Mangrove swamps at Pasir Ris are man-made

National Parks Board plants mangrove trees on reclaimed land at the park to preserve the original environment

By Chan Kay Min

VISITORS to Pasir Ris Park may not realise it, but one of the two groves of mangrove trees there is man-made.

The one stretched along Sungei Api Api was planted there by the National Parks Board (NParks) to maintain the original environment, but casual park-users are unlikely to realise that.

The information the board gained from that experiment done years ago and its efforts to preserve the park's other mangrove swamp has been applied to Pulau Semakau recently.

Part of the reclaimed land there has been planted with these trees to beautify the island and to act as living indicators of the environment there.

The natural swamp habitat in north-east Singapore was in danger of being destroyed when the land on which the park now stands was reclaimed about 20 years ago.

The project extended the shoreline and the mouths of two rivers there - Sungei Api Api and Sungei Tampines - about 100 m towards the sea.

Then, to reduce the likelihood of flooding upstream, Sungei Api Api was deepened. When this was done, the mangrove plants growing naturally along its banks had to be removed.

After the drainage work was completed, NParks laid organic matter down along 2 km of both the river's banks and planted 10,000 seedlings of the Avicennia mangrove tree.

Mr Ng Cheow Kheng, a senior manager with NParks, said: 'There was a conscious decision right from the start to re- establish the original mangrove habitat at Sungei Api Api.

'We wanted to recreate a natural river embankment and to hasten the regeneration of the mangrove plants.'

He added: 'This attempt was new for us - to try and establish plants on a river embankment instead of on dry land. It was challenging.'

He said that the mangrove plants stabilised the embankments and brought back the mangrove habitat fairly quickly.

Now, the site looks so natural that few are aware that nature had a helping hand from man.

The swamp at Sungei Api Api was not the only one which had help. So did the one at the park's other river, Sungei Tampines.

That too was in danger when the park was reclaimed in the late 1970s.

Associate Professor Lee Sing Kong, dean of Graduate Programmes and Research at the National Institute of Education, said: 'The reclamation project would have affected the flow of fresh and sea water at Sungei Tampines.

'This in turn would have killed the mangrove plants in the swamp at the side of the river.'

So the department asked the Housing Board to dig a small channel to connect the swamp with the river.

This allowed the mangrove plot to remain flooded, thus preserving the swamp.

Now, there is a boardwalk at this swamp so visitors can explore the mangrove habitat without getting their feet muddy.

Prof Lee said: 'The reclaimed land offered us a golden opportunity to study how mangrove plants can regenerate on a bare piece of land, especially on the banks of the extended Sungei Tampines.

'We were able to apply this knowledge to another reclamation project at Pulau Semakau some years later.'

Pulau Semakau and its neighbour, Pulau Sakeng, which are south of the main island, are an offshore landfill site for Singapore.

When the two islands were linked by reclamation to provide sites for the dumping of incinerated ash, mangrove trees were planted near the reclamation bunds to relieve the bare look of the site.

The trees also act as 'bio-indicators' of the health of the environment.

If the land becomes toxic due to the dumping, the plants will not be able to thrive there as they are doing now.