Article(DiscoveryNews): Measuring the Earth's Forests

This was sent to me last week-a reminder of the vital role of trees to our earth systems. We can't take trees for granted anymore. (Look into the Resources page, on the right, for additional pertinent and current information to enhance PLT activities).


Measuring the Earth's Forests
By John D. Cox | Thu Jul 22, 2010 05:09 PM ET

A Colorado State University scientist using NASA satellite data has produced a map that provides the first global picture of the height of Earth's forests.

Standing tallest are the ancient temperate conifer forest canopies of parts of Southeast Asia and North America's Pacific Northwest -- the famous Coastal Redwoods and sequoias, Douglas Fir and western hemlock. While some individual redwoods tower over 350 feet, the map depicts average heights in 1.9-square-mile patches.

Broad swaths of shorter boreal forest dominate the Northern Hemisphere across Canada and the eastern United States as well as from Europe across northern Asia. Dense mid-level canopies occupy the Tropics through South America, Africa and south Asia.

Remote-sensing specialist Michael Lefsky, in a study about to be published in the journal Geophysical Research Letters, called his product a "first draft" of information that will help climate scientists create "biomass maps" to better understand the planet's carbon cycle.

Along the way, scientists will get better estimates of the sources and sinks of carbon entering the atmosphere -- an inventory that is critical to model simulations of future global temperature change.

A biomass map will help fill some gaping holes in scientists' accounting of the 7 billion tons of carbon that humans release each year into the atmosphere as carbon dioxide, the dominant greenhouse gas. About 3 billion tons end up in the atmosphere and 2 billion tons are absorbed in the ocean. Scientists think that photosynthesis by vegetation accounts for most of the remaining 2 billion tons per year, but they need more detail of the planet's biomass to be certain.

The new map combines the output of data from two sets of sophisticated instruments -- "multi-spectral" electromagnetic readings from the Terra and Aqua satellites and sensitive LIDAR laser altimetry measurements from instruments aboard the Ice, Cloud and Land Elevation Satellite (ICESat).

NASA said the LIDAR technology "provides a fully-textured snapshot of the vertical structure of a forest -- something that no other scientific instrument can offer."