Patterns of irrigated rice growth and malaria vector breeding in Mali using multi‐temporal ERS‐2 synthetic aperture radar

Abstract

We explored the use of the European Remote Sensing Satellite 2 Synthetic Aperture Radar (ERS‐2 SAR) to trace the development of rice plants in an irrigated area near Niono, Mali and relate that to the density of anopheline mosquitoes, especially An. gambiae. This is important because such mosquitoes are the major vectors of malaria in sub‐Saharan Africa, and their development is often coupled to the cycle of rice development. We collected larval samples, mapped rice fields using GPS and recorded rice growth stages simultaneously with eight ERS‐2 SAR acquisitions. We were able to discriminate among rice growth stages using ERS‐2 SAR backscatter data, especially among the early stages of rice growth, which produce the largest numbers of larvae. We could also distinguish between basins that produced high and low numbers of anophelines within the stage of peak production. After the peak, larval numbers dropped as rice plants grew taller and thicker, reducing the amount of light reaching the water surface. ERS‐2 SAR backscatter increased concomitantly. Our data support the belief that ERS‐2 SAR data may be helpful for mapping the spatial patterns of rice growth, distinguishing different agricultural practices, and monitoring the abundance of vectors in nearby villages.

Acknowledgments

We would like to thank the collaboration of the Niono Health Center, the Office du Niger, the Institute d'Economie Rurale, Niono supervisors and village guides, and Yeya Touré, Robert Gwadz and the members of the MRTC GIS Laboratory in Bamako for their support. Special thanks to Dr.Yongkang Xue, Dr. Seydou Doumbia and Dr. Sassan Saatchi for their very productive comments and Gina Hendricks for help with image registration.

Financial support

This work was supported by the National Institute of Health (NIH), the National Aeronautic and Space Administration through an Interagency Agreement Y3‐AI‐5059‐03 with the National Institute of Allergy and Infectious Diseases and WARDA Africa Rice Center. The ERS‐2 SAR scenes were provided by the European Space Agency as part of the ESA EO Exploitation Project # C1P.1089.