New Zealand’s Unique Geographical History

New Zealand is home to unique and diverse plant and animal species. The biota of New Zealand is regarded as one of the most remarkable on Earth. The long geological isolation from the other continental landmasses led to its distinctively high species endemism. Let’s take a look at some of the geographical events that led to the country’s unique ecosystems.

Ancient Supercontinents

Millions of years ago, the landmass of the Earth was one supercontinent surrounded by the vast oceans. It was called Pangaea. But because of the pressures underneath the Earth’s crust, the Pangea began to break about 250 million years ago (mya). This led to the formation of two supercontinents — Laurasia in the north and Gondwana in the south. And after about 70 million years, Gondwana and Laurasia eventually separated.

The Land That Became New Zealand

A rift began to form and led to the formation of swamps. As the rift deepened and the sea continued to enter, a part of Gondwana was then pushed further south. Eventually, it separated from Gondwana around 80 mya and became a large island in the south-western Pacific Ocean. (Ref. 1)

A Landmass of Birds and Insects

From 65 million years ago, the landmass was inhabited by species that were originally from Gondwana. Some of them were beech trees, ferns, kiwi, moa, tuatara, and wētā. While there is considerable evidence of various early land mammals in different parts of the world, fossil records show that birds, reptiles, and insects were the dominant animal species and the only land mammals were bats on the break-away island. (Ref. 2)

Various geological events occurred in the years that followed. About 5 million years ago, the landmass started to split and eventually led to the formation of the Cook and Foveaux Straits, creating what we now know as New Zealand’s North Island, South Island, and Stewart Island. Species from the nearby landmass, Australia, continued to migrate to New Zealand, including mānuka, rātā, pōhutukawa, saddleback, kōkako, and huia. (Ref. 1)

New Zealand’s Current Form

New Zealand’s major islands are North Island (Te Ika-a-Māui), which is covered largely by volcanic plateaus, and the South Island (Te Waipounamu), which is dominated by the Southern Alps. The highest point is Aoraki (or Mount Cook) at 3,724 m whereas the lowest point is the Taieri Plain at -2m. The climate is mostly temperate. The mean temperatures range from 8 °C (46 °F) in the South Island to 16 °C (61 °F) in the North Island.

A multitude of plant and animal wildlife established on the islands. In the absence of ground-dwelling predators, many of the birds lost the ability to fly as they evolved to be ground dwellers. One of the few predators was a giant bird species, the Haast’s eagle. It had a set of powerful wings, spanning around 3 meters. The eagle preyed on moa, another bird species, yet, flightless. When the numbers of moa dwindled due mostly to human predating, the number of Haast’s eagle also decreased. (Ref. 3) Eventually, both of them became extinct.

All land mammals, except for the native bats, presently found in New Zealand have been introduced. That includes humans; they have been the most destructive mammals. Deforestation has been another significant contributor to the extinction of species. The first Polynesian settlers in 950-1150 AD brought with them the Polynesian rat (kiore). The rat species preyed on a number of small bird species, frogs, and lizards. Then, in the mid-1800s, Europeans began to settle in New Zealand. More mammals were introduced, such as cats, weasels, and ferrets. In the presence of these new predators, many species of frogs, lizards, and small birds became extinct. For instance, the rats and the stoats hunting the native bird species huia. Humans were also hunting them for feathers that had become popular in Europe. Overhunting eventually led to the species’ extinction. The last confirmed sighting of the huia was in 1907. (Ref. 1) In 1948, a bird species, takahē, believed to be extinct was rediscovered. Its discovery led to the conservatory effort to boost the species’ population. (Lesson 4: Takahē – Porphyrio hochstetteri)

In the next lesson, let’s learn about New Zealand’s biodiversity, particularly its unique features and importance in relation to endemism.

References:

1. Our changing ecosystems – timeline. (2016). Science Learning Hub. https://www.sciencelearn.org.nz/resources/1599-our-changing-ecosystems-timeline
2. New Zealand bats – pekapeka. (2018). Science Learning Hub. https://www.sciencelearn.org.nz/resources/2837-new-zealand-bats-pekapeka
3. V. New Zealand’s Extinct Moa. (2014). Fergusmurraysculpture.Com. https://www.fergusmurraysculpture.com/new-zealand/new-zealand-s-unique-biota-the-example-of-the-moa-1-pages/#:~:text=To%20put%20it%20at%20its,million%2Dyear%20experiment%20…&text=Apart%20from%20a%20bat%20and,%2D1300%20AD)%20introduced%20them.
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