Climate change exacerbates public health problems in Tarawa. The incidence of ciguatera poisoning, diarrhoeal disease, malnutrition, and vectorborne diseases, such as dengue fever, rise as a result of increased temperatures and changes in rainfall.
Dengue Fever
South Tarawa is at a relatively high risk of dengue fever epidemics due to a combination of crowded urban areas, ideal climate conditions for the vector (average temperatures of 31 degrees Celsius and rainfall of 500 millimetres a month), the presence of an international airport, and the proliferation of discarded empty bottles and used tires.
A simple model suggests that the risk of dengue fever will increase in the future as a result of climate change, with the epidemic potential – an index measuring the efficiency of disease transmission – expected to increase 22─33 percent by 2050. Most of South Tarawa’s population would be exposed in the event of an epidemic. However, while future epidemics could expand faster, the number of cases would probably not increase from current levels. The increased prevalence of all dengue virus serotypes worldwide could also lead to a higher incidence of severe forms of dengue fever – in particular dengue hemorrhagic fever and dengue shock syndrome, which can be fatal.
Ciguatera Poisoning
Kiribati has one of the highest rates of ciguatera poisoning in the Pacific (Lewis and Ruff 1993). The disease is contracted by consuming reef fish that have been contaminated by ciguatoxins.
A recent study found a statistically significant relation between sea surface temperatures and the reported incidence of ciguatera fish poisoning in Kiribati (Hales and others 1999). This relation was used to model the projected increases in ciguatera poisoning (table 16). The model shows that a rise in temperatures is expected to increase the incidence of ciguatera poisoning from 35–70 per thousand people in 1990 to about 160–430 per thousand by 2050.
These results should be interpreted cautiously, as the model is based on many uncertainties and limited data. The overall impact of climate change on ciguatera should perhaps be measured not in terms of incidence rates but in terms of how people respond to the increased risk (Ruff and Lewis 1997). This may include changes in diets, decreased protein intake, increased household expenditures to obtain substitute proteins, and loss of revenue from reef fisheries. In addition, reef disturbance has been linked to ciguatera outbreaks (Ruff, 1989; Lewis 1992), suggesting that improved management of coastal areas would be an important adaptation strategy.
Diarrhoeal Disease
Increased rainfall would likely result in a reduction in the overall rate of diarrhoea due to improved water quality and availability (though flooding may also lead to groundwater contamination). Decreased rainfall—particularly if it resulted in an increase in droughts—would increase the incidence of diarrhoea, as water shortages exacerbate sanitation problems. The projected rise in temperature may increase the incidence of diarrhoea, primarily by increasing the likelihood of spoiled or contaminated food. Sea level rise could also increase the incidence of diarrhoea by decreasing the size of the freshwater lens, exacerbating overcrowding conditions, and disrupting sanitation and water supply.
Cholera
Tarawa has experienced cholera outbreaks in the past. It is possible that increased temperatures may enhance the pathway of cholera transmission through the high level sewage contamination in Tarawa’s coastal waters.
Indirect Public Health Effects
The indirect public health effects of climate change could be far-reaching. They could include increases in malnutrition due to losses of subsistence agriculture and fisheries; deterioration in standards of living due to impacts on primary sectors; loss of land and infrastructure, leading to increased crowding and land shortages; and the immense economic, social, and cultural impacts associated with population relocation if it was required as a result of inundation or water shortages. These diffuse effects could well prove to be the most important impacts of climate change on the public health of the atoll.
