by William Powers & Glenn Hurowitz

Deep within Madagascar, more than 1,300 square miles of rainforest continue to breathe in carbon dioxide and breathe out oxygen every day, helping to keep the planet cool. That may not seem like a big achievement for a bunch of trees, but elsewhere around the world tropical forests like this one are being felled to make way for timber and mining operations, cattle ranches and, increasingly, sugar and palm oil plantations to fuel the world's growing thirst for ethanol.

So how did this particular rainforest — a tropical paradise whose canopy teems with rare lemurs and serpent eagles — avoid destruction? Its survival is the fruit of one of the first experiments in carbon ranching: allowing polluters to make up for their greenhouse gas emissions by paying third world countries like Madagascar to preserve their tropical forests. Madagascar uses the money it gets from multinational corporations to safeguard the forest and pay for poverty reduction programs.

Programs like this represent the world's best hope to save vanishing tropical forests and avert global climate catastrophe. It's vital that the senators and representatives now racing to create new climate legislation include incentives for carbon ranching. Otherwise they will not come up with the comprehensive solution that's needed to address the climate crisis. Despite all the attention paid to China's industrial pollution splurge, that country's inefficient factories, power plants and vehicles don't contribute as much to global warming as the destruction of the world's tropical forests does.

Reversing tropical deforestation could be surprisingly cheap and easy because it can be driven by simple economics. Right now, it's worth more to a logging company or a peasant to convert the rainforest to stumps or soybeans than it is to leave that rainforest intact. One hectare (about 2.5 acres) of forest cleared and converted to ranchland or crops produces a piece of land worth, on average, $200 to $500. But that's nothing compared to the value of preserving the rainforest as a sponge for carbon dioxide.

On European markets, the right to emit one ton of carbon dioxide trades today at more than $20. With each hectare of intact rainforest storing around 500 tons of carbon dioxide, that means that each hectare has a value of $10,000 as carbon dioxide storage, far more than the value of even the most productive tea or soy plantation.

As a recent World Bank report put it, "Farmers are destroying a $10,000 asset to create one worth $200." To the farmer or agribusiness corporation, of course, that makes perfect sense, because that $10,000 is all theoretical. It can't put food on the table or deliver dividends to shareholders.

That's got to change — or we could see the rapid disappearance of much of the world's remaining tropical forests and the oxygen and animal habitat they provide.

The indigenous people who make the world's forests their home are retreating in the face of agricultural expansion. Their interactions with loggers, miners and ranchers are destroying their cultures and bringing disease to their communities. By providing powerful incentives to leave the forests intact, carbon ranching can allow these people and their cultures to survive as well.

Carbon ranching would also be a good way to bring the developing world into the effort to reduce emissions. A coalition of "rainforest nations" led by Papua New Guinea and Costa Rica has indicated it will participate in carbon ranching projects without demanding any increase in foreign aid.

Corporate polluters also like carbon ranching because conserving rainforest is often cheaper than reducing their own emissions. Some, like Mitsubishi in Madagascar, are already doing it voluntarily because they want to be seen as supporting environmental efforts and anticipate that future legislation will let them get credit for it. Crucially, support from business guarantees that the idea will get a hearing in this polluter-friendly White House.

Indeed, the Bush administration has already financed some relatively small tropical forest conservation projects — most recently forgiving $24 million of Guatemala's debt in exchange for that country's putting the money toward conservation. So carbon ranching may provide a rare piece of common ground for the president and Congress.

To be effective, however, any legislation must include certain safeguards. First, no polluter should be allowed a free pass on cleaning up its own industrial pollution just because it protects rainforest — saving tropical forests should be part of the climate equation, not the whole equation.

Second, if a company pays to protect a forest that for whatever reason ends up getting destroyed anyway — as the politics or economics of the tropical country change — both the company and the country should face strict financial penalties. That would provide a powerful incentive to make sure those forests stay protected.

Time is short. The world's rainforests are shrinking. With global temperatures rising rapidly, it's essential that Congress and President Bush act quickly before the vast forests that cool the planet disappear forever.

William Powers is the author, most recently, of "Whispering in the Giant's Ear." Glenn Hurowitz is working on a book about the importance of courage in Democratic Party politics.
© 2007 The New York Times