Rice irrigation strategies to protect public health in Africa
CGIAR Research Program on Agriculture for Nutrition and Health (A4NH) scientists are examining the interlinkages between agricultural development proposals to expand rice cultivation, and public health plans to eliminate malaria.
Africa suffers 85% of the world’s mortality due to malaria — an African child dies of malaria every two minutes. A4NH researchers are determining how agricultural development can become part of the public health solution, and not part of the problem.
In the 1990s, a series of studies comparing villages with and without irrigated rice concluded that the introduction of rice brings a substantial increase in the local abundance of vector mosquitoes, but seemingly not an increase in malaria in the local human population. As rice productivity led to improvements in household economics and local infrastructure, residents had better access to anti-malaria drugs and bed nets for protection against mosquitoes. This situation reassured agricultural development agencies that irrigated rice schemes did not have the harmful side effect of causing an increase in malaria.
A4NH researchers are determining how agricultural development can become part of the public health solution, and not part of the problem.
Encouragingly, malaria intervention coverage is now substantially higher and more equitable than before. As a result, Africa has enjoyed a reduction of more than 50% in malaria mortality and in the prevalence of malaria infection. However, A4NH researchers recently identified that there was a need to re-examine the relationship between rice cultivation and malaria, to determine whether there was an emerging risk of increased malaria transmission.
A4NH scientists conducted a formal analysis of up-to-date evidence, which confirmed that today the additional malaria mosquitoes coming from rice do, indeed, cause an increase in the intensity of malaria transmission in irrigated rice communities. There is, therefore, a need to find ways of growing rice in Africa without increasing mosquito numbers at the same time.
In 2020, two groups of experts came together — agronomists with expertise in growing rice and entomologists with expertise in the ecology of mosquitoes in African rice fields — and gave A4NH researchers an opportunity to inform the direction of a major development investment strategy, to mitigate any unintended negative consequences on human health.
There is a need to find ways of growing rice in Africa without increasing mosquito numbers at the same time.
The CGIAR Research Program on Rice has been studying cultivation methods, such as alternate wet and dry (AWD) irrigation, which reduces the amount of water required for growing rice and the amount of greenhouse gases produced by the flooded fields. These methods may also affect mosquitoes: AWD has parallels with the intermittent irrigation used to control mosquitoes.
With funding from the Wellcome Trust, A4NH researchers are investigating whether these two approaches can be modified and combined in a way that would effectively minimize emissions of both methane and mosquitoes, while saving water and avoiding any loss of productivity.
Findings suggest that such a win-win-win solution — one that has positive environmental, health, and farming outcomes — is possible. Detailed research on a range of rice management options will be required to develop methods that can produce these co-benefits reliably and in a variety of settings.