Indirect effects of invasive species removal devastate World Heritage Island

Abstract

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.

Alien species in a warmer world: risks and opportunities

“…Hence, some species that increase their range as a result of climate change might be perceived in a new administrative region as alien and could be subject to varying forms of control to prevent their spread [60]. From this perspective, conservation strategies should also respect and consider dynamic ecological processes to preserve biodiversity [81,82], otherwise well-intentioned control measures against invasion might result in unexpected outcomes [83,84].…”

Biological invasions in terrestrial Antarctica: what is the current status and can we respond?

“…The consequences of an eradication may be hard to predict, but could include negative and unforeseen impacts on local indigenous communities, such as a shift in the dominant native biota at a site (Bergstrom et al 2009). Given the contemporary relative scarcity of non-native species in Antarctica, to a large extent habitat restoration in Antarctica is not an issue as yet, though it is clearly important in the sub-Antarctic.…”

“…The position in Antarctica contrasts with the sub-Antarctic islands, each of which is governed by a single sovereign nation, and which have experienced a far greater presence and impact of nonnative species (Frenot et al 2005;Convey and Lebouvier 2009). Here, in recent years, attention has focused on the eradication of various herbivorous and predatory vertebrates, funded either by the national government, or by private or charitable donors (Bloomer and Bester 1991;Frenot et al 2005;Bergstrom et al 2009). Some mammalian eradications have led to unintended consequences, such as the destruction of plant species by increased rabbit numbers following the eradication of cats on Macquarie Island (Bergstrom et al 2009).…”

“…Here, in recent years, attention has focused on the eradication of various herbivorous and predatory vertebrates, funded either by the national government, or by private or charitable donors (Bloomer and Bester 1991;Frenot et al 2005;Bergstrom et al 2009). Some mammalian eradications have led to unintended consequences, such as the destruction of plant species by increased rabbit numbers following the eradication of cats on Macquarie Island (Bergstrom et al 2009). While high profile, vertebrate eradications represent only part of the challenge as non-native plants and invertebrates represent the majority of known introductions and include a range of invasive species having considerable impacts on ecosystems and native biota (Frenot et al 2005).…”

Eradications of invasive mammals from islands: why, where, how and what next?

“…These include changes to the food web such as prey switching, or potential mesopredator release, especially of rabbits and rodents when cats are removed, or of mice when rats are removed (Caut et al 2007;Rayner et al 2007;Witmer et al 2007;Bergstrom et al 2009). A recent study indicates that it is not just numbers but (predation) behaviour of meso-predators that may have been suppressed when cats or rats were present (Hughes et al 2008).…”