NASA has revealed that an unmapped type of wildfire caused by climatic conditions has caused more loss to the Amazon rainforests than deforestation.

Many fires that raged below the treetops of the Amazon forest remained undetected by NASA satellites and hence were not factored as one of the causes of the loss of the rainforests in the Amazon. However, after using an innovative satellite technique, NASA scientists have discovered that wildfires caused by changing climatic conditions have caused more loss in the rainforests than deforestation..

"Amazon forests are quite vulnerable to fire, given the frequency of ignitions for deforestation and land management at the forest frontier, but we've never known the regional extent or frequency of these understory fires," said Doug Morton of NASA's Goddard Space Flight Center in Greenbelt, Md., and the study's lead author. The study was published April 22 in Philosophical Transactions of the Royal Society B.

Fires in the Amazon's savannah areas can burn quickly, spreading up to 330 feet (100 meters) per minute. Grasses and shrubs in these ecosystems typically survive low-intensity surface fires. However, understory fires don't spread out that much but burn for weeks. Nonetheless, they are capable of damaging large areas as Amazon trees are not adapted to fires. NASA reveals that this slow burning fire can cause deaths of up to 50 percent of trees in the burnt area. The recovery process from such fires is also slow.

NASA reveals that between 1999 and 2010, understory forest fires have caused loss of more than 33,000 square miles (85,500 square kilometers), or 2.8 percent of the forest.

"You would think that deforestation activity would significantly increase the risk of fires in the adjacent forested area because deforestation fires are massive, towering infernos," Morton said. "You make a bonfire that is a square kilometer in size, throwing ash and live cinders and preheating the adjacent forest. Why didn't we have more understory fires in 2003 and 2004, when deforestation rates were so high?"