2 
Ganl. Bull. Singapore 70 (Suppl. 1) 2018 
The global and regional importance of freshwater swamp forest, and the national 
significance of Nee Soon freshwater swamp forest in particular, are reviewed by 
Clews et al. (2018). Historically, small areas of freshwater swamp forest are thought 
to have been present in Singapore on the lower reaches of various small river and 
stream systems, upstream of mangroves, and downstream of dryland forest (Corlett, 
1991, 1992). The freshwater swamp forest within each catchment would have been 
physically and biologically partly isolated from that in other catchments, resulting in 
local differences in floral and possibly faunal composition. 
Corner (1978) began studies of freshwater swamp forest in the Malay Peninsula, 
including Singapore, around 1932. His work demonstrated the major ecological and 
floristic features of this forest formation, and indicated floristic differences between 
the forest at Jurong (now gone, in the vicinity of Jurong Lake Park) and that at Mandai 
(now gone, but for the currently studied fragment at Nee Soon, in the vicinity of Upper 
Seletar Reservoir). Turner et al. (1996), Ng & Lim (1992), and Lim et al. (2011) have 
provided further information on freshwater swamp forest in Singapore and at Nee 
Soon. 
The area within Singapore that is likely to have been primevally under 
freshwater swamp forest has been various estimated as 65 km 2 (O’Dempsey, 2014) to 
74 km 2 (Corlett, 1991). Of this possibly half was in the catchment of the Kallang and 
Singapore rivers, one third in the catchment of the Jurong and Pandan rivers, and the 
remainder scattered in many tiny fragments along the middle courses of small streams 
prior to them debouching into coastal mangroves. 
The relatively intact patch of freshwater swamp forest in Nee Soon has long 
been considered the most important area in Singapore for native aquatic fauna and 
flora (Ng & Lim, 1992). Early estimates of its richness suggested that it contains 48% 
of the primary freshwater fish, 71% of the amphibians, 28% of the reptiles and 34% of 
the avian fauna of Singapore. Nee Soon is particularly well known for its importance to 
crustaceans (Ng, 1997; Ng & Yeo, 2005); the freshwater crab Parathelphusa reticulata 
is a global endemic to Nee Soon. The swamp also has the highest percentage of native 
and threatened freshwater fish species on the island, as well as being the main (if not 
the only) habitat of the aquatic plant Barclay a motleyi Hook.f. By 1992 it was also the 
last refuge within Singapore of two mammals, the Raffles Banded Langur, Presbytis 
femoralis femoralis, and the Cream-coloured Giant Squirrel, Ratufa affinis affinis. The 
banded langur has gradually increased in numbers and expanded beyond Nee Soon 
into other parts of the Central Catchment Nature Reserve, whereas the giant squirrel is 
now thought to have become locally extirpated (Davison et al., 2008). 
Study of the swamp forest has until recently been at a survey and discovery 
phase. Research priorities have been primarily to establish detailed species lists, the 
status of endangered species and the extent of buffer zones. There has been little 
documentation of spatial differentiation within the swamp forest. 
