First map of world`s tree heights produced using NASA data
Scientists have produced the world`s first global map showing the height of forests using data compiled over seven years from NASA satellites.
Washington: Scientists have produced the world`s first global map showing the height of forests using data compiled over seven years from NASA satellites.
The map will help scientists work out how much carbon is locked up in forests and how quickly that carbon cycles through the eco-system and back into the atmosphere.
This can be used to calculate whether the planet can continue to soak up so much of the annual carbon emissions and whether it will continue to do so as climate changes.
Aside from tracking carbon, other uses of the map include producing models that predict the spread and behaviour of fires, and ecological models that help biologists understand the suitability of species to specific forests.
The map shows that the tallest forests are in the Pacific Northwest of North America and parts of southeast Asia, CNN reported.
Assistant Professor Michael Lefsky, of Colorado State University, collected the data for the map from laser technology, known as LIDAR, that measures the canopy height by recording how much longer it takes for light to bounce back from the ground than the top of the canopy, the report said.
He based his map on data from more than 250 million laser pulses collected during a seven-year period.
"It is certainly a milestone to demonstrate that this can be done and it will be a technique we can use to go forward. There are already people using the data to do things that could never be done before," Lefsky said.
The map shows the height that 90 percent of trees reach, or are taller than, within five square kilometers regions -- not the maximum heights of individual trees.
The tallest canopies, reaching more than 40 metres are temperate conifer forests. Tropical rain forests reach around 25 metres, a similar height to the oak, beech and birch forests common in Europe and the United States. Boreal forests dominated by spruce, fir, pine and larch usually had canopies of less than 20 meters.
Humans release about seven billion tonnes of carbon annually, mostly in the form of carbon dioxide, of which three billion tonnes go into the atmosphere and two billion tones into the oceans. The remaining two billion tonnes is suspected to be captured by forests and stored as biomass, although this has not yet been proven.
Ecologists are just beginning to work out which types of forests and soils store most carbon and whether they can continue to absorb our carbon emissions.
Lefsky said: "We know there`s a relationship between height of trees and biomass, so we can use it to calculate biomass.