NASA/Doug Morton
Just a few feet tall and slow-burning, understory wildfires have scorched three percent of the Amazon rainforest, far more than logging.

Hidden Amazon Wildfires Devour More Rainforest Than Logging: NASA

June 09, 2013

Hidden, low-undergrowth fires are taking a bigger toll on the southern Amazon jungle than logging, NASA has determined with an innovative use of satellite data that has yielded the first-ever regional estimate of these hidden fires.

Based on the information compiled, they are predicting a higher-than-average fire season in the Amazon for 2013, NASA’s Jet Propulsion Laboratory announced on June 7.

A team of scientists headed by Doug Morton of NASA's Goddard Space Flight Center in Greenbelt, Maryland, discovered that during years with the highest number of hidden fires, known as understory fires—2005, 2007 and 2010 are three of them—such fires burned an area of forest that was several times greater than that deforested for agricultural expansion. In particular, NASA said, 2003–2004 showed the highest-ever deforestation rates along with the lowest number of fires.

Moreover, those peak years implicated climate conditions as more important in determining fire risk than deforestation was, Morton said in a statement from the agency.

Understory fires are low-key: They burn long and slow, advance just a few feet per minute and are only a few feet high, their only aerial evidence the ribbon of smoke that escapes through the forest canopy, NASA said. From 1999 through 2010, NASA’s study found, understory fires scorched 2.8 percent of the Amazon, or 33,000 square miles.

“The long, slow burn gives way to a creeping death that claims anywhere from 10 to 50 percent of the burn area's trees,” NASA said.

The fires, unmapped until now, destroy several times more forest than has been lost through deforestation in recent years, NASA’s Jet Propulsion Laboratory said in a media release. They are called “understory fires,” occurring beneath the treetops and thus hidden from satellite view unless wisps of smoke escape the forest canopy.

To compare, wildfires on Turtle Island in 2012 burned about 14,000 square miles, or 9.2 million acres, the third-worst fire season in U.S. history, according to meteorologist Jeff Masters on

The risk for an Amazon fire season can be determined by measuring a variety of factors months ahead of time, ranging from ocean surface temperature to El Niño wind patterns to soil humidity, researchers said.

"A severe fire season in the Amazon is often preceded by low water storage in the soil, and this water deficit in the soil can be detected by the satellites several months before the fire season," said Yang Chen, a researcher at University of California at Irvine, who is studying the issue with other satellite data.

By studying the data, both groups of scientists are looking to measure the amount of carbon that could be released into the atmosphere from fires in the Amazon. Below, an understory fire doing its work, as recorded by Morton.