KEY POINTS:
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.
A number of orders and families of higher animals (such as tuatara, moa and kiwi) are found only in New Zealand, reinforcing the argument for their ancient Gondwanan origins because such a level of endemism would have required a very long period of isolation.
Of particular significance is the tuatara, its two species being the sole surviving members of the Sphenodontia order - one of the four orders of reptiles. As all the other members of the order died out around 65 million years ago, the tuatara is of international interest to biologists.
New Zealand's other reptiles are a very rich and diverse fauna of endemic skinks and geckos. New Zealand's four species of native frog all belong to the very primitive, endemic Leiopelmatidae family, whose lineage also reaches back to Gondwana.
Moa, which were eventually hunted to extinction by Maori, and New Zealand's other giant ratite group, kiwi, share a very ancient lineage. Kiwi are flightless nocturnal birds with many attributes more typical of mammals. Like cats, kiwis have sensory whiskers and, like most mammals (and unlike birds), an acute sense of smell. They burrow in the ground like moles, exude an earthy musty smell and may use their strongly smelling burrows to mark out their territory. Kiwi are the most unbirdlike of birds. Certainly, they are distinctive - worthy of their status as a national symbol for New Zealand. Another distinctive member of our avian biodiversity is the kakapo, the world's rarest and largest parrot.
The invertibrate fauna is also of interest to scientists. Many spiders, bristletails, moths and dragonflies have features that elsewhere in the world can be found only in fossils.
Caddis flies, stoneflies and mayflies comprise another group with stong links to Gondwana.
A feature of the beetles and other insects is their flightlessness and large size, attributes of invertebrates living in cold, windy climates where there are no mammalian predators.
The land snail fauna of New Zealand is one of the richest in the world, reflecting the primeval wet-forest environment - and, probably, the lack of mammalian consumers.
Weta stand out for their striking appearance and for their antiquity. There are more than 70 species, all endemic.
THE inexorable march towards extinction for many of our plant and animal species is illustrated in DoC's 2007 Threatened Species List, which classifies another 416 taxa as more threatened than when the list was first published in 2002. During this period 40 native birds are considered to have worsened in status, but only four birds are considered to have improved their long-term chances of survival. Almost half of the nearly 6000 native plant and animal species evaluated fall into one of the seven threatened categories; and another 3000 are likely to be threatened.
There are two main approaches in trying to halt the loss of indigenous biodiversity: to increase the area and diversity of land, freshwater and marine ecosystems protected for conservation; or to control more effectively the weed and animal pest threats in areas already under legal protection.
The second approach is probably the biggest biodiversity challenge facing DoC, for the gravity of the pest problem is graphically outlined in the NZ Biodiversity Strategy. Most of these alien plants and animals are well established, having been here for a century or more; others like wasps, sea squirt and didymo are more recent; and the biodiversity threat of the potential entry of myriads of alien organisms (such as fire ants or avian diseases) is the inevitable and unfortunate consequence of globalisation in trade, tourism and immigration.
