Photosynthetic activity on land

A map illustrating the Normalized Difference Vegetation Index (NDVI) calculated from AVHRR satellite data and aggregated over the year 1998. NDVI values vary with absorption of red light by plant chlorophyll and the reflection of infrared radiation by water-filled leaf cells, and provide an indication of photosynthetic activity. The map reveals a clear distinction between areas rich in standing growth of plants, whether cropland or natural vegetation, and areas where standing plant growth is sparse or absent.
Source: modified from image provided by the SeaWiFS Project, NASA/Goddard Space Flight Centre and ORBIMAGE.