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

Abstract

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.

Tropical vegetation productivity and atmospheric methane over the last 40,000 years from model simulations and stalagmites in Sulawesi, Indonesia

“…This is largely due to the major increase in the maritime continent landmass, which, in the model, is ~95% more expansive during the LGM compared with the modern. Additionally, the simulated vegetation type over the maritime continent landmass is dominated by evergreen broadleaf trees, which is likely an overestimate, given the marine and terrestrial proxy data (e.g., Wurster et al, 2019; Nguyen et al, 2022; Cheng et al, 2023). This study, however, investigates the Sulawesi stalagmite δ 13 C record as a possible indicator of local and regional methane emissions via the response of vegetation productivity to climate and environmental conditions.…”

“…For example, the LGM sea-level low stand resulted in Sunda Shelf exposure of ∼2.4 million km 2 (50% more expansive) compared with the present (Sathiamurthy and Voris, 2006). Terrestrial and marine paleoenvironmental studies show evidence for a substantial savannah corridor occupying the interior of the exposed Sunda Shelf during the LGM (Bird et al, 2005;Wurster et al, 2010Wurster et al, , 2019Nguyen et al, 2022;Cheng et al, 2023); however, the spatial extent of savanna versus forest is debated (e.g., Bird et al, 2005;Wurster et al, 2010). Modelled vegetation on exposed continental shelves during the LGM relies on the simulation of dynamic vegetation coverage within SDGVM.…”