On the 11th December 2020, a number of staff from Chemsain as well as Rotarians decided to head over to the Kuching National Wetlands Park to check on the mangrove trees that were planted there during their collaboration in 2017. The trip was quite enlightening for the Chemsain team as they learned how to navigate through the muddy ground with the guidance of the Rotarians. When the group arrived at the Chemsain/Rotary planting zone, it was pleasing to see that the trees grew really well as the trees stood tall and were thick with leaves.

The planting site is the remnants from the abandoned project to connect Sg Sarawak at Batu Kawa to Sg Santubong in order to lead storm water around the old Kuching. The dredging material was dumped inside the Kuching Wetland National Park mangroves. The mangroves cannot on their own re-invade this barren dump. The center of the dump is a dry, sandy dome, where the only sensible thing to plant would be Aru (Casuarina sp.) or Umbrella Tree (Terminalia camaldulensis) as these are beach species well adapted to sandy soils. There are, however, low lying pockets of gray mud where the Forestry Department (Now management has been transferred to Sarawak Forest Corporation, SFC) wants to revegetate with Bakau Minyak (Rhizophora apiculata). Some botanists call it Mangium. Acacia mangium gets its species name from this as its natural habitat is close to Australian mangroves.

Mangroves normally line the seaward shores. They are a good place to study succession.

We have basically four genera of mangrove species: Sonneratia, Avicennia, Rhizophora and Bruguiera.

Succession means that there is a distinct list of species or species groups that succeed each other. One comes first, dies out while the next takes over, which dies out again while the third group takes over and so forth. On a muddy coast, the first species group to establish itself consists of Avicennia sp and Sonneratia sp. You can recognize these by their breathing-roots or pneumatophores. Plants need oxygen around their roots and since the mangrove soil is very anaerobic, they grow these pneumatophores. For both Avicennia and Sonneratia, the pneumatophores are pencil-like nails sticking straight up. The Avicennia pneumatophores are in general thinner than those of Sonneratia, but in both cases, you can see the root systems cover large areas around each tree.

Avicennia and Sonneratia must daily be flooded by salty tide water. They will trap mud and other sediment wherefore the seabed gets higher. The two species cannot thrive in this environment but that is where Rhizophora comes in. Rhizophora is the one with a myriad of stilt roots where it is impossible to walk. That is also the one with the long seeds that germinate while still hanging on the mother tree. It will then drop like a dart and plant itself in the mud. Rhizophora still wants daily flooding but not as semi-permanent as Avicennia and Sonneratia.

Mud will continue to accumulate under the Rhizophora. Flooding will therefore become less frequent or each tidal flood will become shorter in duration. This paves the way for Bruguiera sp. Bruguiera also has pneumatophores, but these are like knees popping up and down again.

When even they must give up, land is prepared for the dryland species such as Catappa and Casuarina as mentioned earlier. Or in Australia, you will find the Acacia mangium.

Mangrove timber is very dense and therefore perfect for firewood or charcoal. The mangroves are also attractive places to make shrimp farming, unfortunately often with disastrous impact on the mangrove areas.

Mangroves are teeming with life, both over and below the water or even buried in the mud. This is an important link in a food chain that even involves crocodiles and deep-sea creatures. It also protects the coast from the forces of the ocean and by trapping the mud and silt, mangroves are part of the land forming processes.