The potential health impacts of climate change would occur via pathways of varying complexity, scale, and directness (Figure 14.1) (see McMichael et al., 1996 and IPCC, 1996 WGII [Chapter 18]). The limited capacity for social adaptation in some populations and the unpredictability of social, economic, demographic change make forecasts of the extent and timing of health impacts difficult.
The direct adverse impacts on human health are likely to be due to changes in exposure to temperature extremes (heatwaves) and increases in the frequency or intensity of other extreme events (floods, cyclones, droughts, etc.). The extent to which the frequency of extreme weather events will be altered by climate change remains uncertain, although a changed pattern of floods and droughts is anticipated. In addition, an increase in winter temperatures may lead to a decrease in winter mortality (Langford and Bentham, 1995; Martens, 1998), since many temperate-zone countries experience significantly higher death rates in winter than in other seasons (Curwen, 1991).
Less direct impacts include net increases or decreases in the geographic distribution of vector organisms such as malarial mosquitoes. The distribution and abundance of vectors and intermediate hosts are determined by meteorological factors as well as by human interventions. Temperature-related changes in the life-cycle dynamics of vector species and pathogens (helminths, protozoa, bacteria and viruses) may change the transmission of certain infectious diseases such as malaria, dengue and leishmaniasis (Patz et al., 1996; Martens, 1998). While most anticipated change would increase the transmission, decreases would occur in some locations (Martens, 1998; Faye et al., 1995). Climate change will require some changes in crops and food production systems. Some regions are likely to benefit from increased agricultural productivity while others may lose out, according to their location and dependence on the agricultural sector.
Other reports in this collection