Leaving our mark: Industrialisation and habitat destruction are just some of the ways we're leaving a significant signature in the stratigraphic record.
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SYDNEY: Man's impact upon the Earth has been so profound that it warrants the formal designation of a new geological epoch, say scientists.
"You can't have 6.5 billion people living on a planet the size of ours and exploiting every possible resource, without huge changes in the physical, chemical and biological environment," said Andrew Gale of the Stratigraphy Commission of the Geological Society of London in England.
Patterns in the rocks
It is the documentation of these changes in the geological record that Gale and 20 other experts have collated into a report, published in the journal GSA Today. The paper makes the first formal case for the recognition of the new epoch, the Anthropocene, which has been used casually by earth scientists since 2002.
Divisions of time over geological history are based upon distinct changes observed in rock and soil strata. For example, the end of the Cretaceous Period (from 145 to 65 million years ago) is marked by evidence of an asteroid collision, including a layer of the rare element iridium.
Though changes in the geological record brought about by man may not be as violent as those from an asteroid, our impression on the geological record has already been massive in its own way, the authors said.
They looked for markers of a boundary point between the Anthropocene and the Holocene, the epoch we still officially reside in, using the same criteria used to distinguish other epochs. These include variations in sedimentary rocks caused by ancient changes in climate.
They found that human activities, such as construction and damming, have led to noticeable changes in the Earth's landforms, including increased erosion, which serves as one distinct signal of the new epoch. The mark of man was also stamped in increased carbon dioxide and methane levels, together with an overall rise in global temperature, predicted to rise by 1.1°C to 6.4°C by the end of this century.
"Drawing a new line"
In addition, the oceans are being altered, the report found. Further acidification could stop coral reefs from growing and halt the deposition of reef limestone, which will also be evidenced in the fossil record, it said.
Together, the evidence collected in the report may help the International Commission on Stratigraphy, the body responsible for the formal establishment of the stratigraphic scale, in approving the addition of the Anthropocene to the geological timescale.
The evidence is a clear sign that we've entered a new era of the planet's history, commented geologist Richard Alley of Pennsylvania State University in the U.S., who was not one of the study's authors.
"In land, water, air, ice, and ecosystems, the human impact is clear, large, and growing," said Alley. "A geologist from the far distant future almost surely would draw a new line, and begin using a new name, where and when our impacts show up."
Human Impact on the Planet
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