REPOSITORY ON COASTAL ECOSYSTEMS:
BRIDGING ARTISTIC, SCIENTIFIC AND COMMUNITY-LED PRACTICES I N THE RIAU ARCHIPELAGO

Dr Timothy Shaw is a wetland scientist and Senior Research Fellow at the Earth Observatory Singapore. In his work, he collects sediments, particularly from mangroves in Southeast Asia, and analyzes how old they are using laboratory tools. He then uses that information to understand past sea levels, the mangrove trees that used to grow there, to anticipate how these forests might respond to future sea level changes.  

Mangrove forests exist in an intertidal zone, which means they are neither fully land nor fully sea, but in a space where sea level rises and falls twice a day. In Singapore, when these tides come in, they can reach a maximum height of 3.5 meters (footnote), similar to the study on the tidal patterns of the East Coast of Bintan. When this happens, the roots of mangrove trees become submerged in water; when the tide moves out, they become exposed once more. Their close proximities to the sea also mean that these forests are heavily influenced by changes in sea level over time. 

Dr Shaw explains the interdependence between sea level changes and the formation of mangrove forests: “These ecosystems exist in equilibrium with sea level rise, a phenomenon which enables the accumulation of sediments to form intertidal zones.”  

However, when sea level rises too fast, a worrying situation that scientists worldwide are now observing, these ecosystems may struggle to adapt quickly enough and could effectively drown. Sea levels today are rising at around 4 millimeters per year while predictions are showing that 7 to 8 millimeters per year could occur before the end of the 21st-century. 

“Under natural circumstances, these forests typically migrate towards the land [when sea level rises], if there is nothing stopping them. But in our modern landscapes, particularly in Singapore, we have built up the environment behind where these mangroves now exist, thus restricting their movement. If they cannot move landward due to coastal development, they become stuck in place with nowhere to go,” Dr Shaw explains. This phenomenon is known as “coastal squeeze”. 

This squeeze occurs when rising seas push ecosystems from the seaward side while human infrastructure, such as roads, seawalls, or coastal developments, prevents them from migrating inland. The physical space available for these intertidal forests to grow becomes progressively smaller, until they have nowhere left to exist. 

Human activities along the coastlines also heavily affect how these sediments travel through water, and how they build up over time. The movement of heavy ships and land reclamation activities can disrupt the flow of sediments. This is significant because mangrove forests depend on the vertical accumulation of sediments to build ground for them to root. Without sufficient sediment supply, coupled with restrictions on their movement, mangroves could eventually drown beneath the sea. 

Dr. Shaw’s research on sea levels and sediment analysis is important in planning forward for anticipated changes in these coastal ecosystems. His data will compare the vertical accretion of mangrove sediments with projected sea level rise, to anticipate the states of these ecosystems in the future. Understanding how they survived past sea-level change and how they are adapting today can help scientists and policy makers plan, so that these ecosystems can still endure in the future.