Anthropocene, a man-made geologic epoch


“Archean to Anthropocene, the past is the key to the future” is the theme of the annual meeting of the Geological Society of America to be held in Minnesota in October 2011. Anthropocene is not part of the geological timescale; it’s the name of a new epoch and is yet to be formally adopted by the International Commission on Stratigraphy. The concept of Anthropocene, proposed in 2000 by Nobel Laureate Paul J. Crutzen, brings into focus the several human activities that have adversely impacted and caused irreversible damage to more than half of the earth’s ice-free landmass.

It also stands to represent the indelible imprint left behind by man on many natural systems. The global concentration of carbon dioxide, coinciding with the advent of the industrial revolution, marks the beginning of the new epoch. Large-scale conversion of forests into cropland and the lethal combination of industrial revolution and fossil fuel use have led to a sudden increase in carbon dioxide and other environmentally harmful gases in the atmosphere.

The increase in CO2 has happened despite the presence of many natural buffering systems — and in an extraordinarily brief geological time frame. The increased levels of the greenhouse gas have caused a cascading effect: the global mean temperature has gone up by 1°C during the last century, and will probably keep rising. The oceans, which act as carbon sinks, have turned acidic by absorbing more carbon. But the expected rise in acidity by 0.3-0.4 pH by the end of this century may affect corals and dissolve the carbonated shells of many marine organisms. Nearly 20 per cent of the species found in large areas are invasive, and the disappearance of many species has certain markings of large-scale extinction.

The current epoch — Holocene — is just about 11,500 years old. Epochs typically extend for many million years, and the beginning is defined as changes preserved in the rocks. Since the epoch-changing events by humans have taken place at an astonishingly accelerated rate, the rocks may not have registered them.

But the chemical and biological changes unleashed by humans are set to have a long-lasting effect on the environment and ecology. They are bound to leave their footprints on the rocks even if the man’s destructive activities were to end tomorrow.

Anthropocene, if it is formally accepted, will probably be called an ‘age,’ a subunit of an epoch. But the concept is powerful: it can bring about radical changes in the mindset of scientists and policymakers in understanding the effects of human-nature interactions.

Published in The Hindu on July 6, 2011