12 January 2006 | EN
Mangrove forests can act as 'bioshields' against storms
Reefbase / Joelle Lai N. Sivasothi
In the wake of the December 2004 tsunami, the Indian Ocean nations affected are admitting that the damage was partially self-inflicted. Over the past 20 years, these countries have systematically destroyed one of the most effective barriers to ocean forces — mangrove forests — in the name of development.
Shrimp farms, tourist resorts and urban expansion have devoured 35 to 50 per cent of these 'bioshields' over the entire region. Many of these deforested pockets of prosperity were hit hardest, the tsunami washing away years of economic growth.
Now, governments in India, Indonesia, Malaysia, Sri Lanka and Thailand all want to restore what nature once provided for free: they plan to spend millions of dollars replanting thousands of hectares of mangrove forest.
Scientists applaud the 'greening' agenda but warn that to succeed, replanting strategies must include workforce training and supervision, maintenance of seedlings, and increased public awareness about coastal land use. Some economists add that we need a better understanding of the relationship between these endangered ecosystems and the communities that rely on them.
"Reforestation is unlikely to succeed in the long term because the underlying policies haven’t changed," says Edward Barbier, an environmental economist at the University of Wyoming, United States, who has done extensive research on Thailand's mangroves. Barbier is not surprised that Thailand suffered such extreme damage; since 1961, more than half its mangroves have been removed.
Replanting is critical to restoring ecosystems, he says, but trees alone cannot create the long-term stability needed for sustainable economic growth.
Mangroves tend to be undervalued in economic calculations, which only include the benefits of developing them (such as woodchips or farmed shrimp). This makes it easy for governments to gamble on 'developing' the forests. The tsunami clearly raised the stakes — and strengthened the case for protection that ecologists and economists have been making for years.
Back to the roots
Properly calculated, it can be shown that the value of mangroves as storm barriers far exceeds any apparent gains made from exploiting them for other forms of land development. A realistic look at their indirect values (see box below) tips the equation even further in the direction of protection.
|Ecological goods and services mangroves provide
More than 70 per cent of South-East Asians live within the coastal zone. Mangroves clearly saved lives when the tsunami struck. The forests provide a double layer of protection against pounding waves: the roots anchor mudflats, while the trunks break the force of incoming seawater. Many modern breakwater systems mirror the way mangrove roots absorb the energy of water without disrupting its flow.
This can be seen in a study of in pre- and post-tsunami satellite images of the coastline of Cuddalore, India, published in Science in October 2005. Exposed villages were completely levelled, but those behind mangrove forests suffered virtually no damage.
The study's lead author, Finn Danielsen of the Nordic Agency for Development and Ecology, says three-dimensional laboratory models have shown how coastline vegetation reduces the size and power of tsunami waves, which behave differently than those generated by winds.
"We found that very few areas with dense tree vegetation were damaged by the waves whereas more than 60 per cent of the areas without trees were damaged," says Danielsen. "Our findings suggest that mangroves act as an effective shield against mid-sized tsunami waves."
|Fish market in Chennai,|
India: millions of Asians
rely on fish as their main
source of protein
Photo credit: (FAO / Bizzarri)
The World Conservation Union (IUCN) reported similar findings in two Sri Lankan villages. Wanduruppa, which is set within degraded mangrove forests, was severely affected: 5,000 to 6,000 of its population died. Nearby Kapuhenwala is surrounded by 200 hectares of dense forest, and lost only two villagers – the lowest death toll of any village in the country.
But the real value of mangroves lies in their day-to-day support of life and livelihoods, says Sanit Aksornkoae, president of the Thailand Environment Institute.
Up to a billion Asians rely on fish as their primary source of protein and make their living from the sea. In Thailand, villagers in mangroves earn up to 95 per cent of their household income from the forests by fishing and collecting shellfish, wood and medicinal plants.
Mangroves straddle land and sea, making them ecologically important to both marine and coastal habitats. At the shoreline, their roots anchor soil that supports a wide range of plants and animals. Their complex underwater root systems provide an ideal habit for fish and shellfish to live, mate and produce young. Mangroves also help maintain nearby wetlands, peat swamps, salt marshes, seagrass beds and coral reefs.
|Many fish live and breed|
among the submerged roots
of mangrove forests
Greenpeace / Gary Bell
Putting a price tag on these 'indirect' goods and services is a complex business. The IUCN assessed the cost of the damage and injuries prevented in Kapuhenwala, and concluded that intact mangroves can have a 'protection value' of around US$2,000 per household; the overall value of each hectare of forest was US$14,000 per household.
Calls for reforestation are now hard to ignore but past efforts show that while planting the trees is relatively easy, the eventual outcome is not always positive. Failed restoration schemes show the need to consider local conditions, select appropriate species and tree spacing, maintain and protect plantations, and engage local communities.
