Driest, coldest and oldest
Surrounded by mountains, Central Otago is cut off from rain-bearing winds. New Zealand is at its widest here, and an almost continental climate has developed.
Central Otago has the country’s driest conditions, the interior valleys having less than 600 millimetres of rainfall a year. The lowest temperatures occur in this region. Dry, droughty summers and cold winters have produced weakly leached, often stony soils, with a tendency to saltiness.
The region also has some of the oldest landforms in New Zealand – the flat-topped schist mountains are part of an ancient eroded surface that has been uplifted.
The driest places in New Zealand are in the south. Some go for 60 days without rain. In Central Otago, potential evaporation always exceeds precipitation, except in winter. Drought conditions are almost continuous.
Before people arrived, open forests of mataī and tōtara grew in the lowlands. Mountain and silver beech covered the wetter uplands in the west.
The main vegetation cover of the central districts was toatoa, kānuka, kōwhai, and grey scrub dominated by muehlenbeckia, coprosmas and olearias. Because of the high evaporation rate in the valleys, this is the only area of New Zealand where salty flats form. Plants and animals have adapted to this environment.
As in other dry districts of the eastern coast, Māori fires almost completely destroyed the original woody cover. In its place, tall tussock grassland grew near the treeline, with dry tussock grassland on lower mountainsides and in valleys.
Before humans arrived, Central Otago had a diverse range of vertebrates (animals with backbones). Among the birds were numerous moa species, Haast’s eagle, Eyles’s harrier, flightless geese and ducks, kākāpō and takahē. Reptiles included tuatara, skinks and geckos.
Most of these are now extinct or lost from the region, but a wide variety of skinks, geckos and insects remain, especially in rocky areas and patches of native scrub.
The stable, flat-topped mountains are capped with alpine grassland and tundra. On some exposed tops the ground is patterned by frost. Tors – pillars of schist rock up to tens of metres tall – harbour small plants, insects and lizards.