Mainland islands are areas, so called islands, where isolation from predators comes from intensive pest management, or fencing. These projects form the stepping stones from island eradication to the large scale projects being undertaken as part of the Predator Free New Zealand goal.
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Department of Conservation Mainland Islands
By the mid 1990s, it was becoming obvious that while native species were flourishing well on predator free islands, something needed to be done on the mainland. Lacking the natural protection of the ocean, novel ways of controlling predators had to be developed. DOC established six “Mainland Island” projects in the mid 1990s and five are still identified as current projects:
- Boundary Stream Mainland Island (800ha) – at the heart of Poutiri to Ao Tane (HPRC) now part of Predator Free Hawkes Bay.
- Paengaroa Mainland Island (107ha) – the smallest of the DOC mainland islands selected due to the high number of endemic plant species.
- Rotoiti Nature Recovery Project (6700 ha)
- Te Urewera Mainland Island (212,673 ha)
- Trounson Kauri Park Mainland Island (586 ha)
These projects focus on whole ecosystem restoration, intensive and integrated pest management. The goal at establishment was to undertake research that could be shared with NZ’s conservation community. At conception they tended to focus on introduced predator suppression rather than eradication.
Rotoiti Nature Recovery Project (6700 ha)
The Rotoiti Nature Recovery Project (RNRP) covers 6700 hectares of honey-dew beech forest in the Nelson Lakes National Park. Over the decades research has focused on how different pest control regimes impact ecosystems. One focus has been monitoring kākā populations and their breeding success. An important lesson has been the proven effectiveness of stoat and possum control for preventing kākā extinction.
Research at the RNRP also demonstrated that controlling stoats without rat control leads to a dangerous rebound in rat numbers.
Located by the village of St Arnaud the RNRP has been supported by a group of committed locals. In 2001 the Friends of Rotoiti was formed as a partnership locals and the Department of Conservation. The impressive work of Friends of Rotoiti is highlighted in this video. Community initiatives like this have demonstrated the amazing work volunteers can do in the conservation space.
Te Urewera (212,673 ha)
The largest of the original mainland islands is Te Urewera. The predator control here focused on intensive trap networks. The impact of this trapping has been astounding for key species. In 1994 only 8 pairs of Kokako were found, by 2010 this had risen to 180 (more than 20% of the national total). Experiments with possum trapping have revealed that to maintain mistletoe (Peraxilla tetrapetala) populations you need to be trapping every two years rather than four. Read more lessons learnt from Te Urewera here.
In 2014, as part of the Tūhoe treaty settlement, Te Urewera ceased to be a national park and became its own legal entity. This was a groundbreaking piece of legislation, returning to iwi the power to make decisions about their lands.
The importance of mātauranga Māori has been recognised as crucial to all conservation efforts in Aotearoa. Te Urewera is an opportunity to observe what this looks like enacted. Read Tuhoe’s management plan Te Kawa o Te Urewera.
Wainuiomata Mainland Island (1200 ha)
Established in 2005 by the Greater Wellington Regional Council the Wainuiomata Mainland Island contains untouched native forest, including rata, rimu and matai. It is situated inside a water control area, supplying a fifth of the region’s water and is closed to the public.
The Greater Wellington Regional Council maintains extensive predator and pest plant control. Possums are below 2% Residual Trap Catch (RTC) at all times and rats at 5% RTC or less. There are efforts underway to reduce mustelids to near zero. The predator control has enabled the native species present to thrive and other natives birds to return to the area. North Island robins were successfully translocated in 2012 and kiwi have made their own way from the Remutaka Forest Park. The local population of tītipounamu has recovered so significantly that, in 2019, 60 tītipounamu were translocated from Wainuiomata to Zealandia.