Why are islands especially vulnerable to invasive species?

Islands are particularly vulnerable to invasive species primarily due to the unique ecological characteristics of their native populations and their geographic isolation.12

The heightened susceptibility of island ecosystems is driven by several key factors:

• Ecological Naivete: Many island species have evolved in isolation without exposure to certain types of predators or herbivores. Consequently, they lack the defensive adaptations necessary to survive when confronted with new threats, such as domestic cats or goats, which can devastate native biodiversity.12
• Endemism and Rarity: Islands often host high levels of endemism, meaning many species are found nowhere else on Earth. Because these populations are often small or restricted to specific habitats, they are more susceptible to localized extinction when faced with competition for resources or predation from introduced organisms.12
• Limited Competition: While island species may be abundant due to having fewer competitors than their mainland counterparts, this same lack of evolutionary pressure means they are often ill-equipped to compete with aggressive, nonnative species that possess built-in competitive advantages.32

Protecting these fragile ecosystems is a critical ethical imperative, as the loss of endemic island species represents an irreversible decline in global biological heritage.41