What is an alpine habitat?
The alpine zone is usually defined as the area between the upper limit of trees (the timberline or the treeline) and the lower limit of permanent snow.
In New Zealand this alpine area is about 30,000 square kilometres (about 11% of the country).
Most of the alpine area is in the South Island, where several mountain peaks in the Southern Alps are higher than 3,000 metres.
In the North Island, alpine terrain is limited to the volcanoes of the central plateau (Ruapehu, Ngāuruhoe and Tongariro), Mt Taranaki (Mt Egmont) to the west, Hikurangi to the east, and the crest of the axial ranges Kaweka, Kaimanawa, Ruahine and Tararua.
Variations in alpine zones
The alpine zone varies from north to south in New Zealand. The treeline is around 1,500 metres above sea level in the North Island, lowering to 900 metres at the bottom of the South Island. This variation in treeline is caused mainly by latitude and distance from the coast.
The North Island's mountains are mainly volcanic and support a much lower diversity of alpine plants than the South.
The South Island, Northwest Nelson and Fiordland are hotspots for alpine plant biodiversity. The Nelson region contains about 80% of all New Zealand's alpine species.
Special and unusual plants live in the harsh alpine zone of our rugged mountains.
Alpine plants have to cope with extremely cold, windy and dry conditions. They often grow in infertile soil or shattered rock, with great changes in temperature from searing heat to extreme cold. They are often lashed by gale force winds.
Most alpine plants don't grow very large in response to the limited resources available. A low-growing, compact form also gives the plants some protection from the wind, cold, snow and ice.
Alpine habitats are home to a range of animals including birds (rock wren, kea, pipit, takahe, great spotted kiwi), lizards (skinks and geckos) and many different invertebrates (weta, grasshoppers, giant snails, moths and butterflies, spiders, cicada and beetles).
These animals have adapted to the harsh alpine environment. Some adaptations include: freeze resistance of invertebrates, dark colouration for heat retention, flightlessness and omnivorous diets.
The cold alpine temperatures limit the activity of mammals, and until recently, it was assumed that native species have been relatively safe from predators. However, there is increasing evidence that predators (particularly stoats, possums and mice) are contributing to significant declines in alpine species. Many are now threatened with extinction, such as our only true alpine bird – the rock wren.
Introduced herbivores such as thar, chamois and hare may also be impacting on the overall health of the habitat.
DOC has identified an increasing need to manage high altitude biodiversity. For example, we are investigating how much pest control is needed in alpine areas, and how we can use it effectively to reverse declines in biodiversity.
We are also focusing research on the potential effects of climate change – both on alpine wildlife, and a predicted increase in predation risk if alpine areas become more suitable for rodents.
Several community groups are involved with alpine predator control, such as the New Zealand Alpine Club who carry out trapping in Fiordland, and the Friends of the Cobb who are based within Kahurangi National Park.