Magazine article American Scientist

Fly-By Forestry Takes Off

Magazine article American Scientist

Fly-By Forestry Takes Off

Article excerpt

Despite some scattered recent gains, the world's forests are in trouble. From 2000 to 2012, the planet lost a net total of 1.5 million square kilometers of forestland, according to a 2013 survey based on NASA satellite data. Much of the decline was due to deforestation in Brazil, Indonesia, and other tropical countries, but there have been many other setbacks as well. In the western United States, for instance, trees face an onslaught of wildfires, insect infestations, and drought. The assaults persist despite a growing awareness of the ecological value of forests, particularly their ability to absorb large amounts of carbon dioxide and sequester carbon.

As they formulate ways to protect endangered woodlands and rehabilitate ones already lost, scientists and governments need detailed information on the structures and vulnerabilities of forests around the world. Traditional ground-based surveys lack sufficient scope, so scientists are turning to another way to take the measure of the trees: light detection and ranging, or LiDAR, remote-imaging technology. Airplaneborne LiDAR scanners shoot 100,000 pulses of laser light per second to record the distance to Öie ground. From those data, researchers can measure the shape, type, and density of forest cover over tens of thousands of square kilometers. "That is the real power of LiDAR," says Van Kane, an ecologist at the University of Washington who uses the technique extensively. "We can build tremendously large databases."

In one notable recent study, Kane and his colleagues used LiDAR to observe how fires of various intensities affect the forests in Yosemite National Park. Some fires are known to help keep forests healthy by creating gaps in their canopies that enable new growth. Kane's LiDAR-based studies show more specifically that lowseverity fires produce favorable density changes in areas dominated by red fir forests, but fires of moderate severity are needed to improve areas dominated by ponderosa and white fir-sugar pine trees. Kane has also combined airborne LiDAR with satellite vegetation data to study how natural fires alter tree density of Yosemite forests. They do so in more irregular ways than was previously known, creating variable mosaics of tree clumps. …

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