Youssouf's charges are part of an innovative Madagascar project which aims to reap the benefits of the emerging market in carbon credits while reconnecting fragmented patches of scarce rain forest.

Making conservation work in ways that also promotes economic development is the key theme of a major conference that opens in Madagascar's capital Antananarivo on Tuesday.

The plan involving Youssouf's saplings is a simple one but may reap big economic and ecological rewards for Madagascar, the Indian Ocean nation offshore Africa that is home to one of the world's most unique ecosystems.

The goal over the next few years is to replant about 3,000 hectares of tropical rain forest to create corridors linking several fragments of habitat which have been cut up by human activities such as slash and burn peasant farming.

These include the 810 hectare Analamazaotra Reserve, home to the fabled indri, the largest of Madagascar's lemurs - dainty primates which are distant relations to humans.

In the process of planting indigenous trees, the local communities will also be creating "carbon sinks" - which means they can trade the carbon absorbed by the new forests on the new market for such credits.

The Kyoto Protocol obliges 35 developed countries to meet greenhouse gas emissions targets by 2008-12, but allows them to buy pollution reduction in units called carbon credits from poor nations, which can reduce emissions by the same amount more cheaply.

"You get 230 tonnes of carbon credit per hectare of new indigenous forest planted," said Rainer Dolch, coordinator of local green NGO Mitsinjo. The basis of the carbon sink concept is that trees soak up more carbon than they emit.

At prices of between 5 and 20 euros per tonne, that could mean a welcome influx of cash into poor local communities, where many peasants live on less than a dollar a day.

The credits will be traded through the World Bank's BioCarbon Fund.

The trees will first be planted out in January, with seven local organisations planting about 45 hectares a piece at first. About 1,000 trees are needed for each hectare.

Youssouf's nursery has 20,000 saplings including 20 species, reflecting the diversity of the regional rainforests. They include sturdy hardwoods such as mahogany.

Reforestation will also provide more habitat for the lemurs, chameleons and other weird and wonderful local creatures which are the big draw for a growing number of ecotourists.