The Aldabra rat and cat eradication (RaCE) feasibility project is vital for determining the feasibility of large-scale eradication of introduced rats and cats on Aldabra. With significant advances in eradication science, strengthened biosecurity measures on Aldabra, and compelling evidence that removing invasive alien species is the most impactful action to enhance island native biodiversity, now is the ideal time to evaluate this eradication initiative on the atoll.
Invasive alien species—animals, plants, or microbes introduced either intentionally or accidentally into non-native environments—pose a serious threat. Unlike native species that have evolved within a balanced ecosystem, invasives spread rapidly, outcompeting local organisms and destabilizing ecological systems. This leads to severe and often irreversible environmental damage.
Globally, numerous invasive alien species have wreaked havoc on native biodiversity. For instance, in Guam, the introduced brown tree snake has led to numerous extinctions of endemic species, nearly decimating native bird populations. In New Zealand, stoats and possums threaten native wildlife, including the iconic kiwi. Meanwhile, on mainland Africa, the water hyacinth clogs waterways, depleting oxygen levels, harming fish, and damaging aquatic ecosystems.
Many invasive species were introduced by humans for short-term benefits, often without grasping the long-term ramifications. A prime example is the introduction of cane toads in Australia in 1935, initially released to control crop pests. Their numbers exploded to over 200 million, resulting in the poisoning of native wildlife, pets, and even humans.
The Seychelles also exemplifies the dangers of invasive species. In 1949, barn owls were introduced to manage rat populations. Instead, they proliferated across the granitic islands, preying on local birds like the Seychelles magpie robin and white tern, all while failing to control rats. Similarly, ring-necked parakeets escaped as pets, establishing wild populations on Mahé and threatening crops and native species, particularly the Seychelles black parrot. Fortunately, the Seychelles Islands Foundation (SIF) successfully eradicated the parakeet, establishing Seychelles as the first country to achieve this milestone.
Across the inner islands, many species have been introduced, both intentionally and accidentally. Among them, rats and cats have proven exceptionally destructive. Rats arrived with early human settlers, while cats were introduced later as domestic pets. Even in isolated ecosystems like Aldabra, these predators have disrupted the delicate balance that evolved without such threats.
Invasive alien species often spread due to global trade, tourism, and shipping. Seeds can hitchhike on shoes or clothing, animals can stow away in cargo, and ornamental plants can escape gardens and invade the wild. Rats have dispersed worldwide via ships, reaching even the most remote islands. Once established, these species are notoriously difficult and costly to remove, highlighting the necessity of prevention as the most effective approach.
Protecting fragile ecosystems like Aldabra demands constant vigilance, supported by trained biosecurity officers, stringent quarantine regulations, and public awareness. The fewer invasive alien species that reach these ecosystems, the greater the chances that native species will survive and flourish in their natural habitats.
SOURCE: SIF
