Adaptation refers to actions taken to lessen the impact of the (anticipated) change in climate. Adaptive actions to reduce health impacts can be thought of in terms of the classical categorisation of preventive measures in public health (Last, 1995):

1. Primary prevention: actions taken to prevent the onset of disease due to environmental disturbances, in an otherwise unaffected population (e.g., supply of bed nets to all members of a population at risk of exposure to malaria).
2. Secondary prevention: preventive actions taken in response to early evidence of health impacts (e.g., strengthening disease surveillance and responding adequately to disease outbreaks).
3. Tertiary prevention: health-care actions taken to lessen the morbidity or mortality caused by the disease (e.g., improved diagnosis and treatment of cases of malaria).

Primary prevention can be addressed at many levels - including, most radically, the mitigation of the climate change process. In general, secondary and tertiary prevention are less effective than primary prevention, although they are often practically and politically easier to implement. In addition, there are both ethical and social reasons to prefer primary preventive action wherever it is feasible. In the long term, secondary and tertiary prevention measures usually turn out to be more expensive than primary prevention.

A three-fold categorisation of strategies to protect population health is: (i) administrative or legislative, (ii) technical/engineering, and (iii) personal (behavioural) (Patz, 1996). Legislative or regulatory action can be taken by government, requiring compliance by all, or by designated classes of, persons. Alternatively, an adaptive action may be encouraged on a voluntary basis, via advocacy, education or economic incentives. The former type of action would normally be taken at international, national or community level; the latter would range from international to individual levels. Adaptation options can operate at different spatial levels, from local to global. Some of the options are of a structural and general kind, facilitating and maximising preventive impacts. Other options are of a more specific kind, entailing procedures, technologies or behavioural changes. Table 14.4. shows the major adaptation options for reducing the health impacts of climate change, and the major considerations that bear upon their effectiveness.

* G = Global, N = National, L = Local.

Actions to reduce the health impacts of climate change are basically public policy response options and are, therefore, in the latter system. The ultimate goal of these interventions is the reduction, with the least cost, of diseases, injuries, disabilities, suffering and death. There is little quantitative information about how humans adapt either biologically or culturally to climate change. Most assessments of the health impacts of climate change have therefore not addressed adaptation explicitly and quantitatively. However, some assessments of the impacts of thermal stress have modelled, by extrapolation from short-term observations, the effect of longer-term acclimatisation at the population level (e.g., Kalkstein and Greene, 1997). The most effective way to reduce potential health impacts will be through adaptation technologies that reduce the overall level of population vulnerability. The potential impacts of climate change on food and water are not seen as the responsibility of public health agencies.

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