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Force of man

Geologists claim man is taking over as a force of nature in new epoch

A COPERNICAN MOMENT

Human impact on Earth is so profound that humans should be seen as a geological force. This is the conclusion that an international working group of geologists presented at the International Geological Congress in Cape Town earlier this fall. After seven years of deliberation, they now say that the current Holocene Epoch we are living in — and have been for the last 12,000 years — should be replaced by a new Epoch. The new proposed time period is called The Anthropocene, or the age of man.” FORESIGHT talked to professor Colin Waters of University of Leicester, who is the secretary of the Anthropocene Working Group that proposed this move.

Q: What is the most important evidence supporting the notion of the Anthropocene?
The important aspect of the Anthropocene concept is that there are a host of key environmental signals that show a broad coincidence of environmental changes. These are witnessed in sediments, glacial ice, corals and trees, even cave deposits, all happening during the mid-20th century — not just one signal. If we look at novel materials, we could identify the appearance of plastics and aluminium in geological successions and a significant increase in the abundance of black carbon and fuel ash (from fossil fuel combustion), nitrogen (twice the abundance a century ago), carbon dioxide (a third higher than during pre-industrial times), methane (double pre-industrial concentrations), radionuclides from atmospheric fallout (plutonium and radiocarbon are good markers) and homogenisation of animal and plant species across the globe. This is partly due to invasive species and partly through transfer of functional species, such as crops and domesticated animals.

Q: The working group has given a very clear recommendation to the International Geological Congress to adopt the Anthropocene as a new Epoch. What is the process from here?
Firstly, the Anthropocene Working Group will need to formulate a formal proposal, published in a peer-reviewed journal. This will require our review and selection of potential Global Boundary Stratotype Section or Point (commonly known as Golden Spike”) showing how the primary and secondary signals range through the succession, and particularly across the boundary that will be chosen to mark the base of the Anthropocene. When completed, we would submit the proposal to the Subcommission on Quaternary Stratigraphy (SQS). The SQS membership must vote on the proposal, and if positive (a supermajority of 60% or more in favour) it would then go to the International Commission on Stratigraphy to vote. Again, if positive, the issue goes to International Union of Geological Sciences who either ratify the proposal, send it back for more work, or reject it altogether.

Q: When do you think we will have to rewrite our geological textbooks?
Typically, for other parts of the geological column this process can take decades. However, we are initially looking at two to three years to make a decision on the environmental signal that should be used for the formal definition. But we would hope to carry out analysis of many signals within a small number of sections in different environments in various parts of the planet. This would show how the signals can be correlated globally. Once we have formulated our proposal, the official route of ratification is also a slow process. Importantly, there is no advantage to submitting a proposal too early, so it shouldn’t be time constrained. •

TEXT Peter Bjerregaard

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