Summary 1.Owing to the detrimental impacts of invasive alien species, their control is often a priority for conservation management. Whereas the potential for unforeseen consequences of management is recognized, their associated complexity and costs are less widely appreciated. 2. We demonstrate that theoretically plausible trophic cascades associated with invasive species removal not only take place in reality, but can also result in rapid and drastic landscape-wide changes to ecosystems. 3. Using a combination of population data from of an invasive herbivore, plot-scale vegetation analyses, and satellite imagery, we show how a management intervention to eradicate a mesopredator has inadvertently and rapidly precipitated landscape-wide change on sub-Antarctic Macquarie Island. This happened despite the eradication being positioned within an integrated pest management framework. Following eradication of cats Felis catus in 2001, rabbit Oryctolagus cuniculus numbers increased substantially although a control action was in place ( Myxoma virus), resulting in island-wide ecosystem effects. 4. Synthesis and applications . Our results highlight an important lesson for conservation agencies working to eradicate invasive species globally; that is, risk assessment of management interventions must explicitly consider and plan for their indirect effects, or face substantial subsequent costs. On Macquarie Island, the cost of further conservation action will exceed AU$24 million.

International audienceInvasive alien species are among the primary causes of biodiversity change globally, with the risks there of broadly understood for most regions of the world. They are similarly thought to be among the most significant conservation threats to Antarctica, especially as climate change proceeds in the region. However, no comprehensive, continent-wide evaluation of the risks to Antarctica posed by such species has been undertaken. Here we do so by sampling, identifying, and mapping the vascular plant propagules carried by all categories of visitors to Antarctica during the International Polar Year's first season (2007-2008) and assessing propagule establishment likelihood based on their identity and origins and on spatial variation in Antarctica's climate. For an evaluation of the situation in 2100, we use modeled climates based on the Intergovernmental Panel on Climate Change's Special Report on Emissions Scenarios Scenario A1B [Nakicenovic N, Swart R, eds (2000) Special Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change (Cambridge University Press, Cambridge, UK)]. Visitors carrying seeds average 9.5 seeds per person, although as vectors, scientists carry greater propagule loads than tourists. Annual tourist numbers (∼33,054) are higher than those of scientists (∼7,085), thus tempering these differences in propagule load. Alien species establishment is currently most likely for the Western Antarctic Peninsula. Recent founder populations of several alien species in this area corroborate these findings. With climate change, risks will grow in the Antarctic Peninsula, Ross Sea, and East Antarctic coastal regions. Our evidence-based assessment demonstrates which parts of Antarctica are at growing risk from alien species that may become invasive and provides the means to mitigate this threat now and into the future as the continent's climate changes

Summary1. Ecosystem change is predicted to become more prevalent with climate change. Widespread dieback of cushion plants and bryophytes in alpine fellfield on Macquarie Island may represent such change. Loss of the keystone endemic cushion plant, Azorella macquariensis, was so severe that it has been declared critically endangered. 2. We document the dieback and its extent. Due to the rapidity of the event, we sought to infer causes by testing two mechanistic hypotheses: (i) that extensive dieback was due to a pathogen and (ii) that dieback was a consequence of a change in climate that induced stress in several susceptible species. We searched for pathogens using both conventional and next-generation sequencing techniques. We examined plant functional morphology in conjunction with a long-term climate record of plant-relevant climate parameters to determine whether environmental conditions had become inimical for A. macquariensis. 3. Dieback was found across the entire range of A. macquariensis. A survey found 88% of 115 stratified/ random sites contained affected cushions and 84% contained dead bryophytes. Within-site dieback increased over time. 4. No conclusive evidence that A. macquariensis deaths were caused by a definitive diseasecausing pathogen emerged. However, the presence of bacterial, fungal and oomycete taxa, some potentially pathogenic, suggested that stressed cushions could become susceptible to infection. 5. The primary cause of collapse is suspected failure of A. macquariensis and other fellfield species to withstand recent decadal changes in summer water availability. Increased wind speed, sunshine hours and evapotranspiration resulted in accumulated deficits of plant available water spanning 17 years (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008). High vulnerability to interrupted water supply was consistent with functional morphology of A. macquariensis, and climate change has altered the species' environment from wet and misty to one subject to periods of drying. Journal of Applied Ecology 2015Ecology , 52, 774-783 doi: 10.1111Ecology /1365Ecology -2664 were complex and multiple stressors appeared to be impacting cumulatively may be relevant to other locations.

