Which brings us to the idea of an Anthropocene – a proposed division of geologic time defined by signs of human activities in the geologic record. If human activities can be associated with divisions of geologic time – as was done for the Meghalayan – and we define geologic time based on various characteristics in rocks, then what to make of the inescapable imprint of human activities in the rock record?
There are good arguments to be made both for and against an Anthropocene.
Human beings have clearly altered landscapes through deforestation, agriculture and industrialization, which among other things have accelerated erosion and sediment accumulation. Plastics are accumulating in our oceans and biosphere, leaving a global-scale marker of these synthetic materials in soils and sediments. People are causing high extinction rates and rapid changes in where species are found around the world. And of course burning fossil fuels and human-induced climate change leave signatures in sediment records worldwide.
But to date, the International Commission on Stratigraphy has not approved the designation of an Anthropocene. One challenge is agreeing on when the Anthropocene should begin. While things such as plastics or carbon dioxide from fossil fuels are geologically recent, human impacts on landscapes, biodiversity and biogeography may extend back thousands of years. It is very hard to pinpoint the first moment in time when our species began to affect the Earth.
The new divisions of the Holocene also cut into the available time for an Anthropocene. The Meghalayan begins 4,200 years ago and continues to the present. Simply put, there is no time left over in the Holocene where we could put an Anthropocene.
For the Anthropocene to be included in the formal geologic time scale, stratigraphers will need to argue that its onset was global in scale, simultaneous around the world and significant in its imprint on the geologic record.
Or maybe these types of formal requirements no longer apply. As scientists recognize that humans are now part of stratigraphy, perhaps we need to rethink our criteria in a way that separates geologic time from human time./>
Steve Petsch, Associate Professor of Geosciences, University of Massachusetts Amherst This article is republished from The Conversation under a Creative Commons license. Read the original article.