About Ahuahu-

Great Mercury Island

Importance of Ahuahu

Some oral histories suggest that Ahuahu is the original landing site of Polynesian settlement in New Zealand. Ahuahu once supported a large human population and has some of the most intact and earliest known archaeological sites in NZ. Ngāti Hei, regarded as keepers of the kumara, have a strong association with Ahuahu.

Size & Significance

Nationally pest-free islands make up 0.4% of NZ’s land area yet are essential for protecting over 50% of NZ’s threatened birds and over 30% of NZ’s threatened reptiles. At 1,872 ha Ahuahu is in the top ten largest pest free islands in NZ. Ahuahu is five times larger than all the other Mercury Islands put together, and almost three times the size of every other pest-free island on the Coromandel combined. The scale of Ahuahu also brings a greater diversity of ecosystems, including permanent water. Ahuahu has great potential to have functioning ecosystems and hold sustainable populations of threatened species. Currently the island is approximately 1/3 sheep and beef farm, 1/3 pine forest (which won’t be logged) and the remaining 1/3 in various types/states of native habitat. Many native species are utilising the pastures and pine forest.

Public Access

The owners have allowed public access to the island for day visitors since the late 1970’s. Ahuahu is a focal point for boating from Mercury Bay and between Tauranga and Auckland.

Species Found on Ahuahu

From translocations, surveys and observations some of the notable species on Ahuahu include tīeke, Mercury Islands tusked wētā, moko skink, shore skink, pacific gecko, common gecko, pāteke, grey-faced petrel, fluttering shearwater, NZ dotterel, kākā, kererū, white-fronted tern, red crowned kākāriki, white-faced storm petrel, Pycroft’s petrel, Caspian tern, bittern, parapara (bird catching tree), milk tree, māwhai, pīngao, katipō, ground wetā and 51 species of native land snail, indicating extremely high levels of biodiversity.

The Mercury Islands Archipelago

The Mercury Islands lie 6-10 kilometers North to Northeast off the Coromandel Peninsula. Six islands, except Ahuahu, are managed by DOC as highly valuable reserves, with access restrictions in place, for the purpose of protecting and preserving in perpetuity indigenous flora and fauna or natural features. The islands are internationally significant, listed as important bird areas primarily for the seabird values, and are included in tentative lists for UNESCO World Heritage status. The criteria for this inclusion is to contain the most important and significant natural habitats for in-situ conservation, containing threatened species of outstanding universal value for science or conservation. The Mercury Islands has an incredibly rich seabird and reptile fauna as well as being home to the Mercury Island tusked wetā and a suite of species dependent on conservation for their survival. Until 11,000 years ago, a land connection existed between the Mercury islands and the Coromandel Peninsula. Thus, the islands are regarded as continental shelf islands. By 6,000 years ago sea level had risen approximately to its current position, marooning species. Middle and Green Islands which have never had introduced mammalian pests support extraordinary densities of seabirds, reptiles and invertebrates, are benchmarks for island conservation.

The Hauraki Gulf Marine Park

The Mercury Islands are part of the Hauraki Gulf Marine Park. The intent of the Hauraki Gulf Marine Park is to integrate the management of the natural, historic, and physical resources of the Hauraki Gulf, its islands, and catchments: recognising the historic, traditional, cultural, and spiritual relationship of the tangata whenua with the Hauraki Gulf and its islands. Whilst Ahuahu’s land is not included in the Park the intent to protect the natural, historic, cultural and spiritual values is recognised. DOC, Regional Councils and District Councils are obligated to give regard to the intent of the Hauraki Gulf Marine Park.

Conservation Action

Beginning with translocations of saddleback in 1966 the Mercury Islands have a long history of conservation action. From the 1980s research on the Mercury islands has been world leading especially restoring seabird-driven island ecosystems. This is been facilitated by DOC and strongly supported by universities and Crown research agencies. Between 1987 and 1992 eradications of kiore and rabbits occurred on 4 of the islands. For species management DOC describes the island sanctuaries off the Coromandel coast as Nationally important for natural heritage, noting that collectively the islands support some of the greatest diversity of reptiles and seabirds in New Zealand. Key actions for the Mercury Islands include managing animal pests and weeds, biosecurity, surveillance, maintaining pest free sites, environmental monitoring, and increasing public understanding and appreciation.

Collaborating & Eradicating

The owners of Ahuahu have a desire to undertake conservation work, protecting natural and historic values whilst being good land managers. DOC has an interest in reducing the risk of threats reaching the other Mercury Islands, improving ecosystems and species values and showcasing conservation. With aligned interests, DOC and the owners of Ahuahu entered an agreement in 2013 to work together. The agreement was primarily for an eradication of pests but also noted intentions for weed control, biosecurity and monitoring. The $1.4 million joint project to eradicate ship rats, kiore and cats occurred in 2014, with a declaration of success in 2016, meaning all mammalian pests have now been eradicated from the Mercury Islands. Weed control work has also been undertaken cooperatively since 2015 targeting moth plant, wildling pines, royal fern, woolly nightshade, Banksia and boxthorn, to protect the entire archipelago.

Information on this page has been written and supplied by Pete Corson.

Background photo by Jamie Reyneke-Barnard