How do alien species such as rabbits and sheep affect Antarctic and subantarctic ecosystems?

The introduction of alien herbivores, specifically sheep and rabbits, has had a devastating impact on the fragile ecosystems of many subantarctic islands.12

These invasive species have significantly altered the landscape through overgrazing, which leads to severe erosion and the destruction of native plant communities. Specific consequences include:12

• Vegetation Loss: On Kerguelen, rabbits have exterminated the native Kerguelen cabbage over wide areas. On South Georgia, sheep have decimated native tussock grass communities.1
• Ecosystem Cascades: On Macquarie Island, the proliferation of rabbits led to the widespread destruction of native vegetation. When authorities attempted to control the rabbit population using the Myxoma virus, the resulting decline in rabbits deprived feral cats—another introduced species—of their primary food source, causing the cats to prey heavily on native seabirds.3

These examples highlight the severe, often interdependent consequences that nonnative species have on the biodiversity and stability of subantarctic environments.32