Forest Vines to Snow Tussocks: The Story of New Zealand Plants
The current estimate for the number of vascular plant species native to New Zealand is about 2200.1 This is a modest total by comparison with tropical floras, but it is of moderate size for a temperate country. About 82 per cent of the species are endemic; a high proportion reflecting New Zealand's isolation.
New Zealand is a generally moist country with mild temperatures in the lowlands. It is believed that before human habitation much of the landscape was covered by dense forests — conifer broadleaf2 forest predominating in the warmer North Island and parts of the South Island and beech (Nothofagus) forest predominating in the South Island and, mostly at higher altitudes, in the North Island. Human activities have greatly reduced this forest cover. Above treeline, ranging north to south from about 1500-1000 m in altitude, there are various types of short alpine vegetation, which sometimes include a belt of shrubs as a transition from the forest (Fig. 1).
Of the world's larger islands, New Zealand's narrowly separated pair are the most remote from any continent. The British Isles and Japan are as close to their adjacent continents, at their nearest points, as the North and South Islands are to each other; the larger islands of Indonesia and the Caribbean form close set series between continents and even Madagascar is, at 400 kilometres from Africa, only one quarter the distance from that continent that New Zealand is from Australia, its nearest continental neighbour.
Most of New Zealand's rocks are sedimentary, laid down originally beneath the sea, and as a basis for our understanding of the history and characteristics of the flora we need to know whether New Zealand emerged in its present isolation or whether it was first connected with a larger landmass.
Before considering what geologists have to say on this point we will page 14see whether the plants themselves can tell us anything. Do floras which have evolved on isolated islands which have never been connected to a continent have any characteristics to distinguish them from continental floras? Studies of both the flora and fauna of Hawaiʻi,3 as well as of other isolated islands,4 suggest that the answer to this question is 'yes'