphere while the rise in CO2 is attributed to the expansion of agricultural landscapes, almost 8000 years ago.

But other scientists pushed the boundary thousand of years before, like Christopher Doughty. He proposed in 2010 that the increase in Birch (Betula) pollen almost 14000 years ago reduced the reflectivity of the land surface causing a regional warming of 1º C. This phenomenon was associated with the disappearance of megafauna and because the extinction of mammoths is  linked to human predation, “human influence on global climate predate the origin of agriculture” (Doughty et al., 2010)

In 2011, Giacomo Certini and Riccardo Scalenghe  used soils to identifying the base of the Anthropocene in stratigraphic sequences, but this method was questioned due to the poor preservation potential of soils. And in an interview in 2012, Eugene Stoermer considered that the geological mark for the Anthropocene was the isotopic signature of the first atomic bomb tests.

Because the different start dates for the Anthropocene a consensus solution to establishing its lower boundary was proposed: “The Holocene and Anthropocene epochs could on practical terms be merged into the Holocene/Anthropocene epoch, easily and efficiently encompassing 10,000 years of human modification of the earth’s biosphere” (Ellis, 2013).

References:

Smith, B.D., Zeder, M.A., The onset of the Anthropocene. Anthropocene (2013), http://dx.doi.org/10.1016/j.ancene.2013.05.001

Ellis, E.C., 2011. Anthropogenic transformation of the terrestrial biosphere. Philosophical Transactions of the Royal Society A 369, 1010–1035.

Link:

The Anthropocene: Humankind as a Turning Point for Earth http://www.astrobio.net/interview/5530/the-anthropocene-humankind-as-a-turning-point-for-earth