Malaria Prevalence Near African Mangroves: Negative Association With Mangrove Extent, but Positive Association With Mangrove Greenness.

Malaria remains a major public health challenge, causing an estimated 600,000 deaths and 250 million infections annually. Most malaria control efforts focus on freshwater mosquito vectors, leaving saltwater-tolerant vector mosquitoes inhabiting coastal ecosystems like mangrove forests understudied. Historically, the role of mangrove forests as breeding grounds for malaria vectors often motivated their destruction. However, mangroves provide crucial ecosystem services, and their impact on malaria transmission remains poorly understood. This study presents the first multi-country analysis linking African mangrove forests to prevalence of malaria (Plasmodium falciparum). We employed piecewise structural equation models to examine the relationships among mangrove land cover and mangrove vegetation greenness across coastal settlements in 27 African countries. We combined satellite-derived land cover, vegetation, and weather data with malaria prevalence records from 11 years, ranging from 1996 to 2020. We found two key associations. First, increasing mangrove land cover is associated with decreasing malaria prevalence at coarse spatial resolution, refuting the traditional view of mangroves as disease-promoting environments. We hypothesise that this relationship may reflect ecological factors such as reduced larval development due to shading, or the presence of predators. Second, at fine and coarse spatial resolutions, increasing mangrove health (i.e., greener vegetation) is associated with increasing malaria prevalence. This trend may be driven by higher mosquito abundance and biodiversity in vegetation-rich mangrove areas, consistent with studies showing vegetation as a positive predictor of mosquito population density. Our findings constitute continent-wide patterns derived from observational data, whereas the precise impact of mangrove vegetation likely depends on the geographic location, configuration of the forests, and the identity and competence of host and vector species. We conclude that mangrove conservation needs to be integrated with locally adapted, context-specific vector management strategies.