By Simon Montlake
In Calang, Indonesia
Along Aceh's battered coastline, work has begun on new housing for those left homeless by the 26 December tsunami.
Government officials estimate that 100,000 new houses will be needed over the next few years.
Rebuilding could put Indonesia's precious resource under pressure
But environmentalists warn that this construction boom poses a major threat to Indonesia's ravaged tropical forests.
About 70% of Indonesia's annual timber output is cut illegally, mostly for export.
Researchers say that at the current rate of cutting, most of Indonesia's rainforests will disappear by the end of this decade.
Many houses and public buildings in Indonesia, particularly in rural areas, are made of wood.
Rebuilding Aceh will increase demand for timber, something that environmentalists say must be closely monitored.
The UN's Food and Agriculture Organization has already sounded the alarm over the issue of logging.
Earlier this month, it advised tsunami-hit countries to protect their forests during the reconstruction period.
It said governments in South and South-East Asia should "avoid over-harvesting and illegal felling of trees".
Campaigners say Aceh, on the northern tip of Sumatra island, needs particular care.
Around 70% of Indonesia's wood is felled illegally
Its extensive rainforest is full of rare animals and diverse habitats, including 4% of all known bird species.
Although logging was banned in Aceh in 2001, unlicensed cutting has persisted.
Much of the logging takes place inside the Leuser ecosystem, a 2.6m hectare reserve running along Sumatra's mountainous spine.
Small populations of endangered Sumatran tigers and rhinos live in the reserve, which has been supported by the European Union.
Indonesian activists say international aid groups must make sure that money spent on housing does not fuel illegal logging.
"The Leuser ecosystem is under serious threat, and we want the international community to be aware of this issue," said Elfian Effendi, executive director of Greenomics Indonesia.
"The international community must have clear policies on the procurement of wood."
Instead of using Indonesian timber, foreign donors should consider importing wood from overseas or supplying it as tsunami aid, he said.
Indonesian officials say the idea of donating wood has been raised with Western donors, including Sweden and New Zealand.
However, diplomats say it may not be practical to try and import wood to a country which already has the material in abundance.
"Our top priority is to get as much value as possible out of our money. It may not be the best strategy to import timber all the way from Sweden," said a Swedish diplomat in Jakarta.
Aid workers point out that wood substitutes like bricks and concrete are available.
They may also be preferable materials in larger buildings, given the risk of future earthquakes or tsunamis in Aceh.
One of the main centres of logging is also a precious ecosystem
In Calang, a town that was levelled by the tsunami, work crews are busy hammering planks together for communal wooden barracks.
Hundreds of similar buildings are going up across Aceh as a temporary solution to the problem of homelessness.
Workers say the planks of wood stacked up by Calang's harbour came from another province on Sumatra island.
But local residents say that wood is also available from nearby forests.
In the provincial capital of Banda Aceh, wood prices have soared by 20% or more over the last month.
Traders say most of the wood arrives by boat from other provinces.
Greenomics estimates that Aceh will require at least 4m cubic metres of raw and processed logs over the next five years.
Last year, Indonesia's licensed production was 17m cubic metres.
But its sawmills and factories have the capacity to process 74m cubic metres.
The shortfall is made up by logging inside protected reserves and on public land.
Indonesia's security forces are widely accused of profiting from illegal logging, particularly in Aceh.
President Susilo Bambang Yudhoyono has called for tougher action on the issue, which is fuelled by rampant corruption.
Environmentalists say the UN and other foreign agencies involved in tsunami relief have a duty to protect Indonesia's forests.
"We must make sure that the wood being used for new houses is certified as coming from sustainable forests," said Dede Suhendra, a programme manager at WWF-Indonesia.
Currently only a tiny percentage of Indonesia's forests is certified by international forestry groups.
Even buying overseas timber as a way to spare local forests carries a risk, according to a UN housing expert.
"Importing wood doesn't necessarily guarantee that the wood doesn't come from illegal logging, because it tends to leave Indonesia illegally and re-enter with some other banner," said Antonella Vitale, a shelter adviser to the UN Development Programme.