Small change in forest cover can double malaria rate
[MONTEVIDEO, URUGUAY] A small reduction in tropical rainforest cover can increase malaria incidence by nearly 50 per cent, a study in the Brazilian Amazon has found.
Open spaces and partially sunlit pools of water, typical conditions of deforested landscapes, provide an ideal habitat in which the Anopheles darlingi mosquito— the main vector of the malaria parasite in the Amazon — can live and lay its eggs, according to the study, published online early in Emerging Infectious Diseases.
The authors, from the University of Wisconsin, Madison in the United States, and Santo Antonio Energia in Brazil, an energy consortium, studied high-resolution satellite data of land cover from 54 Brazilian health districts bordering Peru from 1996 to 2006. They also examined health data collected in the same areas in 2006.
They found that a four per cent change in forest cover was associated with a 48 per cent increase in malaria incidence.
Areas with less deforestation had a lower malaria risk, suggesting a link between conservation practices and health.
"We believe that the small change in deforestation is greatly amplifying the number of mosquito vectors, and thereby increasing malaria risk in humans," said Sarah Olson, lead author of the study.
"Local land management and development policies should weigh this human health risk along with the economic benefits of deforestation."
Kevin Lafferty, an ecologist at the University of California Santa Barbara, who questioned the links between climate change and malaria last year, said:
"Certainly, deforestation can create conditions that favour mosquitoes. Also, human populations tend to move into areas that are recently deforested. If these are migrants that bring malaria with them, they can set off epidemics.
"But it is important to formally quantify the link between deforestation and malaria, whatever the causal chain.
However, he added that "economics trumps climate change [and deforestation] when it comes to determining the future of malaria.
"[Economics] is an overlooked aspect of malaria given the current emphasis on climate change, but there is good evidence that endemic malaria is much more likely in poor countries and that malaria makes poor countries even poorer. It is a vicious cycle."