ALBERT

Description: The environmental ramifications of rapid development on the functioning of warm tropical freshwater ecosystems are poorly understood. Here, a multi-proxy palaeolimnological approach is used to examine the nature and degree of anthropogenic environmental change in a tropical lowland reservoir in Singapore. Singapore has undergone a dramatic transformation over the past century, transitioning from a country with a largely agrarian landscape to one that is highly urbanised. Two radiometrically dated sediment cores were retrieved from one of the country’s oldest reservoirs and analysed for spheroidal carbonaceous particles (SCPs), mercury (Hg), atomic carbon (C) and nitrogen (N), stable C and N isotopes (δ13C and δ15N), and diatoms. The sedimentary data show clear evidence of atmospheric pollution and nutrient enrichment as a result of human activities in Singapore and the region. During the early stages of Singapore’s development (1900s–1960s), the reservoir was minimally impacted and characterised by oligotrophic conditions. As the country began to industrialise and urbanise (1970s–1990s), the SCP data indicate increasing contamination by air pollutants derived from domestic sources of fossil fuel combustion, while the diatom, C/N, δ13C, and δ15N data suggest that the reservoir was becoming more productive, possibly from N depositions arising from an increase in electricity generation and a rapid expansion in transport infrastructure in Singapore. As the pace of development in Singapore slowed down (1990s–the present), the sedimentary data collectively indicate increasing depositions of atmospheric pollutants and nutrient enrichment mediated by a warming climate. A substantial component of increased atmospheric pollution is likely to be of distal, and thus transboundary, origin.

Description: Peatlands are both responding to and influencing climate change. While numerous studies on peatland carbon dynamics have been published in boreal and temperate regions for decades, a much smaller yet growing body of scientific articles related to tropical peatlands has recently been published, including from previously overlooked regions such as the Amazonian and Congo basins. The recent recognition of tropical peatlands as valuable ecosystems because of the organic carbon they accumulate in their water-saturated soils has occurred after most of them have been drained and degraded in Southeast Asia. Under disturbed conditions, their natural carbon storage function is shifted to an additional carbon source to the atmosphere. Understanding the effect of land-use change and management practices on peatlands can shed light on the driving variables that influence carbon emissions and can model the magnitude of emissions in future degraded peatlands. This is of primary importance as other peatland-covered regions in the tropics are at risk of land-use and land-cover changes. A systematic review that synthesizes the general understanding of tropical peatland carbon dynamics based on the published literature is much needed to guide future research directions on this topic. Moreover, previous studies of biogeochemical cycling in tropical peatlands have largely focused on terrestrial stocks and fluxes with little attention given to document lateral and downstream aquatic export through natural and artificial drainage channels. Here, we present a systematic review protocol to describe terrestrial and aquatic carbon dynamics in tropical peatlands and identify the influence of land-use change on carbon exchange. We described a set of literature search and screening steps that lay the groundwork for a future synthesis on tropical peatlands carbon cycling. Such an evidence-based synthesis using a systematic review approach will help provide the research community and policymakers with consistent science-based guidelines to set and monitor emissions reduction targets as part of the forestry and land-use sector.