Scientists have been debating the concept of the Anthropocene — a proposed new epoch in Earth’s history with humans acting as the key drivers of geological and environmental change — for decades, but failing to adopt if officially due to the inability to pinpoint the exact global “signal” which could be detected in the forming geological substratum of the Earth.
Now, a new paper recently published in the journal Scientific Reports by members of the Australian Antarctic Expedition 2013-2014 suggests the exact date to stand between October and December 1965.
The suggestion is based on the discovery of a “golden spike” in the heartwood of the “world’s loneliest tree” — the Sitka Spruce of Campbell Island, located in the middle of the Southern Ocean. The next closest tree is found over 200 km away on the Auckland Islands.
The Sitka Spruce normally grows along the North American Pacific Coast, but in this case it was allegedly brought and planted on the Campbell Island by the Governor of New Zealand in 1901.
Crucially, the radioactive carbon spike was created by the culmination of atmospheric thermonuclear bomb tests in the Northern Hemisphere, which then drifted across the planet and was fixed in the wood of the Campbell Island Sitka Spruce by photosynthesis.
“The global atomic bomb signal, captured in the annual rings of this invasive tree species, represents a line in the sand, after which our collective actions have stamped an indelible mark, which will define this new geological epoch for generations to come,” said co-author on the study Professor Christopher Fogwill of Keele University.
In the Northern Hemisphere, the so-called “golden spike” occurred in 1964 where it was preserved in European trees. Then, over the course of roughly a year, it travelled south and found its way into the “bones” of the Campbell Island Spruce, thereby marking the signal of the Anthropocene becoming global.
“Thousands of years from now this golden spike should still stand as a detectable marker for the transformation of the Earth by humankind,” said lead author on the paper Professor Chris Turney of the University of New South Wales.
While the iconic tree itself remains in a permanent juvenile state — it has never produced cones — it could very well become the symbol of a new epoch where no part of the planet is left untouched by human endeavours.