Prince Charles said there needed to be rewards for preserving the rainforest The halting of logging in the world's rainforests is the single greatest solution to climate change, Prince Charles has said.
He called for a mechanism to be devised to pay poor countries to prevent them felling their rainforests.
The prince told the BBC that the forests provided the earth's "air conditioning system".
He said it was "crazy" the rainforests were worth more "dead than alive" to some of the world's poorest people.
The world's forests store carbon in their wood and in their soils.
But they are being felled for timber products, food and now bio fuels. Experts say this carbon is being released into the atmosphere and contributes to global warming.
The Stern Review on the Economics of Climate Change, published in 2006, suggested that the destruction adds about 18% to the CO2 from human sources.
In an interview to mark BBC World Service's Amazon Day, Prince Charles said: "When you think they [rainforests] release 20 billion tonnes of water vapour into the air every day, and also absorb carbon on a gigantic scale, they are incredibly valuable, and they provide the rainfall we all depend on."
He said a way had to be found to ensure people living in the rainforest were adequately rewarded for the "eco-system services that their forest provides the rest of the world".
"We're asking for something pretty dreadful unless we really understand the issues now" -- Prince Charles
He said: "The trouble is the rainforests are home to something like 1.4 billion of the poorest people in the world.
"In order to survive there has to be an effort to produce things which tends to be at the expense of the rainforest.
"What we've got to do is try to ensure that those forests are more valuable alive than dead.
"At the moment there's more value in them being dead. This is the crazy thing."
Drought and starvation
The prince called on governments, big business and consumers to demand an end to logging in the rainforest.
He said the time was right to persuade business to play its part because there was increasing concern about global warming.
"Halting deforestation would be the easiest and cheapest way in helping in the battle against climate change," he said.
"Waiting for all the new technologies to come on stream is not going to be soon enough."
Charles said if deforestation did not slow down soon there would be "far more drought and starvation on a grand scale".
He said: "We're asking for something pretty dreadful unless we really understand the issues now, and urgency of those issues.
"It is the easiest way to create a win on the climate change front while all sorts of other things come along later."
The BBC's environment analyst, Roger Harrabin, says that Prince Charles' observation that saving the forests is the cheapest and most effective way of cutting CO2 emissions is "widely acknowledged".
At the recent Bali climate conference, developing countries asked for compensation from rich nations if they agreed to avoid future deforestation.
Talks are continuing, but there are issues over sovereignty – and genuine difficulties over who pays, who collects, and how much money should be offered.
Mike Childs, of Friends of the Earth, said: "The Prince is absolutely right to highlight deforestation as the single greatest cause of climate change, but putting a stop to it much more complex.
"Forests are cut down for many different reasons, such as the growing of food, animal fodder and bio fuels."