Replanted mangrove trees at Pengudang, Teluk Sebong, Bintan Regency. Courtesy NTU CCA Singapore.
Found along the coasts in tropical and sub-tropical areas, mangroves are intertidal forests home to over 1,500 plants and animals. These ecosystems hold a rich diversity of trees and animal life, particularly in Southeast Asia where one-third of the world’s mangroves are growing.
Trees that grow here face unique conditions: flooding up to two times a day, soil low in oxygen, salty water, and in some locations, serious disturbances such as floods and tsunamis. They have developed interesting adaptations in response:specialized roots that breathe out of water, leaves that exude excess salt, and saplings, also called propagules, that germinate on the parent tree first, before being released into the soil, therefore increasing their chances of survival.
Propagules of Bruguiera gymnorhiza next to mangrove river in Pengudang, Teluk Sebong, Bintan Regency. Courtesy NTU CCA Singapore.
Stilt roots of Rhizophora trees in Pengudang, Teluk Sebong, Bintan Regency. Courtesy NTU CCA Singapore.
A wide variety of animals can be found in these unique intertidal forests. Oysters attach themselves to tree roots through secreting a special kind of bio-glue, forming oyster reefs that help filter murky water. Crustaceans, such as crabs, create tunnels through the mangrove soil to hide from predators, behaviours that help to oxygenate the soil. This abundance of marine life also attracts a variety of birds, such as kingfishers, herons, and other migratory birds. In the soil, micro-organisms, known as the mycorrhizal fungi, also form structures into the roots of some mangrove trees, helping the trees to better take up nutrients.
Holes in the mangrove soil indicating the presence of crabs alongside riverbank of mangrove forest in Pengudang, Teluk Sebong, Bintan. Courtesy NTU CCA Singapore.
Influenced by many factors such as the height of the ground, soil conditions, and tidal flooding, different species of mangrove trees are observed to grow in different zones, depending on the conditions they grow well in. According to the “State of the Mangroves 2024” report, there are 82 identified mangrove tree species in the world.
There are a few simple ways to learn the names of common mangrove trees. One is through the unique architecture of their root systems which helps them to adapt to the intertidal conditions of the mangroves. The other way is through the shape and colour of their propagules, young saplings that grow first on the mother tree before being carried by the tides to other locations.
Nypa fruticans in mangrove river channel in Pengudang, Teluk Sebong, Bintan. Courtesy of NTU CCA Singapore.
The Nypa fruticans is the only palm tree that grows in the mangrove forest. It is one of the oldest species of palms1, with fossil records tracing its presence back to 65 to 70 million years ago2.
In the Orang Laut community in Kawal, Bintan, this palm holds spiritual significance as a medium through which the living connect with their ancestors.
Sonneratia alba (front) on the shoreline of Pengudang Beach, Teluk Sebong, Bintan, next to another mangrove tree known as the Avicennia sp. Courtesy of NTU CCA Singapore.
The S. alba can grow up to 30 metres in height when mature.
With protruding roots that enable it to breathe during periods of the day when the tides are high, on closer look, their roots are cone-shaped and thicker in size. It has round, green fruits that can be blended into a drink.
Young Rhizophora mucronata trees planted along a mangrove river in Pengudang, Teluk Sebong, Bintan. Courtesy NTU CCA Singapore.
The R. mucronata a common mangrove species in Bintan and Singapore. It can grow up to 15 metres tall at some sites. The stilt roots of the R. mucronata help the tree to stabilize well on shifting soil, enabling it to grow in both the seaward and middle zones.
The young shoots of the R. mucronata can be eaten. The bark can also be used as a source of natural dyes. This is the main tree species grown at the mangrove nursery of Pengudang Village and planted by the Orang Laut community in Kawal.
Brugiera gymnorhiza tree on a muddy riverbank in Pengudang, Teluk Sebong, Bintan. Courtesy NTU CCA Singapore.
The B. gymnorhiza can grow up to 30 metres in some places, though smaller individuals are found.
The roots resemble bent knees; they emerge out of the ground, twist at a joint, before entering the soil again. The propagules of a close relative of this tree may be processed into flour and made into traditional kuehs, a broad term for flour-based desserts in Southeast Asia.