"We must…think not only of the trees, but of the function of the ecosystem as a whole," says Aksornkoae.
He points out that the tsunami created special challenges that will affect any replanting scheme. "Because of the influx of seawater, soil salinity increased. Some soils were removed and other sediments deposited, which can be detrimental to the existing mangroves and must be drawn out before replanting."
Moreover, in Thailand Aksornkoae anticipates that much of the replanting will be in abandoned shrimp farms, whose soils can be quite toxic from the overuse of chemicals and fertilisers. For seedlings to take, this soil must also be rehabilitated.
Indonesia has already replanted 300,000 seedlings and aims to reforest 600,000 hectares over the next five years. Suseno Budidarsono, a research officer at the World Agroforestry Centre (ICRAF) in Bogor, conducted a three-week field study of rehabilitation efforts in late December 2005. In general, he says, the work is 'messy' and poorly planned.
"Local people are doing most of the planting, on a cash-for-work basis, but no one is overseeing them to ensure the seedlings are properly planted," he says.
|Coastal areas without mangrove forests suffered the heaviest|
damage when the tsunami struck
Credit: Selvam Vaithilingam / MSSRF
Budidarsono is particularly troubled by the nearly exclusive focus on mangroves and, in some cases, single species of them. Planting a mixture of mangrove species creates a greater range of protection because they vary greatly in size, root structure and the distance from shore at which they grow best. And, mangroves are not always the answer.
In some places, says Budidarsono, inland mangrove species are being planted on the seashore and will likely be washed away. Other groups are busy planting mangroves on the west coast of Indonesia, an area in which they are naturally rare. Here, coconut palms and rubber trees would provide better protection against the winds and waves characteristic of the region.
These oversights are also problematic because the structure of the forests will determine whether the ecosystem will attract the marine flora and fauna that villagers rely on.
ICRAF's regional coordinator, Meine von Noordwijk, says there is a wide gap in Indonesia between a government keen to be seen making high-level decisions, and action-oriented volunteer organisations eager to report that many mangroves have been planted.
Von Noordwijk says what's missing is a well-informed middle layer — one that gathers together authorities, communities, researchers and non-governmental organisations to shape national policies and implement them locally.
Barbier says that this 'middle zone' of local players is also vital to long-term conservation.
"Central governments have little interest in protecting mangroves," he says. "Officials turn a blind eye to private developers or even provide them with 'certificates of ownership' for land that really belongs to the government. Meanwhile, traditional users lose out because they have no 'legal' rights."
Barbier argues first for strict delineation of conservation and commercial zones, and secondly for a 'community forest' approach that aligns rights and responsibilities with the ecological impacts of each user group. Locals who use forest resources in sustainable ways should have access to both zones. Industry must be restricted to commercial zones and should be liable for ecosystem destruction — owners who abandon shrimp farms, for example, should pay for site restoration.
|Satellite images reveal the extent of mangrove (green) conversion to|
shrimp farms (blue) in Vietnam's Ca Mau province between 1993 and 2002
Thailand has been considering this concept for some 15 years, as its mangroves disappeared at alarming rates. This reluctance to make an apparently straightforward policy decision is, says Barbier, because the idea is "difficult and costly to implement. The government needs to be convinced that there is a serious problem that needs correcting – and they need to weigh that against the economic gains of commercial development."
Thailand's more immediate challenge is how to meet replanting targets. Pre-tsunami, the government relied almost exclusively on volunteers, arguing that those who benefit from the restored forests, such as local fishermen, should help create them.
Scaling up current efforts won't work, says Barbier, because existing policies actually deter participation. "A survey conducted by my Thai colleagues in 2000 shows that one of the factors affecting participation in replanting efforts is whether communities feel they will have any control in the end."
Barbier is happy that the tsunami 'after-shock' is prompting governments to act. But he worries about new challenges in the struggle to balance conservation and development. "The first problem of deforestation is that traditional livelihoods have been ruined; the second is that local people have lost their connection to the mangrove forests."
One year after the tsunami, one can walk into pristine mangroves and find daily life remarkably unchanged. A few kilometres down the shore, where the forests had been felled, industries that needed unskilled labour are gutted. Shrimp farms lie abandoned; tourist resorts are quiet, and locals must wait to see if private investors will risk rebuilding.
While tsunamis are rare, all Asian coastlines are also prone to extreme weather such as tropical cyclones and storm surges. Indeed, mangrove deforestation is thought to have significantly increased the damage from such natural disasters.
Growing awareness of the forests' true economic value, and of the need to factor protection into future development plans, are positive outcomes of the 2004 disaster. But it will take about five years to establish the new forests; perhaps longer for more effective policies to be enacted. For now, the future of this fragile ecosystem remains uncertain.
Alfredo Quarto, Mangrove Action Project ( Mangrove Action Project | United States of America )
22 August 2008
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