English: On these maps, vegetation is pictured as a scale, or index, of greenness. Greenness is based on several factors: the number and type of plants, how leafy they are, and how healthy they are. In places where foliage is dense and plants are growing quickly, the index is high, represented in dark green. Regions where few plants grow have a low vegetation index, shown in tan. The index is based on measurements taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Areas where the satellite did not collect data are gray.The most obvious pattern that the maps show is a global one: vegetation greenness is high around the equator all year long, where temperatures, rainfall and sunlight are abundant. Between the equator and the poles, the vegetation greenness rises and falls as the seasons change.