The long-term conservation of forest diversity in New Zealand

Abstract

The largely endemic flora of New Zealand is a remnant of the Cretaceous flora of Gondwana, supplemented by later additions from Australia and the tropics. Semi-natural plant communities cover about 50% of the country, and a scheme for the protection of supposedly representative areas is in place. Existing reserves do not adequately reflect the patterns of plant species diversity. Many are modified by introduced animals and alien plants. The latter are being actively introduced into New Zealand at the rate of c. 11 species per year. Measures of diversity are discussed and the broad pattern of (gamma) diversity and endemicity in the country is described. A comparison is made between (alpha) diversity levels in Beech Nothofagus solandri var. cliffortioidesand Kauri Agathis australisforest. Within each of these two forest types there are similar levels of alpha-diversity over a wide range of latitude. Altitudinal alpha-diversity trends indicate an average loss of 3.4 species per 100 m of altitude. This can be accounted for by the reduction of land surface area with increasing altitude on conical or ridge-shaped mountains. The altitudinal data emphasize the importance of the lowlands in the conservation of bio-diversity. The Holocene history of the forests in New Zealand suggests that the concept of "representativeness" is flawed: forest varies continuously in time and space. It may be possible to create some "living museums" of the past biota of New Zealand, but unless there are radical changes in our ability to eradicate animal pests and introduced plants, the composition of mainland forest reserves in the lowlands will change dramatically over the next few centuries. Conservation effort on saving endangered birds may have been at the expense of long-term "habitat" survival on the mainland.