A group of scientists says that the scope of human impact on planet Earth is so great that the "Anthropocene" warrants a formal place the Geological Time Scale.
"Our findings suggest that the Anthropocene should follow on from the Holocene Epoch that has seen 11.7 thousand years of relative environmental stability, since the retreat of the last Ice Age, as we enter a more unstable and rapidly evolving phase of our planet's history," said Professor Jan Zalasiewicz from the University of Leicester’s School of Geography, Geology, and the Environment, in a statement released Monday.
The scientsts write:
We conclude that human impact has now grown to the point that it has changed the course of Earth history by at least many millennia, in terms of the anticipated long-term climate effects (e.g. postponement of the next glacial maximum: see Ganopolski et al., 2016; Clark et al., 2016), and in terms of the extensive and ongoing transformation of the biota, including a geologically unprecedented phase of human-mediated species invasions, and by species extinctions which are accelerating (Williams et al., 2015, 2016).
Defining characteristics of the period include
marked acceleration of rates of erosion and sedimentation; large-scale chemical perturbations to the cycles of carbon, nitrogen, phosphorus and other elements; the inception of significant change in global climate and sea level; and biotic changes including unprecedented levels of species invasions across the Earth. Many of these changes are geologically long-lasting, and some are effectively irreversible.
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The findings from the international team led by the University of Leicester were presented last year at the International Geological Congress at Cape Town, South Africa, but were just published online in the journal Anthropocene.
Use of the word coined by Nobel Prize-winning scientist Paul Crutzen in 2000 is not new, but so far it's been merely an informal description of the time period when human activity started significantly altering the planet. The Anthropocene Working Group (AWG), which comprises experts from a range of fields, has been tackling the issue of whether it should be a formal declaration since 2009.
According to the group, the answer is clear: the Anthropocene is real; it should be formalized; and it should be defined as an epoch (rather than another classification such as a sub-age or era). The group suggested that the new epoch's "golden spike" (or physical reference point) that marks its start is the plutonium fallout from nuclear weapons tests in the 1950s.
Going forward, they write, it seems likely that "human impacts will become increasingly significant."
Getting the formal classification is not a done deal, as more analysis is needed, and a stamp of approval from the International Commission of Stratigraphy (ICS) could be years off. Still, says honorary chair of AWG, Colin Waters of the Geology Depart of the University of Leicister, "Whatever decision is ultimately made, the geological reality of the Anthropocene is now clear."