While that kind of agricultural clearing technique has been used for centuries, the setting of such fires is now illegal in Indonesia, but plantation owners are commonly ignoring the law, environmentalists say.
"Widespread, illegal burning to clear rainforests and peatlands for palm oil and pulp and paper plantation expansion is unfortunately a well established yearly ritual in Sumatra," Laurel Sutherlin of the Rainforest Action Network, a San Francisco-based environmental organization, said in an email to the Huffington Post.
A serious consequence of the practice is smog produced by the fires, which recently drove the pollution index in the neighboring city-state of Singapore higher than 400, a level considered life-threatening to sick and elderly people.
Palm oil is the single largest traded vegetable oil commodity in the world and global demand is rising rapidly, the U.S. Department of Agriculture reports.
The satellite image was taken Tuesday by the Moderate Resolution Imaging Spectroradiometer instrument on the Terra satellite, NASA said.
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