The forests in the heart of Borneo are beautiful, bewitching even.

Early in the morning, before the heat, it is surprisingly similar to a wood in Britain, except for the big ferns and gigantic trees with trunks wider across than a dining table. The occasional awesome stump testifies to the depredations of the few illegal loggers who make it this deep into the forest, several hours by canoe from the nearest land-hungry settlers and then a long trudge up a thickly wooded hillside.

These central highlands are the location of the headwaters of Borneo's major rivers, some of which flow for thousands of miles before they reach their estuaries. The protection of this area is therefore critical in ensuring clean water supplies to a large number of human settlements.

Much of Borneo's jungle was hacked down and reduced to ashes long ago. We have driven for miles across a barren landscape of stumps and bushes to reach the river that will take us into the surviving pristine jungle.

In the tree tops, we can see big orang-utan nests made of twigs. Deep in the trees, giant butterflies sail over streams of crystal-clear water. Clouded leopards and pythons stalk the forest floor hunting wild boar and deer and are, in turn, hunted by one of the last truly nomadic forest peoples, the Penan.

It feels utterly timeless, and I may be among the last witnesses to one of the world's most beautiful places before its destruction.

The forest is disappearing at a staggering rate, 366 acres an hour by one estimate. Only half of the island is now covered with forest compared to three-quarters in the Eighties.

WWF is working with the three governments that share Borneo - Indonesia, Malaysia and Brunei - to pledge to protect the Heart of Borneo, a conservation and sustainable management scheme which it is hoped will protect the surviving forest. If they fail, they fear there is a precedent in another part of Indonesia for what will almost surely happen. Conservationists warned in the Eighties that Sumatra would lose all its rainforest unless steps were taken to protect it. Now it has nearly all gone.