How is climate change affecting the coastal and marine environments of Singapore?

Today, close to 1 million plants and animals are threatened with extinction. A century of habitat degradation, driven by land use change, pollution and the spread of invasive species continues to accelerate as climate change amplifies the stress on biological diversity.

Nature is declining at an unprecedented rate in human history.

Amongst the many habitats and ecosystems affected, coastal and marine environments are particularly at risk from climate change, imperiled by the effects of sea level rise, ocean acidification and increased sea surface temperatures. A small, low-lying city-state like Singapore will no doubt face the brunt of protracted changes in climatic events.

Located near the Coral Triangle, the planet’s centre for marine life and coral species, Singapore waters host rich coastal and marine biodiversity. In spite of the country’s busy shipping lanes, decades of coastal urban development and reclamation, and the large amount of debris washed up on its coastlines, Singapore is also home to 55% of mangrove plants in Asia, 52% of Indo-Pacific seagrass species and a third of the world’s coral species. Some supposedly extinct native faunae, such as the Neptune Cup’s Sponge (Cliona patera) and the Basket Star (Family Euryalidae), have even staged a ‘comeback’ after they were last seen in 1822 and 1896 respectively.

Yet, as climate change continues to wreak havoc on the ecosystems around the world, the future for coastal and marine habitats in Singapore is a bleak one.

A recent study[1] projects a potential 20% decrease in Singapore’s mangroves and seagrass meadows by the end of this century due to coastal squeeze. This is probable when naturally occurring landward transgression of habitats, following sea level rise and other coastal processes, is impeded by man-made structures or actions.

In land-scarce Singapore, continued coastal urban developments will inhibit the coastal and marine habitats from shifting landwards in response to climate change. Essentially, Singapore’s coastal and marine ecosystems are less capable of adapting to climate change and more vulnerable to climatic impacts.

Extreme rainfall events as a result of climate change can also advance mass mortality of the intertidal organisms in Singapore. This was believed to be the case for Chek Jawa, Pulau Ubin, in 2007, when unusually intense and prolonged periods of rainfall led to a sustained period of low water salinity that subsequently decimated a number of intertidal macrofaunae such as the Haddon’s Carpet Anemone (Stichodactyla haddoni) and the Noble Volute (Cymbiola nobilis). The chronic destruction made to the intertidal ecosystem also contributed to an opportunistic colonisation by the invasive Asian mussel (Musculista senhousia).

Adding to the casualties of extreme rainfall events, rising sea surface temperatures can further obliterate the coral and sea anemone population. Sustained elevated sea surface temperatures in 1998 and 2010, due to a rapid shift from a strong El Ni?o event to a strong La Ni?a event and prolonged by the anomalous Philippine Sea anticyclone, engendered mass coral bleaching events throughout Southeast Asian regions. When warm waters evoke corals to expel the symbiotic zooxanthellae living in their tissues, corals lose their major source of food and become susceptible to disease and death. Once corals die, the reef ecosystem, on which humans and wildlife depend, may collapse as dead reefs rarely come back to life. The hard coral species, soft coral species, and colonial sea anemones in Singapore have all been affected by such bleaching events.

Finally, with increasing levels of carbon dioxide and other emissions, the coastal and marine environments and biodiversity globally are also susceptible to ocean acidification. When a large amount of atmospheric carbon dioxide dissolves into the ocean it produces hydrogen ions. The problem is that carbonate ions bond with those hydrogen ions, limiting the availability of the carbonate ions that are essential for calcifying organisms to build and maintain their shells, skeletons and other calcium carbonate structures. If the pH of the ocean gets too low, shells and skeletons may even begin to dissolve. This jeopardises the survival of the already declining coral population in the world.

With Singapore already projected in some scenarios, to see a mean sea level rise of 1 metre and warming by 2.7°C to 4.2°C by the end of the century, the country will potentially develop a climate that exists nowhere else on Earth today and that has not been seen for several million years. Singapore must not overlook biodiversity conservation in its planning, as a healthy ecosystem that is resilient to climate change will provide critical ecosystem services that ensure the well-being of a society.

We know that climate change and biodiversity loss are intrinsically related. Singapore now needs to make the investments of time, finance, and labour to tackle these twin crises, to maintain the direct and indirect economic benefits that stem from our island’s rich and diverse ecosystems.

Weiting Liu is a Graduate Climate Consultant at RSK Centre for Sustainability Excellence (CSE), which develops and delivers practical solutions to help businesses, governments and other organisations achieve the Sustainable Development Goals set out by the United Nations. She also assists Nature Positive in delivering nature-based services in Southeast Asia and the region.

Appendix:

Below are some of the intertidal organisms found during one of the intertidal walks RSK Centre for Sustainability Excellence participated in. They include the Haddon’s Carpet Anemone and Noble Volute mentioned in the write-up.

From left to right: Noble Volute (Cymbiola nobilis) , Haddon’s Carpet Anemone (Stichodactyla haddoni), Biscuit sea star (Goniodiscaster scaber)

From left to right: Eight-armed Luidia sea star (Luidia maculata), Brittle star (Subclass Ophiuroidea), Pink warty sea cucumber (Cercodemas anceps)

[1] Nguyen, N. T. H., Friess, D. A., Todd, P. A., Mazor, T., Lovelock, C. E., Lowe, R., Gilmour, J., Loke, M. C., Bhatia, N., Jaafar, Z., Tun, K., Yaakub, S. M., & Huang, D. (2022). Maximising resilience to sea-level rise in urban coastal ecosystems through systematic conservation planning. Landscape and Urban Planning, 221, 104374. https://doi.org/10.1016/j.landurbplan.2022.104374