ias management

Invasive alien species are one of the primary threats to native biodiversity on islands worldwide, and their expansion continues due to global trade and travel. Preventing the arrival and establishment of highly successful invasive species through rigorous biosecurity is known to be more economic than the removal of these species once they have established. However, many islands around the world lack biosecurity regulations or practical measures and establishing biosecurity will require social and financial investments.

Indicators for tracking conservation efforts at a global scale are rare but important tools for understanding trends and measuring progress towards global conservation targets. Eradication of invasive species from islands is an increasingly used conservation intervention in countries and territories around the world. With a goal of collating these efforts, the Database of Islands and Invasive Species Eradications (DIISE) holds records of the location, target species, year and outcome of invasive mammal and bird eradications on islands from around the world.

The 16 UK Overseas Territories (OTs) together account for 94% of the UK’s unique biodiversity and make a significant contribution to global biodiversity. Being predominantly islands, the OTs are very vulnerable to the introduction of potentially harmful invasive non-native species, and pressures are increasing with the continual growth of international trade and impact of climate change. Biosecurity is acknowledged as the most cost-effective means of addressing invasive species threats for small islands, and yet the OTs face many challenges in the implementation of biosecurity controls.

Invasive species, particularly animals, are being eradicated from islands at ever more ambitious scales. In order to protect island biodiversity and the essential ecosystem functions that it provides, however, plant invasions should be given more management attention. While many advances have been made, plant eradication is inherently more difficult than animal eradication due to persistent seed banks, and eradication may not be possible for more extensive populations.

The American mink (Neovison vison) has invaded most of the United Kingdom following escapes from furfarms over decades. Its escalating impact on riparian and coastal biodiversity, including seabirds and water voles, is well documented. Starting in north-east Scotland in 2004, long-term, multi-institution mink control efforts have harnessed the enthusiasm of volunteer conservationists to push back the mink invasion over a vast area.

Invasive alien species represent one of the greatest threats to native plants and animals on islands. Rats (Rattus spp.) have invaded most of the world’s oceanic islands, causing lasting or irreversible damage to ecosystems and biodiversity. To counter this threat, techniques to eradicate invasive rats from islands have been developed and applied across the globe. Eradication of alien rats from large or complex island ecosystems has only been successful with the use of bait containing a rodenticide.

New Zealand has been the world leader in the eradication of invasive mammalian predators from offshore islands. Today, the focus for invasive predator management is shifting to larger landscapes; big inhabited islands or the mainland itself. The most cost-effective approach in the long term will be to eradicate the predators from those areas, ensuring permanent freedom for vulnerable and threatened native biodiversity to recover or be reintroduced. Island eradication technologies cannot always be employed on the mainland (e.g. aerial brodifacoum), so a new approach is required.

Eradication of invasive vertebrates on islands has proven to be one of the most effective returns on investment for biodiversity conservation. To recover populations of the critically endangered Polynesian ground dove (Gallicolumba erythroptera), the endangered white-throated storm-petrel (Nesofregetta fuliginosa), the endangered Tuamotu sandpiper (Prosobonia cancellata) as well as other native plant and animal species, a project was undertaken to eradicate five species of invasive alien vertebrates: Pacific rat (Rattus exulans), ship rat (R.

The control of invasive species would be enhanced through the addition of novel, more effective and sustainable pest management methods. One control option yet to be trialled in the field is to deploy transgene-based ‘Gene Drives’: technologies which force the inheritance of a genetic construct through the gene pool of a wild population, suppressing it or replacing it with a less harmful form. There is considerable interest in applying gene drives to currently intractable invasives across a broad taxonomic range.

We are on the edge of the sixth mass extinction on Earth. Islands represent ca. 5% of the earth’s land area yet are home to 61% of extinctions in the past 500 years, and currently support 39% of critically endangered species. Invasive species are a leading cause of extinction and endangerment on islands. Invasive vertebrates, particularly mammals, are among some of the most damaging invasive species on islands. Eradicating invasive mammals is an increasingly utilised conservation tool.