What can museum and herbarium collections tell us about climate change?

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