By Marci Wills, April 4, 2010
Get out your party hats, because we may soon be welcoming in a new geologic epoch! Some scientists believe that humanity has affected the Earth so drastically over the past two centuries that changes may be significant enough to mark a new age of geologic time. Last week, earth scientists Jan Zalaseiwicz, Mark Williams (University of Leicester, UK), Will Steffen (Australian National University, Canberra), and Paul Crutzen (Max-Planck-Institute for Chemistry, Mainz, Germany) formally made the case for the addition of the “Anthropocene Epoch” to the Geologic Time Scale in the American Chemical Society’s journal, Environmental Science and Technology. More importantly, they warn that the Anthropocene could be accompanied by Earth’s next great mass extinction.
The Geologic Time Scale partitions 4.57 billion years of Earth’s history into four eras which contain shorter periods (For example, the Mesozoic era includes the Triassic, Jurassic, Cretaceous periods) and even finer epochs. Currently we live in the Holocene epoch which began ~11,000 years ago with the end of the most recent ice age.
Transitions between major divisions on the time scale are marked by observable changes in the sedimentary record worldwide. Usually, these are associated with upheavals in the planet’s climate and biodiversity. In their paper last week, the four scientists argue that “The scale of change taken place so far, or that is imminent or unavoidable, appears to have already taken the Earth out of the envelope of conditions and properties that mark the Holocene Epoch”
In addition to widely recognized changes in atmospheric composition, global temperature rise, melting polar ice, and rising sea levels, the study argues that many other human-induced effects are plainly visible on the Planet. Humans have brought about an order of magnitude increase in worldwide erosion rates, and the Anthropocene can be recognized by a variety of human-made sediment layers; the concrete of our roads and cities, the soils of our fields, and the polluted muds of estuaries, to name a few.
Most importantly, these scientists suspect that the Anthropocene may coincide with the world’s 6th mass-extinction event. Already, current extinction rates are estimated to be 100 to 1000 times greater than the normal background level and another 10-fold increase is expected this century.
The geologic time scale is overseen by multiple governing bodies under the International Union of Geological Sciences, all which will have to be convinced before “The Anthropocene” is officially adopted. But according to these four researchers, “However these debates unfold, the Anthropocene represents a new phase in the history of both humankind and of the Earth, when natural forces and human forces become intertwined, so that the fate of one determines the fate of the other. Geologically, this is a remarkable episode in the history of the planet”
Zalasiewicz, J., Williams, M., Steffen, W., Crutzen, P., 2010, The new world of the Anthropocene: Environmental Science and Technology, v. 44, p. 2228-2231.