Standing at the entrance to Lang Co town hall, 69-year-old Mai Truc Lam gestured to the two-story building, the sun-drenched parking lot and two-lane road in front, and described the small coastal community as it once was.

"We are standing in an area that used to be mangroves," the weathered fisherman said, and then described the negative impact deforestation has wrought on the area's sea life. "Now, we do not see some species of fish here anymore."

A few minutes' drive away, on a sliver of sand that forms the Lap An Lagoon on the central coast of Vietnam, lies a modest grove of trees – some evergreens that shed a path of soft needles, and where the land meets the sea, Lang Co's few remaining hectares of mangroves, perched above the water upon their stilted, flying buttress-like roots.

Some of the mangrove trees have torpedo-shaped seeds, which have poked into the ground and given birth to a new generation of delicate seedlings, all too easily trampled upon by oblivious passersby. Yet these remaining mangroves face the threat of being razed entirely to make way for a golf course as part of local economic development plans – part of a global development trend that has seen the clearance of as much as 50% of the world's mangroves over the past half a century.

Mangroves grow along the ocean coasts of 118 countries – with a quarter of the world's 40m hectares being in south-east Asia – but with widespread deforestation due to population pressure, expansion of shrimp farms and development, scientists fear mangroves may disappear altogether in as little as 100 years. At their best, mangroves form a vast coastal barrier of trunks and roots against the sea, controlling erosion, protecting communities from storms, and providing an environment for greater fish diversity.

Furthermore, scientists last year unveiled research pointing to mangrove forests as ideal repositories for carbon storage – containing an average of 1,000 tonnes of carbon per hectare, compared with 300 tonnes per hectare of tropical forest – which could help to fight climate change by keeping carbon locked away on land and out of the atmosphere. The scientists found that most of the carbon in mangrove forests – 49% to 98% – is stored below ground in thick, tidally submerged soil in which decomposition is anaerobic in the absence of oxygen. Yet with mangrove conservation up against economic development, the more obvious path to money wins.

"My sense in Lang Co, and in provinces across Vietnam, is that economic development has become a driving force so dominant that environmental precautions have fallen by the wayside," said Evan Fox, a coastal planning consultant. "In villages where local governments are searching for ways to bolster their economic output, it is difficult to justify preservation of an area if managers and local people cannot discern its tangible benefit."

There are laws that protect the forests and mangroves in Vietnam, but enforcement can be lax, rendering such regulations impotent. "My interpretation is that it's illegal but everything is negotiable in Vietnam and since there is no consequence for breaking the law (at least in the environmental domain), mangroves get cut. Anyway, since there are so many conflicting laws, you can probably legalise what you've done by reference to a previous law," said Jake Brunner, programme co-ordinator for the International Union for Conservation of Nature (IUCN) in Vietnam.

Shrimp farms have been one of the big drivers behind mangrove loss. A 2011 analysis of images of Vietnam's southern Mekong delta – an area that is typically mangroves – found that from 1973 to 2008, more than half of the mangroves were converted into shrimp farms, causing serious erosion. Nonetheless, communities and governments have taken little notice of the protective services that mangroves provide until a disaster of epic proportions strikes – such as the Indian Ocean tsunami that killed some 180,000 people in western Indonesia's Aceh province.

"In Aceh, after the tsunami, the result wouldn't have been like this, if we still had mangroves," said Daniel Murdiyarso, a scientist with the Indonesia-based Centre for International Forestry Research and one of the researchers behind the mangrove carbon-storage findings.

Disaster management and risk reduction are now squarely on the Indonesian government's radar, but in most countries – and most of the time – the impact of climate change is incremental and therefore unlikely to spur governments and communities to action. When typhoons have hit Vietnam, mangroves have helped to save lives.

"That's when people noticed that where there were mangroves, people survived," Brunner said. "Thailand and Indonesia suffered a very high magnitude event, the tsunami, and that sent a very clear message. In Vietnam, there have been higher frequency, but lower magnitude events, so it hasn't quite had the same impact, and you still see mangroves being lost."

Initiatives like the Mangroves for the Future (MFF), established after the 2004 tsunami and co-chaired by IUCN and the UN Development Programme, offer grants to communities like Lang Co to protect their mangroves. Since 2008, MFF has implemented about 90 projects in its eight member countries across south and south-east Asia. The $29,000 project in Lang Co – $23,000 from MFF and $6,000 from the grantee organisation, the Centre for Community Research and Development (CCRD), and the local community – is to focus on supporting natural regeneration of existing mangroves, which is less expensive and more effective than planting. According to CCRD, Lang Co had about 100 hectares of mangroves two decades ago, but today only five hectares of poor-quality mangroves remain.

Under the MFF grant, the Lang Co fishing association has been tasked with looking after these mangroves. Local fishermen will be trained in mangrove and aquatic resource management and protection.

Alisa Tang is a Bangkok-based freelance journalist who reports and edits for organisations including the Centre for International Forestry Research, which supported her reporting trip to Vietnam.