PANGKALAN BUN, Borneo — Homeless, semiparalyzed and blind in one eye, Montana faces an uncertain future. Even if his human friends find somewhere for him to live, the 15-year-old has been weakened by years in assisted care. The lethal dangers of readjustment to life in his natural habitat include not only the kind of men who shot him out of a tree when he was a baby, but the hostile attentions of his stronger neighbors.

But for the source of the greatest threat to Montana's existence, say his supporters, look no further than your handbag and food cupboard.

The orangutan, one of our closest relatives (with whom we share 97 percent of our DNA), and the largest tree-living mammal on the planet, is in deep crisis. Once an orange army of 300,000 that swung through the forests of much of Southeast Asia and parts of China, their numbers are now thought to have dwindled to fewer than 25,000, mainly on the Indonesian islands of Borneo and Sumatra. There, they cling to existence on government-protected nature reserves coveted by developers of one of the modern world's most lucrative commodities: palm oil.

Illegal logging, fires and clearances have decimated the tropical rain forest that is the exclusive home of these peaceful, mostly vegetarian primates that nest high in the trees, and whose name comes from the Borneo word oranghutan, meaning "people of the forest." The casualties join Montana at a care center here near Pangkalan Bun in Central Borneo that is crowded with more than 320 homeless, orphaned and sick or injured orangutans, including some three dozen babies. And their numbers are growing by a barely manageable 20 percent a year, say the workers there.

Montana peers unhappily from his cage; unlike 250 of his predecessors who have been relocated to the jungle since this center was set up in 1998, he is unlikely to ever leave.

"We just can't find homes for all of them," laments Birute Galdikas, a famed anthropologist who runs the care facility. "We are looking at the extinction of orangutan populations in the wild." She estimates that without action, the primates — one of the four nonhuman great apes along with gorillas, chimpanzees and bonobos — have 10 or 15 years left in the wild, leaving around 1,000 living in captivity.

The Borneo orangutan is listed as "highly endangered" by the International Union for the Conservation of Nature and Natural Resources — one short stop on the ladder of extinction above its Sumatran cousin, which is classed as "critically endangered."

"When it goes extinct, it will be a terrible loss," says Galdikas. "I can't tell you how urgent it is."

To grasp this urgency, you have to travel from Pangkalan Bun up the chocolate-colored Sekonyer River to the heart of one of the world's last great wildernesses, the Tanjung Putting Park, a 410,000-hectare nature reserve that is home to perhaps 6,000 orangutans, along with proboscis monkeys, gibbons, macaques and crocodiles. The reserve is an oasis in a landscape pressured by human demands.

Behind the banks of mangroves and pandanus screw pines along the Sekonyer, patches of cleared jungle can be seen from the boat. Guards posted along the river patrol for illegal logging and poaching: some illegally caught orangutans are sold on as pets or to perform in Thai kickboxing matches or circuses.

But the "real issue," say scientists, is palm-oil plantations.

When British actress Joanna Lumley made this journey a few years ago with a TV crew to film orangutans in the wild, she is said to have been "horrified" to discover that her handbag was stuffed with cosmetics containing palm oil.

Extracted from the fast-growing oil-palm tree, this is now probably the world's most popular vegetable oil. It is used in a tenth of all supermarket products, including crisps, biscuits, toothpaste, margarines, detergents and cosmetics — and 85 percent of it comes from Malaysia and Indonesia, in that order. As the world's leading producers, these countries now host countless giant monocrop plantations hewn from the forests and run by agribusiness concerns with powerful political support.

"Greed drives the industry," says Galdikas. "The industry is tied with the political elite, who are making bundles of money off it. You have to see their mansions in Jakarta to understand the money that is coming from it." She calls the clearance of central Borneo for the plantations a "scorched-earth" policy that is "unbelievable."

Conservationists say many of the devastating fires in 1997-98 that robbed the orangutans of perhaps 30 percent of their habitat in Borneo — and blanketed much of Southeast Asia in a dense smog — were caused by forest-clearing for palm-oil plantations. But Indonesia is still converting land at a rate of at least 1,500 sq. km a year, and has plans to raze an area half the size of the Netherlands for the world's biggest palm-oil plantation, according to the British-based Orangutan Foundation.

But local forest guides explain that "nothing is safe," with one explaining that forest hardwoods, including teak and mahogany, are often sold to finance the plantations.

Nowadays, the reserve is dotted with elevated feeding stations, where guides leave ripened bananas and milk to supplement the animals' normal diet of fruits, bark, flowers, leaves and insects. As a small group of tourists wait near to one of these in the sweltering heat, the animals descend from the canopy in ones and twos, first mothers hugging their babies — who they typically spend 6 years teaching how to survive in the forest. Then the dominant male arrives, a huge 115-kg bruiser dubbed Tom by the guides, who has beaten off all the other young pretenders. As Tom peels and eats bananas, the guide tells us he is 24 and, like most nonmothering orangutans, lives alone. "But we don't know where; somewhere high in the trees."

As the forest shrinks around these peace-loving apes, though, so do their sources of food — but the guides say they must not destroy the orangutans' ability to forage, and so make them dependent on human charity. "The only way for them to survive is for us to preserve their habitat," they say with passion, pointing out that as their interbirth cycle is up to 8 years, females are limited to three or four offspring in their 45-year life spans.

However, the destruction of the rain forest here would also deprive many other animals of their habitat, including some possibly as yet unknown to science. And in a bitter twist, they may disappear to meet soaring demand for cleaner energy sources in a world choking on fossil fuels as many countries look to palm oil as a source of biofuel.

Cheap and carbon-neutral, palm-oil diesel was until recently hailed as a safe, renewable alternative to petroleum, but such claims have been undermined, perhaps fatally, by a series of devastating studies.

One of these, published this year by Wageningen University in the Netherlands, found that the peat swamps in Indonesia and Malaysia — drained and burned to plant palm-oil trees — now release 2 billion tons of carbon dioxide a year into the atmosphere, or 8 percent of the world's fossil-fuel emissions.

"It is like kicking your head to get rid of a headache," said Galdikas. "Palm-oil prices are going through the roof because of their use as biofuel, and this — one of the poorest countries in the world — is cutting down its trees to supply the market. It makes no sense."

But demand for palm oil continues to rise: A $48-million palm-oil biodiesel plant opened in Australia's Northern Territories last year, and three 50-megawatt power stations are currently planned in the Netherlands.

However, staff at the Pangkalan Bun center say each such decision made halfway around the world takes the orangutan one step nearer extinction. Senior administrator Mrs. Waliyati fears more for her youngest charge, 9-month-old orphan Britney, than her oldest.

"It might be too late for Montana, but what about the young ones?" she asks. The solution, she says, is: "Don't use palm oil. If you do, it means you are agreeing to cutting down the rain forest. If you don't stop, in 15 years, maybe sooner, there will be no place for these animals to live."