Acaena magellanica, one of the species investigated in the three islands study. Photo by P. Turner

Because Heard Island's terrestrial ecosystems are largely unaffected by human impacts, the island is a unique 'natural laboratory' for measuring environmental changes resulting from regional climate warming.

Heard Island has been playing a key part in an international Scientific Committee on Antarctic Research (SCAR) program looking at the effects of climate change on Antarctic and subantarctic ecosystems - RiSCC (Regional Sensitivity to Climate Change in Antarctic Terrestrial and Limnetic Ecosystems).

Most recently, over the 20003/04 summer, Heard Island was one of three islands visited simultaneously by scientists in an attempt to determine the impact of temperature on species' performance and ecosystem structure.

Heard Island is the most southerly of the three islands, being located below the Antarctic Polar Frontal Zone, while Îles Kerguelen (belonging to France) is located within the Zone, and Marion Island (belonging to South Africa) is located to the north.

The three islands are each warmer than the one further south, so Îles Kerguelen is 2°C warmer than Heard Island, and Marion Island is 2°C warmer than Îles Kerguelen. This natural temperature gradient allows results on the warmer islands to inform predictions of the effects of future climate change on the cooler islands.

There are several aspects to the research but the major components included:

• Investigations of the form, structure and progression of flowering and seed development in four selected vascular plant species at different altitudes. Observations are still being analysed, but early indications are that different species perform in different ways on different islands (and thus in different air temperatures). This gives some indication of which species would be compete better on the colder islands if the climate continues to warm.
• Studies of the carbon uptake and loss of Pringlea antiscorubutica (the 'Kerguelen cabbage'), with the intention of determining how well the species would adapt to further climate warming. Early results indicate that slower growth may occur once the temperature reaches around 10-12°C .
• Collecting particular insects from a range of locations and altitudes for further laboratory studies.