Wednesday, May 16, 2012

Would It Matter Where You Placed The Anthropocene?

I have been listening to an absolutely riveting series of talks hosted at Generation Anthropocene. This is a project dreamed up by young Stanford University researchers and it involves interviewing scientists working on the broad theme of human impact on ecology and environment and consequentially the question of whether there is now a case to be made for defining a new geologic epoch called the Anthropocene.

The answers to where one would place the Holocene-Anthropocene boundary usually converges to either the beginning of Agriculture or the Industrial Revolution because both involve big changes to various aspects of the earth's environment. While these two, especially the Industrial Revolution, came through as a strong candidate, the most thought provoking answer was given by ... well off course .. a geologist... Jon Payne.

He suggested we take a methodological approach and understand how geological boundaries are defined. There has to be a distinctively recognizable sedimentary section which contains evidence of a faunal break i.e. a change in the earth's biota marked by the extinction of some species or the appearance of some new species.  We subdivide geologic time by recognizing that there has been some change in the earth's biota. Looking way back in the earth's past, sedimentary sections containing these transitions cover time periods well beyond the human time scale i.e. the sedimentary layers may represent a time passage of thousands of years.

Sediments usually accumulate in layers quite slowly over time periods longer than the scale of historical events. So, taking a long view, choosing as the beginning of the Anthropocene either the Industrial Revolution or World War II  won't matter, since all these events will collapse as one instance of sediment deposition. A geologist looking back several million years from now won't be able to discriminate events that took place a few tens of years apart.

In my opinion that doesn't make the concept of Anthropocene a useless exercise. For example, the boundary between the Pleistocene and the Holocene is defined by the disappearance of two foraminifera species and is dated as 10,000 BP radiocarbon years. These events mark a passage of few tens of years. Similarly,  today there would be sediment accumulating in a lake or a quiet deep sea that contains very thin layers that mark a sudden rise in a geochemical indicator of the Industrial Revolution or some other human activity.

We may mark that as a beginning of Anthropocene today. These deposits may even get preserved into the geological future. It's just that millions of years from now absolute dating methods like carbon14 that may discriminate events on the order of few tens of years will be useless on these deposits and the error bar on the dates obtained for these rocks will be on the order of hundreds to thousands of years. As a physical entity, the boundary in deep future may be recognizable as a sedimentary layer marking the disappearance of a significant number of species, although correlating that boundary with a specific historical event may not be possible.

Other talks that I liked were by Jon Christensen who talked about the myth of the American Frontier, Rodolfo Dirzo who talked about tropical biodiversity and Doug Bird who spoke about the native Martu peoples of Australia and their history of landscape management.

One refreshing aspect of these talks are that the hosts are all graduate students. What an opportunity to have an extended chat with your intellectual mentors and find inspiration in their work.

And who knows... start thinking of a career in science journalism.

Highly highly recommended.

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