Aliens in an Ancient Landscape: Rabbits, Rats and Tourists on Macquarie Island

Macquarie Island, in the subantarctic south of Tasmania, Australia, is one of the few refuges in the vast Southern Ocean for seabirds, seals and penguins. Their presence contributes nutrients to the substrate upon which cold temperature flora, grasses and mega-herbs (but not trees), rely. Exotic animals such as elephant seals and king penguins, plants and, more generally, the physical vista of the island, are integral to the island tourism experience. The sustainability of Macquarie Island tourism relies in large part on the continued existence of an experience of this calibre and therefore its fortunes are tied to the fortunes dictated by the physical processes that continue to shape the island. Tourism is not a major contributing factor to island disturbance, but it may be a hapless victim of these physical changes. The sustainability of future tourism to Macquarie Island is discussed here in the context of contemporary physical changes to climate and the resulting ecological effects.

Hundreds of thousands of years ago, oceanic crust that was about 9 million years old was thrust out of the Southern Ocean and Macquarie Island was born. It is the only one of the subantarctic islands (Fig. 2.1) to be formed in this way, and earned it World Heritage Area status in 1997. Its modern history began with its discovery by sealers only 200 years ago; there followed a grizzly history of mass slaughter of its wildlife, particularly of seals and penguins, which were clubbed to death or driven alive into trypots and boiled for their oil (Parks Tasmania, 2009a). The legacies from the island's first visitors are a double-edged sword. Macquarie Island 's unusual genesis and the abuse of its wildlife have earned it a host of prestigious designations as a place of outstanding universal value, giving significant protection to its biodiversity. The downside has been the intentional and accidental introduction of non-native species. Today there is evidence of the significant effect of these aliens (especially rabbits and rats) on the endemic flora and fauna. This, in turn, threatens to compromise the island's appeal as a tourist destination in its own right and as a stepping-stone for tourism to East Antarctica.

The early 21st century is a time of transitional climate warming, with the effects being noted first on the subantarctic islands. Early indications, although still somewhat ambiguous, point to the possibility of more extreme local weather conditions, which are already extreme in the subantarctic; conditions that are more conducive to the survival and colonization of introduced species, including microorganisms, with the resultant biosecurity issues; and changing climatic conditions, making Macquarie Island, for example, even wetter and possibly less appealing to all but the hardy few (Pendlebury and Barnes-Keoghan, 2007).

Fragile is not an adjective that is usefully applied to this or the other subantarctic islands that have stood in the path of keening winds, driving rain and chilling temperatures for millennia. Their plants and animals are relatively robust, otherwise they would not have survived in what humans would call an extreme environment. However, these remote subpolar ecosystems are most certainly vulnerable and, in contemporary times, it is the introduction of alien species in a warming climate that will continue to have the greatest effect. It will be impossible for the administrators of any of the subantarctic islands. including Macquarie Island, to ameliorate extrinsic factors, such as the effects of climate warming, but it is possible to manage and regulate intrinsic factors such as the introduction of alien vertebrates and human activity. If the ecological integrity of Macquarie Island can be maintained relatively free from anthropocentric stressors, then there will be a better chance of withstanding the pressure from sources that cannot be controlled.