Helm's butterfly feeds on koromiko flowers in Tongariro National Park. Sometimes called the

Helm's butterfly feeds on koromiko flowers in Tongariro National Park. Sometimes called the "forest ringlet" it is vulnerable to introduced wasps and is now endangered.

The landform diversity of an entire continent has been squeezed into the New Zealand archipelago: over 700 islands and a very long and intricate coastline of more than 15,000 km; fiords, some reaching more than 30km from the Tasman Sea into the remote mountainous interior of Fiordland; the extinct shield volcanoes of Banks Peninsula, Otago Peninsula and Chatham Island; karst landforms; cone volcanoes; the huge outwash fan of the Canterbury Plains; the Alpine Fault through the West Coast; uplifted marine terraces; geothermal features.

Before the arrival of humans, dense, evergreen forests would have dominated the landscapes of the archipelago. However, the alpine zone of permanent ice and snow, fellfield, herbfield and snow tussock grassland covered 14 per cent of the total land and was a major feature of the South Island. Colonisation by forests and shrubs would have been greatly aided by birds distributing seeds, especially those of the lage podocarp trees - matai, totara, kahikatea, rimu and miro.

Biologists describe the New Zealand biota as being depauperate (lacking in major groups of plants and animals) but very rich in life forms that have developed from the limited parent stock or have been eliminated elsewhere.

In essence, then, while there is great diversity in some biota - such as seabirds and alpine plants - the attraction of most of New Zealand's biodiversity stems from its antiquity and its many curiosities. Ancient species include tuatara, wrens, Peripatus (a zoological oddity which is neither worm, centipede nor caterpillar but with an affinity to all three) and the plant "living fossil" Tmesipteris. Among the curiosities are not only the kakapo, weta and kiwi but also alpine geckos and parrots, "vegetable sheep" (Raoulia and Haastia) and a preponderance of inconspicuous flowers which are generally de-colourised (mostly white) and de-specialised.

New Zealand's higher plants have a high level of endemism at the species level (around 85 per cent) and this gives the natural landscape its own distinctive character.

But it is New Zealand's alpine vegetation which is its botanical glory, both aesthetically and scientifically. Diverse ecological niches - whether mobile scree slopes, splash zones beside rivulets of showfield meltwater, boggy, peaty margins of alpine tarns; exposed rock outcrops; or sheltered, shady crevices among moraine boulders - allowed a wide range of alpine plant communities to evolve.

The snow tussock herbfields are the most distinctive element of this alpine landscape, because of the sheer size of the Chionochloa snow tussocks (1m-2m tall) and their tawny colour. They are remarkably long-living perennial grasses, larger specimens being several centuries old. Like beech trees they seed infrequently but profusely, probably as a result of a warm summer the previous year.