Flora thrives on neighbouring pig-free Adams Island
Image: Paul Sagar ©
A thriving New Zealand Subantarctic Islands Area free of mammalian pests.
The Auckland Islands lie within the New Zealand Subantarctic Islands Area, a World Heritage Site (1998) that contains some of the world’s most extraordinary natural heritage and includes some of the world’s least modified islands.
Auckland Island (46,000 ha) is the main island of the Auckland Island group (57,000 ha). The Auckland Island archipelago is the largest and biologically richest of the five island groups that make up the New Zealand Subantarctic Islands Area (76,500 ha).
The Auckland Islands are located 465 km south of New Zealand’s South Island. Auckland Island is the only site within this area where mammalian pests remain.
Auckland Island is approximately 43 km long at its longest point, 27 km wide and has a coastal perimeter of 374 km. The terrain is typically mountainous with peaks up to 650 m high. Its western side is dominated by formidable cliffs up to 400 m high carved by the pounding seas. The eastern side is a series of deeply incised cirques and glacial fiords, which are considerably more sheltered than the west. Two large harbours, Port Ross at the northern end, and Carnley Harbour in the south, and some of the narrow inlets on the eastern side, usually offer sheltered anchorage. Infrastructure is limited to a 6-person hut at Deas Head and several derelict historic structures. The climate is persistently wet, cold and windy.
Feral pigs, cats and mice are present and have inflicted severe ecological damage over the past 150–200 years.
Comparison with pest-free Adams Island shows the severity of the detrimental impacts of pigs, cats and mice on Auckland Island.
- Pigs have devastated floral communities, restricting understorey regeneration, seabird survival and recruitment; grossly lowered vegetation biomass and damaged soils.
- Of the 44-bird species that breed in the archipelago only 12 native species persist on Auckland Island, none of which are endemic.
- Pigs and cats have caused the local extinction of the rest of the bird species including the burrowing seabirds, majorly disrupting nutrient cycling.
- Mice have altered the abundance and composition of invertebrate fauna, compete for food with native birds and pose a risk of future attacks on seabird chicks.
The objectives of the proposed project are to eradicate pigs, cats and mice from Auckland Island. The long-term outcomes of the project are recovery and preservation of native flora and fauna.
The objectives are aligned with the Predator Free 2050 initiative.
Benefits of eradicating pests
- Completion of the removal of all introduced mammalian pest species from the New Zealand Subantarctic Islands World Heritage site, expanding the pest-free habitat in the area from 30,500 ha to 76,500 ha.
- Auckland Island is New Zealand’s 5th largest island and would be the largest pest-free island; requiring zero future investment on pest management beyond biosecurity.
- Protection at their breeding sites of 38 species of bird including 9 endemic species.
- Rapid recovery of 280+ species of native insects, including 95+ endemic species, which will provide pollination and nutrient cycling that will promote the recovery of 196+ species of native flora.
- Greatly improved biosecurity protection for other island sanctuaries in the region.
- Recovery of species on Auckland Island is expected to occur through natural processes and dispersal from neighbouring islands, without management input.
- Improved public engagement with the New Zealand subantarctic region.
The project is a huge challenge. Mice and pigs have never been eradicated on an island anywhere near this large, and eradication of cats has only been attempted on one larger island, in arid Western Australia.
The success of such a large complex project requires initial trials in order to test the feasibility of eradication before comitting to a project.
Trials in 2015 aimed to find out the following:
- What is the status of mice in autumn?
- Can cats be monitored using hair sampling?
- What bait is most appealing to pigs?
- Are coral-style traps suitable for catching pigs?
- What is the diversity of invertebrates?
2018/19 summer trials
Further trials will be conducted on Auckland Island to reduce uncertainties before the feasibility of an eradication can be confirmed.