Saving fragile forests

David Thomas reports on the international effort to preserve the lifeblood of Vietnamese coastal communities from further destruction

Between 1961 and 1971, 19 million gallons of the deadly herbicide agents Orange, Purple, Blue and Green were poured onto the jungles and forests of Vietnam, destroying a quarter of the Vietnamese mangroves. Not only was the vegetation lost, but whole ecosystems were crippled along with the livelihoods of the people living in these coastal regions. In an ironic turnabout, this devastation has opened up a most unlikely natural experimental plot for European and Vietnamese scientists to unravel the secrets of mangrove ecosystems.

One of the hardest hit regions was the Mekong Delta in the south of Vietnam. At the end of the war the mangroves of Can Gio province were a blackened wasteland. A quarter of a century later, this crippled landscape has been turned into a remarkable testament to an industrious nation: 40,000 hectares are now covered by hand-planted mangrove forests, impenetrable masses of aerial roots and branches. "It is like trying to battle through spaghetti as thick as an arm, and the whole forest is sitting on a bed of thick mud that engulfs the unprepared," says Hilary Kennedy, the British team leader.

Biologists and chemists from Spain, Portugal, Denmark, the Philippines and Wales have joined together in a two-year European Union-funded programme to study mangrove sites in Southeast Asia. They want to understand the resilience and recovery of disturbed mangroves. The well-documented and well-defined recovery of the Can Gio region makes it an ideal study site. The aim of the work is to develop models to predict the resilience of Southeast Asian seagrass and mangrove ecosystems against human pressure. These can in turn be used by coastal managers and policy-makers at other sites under threat by damage from tree felling, urbanisation, boat traffic, tourism and the almost unrestricted expansion of fish and shrimp ponds.

The teams assembled for the first time in April and May last year for a five-week field campaign. Between the various groups all elements of the systems - including the sediments, water, plant populations and food webs - were covered. Dr Kennedy from the University of Wales-Bangor recounts how the campaign was far removed from the comforts of modern laboratories. "Guest house and hotel balconies became makeshift laboratories for bits of mangrove trees, crabs, fish and snails. Mini-bar fridges were emptied purely to make room for vital samples."

The vulnerability of mangroves is highlighted in work published by the climatic research unit at the University of East Anglia. They point out how vital mangroves are for the preservation and protection of coastal and estuarine regions, especially in the light of climate change and predicted sea level rises.

The sea is already encroaching on coastal regions, and over the past decade more than 600 hectares of land has been eroded from the mouth of the Bo de River. Increasing rates of sea-level change may result in sea level being up to 64cm higher by 2100, with dramatic consequences for a country where most of the 3,000km coastline is at or below 100cm elevation. Some 50 per cent of the population is also centered in low-lying delta regions.

The consequences of these global warming-induced changes for the livelihoods and socio-economic viability of these regions is obvious. The local people fish in the rivers and collect shellfish, mudskippers and other animals living on the mangroves. Wood is used for building, but also for fuel and making charcoal, an illegal but little policed trade.

Mick Kelly of the school of environmental sciences and Neil Adger of the centre for social and economic research on global environment at UEA, together with Vietnamese partners, have assessed the effects of mangrove rehabilitation on local economies.

"Replanting mangroves makes sense because of the immediate improvement in the livelihoods of the local people," said Kelly.

After all the hard work that has gone on in re-establishing the forest following the ravages of war, the next task is to put as much effort into preserving these fragile forests from problems brought about by more subtle, but no less sinister consequences of man's ineptitude.

DOWN WITH THE MUD-DWELLERS

The muddy quagmire of the mangrove forest was a frenzy of burrowing and feeding. Blue spotted mudskippers scuttled and flipped into tiny pools propelled by their fins, which enable them to venture out of the water. Palm-sized fiddler crabs edged warily away from their burrows daintily picking up tidbits with their spindly front claw, a fraction of the size of the huge extended claw behind which they shielded their bodies.

In between these major stars of the mire were myriad smaller crabs and prawns gorging themselves on the invisible mats of algae and leaf litter that cover the

surface.

Lying back in the sea of mud, it was sobering to consider that 30 years ago these mud flats were not the refuges of crabs and mudskippers, but rather the hiding place to escape armies and the drenching with deadly herbicides. This is where some of the hardest battles of the Vietnam war had taken place.