This pair of digital maps shows the time-integrated Normalized Difference Vegetation Index (NDVI) over the American Midwest in 1991 (left) and 1993 (right). The integrated NDVI is a measure of the total biomass produced in a complete growing season. In these maps, greener colors indicate higher production levels. In 1991, drought conditions prevailed in the Texas Panhandle and the eastern portions of Oklahoma, Kansas, and Nebraska, while normal rain and plant growth existed in the crop heartland of Iowa and Illinois. In contrast, 1993 saw record rains over the entire Midwest, producing heavy plant growth across much of the area, including normally dry lands in the extreme western plains. At the same time, the excess rain caused extensive flooding along major river channels, leading to poor crops in the normally productive areas of southern Minnesota and western Iowa. Images: From an article by Bradley C. Reed of the EROS Data Center.
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