Environmental change since the Last Glacial Maximum: palaeo-evidence from the Nee Soon Freshwater Swamp Forest, Singapore

Our examination of pollen, microcharcoal, and sediment material in Nee Soon Freshwater Swamp Forest in Singapore revealed the following regarding its more than 20 000-year history: (1) the pollen record supports the presence of a savanna corridor in this part of South-East Asia during the Last Glacial Maximum (LGM); (2) a high abundance of charcoal at depths greater than 1.5 m supports the existence of a dryer climate and/or more frequent fires until about 18 000 cal bp; (3) missing sedimentary material in the upper 30-40 cm, ranging in age from 64 to 7500 cal bp, was likely removed during recent construction work in the 1950s; (4) there is evidence of sea-level influences on the site from the presence of mangroves from 9000 cal bp to present but it is difficult to determine whether this impacted the site because of the missing sediments; and (5) the low organic carbon content throughout the stratigraphy indicates that the swamp is not a peatland. The results indicate that the forest in this protected area of Singapore developed from a grassland-dominated landscape after the LGM as the climate warmed and became wetter, and therefore, may not be as resilient to long-term drought conditions as previously believed. Further, the stratigraphy contains evidence that the swamp and stream system have been highly dynamic, both naturally and in response to anthropogenic disturbance.

Automated summary

The study of pollen, microcharcoal, and sediment materials in the Nee Soon Freshwater Swamp Forest in Singapore revealed its over 20,000-year history, including the presence of a savanna corridor during the Last Glacial Maximum, evidence of dryer climate and fires, missing sediments likely due to construction work in the 1950s, sea-level influences, and the swamp not being a peatland. The forest in this protected area of Singapore developed from a grassland-dominated landscape after the Last Glacial Maximum, possibly making it less resilient to long-term drought conditions, and the swamp and stream system show high levels of dynamism.