The subantarctic islands lie in a vast belt of waves and wind that encircle the mid- latitudes of the southern hemisphere. The region has acquired dramatic names—the ‘screaming sixties’, the ‘furious fifties’, the ‘roaring forties’— because of the temperature difference of several degrees over a relatively narrow band of latitude. Disentangling the mechanisms of past change and the role of westerly airflow, however, has proved difficult due to the dearth of published records. By analysing peat, lake and ocean sediments back through time it’s possible to reconstruct past environmental, climate and human impacts. The subantarctic islands offer the chance to resolve questions on what drives global climate change and whether we have entered a new geological epoch: the Anthropocene.
From the rear deck of the expedition vessel we cored the subantarctic ocean floor sediments to reconstruct environmental changes over the past 10,000 years
Using the past to reconstruct climate and vegetation changes
The research program
Human activity is now recognised as having profoundly and permanently altered our planet, suggesting we have entered a human-dominated geological epoch, the ‘Anthropocene’. But to formally define the onset of the Anthropocene, the same signal must be found in geologic-forming materials around the world and date to the same time. Here we report a series of precisely-dated trees from Campbell Island that preserve the peak atmospheric radioactive carbon (or radiocarbon) in their growth rings, a signal created from Northern Hemisphere-dominated thermonuclear bomb tests during the 1950s and 1960s. A single Sitka spruce on the island - ‘The Loneliest Tree in the World’ – allows us to resolve the timing of peak radioactivity to the last few months of 1965, the same time as the signal in the north. Our findings provide a precisely-resolved potential Global Stratotype Section and Point (GSSP) or ‘golden spike’, marking the onset of the Anthropocene Epoch.Download
Alien plants are species that have established themselves outside their natural distribution and are now a recognised threat to biodiversity around the world. On Campbell Island is a single Sitka spruce tree - ‘The Loneliest Tree in the World’ – a species more commonly found along the North American Pacific coast. Here we report a study looking at the tree’s past growth rates and likely future response to climate change. Although the tree is growing extremely well, the absence of cones and the likely continuing wet climate suggests the Sitka spruce is a limited threat to the long-term ecology of Campbell Island.Download
Testing the impact of large herbivore extinction remains a major challenge. Here we use a peat core from subantarctic Enderby Island to investigate how dung fungi alongside pollen can be used to reconstruct the impact of mammals on vegetation.Download
On the subantarctic islands, peat exposures show Dracophyllum once grew above present day tree line. Here we find there was a major collapse in the altitudinal limit of growth between approximately 2000 and 1000 years ago suggesting westerly winds were stronger at this time.Download