Jj Scott

Impacts of local human activities on the Antarctic environment.

Abstract We review the scientific literature, especially from the past decade, on the impacts of human activities on the Antarctic environment. A range of impacts has been identified at a variety of spatial and temporal scales. Chemical contamination and sewage disposal on the continent have been found to be long-lived. Contemporary sewage management practices at many coastal stations are insufficient to prevent local contamination but no introduction of non-indigenous organisms through this route has yet been demonstrated. Human activities, particularly construction and transport, have led to disturbances of flora and fauna. A small number of non-indigenous plant and animal species has become established, mostly on the northern Antarctic Peninsula and southern archipelagos of the Scotia Arc. There is little indication of recovery of overexploited fish stocks, and ramifications of fishing activity on bycatch species and the ecosystem could also be far-reaching. The Antarctic Treaty System and its instruments, in particular the Convention for the Conservation of Antarctic Marine Living Resources and the Environmental Protocol, provide a framework within which management of human activities take place. In the face of the continuing expansion of human activities in Antarctica, a more effective implementation of a wide range of measures is essential, in order to ensure comprehensive protection of the Antarctic environment, including its intrinsic, wilderness and scientific values which remains a fundamental principle of the Antarctic Treaty System. These measures include effective environmental impact assessments, long-term monitoring, mitigation measures for non-indigenous species, ecosystem-based management of living resources, and increased regulation of National Antarctic Programmes and tourism activities.

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 islands 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.

Rabbits, landslips and vegetation change on the coastal slopes of subantarctic Macquarie Island, 1980–2007: implications for management

Subantarctic tall tussock grassland and megaherb vegetation has been massively affected by feral herbivores on islands where both occur. The effects of rabbits in this vegetation on Macquarie Island were monitored using 66 permanent quadrats and numerous photo-points on the steep coastal slopes of the island from 1980 to 2007. Vegetation change after landslips was also monitored. At the start of this period rabbit numbers plummeted due to the introduction of myxoma virus, but then increased from the late 1990s. Over the years of reduced rabbit numbers, some recovery of tall tussock grassland took place. With the resurgence in rabbit numbers, successional patterns converged towards a uniform pattern of degraded vegetation with more bare ground. The patterns of vegetation change indicate that recovery of the vegetation, after eradication of rabbits, rats and mice, is likely to be rapid where degradation is recent and where seed sources are in close proximity. The exotic plant species currently on the island are unlikely to present a problem.

Probable long distance dispersal of Leptinella plumosa Hook.f. to Heard Island: habitat, status and discussion of its arrival

During the 2003–2004 austral summer the number of vascular plant species recorded from Heard Island rose from 11 to 12 with the discovery of one small plant of Leptinella plumosa Hook.f. (Asteraceae), an indigenous subantarctic species. It is described and its habitat, likely status and possible means of arrival on the island are discussed. We conclude that the species probably arrived by natural means with a seabird as its most likely dispersal vector. The life history and biology of L. plumosa indicates its likely persistence on Heard Island.

Changes in Vegetation on Heard Island 1947–1987

The Heard and McDonald Islands are the only subantarctic island group which appears to be free of human-introduced animals and plants. Vegetation changes in its species-poor flora are therefore likely to be due to natural factors. Significant glacial recession has exposed new areas for colonisation over the past 40 years. Analysis of vegetation transect data from seven glacier retreat zones and adjacent areas indicates four main patterns of primary colonisation, with moisture availability and effects of animal disturbance being major differentiating environmental factors. Vegetation colonisation can be rapid under the most favourable environmental conditions, for example abundant surface drainage from springs or snow melt with or without effects of nutrient enrichment by animals. It can be expected that with continuing climatic amelioration and glacial recession, the size of vegetated areas will expand. Changes in distribution of some vascular plant species around the island have been noted and tentatively linked with climatic warming, and additional changes are predicted. Future effects of changing trends in population numbers of animals utilising and interacting with terrestrial vegetation communities are uncertain. Further changes can now be monitored from recently established reference points.

Changes in the cover of plant species associated with climate change and grazing pressure on the Macquarie Island coastal slopes, 1980–2009

Climate change and alien species have affected the vegetation of subantarctic islands. Long-term monitoring of vegetation change on the steep coastal slopes of subantarctic Macquarie Island has allowed responses of plant species to various disturbance regimes to be well documented, although, until recently, the confounding effect of feral herbivore disturbance obscured any responses that might be attributed to climate change. The uncoupling of climate change from variation in feral rabbit numbers allowed us to test whether any plant species were increasing or decreasing on the coastal slopes of the island between 1980 and 2009, independent of rabbit grazing pressure. We used analysis of variance to test for differences in species cover classes between four measurement times on each of 101 quadrats in each of 1980/1981, 1995, 2003 and 2009. We had 54 quadrats on landslips and 47 elsewhere. Approximately two-thirds of the species with significant temporal change exhibited changes that could be expected from variation in rabbit grazing pressure. However, approximately one-third of the species increased in cover irrespective of grazing pressure. On landslips, variation in the cover of these increaser species was largely related to time in a linear mixed model, whereas elsewhere altitude and time were both important. The increase in both atmospheric dryness and episodic soil water-logging that has been described for the island since 1980 may best explain the increaser species.

Change in Undisturbed Vegetation on the Coastal Slopes of Subantarctic Macquarie Island, 1980-1995

The vegetation of 30 undisturbed permanent quadrats on the steep coastal slopes of subantarctic Macquarie Island was recorded in 1980-81 and 1994-95, a period in which temperatures rose briefly then declined, precipitation increased and rabbit grazing pressure decreased. Previous investigators of the plant ecology of the island have suggested a successional sequence, in the absence of disturbance, towards total dominance of the two major plant species on the coastal slopes, the tall tussock-forming grass Poa foliosa and the megaherb Stilbocarpa polaris, with a concomitant reduction in the diversity of subordinate species. Our observations demonstrate a more complex reality. Dense tall tussock grassland became more open, resulting in an increase in quadrat species richness. The more open tussock grassland on the upper slopes became more dense, with a concomitant decrease in quadrat species richness. The large herb S. polaris changed little in its abundance over the period, perhaps reflecting a need for disturbance for its expansion. The opening of dense stands of P. foliosa may be part of a previously unrecorded endogenous successional process, while the closure of open stands of Poa could be a response to improved growth conditions, including relief from rabbit grazing and the relatively high temperatures in the initial years of monitoring, but may also be endogenous in origin.