Climate impacts are determined not just by the magnitude of environmental change
but also by the vulnerability of exposed populations. Examples of biophysical
vulnerability are the susceptibility of pale-skinned populations to the effects
of UV radiation and the vulnerability of isolated island ecosystems such as
New Zealand's to invasion by exotic species (including disease vectors).
Another example is infections spread to humans from animals, such as cryptosporidiosis.
New Zealand has relatively high rates of notified cases of this infection (Russell
et al., 1998). This may be related to the conjunction of high densities
of livestock and unprotected human drinking water supplies. In such a setting,
increased rainfall intensity would promote transmission of the pathogen (by
washing animal excreta containing the organism into the water supply).
Woodward et al. (1998) reviewed social determinants of vulnerability
to health effects of climate change in the Pacific region. Australia and New
Zealand are two of the wealthiest countries in the region, with relatively low
population densities and well-developed social services. For these reasons,
Australia and New Zealand are likely to be less vulnerable overall to many of
the threats to health from climate change than neighboring countries. However,
within both countries there are groups that are particularly susceptible to
poor health. Sources of disadvantage include poverty, low housing standards,
high-risk water supplies, lack of accessible health care, and lack of mobility.
These factors tend to be concentrated in particular geographical locations and
ethnic groups (Crampton and Davis, 1998) and carry with them increased vulnerability
to most of the hazards that are associated with climate variability and climate
There have been no studies in New Zealand or Australia that have attempted
to quantify vulnerability to disease and injury. Some work has been carried
out on indices of environmental vulnerability (e.g., Kaly et al., 1999).
These studies have focused on measures of the resilience and integrity of ecosystems;
with further development, they may assist in future forecasts of the impacts
of climate change on human health.
12.7.3. Complexities of Forecasting Health Effects
There is no opportunity to study directly, in a conventional controlled fashion,
the effects on health of climate change. Research to date in Australia and New
Zealand has concentrated on the association of climate variability, at relatively
restricted spatial and temporal scales, with the incidence of disease. It is
not simple to extrapolate from these findings to long-term climate change. This
problem is not particular to Australia and New Zealand, but there are informative
local examples in the literature. These include analyses of roles of climate-related
variables other than temperature (e.g., the critical effects of wind on air
pollution, rainfall density on mosquito breeding, and humidity on heat stress);
interactions with local ecosystems (e.g., the potential for amplification of
certain arboviruses in New Zealand wildlife); and human behaviors that influence
exposures (such as changing patterns of skin protection and the implications
for UV exposures) (Hill et al. 1993; Russell, 1998b).
12.7.4. Public Health Infrastructure
A major challenge in Australia and New Zealand is how to protect and improve
public health systems that deal with threats to health such as those that will
potentially accompany climate change. Examples include border controls to prevent
introduction of pathogens (including those from livestock and animal imports),
measures required to ensure safe food and clean water, and primary health care
services that reach the most disadvantaged and vulnerable members of the community.
Threats to these systems include restrictions on government spending, increasing
demands, and fragmented systems of purchase and provision of services.
With vector-borne diseases, the major challenge in Australia will be to control
the expansion and spread of diseases that already are present in the country,
such as Ross River virus and Murray Valley encephalitiswhich are strongly
influenced by climatic events. Introduction of new pathogens from close neighbors
such as Papua New Guinea also is possible. Imported Japanese encephalitis and
malaria remain serious threats, influenced principally by the numbers of people
moving across the Torres Strait and the effectiveness of health services in
the far north of Australia.
In New Zealand, the key issue for the health sector is how to prevent the introduction
of vector-borne disease, particularly arboviruses carried by mosquitoes. Competent
vectors for conditions such as Ross River virus and dengue have been detected
frequently at entry points in recent years. This is likely to be a result of
increasing trade and passenger traffic between New Zealand and other countries,
as well as heightened awareness and better reporting. Eradication programs are
expensive, and they are feasible only when the spread of exotic mosquitoes is
confined. With repeated incursions and/or dispersion, the emphasis is likely
to shift to control strategies.