A baby Sumatran orangutan swings playfully on a branch at an Indonesian rescue centre, a far cry from the terror he endured when his pristine rainforest home was razed to the ground.

Now alarm is growing at a plan activists say will open up new swathes of virgin forest on Sumatra island for commercial exploitation and lay roads through a vital ecosystem, increasing the risk to many endangered species.

The plan, which Aceh authorities say aims to open up a small amount of forest for communities to develop, is set to be approved by Jakarta despite its moves towards extending a national moratorium on new logging permits.

Green groups say such policies illustrate how the ban can be circumvented to open up new areas for deforestation, threatening to boost Indonesia's already high emissions of carbon dioxide.

"This plan is a huge threat to species living in the forest, especially orangutans, tigers and elephants that live in the lowland forests that will likely be cleared first," Ian Singleton of the Sumatran Orangutan Conservation Programme told AFP.

Environmentalists warn that some one million hectares (2.5 million acres) -- around the size of Cyprus -- could be opened up in Aceh province for exploitation by mining, palm oil and paper companies. Officials dispute that figure.

There are particular fears about part of the project which would lay roads through the Leuser ecosystem, an area of stunning beauty where peat swamp and dense forest surround waterfalls and mountains poking through clouds.

The area, mostly in Aceh, is home to around 5,800 of the remaining 6,600 critically endangered Sumatran orangutans as well as elephants, bears and snakes including King Cobras.

Singleton warns that cases like that of the baby ape, rescued from Leuser, would rise dramatically if the road project goes ahead, as orangutan populations need long, uninterrupted stretches of forest to survive.

Named Gokong Puntung after the Chinese monkey god, the young ape had been living in an area where several companies cleared the land despite the tough protection it was supposed to have been afforded.

The primate was left stranded and clinging to his mother in a lone tree with no others to swing to. His mother was beaten by a group of passing men, and the baby was sold to a plantation worker for $10.

He was rescued in February and taken to the centre run by Singleton's group across the Aceh border in Sibolangit district, North Sumatra province.

"Genetic experts say you need 250 to 500 orangutans minimum to have a population that's viable in the long term without too many bad inbreeding effects," said Singleton.

"We've only got about six of those populations left, and every time you put a road through the middle of one, you effectively cut it in half."

Aceh forestry department planning chief Saminuddin B. Tou insists the roads will help link remote communities to the outside world -- although activists say there are few buildings in the area and the network mainly helps big companies with access.

-- A murky web --

Jakarta has signalled it will sign off on Aceh's plan in the coming weeks, even as it is expected to extend the moratorium on new logging permits which expires on May 20 and has been in force for two years.

There is also strong support in the Aceh parliament which has the final say, and officials say they hope it will pass soon.

Although it seems to fly in the face of the national moratorium, the project is possible because it hinges on Aceh's decision to overturn its own deforestation ban which was introduced at the local level six years ago.

The ban, stronger than the national measure, was brought in by the previous local administration -- but it will be scrapped under the plan.

Environmentalists say it is one of the more glaring examples of how officials are using a murky web of local laws and technical explanation to push through new deforestation in defiance of the national moratorium.

"Companies and local governments have found all sorts of ways to get around the ban," Friends of the Earth forest campaigner Zenzi Suhadi said.

However, the head of the Aceh forestry department, Husaini Syamaun, said in a statement that the plan "was not aimed at the development of mines and plantations" and did not break any laws.

The administration insists it will only free up around 200,000 hectares of new forest for exploitation.

But in reality a much larger area will be opened up, activists say.

Prior to the local ban, many mining and palm oil companies were granted concessions to chop down virgin rainforest in Aceh, but they had to freeze their activities when the province's moratorium came in.

Officials argue that the plan will simply "reactivate" these areas of forest that had been open for logging in the past, so do not include them in their calculations.

Tou also insisted most of the project was an "administrative change" as a lot of forest had in reality been cleared by local communities already. "It's not still virgin forest, it's already been converted by the people," he said.