Green: Vegetation on Our Planet (Plant Density [NDVI])
The first dataset in the visualization shows the density of green-leaf vegetation on Earth. The darkest green areas have the most plants, while the pale colors are sparsely vegetated because of snow, drought, rock, or urban development. Scientists use an algorithm called the Normalized Difference Vegetation Index (NDVI) to quantify the global density of plants, which is derived by measuring the wavelengths and intensity of visible and near-infrared light reflected by the land surface back into space. Data acquired from the VIIRS sensor aboard the NASA/NOAA Suomi-NPP satellite from April 8 to August 26, 2013, was used to generate this segment, which highlights the summer “green-up” of vegetation in the Northern Hemisphere. For more information on this dataset, see Green: Vegetation on Our Planet at the NOAA Environmental Visualization Laboratory.
The three colors of green in the next dataset indicate three classes of vegetation in the Arctic region. They include the northern limit of forests (dark green) as well as shrubs (medium green) and low-growing tundra plants such as grasses, sedges, and mosses (light green). This progression of tall, dense vegetation in the south to shorter, sparser vegetation in the north directly relates to the amount of warmth available for growth—the warmer the summer temperatures, the greater the size, abundance, and variety of plants. The classes were modified from those identified by American Museum of Natural History research associate Richard Pearson and his colleagues using data from the Circumpolar Arctic Vegetation Map (CAVM). The CAVM was developed using a variety of data from satellites as well as on-the-ground research.
Summer greenness, 1982 – 2010
Satellite images of global vegetation density are available since 1982, allowing scientists to understand where and how the productivity of Earth’s vegetation has changed in the last 30 years. This pair of images shows the greenness of vegetation during the periods 1982 to 1986 and 2006 to 2010 compared to the full satellite record period from 1982 to 2010. Like the first dataset in the visualization, these images are based on the Normalized Difference Vegetation Index. At high northern latitudes, vegetation has predominantly become greener (more productive) over time, with productivity being relatively low in 1982 – 2006 (browner colors) and higher in recent years (2006 – 2010, greener colors). These images were produced for this data visualization by Scott Goetz, Pieter Beck, and Kevin Guay at the Woods Hole Research Center.