Some relatively simple direct (and therefore more readily predictable) impacts of, for example, heatwaves, sotrms or rising seas could be anticipated. Via less direct pathways, changes in background climate may, for example, alter the distribution and behaviour of mosquitos and the life-cycle of the malarial parasite, so that malaris patterns change. Many other vector-borne diseases could be affected in a similar way. Climate change would also affect agricultural productivity, and could therefore influence nutritional status, hunger and health. More generally, the physical damagae, habitat loss and species depletion suffered by the marine and terrestrial ecosystems --- such as pastoral lands, ocean fisheries, and wetlands --- that maintain environmental services essential to sustained human health, may be exacerbated by climate change. The different aspects of climate change would of course vary in their relative importance for different health impacts. This is illustrated in Table 1.1 However, our knowledge in this area is incomplete.