ANDASIBE, Madagascar - Every morning and evening the Andasibe forest echoes to the ululating cry of the indri, Madagascar's largest lemur.

For many people who hear it, the cry of the indri has a mournful quality. In truth there is good reason for these remarkable creatures, which are found only in Madagascar's eastern rainforests, to lament. Their habitat has been steadily disappearing for generations and the indri themselves have been forced into ever smaller pockets of forest to survive. According to local people, only 62 families remain.

Now, there's hope not only for bringing the indri back, but improving farming techniques on the island and earning it lucrative carbon credits, combining conservation with development.

The AndasibeMantadia Corridor Restoration and Conservation Project is a collaboration between the Malagasy government and other major partners, including Conservation International and the World Bank.

Joana Coutinho, a consultant working on the project, said the goal is to link the patches that are what's left of eastern Madagascar's rainforest with new plantings until an unbroken stretch of green is restored.

Reforestation began last year and over the next seven years the hope is that what remains of the forest can be protected and nearly 3,035 hectares of new forest planted. Conservation International says more than 405,000 hectares of forest will be preserved or restored.

"In each hectare of forest we plan to plant 1,000 trees, so in total we will be planting 3,020,000 trees," said Claude Rakotoarivelo, who is helping with the restoration. "We are hoping to restore the forest as it was before, with the same trees. In perhaps 18 years' time we will be able to see proper young forest again."

Rakotoarivelo points to an area of cleared land on the forest edge. It is still possible to see the blackened stumps of the trees that once grew there. Now the land is being used for rice cultivation.

The slash-and-burn technique locals farmers call tavy "has a very big impact on the forest, firstly on the biodiversity and secondly on the soil. When the rains come all the goodness of the soil is washed away and the land becomes very poor. It is very bad," Rakotoarivelo says quietly, turning away.

Project workers "are trying to change generations of farming practice," Coutinho said.

Amadee Ramarolahy, a 58-year-old farmer in the village of Andranolava, on the very edge of Andasibe's forest, is open to new ideas.

"I have learned to terrace my fields. I am also learning more intensive agricultural practices so that my productivity will increase."

Ramarolahy receives around $2 a day for his help in replanting the forest with trees grown in local nurseries.

"Local people are starting to care about the forest and conserve it," he said.

The carbon credit element gives the project a potential importance far beyond the mist shrouded valleys of Andasibe.

"It turns out that about 20 per cent of the world's carbon dioxide emissions come from the destruction of forests and its conversion into other types of land. That makes it even more significant than the transport sector. It is the second biggest source of emission after electricity," said James Mackinnon, Conservation International's representative in Madagascar.

He hopes the AndasibeMantadia project can provide a model to help reverse this trend.

"There are two parts to this. The first is conservation, which is stopping the carbon being released in the first place, by protecting the forest. This should mean that around 10 million tons of carbon won't get into the atmosphere. The second part is restoration where the trees actually store the carbon we produce and we estimate that we can capture another one million tons of carbon dioxide in the 30-year year lifespan of the project."

Mackinnon said carbon credit prices on the market are around $5 per ton, although he said it is a very new market and he expects the price to go higher over the period of the project.

Ramarolahy also is enthusiastic, both because of the techniques he is learning that have increased yields, and because he wants to save the forest and wild inhabitants like the wailing indri lemur.

"Before we used to see indri but now we don't see any," he said. "They are not comfortable here anymore. We didn't realize we were having such a big impact on the forest."