Mangrove's many uses: Good news, bad news, ugly truth

By Peter Ng, Wang Luan Keng & Kelvin Lim
Straits Times 22 Nov 08;

Sweet offeringsThe Nipah Palm is the only true mangrove palm in Singapore. The attap chee commonly found in chendol desserts are nipah palm seeds preserved in heavy syrup. The sugary sap from the inflorescene stalk can be used to make toddy (an alcoholic beverage), fermented to vinegar, or boiled down to make palm sugar, known locally as gula melaka . The large, feathery leaves can be used for thatching huts (hence the term attap huts). Bags, baskets, hats and brooms can be made from the mid-rib of the leaflets. The young leaves may also be used as cigarette wrappers. Leaves grow up to 9m long.-- PHOTO: COURTESY OF WANG LUAN KENG

Water purifier
The Avicennia spp found in mangroves are able to desalinate the water their roots dwell in, leaving pure salt crystals on their leaf surfaces that fall off in the breeze. Scientists hope it could help them uncover cheaper ways to desalinate water. -- PHOTO: COURTESY OF JEAN YONG

A sturdy presenceAn extremely sturdy wood, timber from mangrove trees is used in scaffolding for builders and to prevent landslides. One of the best sources of charcoal is wood from the mangroves, Rhizophora apicolata is grown throughout South-east Asia to make charcoal. After controlled burning, the charcoal absorbs odours, pesticides, chemicals, metals and even drugs from the air and water. -- PHOTO: COURTESY OF JEAN YONG

See, food
One of four species of mud crabs found in Singapore, the Giant Mud Crab is the largest of the edible crabs which can be found in mangroves. This ferocious species is named after Scylla, the many-headed monster in Greek mythology. It feeds on cockles, clams and oysters. It is found in many parts of the Indian Ocean and the Pacific. It weighs close to 3 kg. -- PHOTO: COURTESY OF PETER NG

Clotting agent
There are two species of Horseshoe Crabs in Singapore. In existence for more than 400 million years, they have blue blood which has, for decades, been tapped for medicine because it clots in the presence of bacteria toxic to man. After being killed for years for this property, researchers at the National University of Singapore learnt how to clone the proteins responsible for this important clotting activity. The crabs can measure up to 45cm, including the tail. -- PHOTO: COURTESY OF WANG LUAN KENG

ONE of the classic westerns is Sergio Leone's The Good, The Bad And The Ugly. In this movie, the moral lines between the good, bad and ugly are often blurred. Good men turn bad, and 'criminals' become heroes.

As to man's use of mangroves, the issues can be just as confusing.

As much as we realise how important mangroves are to us in terms of coastal protection, useful products and seafood, we also destroy them as we develop our economies, build new factories, start new developments and begin fresh ventures.

Mangroves can also be killed, damaged or affected by many indirect human activities.

Huge amounts of human waste, dumped in the seas, end up on the shores of mangroves. And nylon nets continue to tangle and kill crabs and fish years after they have been discarded.

Mangrove forests are very much a threatened habitat. Two-thirds of the world's mangroves were lost during the 20th century.

There is a regional awareness to want to reverse what has been done - replanting mangroves, mitigating developments and factoring conservation into projects.

Take, for example, Singapore's Semakau Landfill - even a national marine landfill that started in controversy over a decade ago had a mangrove replanting programme.

Ten years down the road, these mangroves have grown - and stand as a symbol of how Singapore can balance development and conservation.

Well-managed mangrove forests like Sungei Buloh Wetland Reserve and Pasir Ris Park are fantastic outdoor classrooms for students to learn about habitats, conservation and sustainable living.

If for nothing else, mangroves need to be conserved for our own selfish human needs.

Mangroves provide many important ecological services. Perhaps one of the most important of these is coastal protection. Mangrove forests not only reclaim land naturally, but also can prevent shoreline erosion and reduce sedimentation in coastal waters.

Their roots can absorb heavy metals and certain pollutants. The development of a mangrove forest stabilises sediment profiles and improves soil chemistry.

Various studies have also shown that areas with healthy mangroves have better quality sea water.

Mangrove trees are the best natural protection against tsunamis.

During the catastrophic tsunami in December 2004, many coastal zones and towns in Aceh, Sumatra, were wiped out. However, in areas where mangrove forests were still intact, the villagers escaped unscathed.

The mangrove forests, with their complex natural barrier of roots and trunks, substantially reduced the force of the destructive waves.

This prompted some governments in South-east Asia to start planting mangroves as a natural defence against storms.

In Singapore, Nyrieh, or xylocarpus granatum, is a useful tree species that assists in the removal of the dangerous metal boron - used in the metal industry - from coastal mangrove areas.

Such multiple roles of mangroves are important for Singapore as the country is becoming increasingly reliant on coastal sea water for desalination.

In addition, there is emerging scientific evidence that mangroves are important for the well-being of coral reefs and even the ocean's bio-geochemical cycle, with regard to its sources of marine organic carbon.

On Semakau, the mangroves planted there not only help to protect the shore, but also act as an excellent bio-indicator for the landfill. If any of the toxic substances inside the landfill leak (though the engineers assure us this cannot happen), the trees will be among the first to feel the effects.

Their death will be a sure sign that something has gone wrong.

More recently, the idea of mangrove forests as 'carbon sinks' is becoming more apparent.

It has been estimated that one hectare of mangrove forest can roughly absorb 1.5 tonnes of carbon dioxide generated by a vehicle (using about 2,500 litres of fuel) in a year.

Indonesia, with its 4.5 million hectares of mangroves, can thus use them to absorb the carbon dioxide emissions of about five million cars, a scenario presented by Professor Ong Jin Eong, a mangrove expert from Penang, Malaysia.

This surely is a bargaining chip for any carbon sequestration and trading, given that mangrove plants are able to photosynthesise and grow using undrinkable sea water, unlike our inland rainforest plants.

A group of scientists from the National Institute of Education (Nanyang Technological University), Universiti Sains Malaysia and Australian National University are building on these earlier findings and conducting further experiments to understand how tides and increased air temperatures due to global warming will affect the ability of our mangrove forests to absorb carbon dioxide.

We are only beginning to realise how valuable mangroves are to us. How many more bioactive substances do the plants and animals there have? How much can we learn from them about building and architecture? Can they help us reduce erosion and in greening Singapore? Can they help desalinate sea water to help with Singapore's freshwater needs?

The good news is that despite the grave threat to mangroves, a large number of new discoveries have been made in recent years, including new species found in Singapore.

The bad news is that very little is known about this complex ecosystem.

The ugly truth: Mangrove forests are greatly under-appreciated and undervalued.

We must not lose them only to then realise that their loss is fatal to our own survival.

This passage was adapted from a new book, Private Lives: An Expose Of Singapore's Mangroves.

Professor Ng is the director of the Raffles Museum of Biodiversity Research at the National University of Singapore, Ms Wang is an education and research officer at the museum, and Mr Lim is its collections manager.

Mangroves - more than mud and mozzies
Only about 5 per cent of mangrove swamps are left in Singapore, but this muddy land where salt water meets fresh is a safe haven for a wealth of plants and animals, as highlighted in a new book here.