Radioactive carbon locked in ‘loneliest tree’ pinpoints new human era

19 Feb 2018

Carbon-14 found in the rings of the ‘loneliest tree’ reveals the dawn of the newest human era. Image: lcrms/Shutterstock

The so-called loneliest tree in the world is helping to reveal when exactly humans began to shape our planet’s climate.

In one of the most remote parts of the world, a single tree is helping to shed light on the answer to a single question: what year marks the ‘golden spike’ of the latest human era, referred to as the Anthropocene epoch?

This period of time is considered a massive acceleration not only in the technological development we have experienced, but in what effect we have had on the planet as a whole.

According to the BBC, because of the isolation and location of this Sitka spruce tree in Campbell Island, New Zealand, on the southern hemisphere away from much human activity, it can help find the golden spike that indicates when this era started.

This history of the tree is interesting in itself because it is most definitely not native to the region, having been planted there in 1905, possibly as the starting point of a whole new plantation, and it is now the only tree in an area spanning 200km.

The nuclear option

In a paper published to Scientific Reports, the research team led by the University of New South Wales, Australia, found that a drilled core sample of the tree showed a doubling of the amount of carbon-14 in an area of the ring identified as being around in 1965.

The reason for this sudden spike in the radioactive isotope is no coincidence because it marks an important moment in the era of nuclear weapon testing during the Cold War between the US and the former Soviet Union.

Two years after the signing of a ban on atmospheric nuclear testing, the rings show it was too late to prevent the global spread of radioactive fallout.

This isotope would have eventually entered the tree through carbon dioxide absorbed as part of photosynthesis, leaving its legacy deep within its trunk.

The perfect record

“If you want to represent the Anthropocene with the start of ‘The Great Acceleration’, then this is the perfect record to define it,” said Mark Maslin, a co-author of the paper from University College London, who also worked on the project.

“And what’s really nice is that we planted a tree where it shouldn’t be, which has then given us this beautiful record of what we’ve done to the planet.”

With this new data, the international geological community will spend some time to decide on how best to update the timeline of human history portrayed by the Chronostratigraphic Chart.

Once updated, it will become the newest period in human history after the 11,700-year-old Holocene era.

Colm Gorey was a senior journalist with Silicon Republic