Recent assessments of the biodiversity value of Earth's dwindling wilderness areas 1,2 have emphasized the whole of Antarctica as a crucial wilderness in need of urgent protection 3 . Whole-of-continent designations for Antarctic conservation remain controversial, however, because of widespread human impacts and frequently used provisions in Antarctic law for the designation of specially protected areas to conserve wilderness values, species and ecosystems 4,5 . Here we investigate the extent to which Antarctica's wilderness encompasses its biodiversity. We assembled a comprehensive record of human activity on the continent (~ 2.7 million localities) and used it to identify unvisited areas ≥ 10 000 km 2 (1,6-8) (i.e. Antarctica's wilderness areas) and their representation of biodiversity. We show that, at best, 7 770 000 km 2 of wilderness remains, covering 56.9% of the continent's surface area, however it captures few important biodiversity features. Important Bird Areas 9 , ice-free Antarctic Conservation Biogeographic Regions crucial for biodiversity 10,11 , and areas with verified biodiversity records 12 are largely excluded. Our results demonstrate that Antarctica's wilderness Antarctica? Environ. Res. Lett. 5, 041001 (2010).
The impact of invasive species at seabird breeding islands causes a breakdown of important ecological functions such as prey consumption and nutrient transfer, and elevates extinction risk in impacted taxa. Eradicating invasive species from islands can result in substantial short-term recovery of seabird populations and consequently the prevalence of eradication programs as conservation tools is increasing. However, as the scale and complexity of eradications has increased, quantitative data on rates of recovery, especially from larger islands, remain limited. Furthermore, the mechanisms that govern recovery are poorly understood, limiting our ability to forecast outcomes and therefore prioritise effectively. Here, using the world's largest multi-species vertebrate eradication from Macquarie Island as a case study, we show how responses to invasive species and their eradication differ. Species with broad realised niches whose breeding phenology minimizes time on land and corresponds with summer resource abundance remained extant alongside invasive species while more habitat-specific species present in winter were extirpated. Following eradication, immigration and flexibility to colonise under-utilised optimal habitat appears to be boosting population growth in recolonising species, whereas established populations appear to be tethered to refugial habitats by the influence of philopatry, and their recovery is slower as a result. Unpicking these differential responses and the mechanisms behind them provides valuable information to help predict responses in other systems as future eradications are planned.
Maximising survey efficiency can help reduce the trade-off between spending limited conservation resources on evaluating performance of past interventions and directing those resources towards future interventions. Seabird responses to island eradications are often poorly evaluated owing to financial, logistical and methodological challenges associated with remote field work and species ecology. We surveyed an assemblage of threatened seabirds following the world's largest island eradication of multiple invasive species, testing multiple survey designs and outputs. We compared the outcomes of two important choices made during survey design: 1) whether to use unbiased or targeted surveys; and 2) implementing design-based or model-based analyses. An unbiased whole-island stratified randomised survey design performed well in terms of confidence in the final population estimates for widespread species, but poorly for localised recolonising species. For widespread species, model-based analyses resulted in slightly lower population estimates with narrower confidence intervals than traditional design-based approaches but failed to capture the realised niches of recolonising species, resulting in population estimates three orders of magnitude higher than current best estimates. We conclude that a multi-method approach to survey design best captures the size and distribution of recovering populations when the study system is ecologically diverse - importantly our results suggest there is no single strategy for efficient surveys of diverse seabird communities following large island invasive species eradications.
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