Invasive species do much more damage in Australia and NZ than elsewhere. But why?
Isolation has been both blessing and curse for the wildlife of both countries.
Australia and New Zealand frequently experience significant damage caused by invasive species, despite having stringent biosecurity measures, a modest population, and being surrounded by the sea. These countries rank among the top three most affected nations globally due to introduced species. In Australia alone, over 4,000 species have been introduced, with 3,000 posing invasive threats.
The economic damage caused by these invasive species amounts to approximately 1.25% of the nation's GDP, comparable to the amount spent on aged care.
The reason behind Australia's vulnerability to feral species lies in its unique island biogeography, a subject pioneered by Alfred Russell Wallace. Islands tend to harbor unique species that evolve due to isolation. However, this isolation also leaves island species particularly vulnerable to invasive species. As an "island continent," Australia, with its high number of endemic species, is a prime example of this phenomenon.
Australia's diverse and rich biodiversity, largely an accident of its insular history, makes it unusually susceptible to invasion. The continent was near the South Pole when it separated from Gondwana, resulting in a cold climate that limited animal diversity. The species that did migrate to Australia found a sparsely inhabited land, allowing them to diversify into a wide variety of species. Consequently, Australia has a high number of unique species and is considered one of only 17 megadiverse nations.
Australia's lopsided biodiversity, characterized by a lack of ground-dwelling placental mammals and an abundance of venomous snakes, makes it particularly vulnerable to invasion. This lopsidedness stems from three main factors: firstly, invasive species can fill ecological niches not well-utilized by native species; secondly, unfamiliar predators or competitors can pose significant threats against which Australian species have little defense; and thirdly, invasive species are more likely to evolve on larger continents and subsequently invade Australia rather than the other way around.
Super-invaders, fast-breeding species capable of consuming a broad range of foods, tolerating various environments, and spreading rapidly, are a significant concern. Cane toads and fire ants, among others, are prime examples of super-invaders in Australia. However, feral cats and rabbits emerge as the two most costly invaders. These species have broader diets, habitats, and evolutionary adaptations compared to native Australian predators, enabling them to outcompete and threaten native species on multiple fronts.
Written by urgent.news from The Conversation AU's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
