Which is a More Important Determinant of Malaria -- Climate Change or Socioeconomic Development?

Béguin et al. (2011) quantifed the independent effects of climate and socio economic factors on the historical and future global distribution of malaria. The authors also provides estimates of their separate and combined contributions to the populations at risk of malaria. Specifically, they estimate populations at risk of malaria (PAR) based on climatic variables, population growth and GDP per capita (GDP_pc). GDP_pc is an approximation for per capita income ("income" for short) for 1990, 2010 and 2050, based on a sensitivity analyses for the following three scenarios: (1) a worst-case scenario, in which income declines to 50% of its 2010 values by 2050, (2) a ''growth reduction'' scenario, in which income declines by 25% in 2030 and 50% in 2050, relative to the A1B scenario, and (3) a scenario in which income stays constant at 2010 values.

The PAR is derived from information on the presence or absence of P. vivax malaria in 1990 based on a logistic model for malaria presence that used three parameters: the mean temperature of the coldest month, and the mean precipitation of the wettest month during the period 1961-1990, and the square root of income. Accordingly, the PAR is not directly reflective of the health impacts of malaria. Secular technological change was ignored in this study.

The results are indicated in the table below.

In the words of the authors, "under the A1B climate scenario, climate change has much weaker effects than GDP_pc increase on the geographic distribution of malaria." This result is consistent with the few studies that have considered the impact of climate change and socioeconomic factors on malaria. See, e.g., (Tol and Dowlatabadi, 2001; Bosello et al., 2006). With respect to malaria, therefore, climate change is a relatively minor factor compared to economic development. In other words, it is more important to pursue economic development rather than to pursue reductions in climate change.

Addendum: The study makes a gratuitous claim that the above result is "dependent on optimistic, and potentially unsustainable, economic growth. Even then, climate change has important effects on the projected distribution of malaria, leading to an increase of over 200 million in the projected population at risk." (p. 1214). However, it should be noted that if the growth rate is unsustainable then the emission estimates, and the estimated climate change for the A1B scenario is, likewise, overstated, as would be the impacts of climate change.

Additional References
Bosello, F., Roson, R. and Tol, R.S.J. 2006. Economy-wide estimates of the implications of climate change: human health. Ecological Economics 58: 579-591.

Tol, R.S.J. and Dowlatabadi, H. 2001. Vector-borne diseases, development & climate change. Integrated Assessment 2: 173-181.