Biological invasions

Abstract

At first sight, and certainly in comparison with most other land areas worldwide, Antarctica appears exceptionally well protected against the dangers of invasion by non-indigenous (alien) species. It is geographically isolated from other Southern Hemisphere continents and smaller landmasses, historically lacks indigenous human populations or contact, and presents extreme environmental challenges that must be survived both during any transfer process and after establishment at an Antarctic location. Despite this, it is clear that biological invasions have taken place, and have led to serious impacts on indigenous biota, ecosystems, and ecosystem functions, posing a serious risk to the Antarctic region (Dingwall 1995, Smith 1996, Chown et al. 2001, Greenslade 2002, Frenot et al. 2005). In common with elsewhere, parts of the Antarctic have been experiencing a period of very rapid environmental change, relating to a number of significant variables, over the last 50 or more years (Huiskes et al. this volume, Convey this volume, Lyons et al. this volume). In addition to confirming the significant influence of some existing biological invasions, Frenot et al. (2005) have identified that rapid climate change, in combination with increased human activity, is likely to increase the frequency and significance of future invasions, and increase the impacts of alien biota that are already established. Worldwide, biological invasions are one of the most important threats to biodiversity (McKinney and Lockwood 1999, Sala et al. 2000, Courchamp et al. 2003) and ecosystem processes (Heywood 1989, d'Antonio and Dudley 1995, Mack et al. 2000). In an Antarctic context, these threats are serious. The subantarctic islands, continental margin, packice and surrounding seas are home to spectacular concentrations of marine megafauna, including a large proportion of the world's seabird species and marine mammals. Life on land, while species poor and less visually spectacular (Gressitt 1970, Chown et al. 1998, Vernon et al. 1998, Convey 2001) is no less significant, and terrestrial biotas often include a particularly high proportion of endemic taxa (as illustrated by lichens, liverworts, flowering plants, arthropods and nematodes). Antarctic terrestrial habitats are typified by low species richness and the absence of many functional groups that are present elsewhere. This itself may be sufficient to render the sub- and maritime Antarctic islands, and the ice-free islands of exposed land on the continent, susceptible to alien invasion (Bergstrom and Chown 1999, Chown et al. 2000). Furthermore, island biotas may be more susceptible to invasion as indigenous species are less able to cope with the associated change (d'Antonio and Dudley 1995, Vermeij 1996, Williamson 1996, Bowen and van Vuren 1997). Although human contact with the Antarctic has occurred only over the last two centuries, our influence has increased rapidly. Initially, effort was almost exclusively focused on economic activity. On land, this related to the support requirements that were necessary to allow the excessive commercial exploitation of marine resources (whales, seals, penguins) from the Southern Ocean. In parallel, some farming, social and recreational development also occurred, resulting in many of the introductions of grazing and predatory vertebrates that remain on most of the subantarctic islands today. Throughout this period, concerns over human impact on indigenous Antarctic biota received scant attention, even in the context of the virtual extermination of successive target industrial species. The second phase of human impact in the Antarctic became apparent through the importance attached to scientific research as being integral to the expeditions of the 'heroic age' of exploration of the early 20th Century. The initially piecemeal and competitive development of scientific activities eventually led to a large and coordinated Antarctic contribution to the International Geophysical Year (1958) and, soon after, to the development of the Antarctic Treaty System (Hull and Bergstrom 2006). Subsequently, research stations have been established by over 30 nations across the Antarctic and approximately 45 are now signatories to the Treaty. In recognition of the need to protect the Antarctic environment in a comprehensive and legally binding form, in 1991 the Madrid Protocol was established. Within the protocol, in the context of this paper, are included the prohibition of introduction of fauna or flora and the establishment of protected areas in Antarctica. A third phase of human impact on the continent - tourism - developed during the latter decades of the 20th Century, with tourists (mostly arriving on specially designed cruise ships) now numerically outnumbering the scientific and associated logistical operations of national operators by a factor of four to five, and numbers continuing to increase rapidly (Frenot et al. 2005). In the austral summer season of 2004/05 just under 50 000 people (tourists and crew) visited the region with 27 950 tourists on expeditions that included a landing component (http://www.IAATO.org). © 2006 Springer.