Thaindian News

WASHINGTON, D.C. (BNO NEWS) — NASA on Tuesday announced that scientists produced a first-of-its kind map of the height of the world’s forests by combining data from three NASA satellites.

Scientists will be able to use the map to build an inventory of how much carbon the world’s forests store and how fast that carbon cycles through ecosystems and back into the atmosphere.

Even though maps have been previously produced of local and regional forest canopy, the new map is the first that spans the entire globe using one uniform method. The map was based on data collected by NASA’s Terra and Aqua satellites, along with the Ice, Cloud and land Elevation Satellite, or ICESat.

The world’s tallest forests are shown to be gathered in North America’s Pacific Northwest and portions of Southeast Asia, while shorter forests are found in broad swaths across northern Canada and Eurasia.

Michael Lefsky, a remote-sensing specialist from Colorado State University in Ft. Collins, produced the final product, in which the primary data he used was from a laser technology called lidar on the ICESat.

Lidar can capture vertical slices of forest canopy height by shooting pulses of light at the ground and observing how much longer it takes for light to bounce back from the surface than from the top of the forest canopy. Since lidar can penetrate the top layer of forest canopy, it provides a detailed snapshot of the vertical structure of a forest.

“Lidar is unparalleled for this type of measurement,” Lefsky said. “It would have taken weeks or more to collect the same amount of data in the field by counting and measuring tree trunks that lidar can capture in seconds,” Lefsky added as he utilized over250 million laser pulses collected during a seven-year period for the map.

Because each pulse returns information about a tiny portion of the surface, lidar offered direct measurements of only 2.4 percent of the Earth’s forested surfaces. To complete the map, Lefsky combined the lidar data with information from the Moderate Resolution Imaging Spectroradiometer (MODIS), an instrument aboard NASA’s Terra and Aqua satellites. MODIS observes a broad swath of Earth’s surface, even though it does not supply the vertical profile.

The new forest height map is a step toward a global map of all above-ground biomass. Sassan Saatchi, senior scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, already has started combining the height data with forest inventories to create biomass maps for tropical forests. Global biomass inventories will eventually be used to improve climate models and guide policymakers on carbon management strategies. Lefsky describes his results in a journal paper to be published next month in Geophysical Research Letters.