16 
Ganl. Bull. Singapore 70 (Suppl. 1) 2018 
species found only in single locations. Furthermore, the critically endangered Betta 
persephone, B. miniopinna and B. spilotogena are listed on the IUCN Red List as 
highly threatened by extinction as a result of declines in area of occupancy, extent of 
occurrence and quality of habitat. Additionally, there are 17 species of swamp forest 
fish on the IUCN Red List classified as vulnerable or endangered, 12 of which are 
point endemics (Posa et al., 2011). Comprehensive studies of freshwater swamp forest 
fish have been carried out in only a few regions such as Thailand, central Sumatra, 
Peninsular Malaysia and the Riau Archipelago (e.g. Ng et al., 1992; Tan & Tan, 1994; 
Vidthayanon, 2002; Tan & Kottelat, 2009), and all indications point to even greater 
fish diversity in unexplored locations. 
Far less is known about the invertebrates of swamp forests, as most swamp 
invertebrates have not been extensively studied and furthermore, organisms are rarely 
identified to the species level. Johnson (1968) did note that Coleoptera, Hemiptera 
and Diptera may be abundant and diversified in small blackwater pools but in most 
blackwater habitats, freshwater macroinvertebrates are rather scarce and have poor 
diversity, with Cheng & Fernando (1969) listing only six hemipteran species from 
Malaysian blackwaters. Although there seem to be few if any invertebrate species 
specific to or characteristic of swamp forest (e.g. Ng et al., 1992; Abang & Hill, 2006), 
rotifer and decapod crustacean species have been found in these habitats (see Ng et 
al., 1992). For instance, a total of 133 rotifer species were identified from five coastal 
peat swamps on Phuket Island, Thailand (Chittapun et al., 2007), whilst Wowor et 
al. (2009) found four species of the freshwater Macrobrachium prawns occurring in 
acidic peat habitats. 
General climatology of Singapore 
Historical trends in precipitation 
Nine rain gauges in Singapore (Fig. 2; Liong & Raghavan, 2004), selected for their 
data comprehensiveness and relevance to Nee Soon freshwater swamp forest, provided 
the daily rainfall data from 1961 until 2007 used for the present study. From some 
of the stations the time series was incomplete. Table 1 provides the periods of data 
availability for the nine stations considered. 
Historical trends in temperature 
The trends in daily temperature observations for Singapore reveal evidence of a 
warming trend since 1970 that is consistent with broader evidence of global warming 
and other temperature trend analyses in the region. Daily maximum and minimum 
temperature data are available from four observation stations in Singapore, for varying 
periods (shown in Table 4). The station-averaged absolute change values compared 
to baseline 1961-1990 show the rise in surface temperatures since 1961-1990, as 
recorded at all stations. 
