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- Two new studies confirm that agriculture is linked to increased malaria transmission in Africa.
- Agriculture and malaria have always been closely linked. The agricultural revolution brought people to live close to each other – and close to water.
- Three agricultural landscapes were associated with a higher risk of childhood malaria in sub-Saharan Africa: rainfed cropland in rural areas, irrigated cropland near urban areas, and full forest cover.
Africa’s population is expected to triple by 2100. This means more food, water and agricultural products are needed. To meet these needs, African governments and development agencies have implemented major agricultural projects.
For example, the Coalition for African Rice Development, a policy framework, has set a goal to double rice production from 28 million tonnes in 2018 to 56 million tonnes by 2030. Governments are also increasing international trade in agricultural products.
Agricultural development involves both expansion into new agricultural land and more intensive farming, using irrigation or fertilizers to improve crop yields. Such development can improve household wealth, health care, education, and national gross domestic product.
Unfortunately, when done the wrong way, it can also harm the environment. Agriculture can contribute to deforestation, carbon emissions, water and air pollution, and biodiversity loss.
In turn, these effects can harm human health. Some infectious diseases – malaria, schistosomiasis and Buruli ulcer – have been linked to agriculture.
Agriculture and malaria have always been closely linked. The agricultural revolution brought people to live close to each other – and close to water. But researchers have failed to fully understand, quantify or predict the links between agriculture and malaria.
To add to what is known about this, we investigated whether childhood malaria in sub-Saharan Africa varied across different types of agricultural landscapes. We asked whether different forms of agriculture increased or reduced the risk of childhood malaria. The land uses we considered were irrigated and rainfed cropland and systems that mix natural cover and crops.
We found models that suggest how farmland could be better managed to reduce health risks. This is important because the African continent still suffers over 90% of malaria deaths worldwide. And the region’s progress towards eliminating malaria has stagnated in recent years.
Reduce malaria and improve biodiversity
We combined remote sensing data on land cover and land use with a georeferenced malaria dataset of 24,034 children in 12 countries. The malaria data covered the period from 2010 to 2015. Our analysis controlled for factors known to impact childhood malaria, such as the use of mosquito nets and insecticides.
Our study showed that the following agricultural landscapes increased the risk of childhood malaria in sub-Saharan Africa:
- Rural Rainfed Cropland
- Irrigated cropland in or near urban areas
- Full forest cover
We have also found that the presence of natural vegetation in agricultural land can reduce malaria.
Agricultural expansion through rain-fed or irrigated cropland appears to increase the risk of childhood malaria in sub-Saharan Africa. This is true for rural or urban contexts. But retaining some of the natural vegetation in cropland could reduce the risk.
Maintaining vegetation in agricultural land is also known to protect biodiversity and ecosystem functions and services. This makes farmland more sustainable in the long term.
Increased risk of malaria
In another study, we partnered with AfricaRice and the International Institute of Tropical Agriculture to examine the link between rice and malaria in sub-Saharan Africa. Rice paddies make excellent breeding sites for mosquitoes, but it has often been argued that rice-growing communities do not necessarily suffer from more malaria. This counter-intuitive discovery has been called the “paradox of the paddy fields”.
But our study found that irrigated rice-growing communities are exposed to more mosquitoes and also to a higher risk of malaria. The paradox is therefore resolved. This can be explained by recent changes in Africa: greater equity in the distribution of antimalarial interventions, which has reduced the overall intensity of transmission.
Our two studies confirm that agriculture is linked to increased malaria transmission in Africa.
This is worrying because, currently, three branches of development are trying to achieve their goals in isolation. African Ministries of Agriculture are planning the expansion and intensification of agriculture. Ministries of health plan to eliminate malaria. And environment ministries are trying to deal with the impacts of deforestation, climate change and land use.
Surprisingly little has been done to reconcile these competing priorities. Clearly, greater collaboration across sectors is needed to achieve all of these goals.
Policy makers need more evidence on the causality of the agriculture-malaria relationship. This would help them choose between land use policy options in rural and urban systems. They would have a better understanding of how different metrics, such as water availability, biodiversity loss, malaria eradication, carbon emissions, soil health, and economic productivity, affect multiple aspects of sustainability.
Hiral Anil Shah is a health economist at Imperial College London. Kallista Chan is a PhD candidate, agriculture and infectious diseases, and Kris Murray is an associate professor, environment and health – both at the London School of Hygiene & Tropical Medicine. Murray is also a lecturer in ecological health at Imperial College London.
This article was republished from The conversation.