Abstract

recent decline of the quiver tree (Aloe dichotoma) in South Africa and Namibia. This species appears to conform to these trends: it is disappearing in the north of its range in northern Namibia; and at lower altitudes. So far, it has been unable to establish itself in the cooler south, seemingly because rains are not heavy enough. Reduced rainfall is expected to accompany rises in temperature in Africa, and is likely to have severe effects on biodiversity. South Africa’s dry west will be worst affected, and it includes two biomes with particularly diverse plant species, the Fynbos and the Succulent Karoo, in which species numbers are predicted to fall. But why are collections of old dead biological specimens potentially interesting? The answer is that they offer us a temporal perspective which experiments or contemporary observations often cannot do. Foden was fortunate in that she was able to use photographs of quiver tree ‘forests‘ taken last century, in which individual trees could be identified, to document their decline. Good museum and herbarium collections—often combined with contemporary surveys—can inform us not only of temporal shifts in distribution, but changes in morphology, size or colour; and even life-history variables such as changes in breeding season, or the emergence of adult stages. Hamer found over 70 studies in the northern hemisphere which have used natural history collections to monitor climate change. She could find none, by contrast, in South Africa. In an interesting recent example from the northern hemisphere, Moritz et al. 3

Highlights

  • This was the question discussed at the annual meeting of the South African Biosystematics Initiative (SABI) in Bloemfontein in November 2008

  • Studies suggest that global warming is driving species ranges poleward and towards higher elevations, but evidence for range shifts is scarce for the tropics, where the upslope shifts are predicted to be more likely than poleward shifts

  • One of the two local examples was a field study by Wendy Foden et al.,[2] formerly of South African National Biodiversity Institute (SANBI), which documented the recent decline of the quiver tree (Aloe dichotoma) in South Africa and Namibia

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Summary

Introduction

This was the question discussed at the annual meeting of the South African Biosystematics Initiative (SABI) in Bloemfontein in November 2008. Studies suggest that global warming is driving species ranges poleward and towards higher elevations, but evidence for range shifts is scarce for the tropics, where the upslope shifts are predicted to be more likely than poleward shifts. They conclude that tropical lowland biotas may face a level of net lowland biotic extinction far greater than at higher latitudes (where range shifts may be compensated for by species from lower latitudes) and that the elevational ranges of many remaining tropical species are likely to change.

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