Geoengineering to prevent the worst impacts of climate breakdown could expose up to a billion more people to malaria, scientists have found.
The report, published on Wednesday in Nature Communications (“Solar geoengineering could redistribute malaria risk in developing countries), is the first assessment of how geoengineering the climate could affect the burden of infectious diseases.
Scientists from icddr,b and other international research institutions conducted pioneering research to understand how solar radiation management (SRM) geoengineering could affect some of the world’s poorest and most vulnerable regions.
The study was led by Colin Carlson, an assistant research professor at the Center for Global Health Science and Security at Georgetown University Medical Center, where focuses on SRM, a hypothetical emergency intervention aimed at reducing the dangerous impacts of climate change.
By injecting aerosols into the stratosphere that reflect incoming sunlight, some researchers have suggested that it may be possible to temporarily “pause” global warming. Though SRM is often discussed as a way to reduce climate injustice, its potential impacts on health have barely been studied.
In the study, a team of eight researchers from the United States, Bangladesh, South Africa, and Germany used climate models to simulate what malaria transmission could look like in two future scenarios, with medium or high levels of global warming, with and without geoengineering. The models identify which temperatures are most conducive for transmission by the Anopheles mosquito vectors, and identify how many people live in areas where transmission is possible.
In both scenarios, malaria risk was predicted to shift significantly between regions. However, in the high warming scenario, simulations found that a billion extra people were at risk of malaria in a geoengineered world.
“In a planet that’s too hot for humans, it also gets too hot for the malaria parasite,” said Carlson. “Cooling the planet might be an emergency option to save lives, but it would also reverse course on those declines.”
A malaria specialist Mohammad Shafiul Alam, who is a Scientist at icddr,b said that “This is the first of its kind study that examined the likely impact of geoengineering techniques on vector-borne diseases. It revealed that if such techniques are implemented, it may cut both ways: some countries will benefit and other countries will suffer.”
The study follows a 2018 commentary in Nature Climate Change by Carlson and the study’s senior author, Christopher Trisos, a senior researcher at the University of Cape Town. In the commentary, the researchers proposed a hypothesis now confirmed in the new study: because malaria transmission peaks at 25°C, cooling the tropics using geoengineering might ultimately increase malaria risk in some places relative to not only alternative futures but also the present day.
“The potential for geoengineering to reduce risks from climate change remains poorly understood, and it could introduce a range of new risks to people and ecosystems”, said Trisos.
The implications of the study for decision-making are significant. “Geoengineering might save lives, but the assumption that it will do so equally for everyone might leave some countries at a disadvantage when it comes time to make decisions.
If geoengineering is about protecting frontline populations, we should be able to add up the risks and benefits—especially in terms of neglected health burdens like a mosquito-borne disease.”
Carlson says that one of the most surprising findings was the scale of potential trade-offs between regions. For example, in both scenarios, the authors found that geoengineering might substantially reduce malaria risk in the Indian subcontinent even compared to the present day.
However, that protective effect would be offset by an increase in risk in Southeast Asia. For decision-makers, this might complicate the geopolitical reality of climate intervention.
“We’re so early in this process that the conversation is still about increasing Global South leadership in geoengineering research. Our study highlights that the frontlines of climate injustice aren’t one monolithic bloc, especially when it comes to health,” he added.
