Focusing conservation efforts on 169 islands, including five in New Zealand, could help to combat the global extinction crisis.
This is according to the findings of a collaborative study between forty institutions, including universities and conservation organisations, published in PLOS ONE last week. The researchers combined conservation benefit with feasibility to assess 1,279 islands worldwide, whittling the list down to 169. These are the islands on which concentrating of conservation efforts could prove most valuable for protecting species biodiversity.
Eradicating invasive species such as rats and cats from the islands identified by the study could improve the chances of survival for 9.4% of the world’s most highly threatened terrestrial vertebrates. That’s 111 of the species of mammals, birds, reptiles, and amphibians that are currently listed as Endangered or Critically Endangered on the IUCN Red List. In addition, other threatened but less critical species would also be expected to benefit from removal of invasive species.
The concept of eradicating invasive, alien species from islands in order to protect and restore the native species that live there will be familiar to many New Zealanders. Just as the arrival of rats and stoats meant devastation for Aotearoa’s native species, invasive species been directly responsible for the critical status of native terrestrial species on many islands worldwide.
Many unique fauna make their home on islands, but islands also have much higher extinction rates than other landmasses. Islands make up just 5.3% of the land area of the Earth, but have been the site of 75% of all vertebrate extinctions since the year 1500. In addition, 36% of the species on the current IUCN Red List are island-dwelling species.
According to University of Auckland conservation biologist Associate Professor James Russell, who contributed to the study: “We already know islands are a vital conservation opportunity but this study gives us the bigger picture, a list of locations where the most progress could be made.”
Globally, the extinction crisis is growing, but action to counteract biodiversity loss is complicated by requirements for financial resources, political will, and public support. Having a clear focus on projects which will be most important and most achievable could make a significant difference.
Dr Russell said the study was important because “it not only assesses the feasibility of eradicating predators on these islands but assesses how feasible this work would be from a political and socio-economic point of view”.
Social and political factors influence the acceptability of a conservation strategy so have a vital influence on the success of a project, but have not previously been incorporated into this type of assessment.
The study combined island characteristics with information on the distribution of 1,184 threatened native vertebrate species on 1,279 islands worldwide, as well as considering the introduced species that pose a threat to the endangered species survival.
For all islands where it was judged that eradication of invasive species would have conservation benefit to threatened species, socio-political feasibility of such a project was evaluated, with input from conservation experts with local and regional knowledge.
Of the islands identified, 107 could begin eradication projects by 2020, with benefits for 80 threatened species, while the others could begin eradication by 2030. In fact, since the collection of data for this study, several of the 107 islands have already completed successful eradications of invasive species, a sign of progress for biodiversity conservation.
Five New Zealand islands are included on the list of 169: Slipper, Great Barrier (Aotea), Kawau, Motukawanui, and Auckland Island. Funding for eradication on Auckland Island was announced last year, and if successful this would become New Zealand’s largest pest-free island yet. Perhaps the study’s results will encourage prioritising the other four islands as the next steps in New Zealand’s predator-free movement.
Feature Image: Humboldt Penguin, Choros Island, Chile. Maria Jose Vilches, supplied.