Global significance of freshwater swamp forest 
23 
the thin layer of peat present in the swamp forest causing the release of humic acid, the 
mechanisms of which were explained above. 
Ecology of Nee Soon freshwater swamp forest 
Through the collation of data from published articles—mostly from the Gardens’ 
Bulletin Singapore and The Raffles Bulletin of Zoology , as well as unpublished data 
retrieved from the National Parks Board (NParks), the number of faunal species 
recorded in the Nee Soon freshwater swamp forest was determined to be at least 346. 
However, this is probably a highly conservative figure, and it is likely that this is only 
a small proportion of the species present in the forest. 
A series of field surveys was conducted in the 1990s, and their results published 
in 1997 in the Gardens’ Bulletin Singapore (Chan & Corlett, 1997). This contributed 
immensely to the inventory of biodiversity knowledge in Singapore, especially in the 
Bukit Timah and Central Catchment Nature reserves. Among the groups surveyed were 
vascular plants, fish, prawns, crabs, butterflies, stick and leaf insects, semi-aquatic 
bugs, dragonflies and damselflies, and water beetles. 
Based on our compilation of known faunal species in the Nee Soon freshwater 
swamp forest, insects and birds make up the largest proportion of animals recorded. 
Molluscs and annelids, on the other hand, make up only 3% of the total number of 
species which have been documented in this forest patch. 
While the Nee Soon freshwater swamp forest has lost much of its original 
vertebrate fauna, it is still a very important site for the conservation of Singapore’s 
remaining forests (Corlett, 1992). In fact, Yeo & Lim (2011) commented that Nee 
Soon freshwater swamp forest supports the highest diversity of native freshwater 
organisms in the country, reflecting its high conservation value and in particular 
supporting freshwater fish, amphibians, reptiles, freshwater prawns and crabs and 
bird species (Ng & Lim, 1992; Yeo & Lim, 2011). Many species, especially primary 
freshwater fish, have their main populations in Singapore located in the Nee Soon 
freshwater swamp forest and some others can be found nowhere else in Singapore, or 
even globally, such as the swamp forest crab, Parathelphusa reticulata (Davison et al., 
2008; Cumberlidge et al., 2009; Lim et al., 2011). This makes the Nee Soon freshwater 
swamp forest a vital refugium for many forest or swamp-adapted species in Singapore, 
and gives it a very high conservation value (Ng & Lim, 1992; Lim et al., 2011). 
Freshwater flora of the Nee Soon freshwater swamp forest 
Parts of the Nee Soon forest were cleared during the late 19 th and early 20 th century 
for rubber and pepper plantations (Turner et al., 1996). Other parts have been drained 
or turned into reservoirs (Ng & Lim, 1992). The remaining vegetation consists of a 
mixture of primary and secondary forest (Corner, 1978; Ng & Lim, 1992). Given its 
history, the species composition and structure differ across the forest, suggesting a 
mixed swamp forest. Many of the tree species in parts of the forest, such as Palaquium 
xanthochymum (de Vriese) Pierre ex Burck and Xylopia fusca Maingay ex Hook.f. & 
Thomson, exhibit adaptations to flooding, including buttress roots, prop roots, and 
pneumatophores whereas some areas are dominated by plant species similar to those 
