South Canterbury straddles three climatic zones: the Southern Alps, the Mackenzie Basin, and the downlands and coast.
The Southern Alps receive heavy rainfall from the west. At Mt Cook village an average of 4,500 millimetres falls each year. Summers are mild, with maximum temperatures averaging 20°C. In winter there is frost and snow, with average maximum temperatures of 7°C. Annual sunshine hours average 1,580. (In winter especially, possible sunshine hours are reduced by the nearby mountains.) North-westerly winds prevail.
The Mackenzie Basin is a drier region in the ‘rain shadow’ of the Southern Alps, with an annual average rainfall of just 600 millimetres. Summers are warm and dry, with maximum temperatures averaging 21°C and sometimes rising into the 30s. Winters are cold and frosty, with some snow and an average maximum temperature of 8°C. On winter nights the thermometer usually falls below zero. Annual sunshine hours at Lake Tekapo average more than 2,400, making it one of the sunniest places in the country. North-westerly winds prevail, and are often hot and dry in summer.
The downlands and coast have warm summers and cool winters. The average maximum temperature is 21°C in summer and 11°C in winter. Timaru’s average annual rainfall of 550 millimetres is one of New Zealand’s lowest. Annual sunshine hours average 1,930. North-east (coastal) winds prevail. The zone is also exposed to cold, damp south-west and hot, dry north-west winds.
The highest flowering plants growing in New Zealand are Graham’s buttercup (Ranunculus grahamii), Haast’s hebe (Hebe haastii) and a parahebe (Parahebe birleyi) found at up to 3,000 metres on exposed rocks in Aoraki/Mt Cook National Park. On the highest rocks of all, on Aoraki/Mt Cook, only lichens and mosses can survive.
By the 19th century, glaciation and fires started by Māori had severely reduced South Canterbury’s forest cover. The only significant areas of podocarp forest – tōtara, kahikatea and mataī – were at Arowhenua and along the foothills of the interior ranges. Other remnants comprised kōwhai, matipo and similar species. There were small areas of beech and mountain tōtara forest at Aoraki/Mt Cook and along the Ben Ōhau Range.
In the mid-19th century most of South Canterbury was a mosaic of flax, fern, scrub and tussock. Cabbage trees (Cordyline species) were abundant. Early pastoralists burned tussock to promote edible shoots, or resowed their land in exotic grasses. Most native vegetation has now been superseded by introduced species. After the milling and fires of early European settlement, no more than pockets of native forest remained. The largest remnant is Peel Forest, near Geraldine.
Exotic forestry has never been important in South Canterbury. Planting of the largest exotic forest at Kakahu (2,900 hectares) did not begin until the late 1950s. A widely spread exotic pest is hieracium (hawkweed).
South Canterbury was a habitat for the giant flightless moa, now extinct. In 1895 Kapua (near Waimate) was the scene of a major dig for moa bones. In the 1960s bones were discovered in the Albury Park swamp.
Today, the main birds that are distinctive to the region live by the rivers. They include the black-fronted tern, wrybill plover and black-billed gull. There are few forest birds, because of the lack of forest cover. However, restoration projects in Waihī and Conways Bush reserves have increased kererū and bellbird numbers. The kea, the world’s most alpine parrot, is often seen around Aoraki/Mt Cook. The grasshopper-like black alpine wētā, known as the Aoraki/Mt Cook flea, is found above the snowline.
South Canterbury has the only known long-tailed bat population on the South Island’s east coast. They are found from Peel Forest to Ōpihi River. The main population is at Hanging Rock, near Pleasant Point.
Wallaby, tahr and chamois
These species were introduced for sport. Wallabies were released near Waimate in 1874, and are mainly confined to the Hunters Hills. Tahr (also spelled thar) and chamois were released in 1904 and 1907 respectively at Aoraki/Mt Cook, and soon spread to other mountain areas. All three are periodically culled to reduce damage to native vegetation.
Heavy rabbit infestations remain a periodic problem, particularly in the Mackenzie Country. In the 1950s rabbits were brought under control with poison, but by the 1980s their numbers had increased again. In the 1990s, Mackenzie Country farmers were implicated in the illegal introduction of the rabbit-killing calicivirus, to which some rabbits are now immune.