09 August 2009

Secret mangroves of St. John's Island

Most people will notice the mangroves fringing the outer side of the island as they land at the jetty.
But St. John's Island also has a hidden patch of mangroves further inland. Which alas, has a rather sad secret as well.

After checking out the other side of St. John's Island, I had a quick look at the tiny patch of fringing mangroves.
It's quite lush now and seems to have a lot of saplings. Possibly replanted?
This is a great place to look at the often confusing Bakau pasir and Bakau kurap as these two species grow side by side here.

Bakau pasir (Rhizophora stylosa) has flowers with a long style (the pointy thing at the top of the bump in the middle of the remains of the flower), and the 'fruit' is small compared to the sepals (the pointy green things at the top of the brown 'fruit'). The leaves are also smaller and the propagule (long green thing under the brown thing) much shorter and less warty.
Bakau kurap (Rhizophora mucronata) has flowers with a short style, and the 'fruit' is large compared to the sepals. The leaves are also larger and the propagule much longer and more warty.
It's not easy distinguishing the two species on their own, but when you see them side by side, the differences become quite obvious!

There's also a big old Tumu (Bruguiera gymnorrhiza) there, with lovely knee roots!
But the secret mangrove is further in, along an increasingly fenced up St. John's Island.
Later on, I figured out why there was a beaten path to the mangroves, when it seems no one would visit it otherwise.

The mangrove is small but interesting. I saw the usual common mangroves trees, as well as specials such as Nipah palm (Nipa fruticans), nice large Teruntum trees (Lumnitzera sp.), Mangrove cannon-ball tree (Xylocarpus granatum) and what seems to be a Tengar (Ceriops tagal).
I have heard that there is an Api-Api jambu (Avicennia marina) in this mangrove, and wonder if this tree might be it? This species is listed as 'Critically Endangered' in our Red List and there are very few specimens of this tree in Singapore, and possibly only one on St. John's Island?
Unfortunately, the reason for path to the secret mangrove became clear when I followed it. To an area where leaves probably swept up from elsewhere on the island was dumped. The Rhu twigs were a dead give away.
The dumped leaves were about a metre thick and covered an area of about 5 metres square.
The tree that I think is Avicennia marina is very close to this leaf dump site. Dumping leaves in such large quantities smother mangrove roots and prevent young mangroves saplings from growing in the mud.

As I rounded the corner to another edge of this very small mangrove, an even more heartbreaking sight. A similarly sized area is full of rubbish that was not only dumped there but also burnt there.
The burning had probably killed this large mangrove tree nearby. It was completely dead and had blistered bark.
Next to the burning area was the remains of a mattress!
Again, the pile of burnt material and dumped leaves and other trash in this second area was about 1m thick and about 5m square.

There was a beaten path from the burning site to the nearby building.
Where a stack of rubbish was located. Waiting to be burnt in the mangroves?
How tragic that such a precious mangrove is treated as a dumping site.

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