for National Geographic News
The fires are lit annually to clear land for oil palm plantations and agricultural fields. Many of the blazes quickly rage out of control.
The orangutans are forced to flee the forests and often end up on nearby plantations, where they are beaten and sometimes killed as pests, according to Michael Booth, a spokesperson with the International Fund for Animal Welfare in Mexico City, Mexico.
"Apart from losing precious land they use to survive, they're forced into conflict with the human element," Booth said in an interview for today's National Geographic News podcast.
Booth, who recently returned from a trip to Borneo to help rescue stranded orangutans, says unusually dry conditions have made for the worst fire season there in a decade.
Rains usually arrive by the beginning of October to douse the flames. This year the rains didn't start until November, leaving Southeast Asia cloaked in a thick haze.
And conservationists fear strengthening El Niño conditions in the region could make next year even worse.
El Niño is a periodic warming of the tropical Pacific Ocean that disrupts weather patterns around the world. In Southeast Asia the phenomenon is associated with drought.
"There's a big fear that next year will be an even drier season and the fires will be even stronger," Booth said.
Extinct Within a Decade?
Wild orangutans are only found on the Indonesian islands of Sumatra and Borneo. Borneo is shared by Indonesia, Malaysia, and Brunei.
Conservationists believe approximately 60,000 of the great apes remain on the islands.
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