Effects of human trampling on the sub-Antarctic vegetation of Macquarie Island

The effects of trampling on six types of vegetation and their underlying soils were investigated on sub-Antarctic Macquarie Island. One hundred and fifty foot-passes per year for at least the past 10 years have occurred on a typical 6-km stretch of walking track on the island's upland plateau. Trampling favours vascular plants including exotics, especially Poa annua, while bryophytes and lichens are more common in undisturbed vegetation. The abundance of 19 of the 39 most common species appears to be affected by trampling. Track width is positively correlated with exposure and wet soils, and trampling increases the soil bulk density of the track. The contrast between the soil bulk density of the trampled and untrampled soils increases with increasing exposure. While present environmental damage is within an acceptable range over the majority of the island, the extreme environments are likely to suffer unacceptable levels of damage if increased usage occurs with more tourism or expansion of scientific and related activities. This is demonstrated by the diversion of a short section of plateau track in an atypically heavily used area; the diversion sustained substantial damage after 890 foot-passes during a 15-month period.