International audienceDespite considerable research on biological invasions, key areas remain poorly explored, especially ways to reduce unintentional propagule transfer. The Antarctic represents a microcosm of the situation, with the numbers of established non-native species growing. Information to help reduce potential impacts is therefore critical. We measured the propagule load of seeds, and fragments of bryophytes and lichens (the number of other plant or animal fragments was too low to draw any conclusions) carried in the clothing and gear of visitors to the Antarctic, during the 2007/08 austral summer. Samples were collected from different categories of visitors associated with national research programs and tourism and different categories of clothing and gear, new as well as used. We also collected information about the timing of travel and the regions visitors had travelled to prior to Antarctic travel. Seeds were found in 20% and 45% of tourist and science visitor samples, respectively. For bryophyte and lichen fragments the proportions were 11% and 20%, respectively. Footwear, trousers and bags belonging to field scientists were the highest risk items, especially of those personnel which had previously visited protected areas, parklands/botanic gardens or alpine areas. Tourists who visited rural/agricultural areas prior to travel, and/or travel with national programs or on smaller tourist vessels had the highest probability of transferring plant propagules. Travel either during the boreal or austral autumn months increased the probability of propagule presence. Our assessment is applicable to other areas given evidence of propagule transfer patterns in those areas that are broadly similar to those documented here. The current work provides a sound evidence base for both self-regulation (e.g. taking care of personal equipment) and organization-based regulation (e.g. issuing guidelines and holding regular inspections) to reduce propagule transfer of plants to the Antarctic

Summary1. The management of non-indigenous species is not without its complications. In Bergstrom et al.'s (2009) study, we demonstrated that feral cats Felis catus on sub-Antarctic Macquarie Island were exerting top-down control on the feral rabbit Oryctolagus cuniculus population, and that the eradication of the cats led to a substantial increase in rabbit numbers and an associated trophic cascade. 2. Dowding et al. (2009) claim our modelling was flawed for various reasons, but primarily that a reduction in the application of the rabbit control agent, Myxoma virus, coinciding with cat removal, was a major driver of rabbit population release. 3. We explore this proposition (as well as others) by examining rates of Myxoma viral release between 1991 and 2006 (with an attenuation factor for the years, [2003][2004][2005][2006] in association with presence ⁄ absence of cats against two estimates of rabbit population size. Myxoma viral release was a significant factor in the lower estimates of rabbit population, but the effect was small, and was not significant for higher rabbit population estimates. By contrast, the presence or absence of cats remained highly significant for both estimates. 4. Synthesis and applications. We re-affirm our position that top-down control of rabbit numbers by cats, prior to their eradication, was occurring on Macquarie Island. Nonetheless, we agree with Dowding et al. (2009) that systems with multiple invasive species represent complex situations that require careful scrutiny. Such scrutiny should occur in advance of, during, and following management interventions.

Antarctic ecosystems are at risk from the introduction of invasive species. The first step in the process of invasion is the transportation of alien species to Antarctic in a viable state. However, the effect of longdistance human-mediated dispersal, over different timescales, on propagule viability is not well known. We assessed the viability of Poa trivialis seeds transported to Antarctica from the UK, South Africa and Australia by ship or by ship and aircraft. Following transportation to the Antarctic Treaty area, no reduction in seed viability was found, despite journey times lasting up to 284 days and seeds experiencing temperatures as low as -1.5°C. This work confirms that human-mediated transport may overcome the dispersal barrier for some propagules, and highlights the need for effective pre-departure biosecurity measures.

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