Last week I bore witness to the re-wilding of an entire island ecosystem. Invasive mammalian predators were eradicated from Ahuahu (Great Mercury Island) in 2014, and the original predators and keystone species are now returning naturally. Most exciting is witnessing the changes in the ecosystem having surveyed the island before and after predator eradication. Thanks to the hard work of Department of Conservation staff and particularly project leader Pete Corson, Great Mercury Island is now in the top ten list of islands to be made predator-free in New Zealand, and ensures the protection in perpetuity of the neighbouring smaller Mercury Islands.Ahuahu/Great Mercury Island looking south along the white cliffs (Photo by James Russell)
In 2012 before the eradication we confirmed the ongoing persistence of grey-faced petrels despite the presence of invasive cats and rats. Now, in 2016, we are witnessing the smaller petrel species naturally returning to the island and re-wilding it. Last week University of Auckland team members working with the Department of Conservation identified the first record of Pycroft’s petrel in recent history. This species was presumably present in ancient times, but had since gone extinct, and now only persisted on the smaller Mercury Islands lying offshore. Another population can now be added to the beneficiaries of invasive mammal eradication.
Ahuahu is also a site of great historical importance for the indigenous Māori people of New Zealand/Aotearoa, and archaeology researchers from the University of Auckland have been undertaking digs on the foreshore to understand the history of the first inhabitants of the island – one of the first locations of New Zealand colonisation. Alongside amazing cultural discoveries, their work also enables us to understand the original ecosystem functioning of the island, by documenting the bird species found in fossil and midden deposits, and using pollen cores to describe the original forest cover of the island. These discoveries will all contribute to the re-wilding of the island in to the future.