The nine-meter tall fir tree holds the Guinness World Record title for the “farthest tree” on the planet. It is the only tree on the bushy, windswept island, 700 kilometers south of New Zealand in the Southern Ocean. It is the only tree for 222 km. Its nearest neighbor grows in the Auckland Islands. Before the Campbell Island Spruce, the Tenere Tree in Niger was said to be the most isolated tree on the planet, until it was killed by a driver in 1973. The Sitka Fir is believed to have been planted by Lord Ranfurly, the then Governor of New Zealand, in the early 1900s – hence its nickname the Ranfurly Tree. However, studies have not been able to confirm its exact age, and Guinness World Records notes that although it is widely cited as the loneliest tree in the world, “there is no universally recognized precise definition of what constitutes a ‘tree’”. It’s also classified as an invasive species, and some scientists would be happy to see it go. But for the leader of radiocarbon science at GNS Science, Dr Jocelyn Turnbull, the tree could be a valuable tool for understanding what’s happening with carbon dioxide uptake in the Southern Ocean. “Of the CO2 we produce from burning fossil fuels and put into the atmosphere, only about half stays there and the other half goes to the land and the ocean,” Turnbull said. “It turns out that the Southern Ocean – one of those carbon sinks – has absorbed about 10% of all the emissions we’ve produced over the last 150 years.” Turnbull is working with New Zealand’s Deep South National Science Challenge, the Antarctic Science Platform and the National Water and Atmospheric Institute to understand what happens to carbon in the Southern Ocean. The groups ask two key 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 absorb even more carbon and reduce global warming? Previous studies looking at carbon uptake by the Southern Ocean have produced conflicting results. the current theory is that recruitment is rising and Turnbull wants to understand what’s driving it. Atmospheric sampling is the best method for measuring CO2 concentrations and can be supplemented by deep-water radiocarbon dating samples. But it comes with limitations. “You can’t collect air that was there 30 years ago, because it’s not there anymore,” Turnbull said. “So we came up with this idea of using tree rings. Plants, when they grow, take carbon dioxide from the air through photosynthesis and use it to develop their structures, and the carbon from the air ends up in the tree rings.” This is useful when there is an abundance of established trees, but these are rare in the Southern Ocean. Enter Sitka spruce—the southernmost tree the team could find that would yield good data. “It’s grown a lot faster than anything else [in that region] and the rings are bigger and easier to pick out and get records.” Using a hand drill, Turnbull extracted a 5mm core sample from the tree in 2016, but the results have yet to be published. As for the loneliness of the tree: description may be in the eye of the beholder. “To get out of the entrance [to the tree] you have to walk through elephant seals and sea lions and penguins and albatross,” Turnbull said. “[The tree] doesn’t look lonely… looks quite content actually.”
