The New Zealand alpine zone is less disturbed, and less compromised by introduced plants and animals, than many other native ecosystems. Māori settlement probably had minimal impact on alpine areas, although some large browsing birds were reduced or eliminated.
European settlement had a much greater impact. Some introduced plants are now abundant and widespread. The introduction of browsing mammals (tahr, chamois, red deer, sheep and hares) has proved harmful to native plants. Once the palatable alpine herbs, tussocks and shrubs are selectively eaten, they are replaced by unpalatable plants such as speargrasses (Aciphylla species), mountain daisies (Celmisia species), fescue tussock (Festuca novae-zelandiae) and bristle tussock (Rytidosperma setifolium). Sheep have been grazed up into the alpine zone on South Island runs since the 1840s, but much of the higher land has now been retired from grazing, and wild sheep do not live at such altitudes. Chamois and tahr, introduced to South Island mountains in the early 20th century, and red deer, introduced in the mid-19th century, quickly established wild herds. As well as eating alpine plants, they trample vegetation and contribute to soil erosion in the mountains.
Some introduced plants are now naturalised and abundant in the alpine zone, including catsear (Hypochoeris radicata), hawkweed (Hieracium species, especially H. praealtum), sheep’s sorrel (Rumex acetosella) and the grass browntop (Agrostis capillaris). These European natives are not confined to the alpine zone – they are opportunistic, with a wide altitudinal range in both Europe and New Zealand.
The effects of global warming can be expected to show up clearly on high mountains, with likely elevation of tree- and snowlines, invasion upwards by lower-altitude species, and possibly major disruption and change to alpine ecology.