By David Shukman
Science correspondent, BBC News, Danum Valley, Borneo
On a muddy track in the tropical heat of Malaysian Borneo, the dilemma of how a poor nation should handle its globally-important rainforest becomes painfully clear.
Just beside the track, in a spectacular landscape of mist woven among the towering trees, a team of forestry workers is busy planting a sapling, one of thousands in a project to rehabilitate woodland ravaged by decades of logging.
A young tree is gingerly lowered into the soil amid hopes that it will grow to a majestic height, absorbing carbon dioxide as it soars and locking away the carbon for centuries to come.
Yet no sooner have the workers finished then a loud rumbling can be heard. A huge truck approaches carrying a vast load of freshly-felled timber.
It is the first in a convoy. In the space of a few minutes, I see at least twenty massive tree trunks hauled past us, each representing a tidy profit - and another loss in the rainforest's ability to soak up greenhouse gases.
It is because the rainforests are seen as key to the future course of climate change that their fate is now centre-stage in negotiations on tackling global warming.
Deforestation is estimated to be responsible for around 20% of all greenhouse gas emissions - more than all forms of transport put together.
Proposals to reward the rainforest nations for leaving their trees intact will be discussed during this week's UN climate conference in Bali.
Money for old wood
As the logging trucks thunder by, I turn to Dr Waidi Sinun, a senior official with the Sabah Foundation, a government-owned charity that manages the lands in this area of Malaysia.
The timber trade brings much-needed money to the region
For years, this organisation has funded scholarships with the proceeds of logging, while at the same time being noted for conserving large areas of forest.
"I am a product of timber," Dr Sinun tells me. He himself received a scholarship that eventually led to a doctorate in the UK.
"I wouldn't have gone to school or be here talking to you now if it wasn't for timber - but I'm also sad when I see what's happened to the forest. It's a question of balance."
And there's the dilemma: in a developing country, timber fetches a good price and, if the forest is cleared, then plantations of oil palms do very well too. But there is a cost, which is becoming more widely understood.
The tropical rainforests - running in a belt around the Equator from the Amazon, through Congo to South-East Asia - are not only a vast store of carbon, but also have a direct impact on global weather patterns.
The problem is that the "rainforests are worth more dead than alive", according to Dr Glen Reynolds, senior scientist at the Danum Valley Field Centre, a research station sponsored by the Royal Society.
The centre has pioneered the study of the so-called rainforest canopy, the interface between the trees and the atmosphere.
Carefully roped up, I make the hair-raising climb up to one tree-top 33 metres above the forest floor.
There, perched on a tiny platform, I meet Kalsum Mohammed Yusah, a young Malaysian researcher who is currently studying at the University of Cambridge.
What does she think about the loss of the rainforests? "They are storing carbon; chopping them down means less leaves to absorb it."
But stopping that process will require ingenious diplomacy and generous financing. In the meantime, the mud of the jungle tracks will continue to be churned by the crushing weight of the timber lorries.
You can watch David Shukman's report from Borneo's rainforest on the Ten O'Clock News on BBC One and this website, Monday 10 December, 2200 GMT