How man has tipped Earth into a new epoch

THE world may not feel any different, but – for the first time in more than 11,500 years – we are living in a new epoch, scientists believe.

Our impact on the planet has now become so significant that it has pushed us into the Anthropocene epoch, meaning that human activity is now the dominant influence on climate and the environment.

This has been caused by the rapid industrialisation of the past century, including the worldwide spread of plastics, metals and concrete, combined with manmade climate change, say an international team of researchers.

They believe that the recent changes to global systems are sufficiently simultaneous and significant to justify the adoption of a new geological time unit that takes over from the Holocene ep- och, which began around 9,700 BC. The Working Group on the Anthropocene (AWG), meeting in Cape Town this week, wants the starting date for the new epoch to be set around 1950.

The group’s committee of 35 members voted by a majority of 20 to recognise the new time division as an epoch, rather than a new subdivision of the Holocene epoch. The largest unit in the geological time scale is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs and ages. We are currently living in the Quaternary period of the Cenozoic era.

The search is now on to find what geologists call a “golden spike”, a physical reference point that can be dated and taken as a representative starting point for the Anthropocene epoch.

A river bed in Scotland, for example, is taken to be the representative start- ing point for the Holocene epoch, which is translated as “recent” and defined as beginning when glaciers began to retreat from the most recent ice age. Prof Jan Zalasiewicz, a palaeobiologist at the University of Leicester and a member of the working group, said carbon and nitrogen levels in the at- mosphere had remained reasonably steady before the “great acceleration” of the 20th century.

“Human action has certainly left traces on the earth for thousands of years,” he said. “The difference between that and what has happened in the last century or so is that the impact is global and taking place at pretty much the same time across the whole Earth. It is affecting the functioning of the whole earth system.”

The concept of an Anthropocene epoch was first proposed by Nobel-prize winning chemist Paul Crutzen and colleague Eugene Stoermer in 2000. This week’s AWG vote is scientific endorsement that the epoch is geologically real and of a sufficient scale to be considered for formal adoption as part of the International Chronostratigraphic Chart.

Prof Colin Waters, principal geologist at the British Geological Survey and AWG secretary, said: “Being able to pinpoint an interval of time is saying something about how we have had an incredible impact on the environment of our planet. The concept of the Anthropocene pulls all these ideas of environmental change together.”

Changes to the Earth system which characterise the potential Anthropocene epoch include the presence of plastic and aluminium particles and high levels of nitrogen and phosphates in soils, as well as “large-scale chemical perturbations to the cycles of carbon and nitrogen”, according to the AWG.

Once one or more candidate sites have been selected, a proposal for the formal recognition of an Anthropocene epoch will be made to a series of commissions, culminating in the Executive Committee of the International Union of Geological Sciences. The process is likely to take at least three years.