8.3 Assumptions about future trends
The impacts of developmental, climatic and environmental scenarios on population health are important for health-system planning processes. Also, future trends in health are relevant to climate change because the health of populations is an important element of adaptive capacity.
8.3.1 Health in scenarios
The use of scenarios to explore future effects of climate change on population health is at an early stage of development (see Section 8.4.1). Published scenarios describe possible future pathways based on observed trends or explicit storylines, and have been developed for a variety of purposes, including the Millennium Ecosystem Assessment (Millennium Ecosystem Assessment, 2005), the IPCC Special Report on Emissions Scenarios (SRES, Naki?enovi? and Swart, 2000), GEO3 (UNEP, 2002) and the World Water Report (United Nations World Water Assessment Programme, 2003; Ebi and Gamble, 2005). Examples of the many possible futures that have been described include possible changes in the patterns of infectious diseases, medical technology, and health and social inequalities (Olshansky et al., 1998; IPCC, 2000; Martens and Hilderink, 2001; Martens and Huynen, 2003). Infectious diseases could become more prominent if public-health systems unravel, or if new pathogens arise that are resistant to our current methods of disease control, leading to falling life expectancies and reduced economic productivity (Barrett et al., 1998). An age of expanded medical technology could result from increased economic growth and improvements in technology, which may to some extent offset deteriorations in the physical and social environment, but at the risk of widening current health inequalities (Martens and Hilderink, 2001). Alternatively, an age of sustained health could result from more wide-ranging investment in social and medical services, leading to a reduction in the incidence of disease, benefiting most segments of the population.
Common to these scenarios is a view that major risks to health will remain unless the poorest countries share in the growth and development experienced by richer parts of the world. It is envisaged also that greater mobility and more rapid spread of ideas and technology worldwide will bring a mix of positive and negative effects on health, and that a deliberate focus on sustainability will be required to reduce the impacts of human activity on climate, water and food resources (Goklany, 2002).