The European Space Agency’s (ESA) Envisat satellite has provided the Earth observation data for scientists to create the highest-resolution biomass map to date of forests in the Northern Hemisphere.
Created from an analysis of more than 70,000 radar images dated from October 2009 to February 2011, the new map has a ground sampling distance of 1 kilometer (where 1 pixel is 1 kilometer on the ground). This is the first biomass output covering the entire northern zone that was radar-derived and obtained by a single approach.
“Single Envisat radar images taken at a wavelength of approximately 5 centimeters cannot provide the sensitivity needed to map the composition of forests with high density,” said Maurizio Santoro from Gamma Remote Sensing in an article on the ESA website.
“Combining a large number of radar data sets, however, yields a greater sensitivity and gives more accurate information on what’s below the forest canopy.”
Interest in Northern Hemisphere forests stems mostly from its impressive carbon stores. Northern forests store a third more carbon stocks per 100 acres compared to tropical forests. These boreal forests consist mainly of pines, spruces, and larches. The forests cover Alaska and Canada in the Western Hemisphere and span from Scandinavia across Russia to parts of Japan in the Eastern Hemisphere.
More accurate biomass measurements will help scientists better track forests and vegetation. Since vegetation plays such a significant role in the global carbon cycle, these measurements will improve our understanding of the carbon cycle and help scientists better predict the future of Earth’s climate.
When Envisat was launched in 2002, it was the largest Earth observation satellite ever built (a record now held by the Landsat satellite). The satellite’s key instruments were the Advanced Synthetic Aperture Radar (ASAR) and the Medium Resolution Imaging Spectrometer (MERIS). ASAR was tasked with collecting various data about ice sheets, sea ice, vegetation, and pollution. MERIS collected data on sea color, which can be used to extrapolate information about chlorophyll content, suspended sediments, and aerosols.
Contact with Envisat was unexpectedly lost in April 2012, though the satellite lasted twice as long as its intended lifetime of 5 years. To date, project scientists are not sure what caused the satellite’s failure.
The full-resolution map is available by request from Biomasar.