By Mark Kinver
BBC News science and nature reporter
Healthy mangrove forests helped save lives in the Asia tsunami disaster, a new report has said.
Researchers say mangroves absorbed the impact of the tsunami
The World Conservation Union (IUCN) compared the death toll from two villages in Sri Lanka that were hit by the devastating giant waves.
Two people died in the settlement with dense mangrove and scrub forest, while up to 6,000 people died in the village without similar vegetation.
Many forests in the past were felled to build prawn farms and tourist resorts.
The IUCN said it showed that healthy ecosystems acted as natural barriers.
"It saved a lot of lives as well as properties," said Vimukthi Weeratunga, the union's biodiversity coordinator in Sri Lanka.
"We have carried an out ecological assessment of the damage caused by the tsunami. In some areas the damage was very minimal, and mangrove vegetation had played a role."
Research has shown mangroves are able to absorb between 70-90% of the energy from a normal wave.
There is, however, no reliable data on how the trees mitigate the impact of a tsunami.
Many people living in coastal areas now want to see their communities benefit from the apparent protection offered by mangrove forests.
"People tend to respect these natural barriers even more, especially after the tsunami," Mr Weeratunga said.
"Now everyone is keen to plant a lot of mangroves in the coastal areas but unfortunately we cannot plant mangroves everywhere."
Coral reefs were also in the direct path of the tsunami. Fears for these ecosystems were allayed after initial surveys found that there had not been widespread, long-term damage.
But they did not escape unharmed. Debris and silt from the shore was washed out to sea and covered the reefs.
Twelve months later, the IUCN has found that reefs which were in good shape before the waves struck are recovering much more quickly than degraded sites.
Lucy Emerton, head of the union's ecosystems and livelihoods group in Asia, explained why.
"Healthy coral reefs are much more robust in terms of recovering from either natural or man-made disasters," she told the BBC News website.
"Physically, you see a beautiful coral reef that is coming back to life rather than one that is still smothered in debris."
Many of the reefs in the Indian Ocean had been damaged from dynamite fishing, coral mining and bleaching.
The protection that healthy marine and coastal ecosystems provided during the disaster highlighted the need for effective environmental policies, Ms Emerton said.
"It was immediately obvious what an important role mangrove forests, wetlands and coral reefs played in mitigating the impact [of the tsunami]," she argued.
Damaged coral has been slower to recover from the tsunami
"It has led to a real step forward in looking at integrated coastal management systems."
She said strong conservation laws already existed but there had been questions about how effective they had been enforced.
One example of a local government flexing its conservation muscles is the recent declaration to establish two new turtle sanctuaries in southern Sri Lanka.
Elsewhere, four international conservation groups, led by Wetlands International, have launched a project called Green Coast.
Working alongside local governments and construction companies, the project hopes to rehabilitate the habitat in areas affected by the disaster.
Both mangrove forests and coral reefs found in coastal areas provide vital protection and breeding grounds for fish - a key source of income and nutrition for people in the region.
A report published by the Malaysian-based WorldFish Center has warned that misplaced investment by donors could do more harm than good in the long term.
When the giant waves swept inland in December 2004, between 80-90% of the fishing fleet was destroyed.
This prompted a massive effort by the international community to replace lost vessels and gear.
While welcoming the overwhelming response, the centre's director general, Stephen Hall, said it was important for donors to coordinate their efforts with the governments.
International donors were quick to replace destroyed fishing boats
"There is a real danger that we are going to set these communities back on the downward spiral of unsustainable fish stocks," he said.
"The Indonesian government estimates that 10,500 boats were lost [in Aceh]. Of those, around 2,500 were repaired. Recent estimates put the number of boats that have been built or in the process of being built at around 10,800.
"So we now have 2,800 more boats than we started with."
Dr Hall said this created the potential to place even greater pressure on already overexploited stocks.
This view is shared by the IUCN's Vimukthi Weeratunga.
"Immediately after the tsunami, a lot of the NGOs and other well wishers were distributing boats.
"But we saw the distribution of too many boats and an increase in fishing."
Latest figures from the UN Farming and Agriculture Organization (FAO) show fish catches in Aceh for 2005 are down 41% for marine fishing and 26% for brackish water aquaculture.
The United Nations Environment Programme (Unep) published a report in November highlighting the challenges of meeting the demands of the mammoth relief effort without exacerbating the damage to the environment.
It warned that haphazard groundwater extraction, unsanitary disposal of waste, chaotic rebuilding of homes and unsustainable timber harvesting could result in more environmental damage, leading to an increase in poverty and greater vulnerability to future disasters.
A number of agencies, including the FAO and Unep, are working closely with the governments of nations affected by the disaster.
Help is being provided in a number of areas, such as offering technical assistance to overstretched environment ministries and coordinating the mobilisation of funding.
As attention begins to focus on the future, Vimukthi Weeratunga warns that there are no quick fixes when it comes to repairing the environmental damage.
"It will take five to seven years, at least, to get to the pre-tsunami stage - and that is a conservative estimate."