Natural history of New Zealand

The natural history of New Zealand began when the landmass Zealandia broke away from the supercontinent Gondwana in the Cretaceous period. Before this time, Zealandia shared its past with Australia and Antarctica. Since this separation, the New Zealand landscape has evolved in physical isolation, although much of its current biota has more recent connections with species on other landmasses. The exclusively natural history of the country ended in about 1300 AD, when humans first settled, and the country's environmental history began.^[1][2] The period from 1300 AD to today coincides with the extinction of many of New Zealand's unique species that had evolved there.

The break-up of Gondwana left the resulting continents, including Zealandia, with a shared ecology. Zealandia began to move away from the part of Gondwana which would become Australia and Antarctica approximately 85 million years ago (Ma). By about 70 Ma, the break up was complete.^[3][4] Zealandia has been moving northwards ever since, changing both in relief and climate. Most of the present biota of New Zealand has post-Gondwanan connections to species on other landmasses, but does include a few descendants of Gondwanan lineages, such as the Saint Bathans mammal. Overall, trans-oceanic dispersal has played a clear role in the formation of New Zealand's biota.^[5] Several elements of the Gondwana biota are present in New Zealand today: predominantly plants, such as the podocarps and the southern beeches, but also distinctive insects, birds, frogs and the tuatara.^[6]

In the Duntroonian stage of the Oligocene, the land area of Zealandia was at a minimum. It has been suggested that water covered all of it,^[7] but the consensus is that low-lying islands remained, perhaps a quarter of the modern land area of New Zealand.^[5][8]