Climate-Change Effects on Alpine Plant Biodiversity: A New Zealand Perspective on Quantifying the Threat

Abstract

New Zealand’s alpine region is populated by many (∼613) species of vascular plants with a high endemism (∼93%). To investigate the potential impact of climate warming, we used species-area relations to estimate current and projected vascular plant floras and tested model sensitivity scaling from the whole world to small alpine regions.Within their limitations, these models show that if the present mean temperature of ∼0.6°C higher than in 1900 were maintained, together with a large pool of exotic species, 40–70 species of native plants could become at risk. With a rise of 3°C, an approximate expectation for the following 100 yr, the total New Zealand alpine vascular flora could reach ∼550–685 species and lose 200–300 indigenous alpine species, the rest being exotic. Fragmentation of alpine areas could, over millennia, favor speciation, but in the short term, the loss of ∼80% of existing alpine islands will severely increase extinction risks.These model projections will be modified by downward extension of species through unplanned vegetation destruction, or following deliberate vegetation clearance to create habitats favorable to alpine species, as well as through a number of other as yet unquantified factors. These projections are not predictions of extinctions but rather broad probabilities of risk to a whole flora.