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Fig. 5. Mean population abundance of terrestrial snails and slugs at all survey sites. 
We observed that the relative moisture level of the area plays an important role 
in the distribution of the land snails. Based on the survey results, the Middle Swamp 
and Lower Swamp generally exhibit a higher diversity and richness as compared to the 
Upper Swamp. This may be due to the wetter and more humid habitat in the Middle 
Swamp and Lower Swamp. Many species such as Cyclophorusperdix aquila, Cyclotus 
rostellatus and Japonia ciliocinctum were only observed in partially waterlogged 
areas, in close proximity to forest streams. Thus, any change in the hydrology of the 
Nee Soon catchment may have adverse effects on the diversity and distribution of the 
land snails. 
Nee Soon freshwater swamp forest is the last remaining freshwater swamp 
forest in Singapore. Not only does it harbour a rich diversity of land snails and slugs, 
it houses a significant population of the endemic Amphidromus atricallosus temasek. 
The discovery of the newly recorded Damayantia cf. simrothi also indicates that there 
may be more species waiting to be discovered. Unfortunately, the freshwater swamp 
forest ecosystem is extremely fragile, facing threats from environmental changes and 
urban development (Clews et al., 2018). Furthermore, the changes in global climate 
leading to extreme weather events will put additional stress on the forest (Sun et al., 
2018). Unless measures and precautions are taken to safeguard the Nee Soon freshwater 
swamp forest, the rich biodiversity and heritage might be lost forever. 
ACKNOWLEDGEMENTS. We would like to thank Drs Lena Chan and Geoffrey Davison 
for their support, Tan Siong Kiat for assistance in species identification and colleagues for 
helping in field surveys. This study forms part of the Nee Soon Swamp Forest Biodiversity 
and Hydrology Baseline Studies Project funded by the National Parks Board (FC 12302501). 
