Climate change impacts agriculture in many ways, with changes in temperature, precipitation and climatic variability affecting the timing and length of growing seasons and yields and thereby exacerbating land degradation and contributing to water scarcity (Agrawala and Fankhauser, eds., As a proxy, the remotely sensed NDVI, which has been shown to be related to biophysical variables that control vegetation productivity and land/ atmosphere fluxes, is also used to estimate vegetation change (Bai and others, 2008). For instance, it is estimated that, in Southern Africa, yields could fall by up to 50 per cent between 2000 and 2020 (Intergovernmental Panel on Climate Change, 2007b), and that, by 2080, 600 million additional people could be at risk of hunger as a direct consequence of climate change (United Nations Development Programme, 2007, overview, p. 9). They also impact land-surface albedo so as to engender adverse weather patterns (University of East Anglia, Overseas Development Group, 2006).