It is regarded as the “loneliest tree in the world” but the Sitka spruce on uninhabited Campbell Island has been keeping good company of late – with a team of New Zealand researchers who believe it could help unlock climate change secrets.
The nine-metre tall spruce holds the Guinness World Record title for the “remotest tree” on the planet. It is the sole tree on the shrubby, windswept island, 700 kilometres south of New Zealand in the Southern Ocean. It’s the only tree for 222km around; its nearest neighbour grows on the Auckland Islands.
Prior to the Campbell Island spruce, the Tree of Ténéré in Niger was said to be the most isolated tree on the planet, until it was killed by a driver in 1973.
It is believed the Sitka spruce was planted by Lord Ranfurly, New Zealand’s then governor, in the early 1900s – hence its nickname the Ranfurly tree.
Studies have not been able to confirm its exact age, however, and Guinness World Records notes that although it is popularly referred to as the world’s loneliest tree, “there is no universally recognised precise definition of what constitutes a ‘tree’”.
It is also classified as an invasive species and some scientists would be happy to see it go. But for radiocarbon science leader at GNS Science, Dr Jocelyn Turnbull, the tree could be a valuable tool to understand what is happening with the uptake of carbon dioxide in the Southern Ocean.
“Of the CO2 that we produce from burning fossil fuels and put into the atmosphere, only about half stays there and the other half goes into the land and the ocean,” Turnbull said.
“It turns out the Southern Ocean – one of those carbon sinks – has taken up about 10% of all of the emissions that we have produced over the last 150 years.”
Turnbull has been working with New Zealand’s Deep South National Science Challenge, the Antarctic Science Platform and the National Institute for Water and Atmospherics to understand what is happening to carbon in the Southern Ocean.
The teams are asking two major questions: if the carbon sinks “fill up”, will it cause a massive acceleration of global warming? Or, by learning how they work, can these sinks be helped to take up even more carbon and reduce global warming?
Previous studies looking at the Southern Ocean’s uptake of carbon have produced conflicting results; the current theory is that the uptake is increasing, and Turnbull wants to understand what is driving it.
Taking samples of the atmosphere is the best method for measuring CO2 concentrations, and can be complemented with radiocarbon dating samples of deep water. But it comes with limitations.
“You can’t collect air that was there 30 years ago, because it is not there any more,” Turnbull said.
“So we came up with this idea of using tree rings. Plants, when they grow take carbon dioxide out of the air by photosynthesis and they use that to grow their structures and the carbon from the air ends up in the tree rings.”
This is helpful when there is an abundance of established trees, but those are a rarity in the Southern Ocean. Enter the Sitka spruce – the southernmost tree the team could find that would offer up good data. “It’s grown a lot faster that anything else [in that region] and the rings are bigger and easier to separate out and get a record from.”
Using a hand drill, Turnbull extracted a 5mm core sample from the tree in 2016, but the results are yet to be published.
As for the tree’s lonely status: the description may be in the eye of the beholder.
“To get from the inlet [to the tree] you have to walk through elephant seals and sea lions, penguins and albatross,” Turnbull said. “[The tree] doesn’t look lonely … it looks quite content actually.”
