3.2.4.6 Global population futures
Health impacts of global environmental change
Any calculations of global population futures will have to take into consideration existing and emerging
threats such as ozone (O3) depletion and climate change. These may well impact both numbers and
distribution of population.
Climate change
A change in climatic conditions can have three kinds of health impacts:
- Relatively direct impacts, usually caused by increases in the frequency or severity of extreme
weather events such as:
o Storms which increase the risk of dangerous flooding, high winds, and other threats.
o Warmer average temperatures leading to hotter days and more frequent and longer
heat waves.
- Consequences of environmental change and ecological disruption that occur:
o Increases concentrations of unhealthy air and water pollutants.
o Changes in temperature and precipitation patterns could exacerbate the spread of
some diseases.
- Consequences associated with demoralised populations in the wake of climate-induced
economic dislocation, environmental decline, and conflict situations. For example:
o Greater frequency of infectious disease epidemics following floods and storms.
o Substantial traumatic, nutritional and psychological health effects following
population displacement from sea level rise or increases storm activity.
Although global warming may bring localised benefits such as fewer winter deaths in temperate
climates and increased food production in certain areas, the WHO suggests that the overall health
effects will be overwhelmingly negative between 2030 and 2050, with approx. 250,000 additional
deaths per year from malnutrition, malaria, diarrhoea and heat stress.
Certain groups will be particularly vulnerable. Vulnerability depends on population density, level of
economic development, food availability, income level and distribution, local environmental
conditions, pre-exiting health status and the quality and availability of public healthcare. Those most
at risk from being harmed by thermal extremes include the elderly and the poor.
, Heatwaves and thermal stress
The main risks posed by heatwaves are dehydration, overheating, exhaustion and heatstroke. The very
young, the elderly and the seriously ill are most at risk. During the summer heatwave in northern
France in August 2003, unprecedented high day- and night-time temperatures for three weeks
resulted in 15,000 excess deaths.
Heatwaves can lead directly or indirectly to other health risks:
- Smogs, which can lead to high concentrations of nitrogen dioxide and particulate matter in
the atmosphere.
- The growth of blue-green algae in water courses, which can cause problems for aquatic life,
including fish, as well as toxic algal blooms, causing problems for public recreational water
activities.
- Health and environmental problems including odour, dust and vermin infestation. Additional
measures may be necessary to mitigate these problems, including more frequent waste
collections and extra pollution control measures at landfills and other waste treatment
facilities.
- Wildfires.
- Water shortages.
Heatwaves have a much bigger health impact in cities than in surrounding suburban and rural areas.
The impact on mortality from heat stress may be more significant in developing-country cities such as
Mexico City or New Delhi, where populations are especially vulnerable as they lack the resources to
deal with heatwaves.
Cold spells
Death rates in winter can be 25% higher than in summer in temperate countries. Extremes of cold
impact severely on those suffering with both cardiovascular and respiratory diseases and lead to an
increase in mortality. However, annual winter outbreaks such as influenza, which have a large
influence on winter mortality, are not strongly associated with colder temperatures.
Climate change is likely to bring milder winters in temperate regions. Global climate change is likely
to lead to a reduction in mortality rates due to decreasing winter mortality. This is most pronounced
for cardiovascular mortality in elderly people in cities which experience temperate or cold climates at
present. There is conflicting evidence as to whether the decreases in winter mortality are greater or
less than the increase in summer deaths due to heatwaves. The net impact on mortality is likely to
vary between populations.
Health impacts of global environmental change
Any calculations of global population futures will have to take into consideration existing and emerging
threats such as ozone (O3) depletion and climate change. These may well impact both numbers and
distribution of population.
Climate change
A change in climatic conditions can have three kinds of health impacts:
- Relatively direct impacts, usually caused by increases in the frequency or severity of extreme
weather events such as:
o Storms which increase the risk of dangerous flooding, high winds, and other threats.
o Warmer average temperatures leading to hotter days and more frequent and longer
heat waves.
- Consequences of environmental change and ecological disruption that occur:
o Increases concentrations of unhealthy air and water pollutants.
o Changes in temperature and precipitation patterns could exacerbate the spread of
some diseases.
- Consequences associated with demoralised populations in the wake of climate-induced
economic dislocation, environmental decline, and conflict situations. For example:
o Greater frequency of infectious disease epidemics following floods and storms.
o Substantial traumatic, nutritional and psychological health effects following
population displacement from sea level rise or increases storm activity.
Although global warming may bring localised benefits such as fewer winter deaths in temperate
climates and increased food production in certain areas, the WHO suggests that the overall health
effects will be overwhelmingly negative between 2030 and 2050, with approx. 250,000 additional
deaths per year from malnutrition, malaria, diarrhoea and heat stress.
Certain groups will be particularly vulnerable. Vulnerability depends on population density, level of
economic development, food availability, income level and distribution, local environmental
conditions, pre-exiting health status and the quality and availability of public healthcare. Those most
at risk from being harmed by thermal extremes include the elderly and the poor.
, Heatwaves and thermal stress
The main risks posed by heatwaves are dehydration, overheating, exhaustion and heatstroke. The very
young, the elderly and the seriously ill are most at risk. During the summer heatwave in northern
France in August 2003, unprecedented high day- and night-time temperatures for three weeks
resulted in 15,000 excess deaths.
Heatwaves can lead directly or indirectly to other health risks:
- Smogs, which can lead to high concentrations of nitrogen dioxide and particulate matter in
the atmosphere.
- The growth of blue-green algae in water courses, which can cause problems for aquatic life,
including fish, as well as toxic algal blooms, causing problems for public recreational water
activities.
- Health and environmental problems including odour, dust and vermin infestation. Additional
measures may be necessary to mitigate these problems, including more frequent waste
collections and extra pollution control measures at landfills and other waste treatment
facilities.
- Wildfires.
- Water shortages.
Heatwaves have a much bigger health impact in cities than in surrounding suburban and rural areas.
The impact on mortality from heat stress may be more significant in developing-country cities such as
Mexico City or New Delhi, where populations are especially vulnerable as they lack the resources to
deal with heatwaves.
Cold spells
Death rates in winter can be 25% higher than in summer in temperate countries. Extremes of cold
impact severely on those suffering with both cardiovascular and respiratory diseases and lead to an
increase in mortality. However, annual winter outbreaks such as influenza, which have a large
influence on winter mortality, are not strongly associated with colder temperatures.
Climate change is likely to bring milder winters in temperate regions. Global climate change is likely
to lead to a reduction in mortality rates due to decreasing winter mortality. This is most pronounced
for cardiovascular mortality in elderly people in cities which experience temperate or cold climates at
present. There is conflicting evidence as to whether the decreases in winter mortality are greater or
less than the increase in summer deaths due to heatwaves. The net impact on mortality is likely to
vary between populations.
