According to Booth, close to a thousand orangutans died this year, mostly due to the forest fires. If the pace of destruction continues, the animals may be extinct within a decade.
Cheryl Knott is an anthropologist at Harvard University in Cambridge, Massachusetts, who studies orangutans and promotes their conservation. She says rampant illegal logging dries out the forests, which exacerbates the fires.
"The real wet primary forest areas don't burn," she said. "But illegal logging opens up the forest canopy, and there's lots of dry wood on the ground from the remnants of the big trees."
When fires are intentionally lit to clear fields, the flames spread to the degraded forests.
"A lot of the areas that have been somewhat degraded if left alone will come back," she added. "But once they're burned, they're cleared further and then they're totally gone."
The combination, she says, amounts to a no-win situation for the orangutans.
They can stay in their burned-out habitat and starve to death or move into habitat already occupied by other orangutans.
Though orangutans are not territorial, their natural population densities are quite low, she explains.
"Eventually you have animals that die because the habitat can't support the increase in density," Knott said.
Booth says he was surprised at the scant local awareness of the problem the forest fires pose to the orangutans.
"It's hard to understand why people don't relate these huge forest fires to an immediate threat to the wildlife that lives in these sanctuaries," he said.
From conversations with locals, Booth says he learned that many people consider orangutans to be pests, even though research has found them to be highly intelligent, social animals.
"It takes just a few minutes of interacting with them to realize there is not a lot of difference between you and them," he said.
The local indifference to the plight of the orangutans, Booth adds, is reflected in the limited effort to fight the fires.
"It's a fight that is almost lost from the get-go, because the resources put into it and the extent of the fire are so opposite," he said.
Knott, the Harvard University anthropologist, holds out hope that conservation efforts will help protect the orangutans.
She directs a conservation program that educates local schoolchildren about the plight of the orangutans, teaches village leaders about the pros and cons of the oil palm industry, and supports anti-logging and firefighting efforts in the national parks.
(Knott's program receives funding from the National Geographic Society's Conservation Trust. National Geographic News is part of the National Geographic Society.)
"We're working on different fronts to try to address these issues," she said.
"But the fire one is tough," she added. "People forget about it. The frustrating problem with fire is it takes one person to light a fire, and it can impact a huge area."
Peter Standring contributed to this report.
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