Low-lying vegetated area, seals and Big Ben. Photo by K. Kiefer

There is considerable evidence that the climate of Heard Island and McDonald Islands (HIMI) is changing.

The warmer trend observed at HIMI mirrors similar changes at the nearby Îles Kerguelen and elsewhere in the southern Indian Ocean.

These increased temperatures are having a significant effect on the terrestrial environment, with glacial retreat leading to the formation of lagoons and freshwater lakes, and exposing new land for colonisation by plants and animals.

Consequently, Heard Island has one of the most rapidly changing physical settings in the subantarctic.

The increase in available habitat for plant colonisation, in conjunction with the combining of previously discrete ice-free areas, has lead to dramatic changes in the vegetation of Heard Island in the last 20 years or so.

Some plant species are spreading and the structure and composition of plant communities is being modified.

It is considered likely that further changes will occur, and possibly at an accelerated rate. Changes in population numbers of seal and seabird species are also expected - this may affect the vegetation through changes to the nutrient regime and level of physical disturbance through trampling.

Scientists are studying the terrestrial ecosystems at Heard Island in an attempt to understand how it is likely to change if the climate at HIMI continues to warm, as is currently predicted.