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  • Writer's pictureThe Last Straw

Why mangroves matter

Mangroves are very unappreciated! Like tropical rainforests, mangrove ecosystems are very important habitats for plants and animals, help to regulate climate and also serve as water catchment areas. 26 July is celebrated every year as the International Day for the Conservation of the Mangrove Ecosystem. However, the importance of mangroves is poorly understood by many people and as such, these unique forests are not often taken into consideration in government conservation plans. In case you are in the dark about mangroves, here's a quick primer on what these amazing ecosystems are.

What is a mangrove?

Actually the term mangrove can refer to several related but distinct subjects depending on the context. In its broadest sense, a mangrove, or mangrove forest or mangrove swamp, is a specific type of ecosystem found in coastal areas or near estuaries. The plants that grow in a mangrove have evolved to cope with changing tides and the high degree of salinity in the water. More specifically, a mangrove tree is a member of Rhizophoraceae, which may be referred to as the mangrove family of plants. Some scientists are even more particular about the usage of mangrove and exclusively use it only for species in the genus Rhizophora (within Rhizophoraceae). Not all plants in a mangrove swamp are mangrove trees, but due to the dominance of said trees, the entire assemblage of plants in the swamp is collectively called a mangrove.

Location of mangroves worldwide

Where can you find mangroves?

Mangroves are found in brackish water near coastlines in many tropical and subtropical countries. The majority are located between latitudes 25° N and 25° S. The Great Sundarbans in the Bay of Bengal is the largest mangrove region in the world and a UNESCO World Heritage Site. It is straddled between India and Bangladesh, covering parts of Bangladesh's Khulna Division and the Indian state of West Bengal. As you can see from the map, mangroves are also found throughout Southeast Asia and parts of Oceania.

In Malaysia, mangroves cover an estimated 1,089.7 square kilometres in West Malaysia while most of the remaining 5,320 square kilometres of mangroves in the country are on the island of Borneo. Mangroves can be found as far north as the Ryukyu Islands of Japan, parts of eastern China and the southern United States.

What is a mangrove tree?

The most distinctive lifeform in a mangrove swamp is of course, the mangrove tree itself. It certainly stands out because of its unique shape which is very different from a typical tree. Probably the the first thing you will notice about the mangrove tree is its unusual root. In the picture above, you can see the roots of the tree poking out above the water line.

Mangrove trees need to be very specialised in order to live where they do. The buttress roots of these trees function as stilts, propping the tree up above the water so they aren't damaged by wave energy. The parts of the root that stick up like tubes are used for breathing and are capable of reaching heights of up to three metres in certain species. Water in a mangrove swamp can be low in oxygen, which forces the trees to use breathing roots to get as much oxygen as they need.

Frequent inundation by sea water also means that these trees are exposed to large amounts of salt. Too much salt will normally result in excessive loss of water, but mangrove trees have a solution to this problem as well. The various species of mangroves have their own adaptations to coping with salt intake and water loss. Some restrict the entry of salt into their tissue by filtering it out through the roots. Other species have special leaves whose pores can be closed to prevent water from escaping or angle their leaves to avoid intense sunlight.

There are about 110 recognised mangrove species. Many species are only distantly related but due to growing in a similar environment, most have evolved similar solutions to coping with conditions of variable salinity, tidal inundation, anaerobic soils and intense sunlight. Not every mangrove tree can survive all the possible hazards of a mangrove swamp and each has its own adaptations for survival. This is why in some mangrove regions, you can see a distinct zonation with certain species restricted to specific locations on the shore.

Why are mangroves important?

Mangroves play many important roles!

The water beneath their roots is an important breeding centre for fish, crustaceans, mollusks and other wildlife. Barnacles, oysters, sponges, and bryozoans anchor onto the roots of mangrove trees while they filter feed. Shrimps and lobsters live in the mud at the bottom and crabs feed on the leaves. All these animals are part of a larger food web that also involves fish, insects, frogs, birds and mammals.

There are benefits to us humans too. The fine, anoxic sediments under mangroves absorb heavy metals which are hazardous to life. The clearing of mangrove trees disturbs these underlying sediments, creating problems of trace metal contamination of seawater. Mangroves are also carbon sinks, taking out carbon from the atmosphere and helping to alleviate the effects of global warming.

Lastly, mangrove swamps protect coastal areas from erosion and can reduce the damage from typhoons and tsunamis. Their massive root systems are efficient at dissipating wave energy and can slow down tidal water.

Protect our mangroves!

Malaysia is blessed to have mangrove forests along its shores. Unfortunately, most of them are threatened by urban development, particularly in the state of Selangor which once boasted large swathes of mangrove swamps.

The Malaysian Mangrove Research Alliance and Network, or MyMangrove, is an inter-disciplinary scientific group of researchers from local universities, research institutions and relevant environmental NGOs focusing on the ecology, conservation and management of mangroves in Malaysia. Radio station BFM recently conducted an interview with Dr. Ahmad Aldrie Amir, a professor at Universiti Kebangsaan Malaysia and the coordinator of MyMangrove. Listen to the podcast here.

Over in Indonesia, the Mangrove Ecosystem Restoration Alliance (MERA) is a national platform for all stakeholders to work together for the protection and restoration of mangrove ecosystems. This project is a joint effort between the NGO Yayasan Konservasi Alam Nusantara (YKAN) and the Jakarta Natural Resources Conservation Agency of the Ministry of Environment and Forestry. Private organisations have contributed to MERA such as paper and pulp conglomerate Asia Pulp & Paper Sinar Mas, which recently came on board with a US$300,000 pledge.

Let's hope that many more members of the public and corporations will also join in the effort to save our mangroves before it's too late!

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