SINGAPORE – Reclamation works are planned to begin to the east of Pulau Sudong from 2024 to upgrade its existing runway for military aircraft – a development that could result in the loss of 2ha of coral reefs, as well as seagrass habitats and swathes of mangrove forests.

To mitigate the environmental impact of the project, the authorities will relocate rare and vulnerable species, and carry out habitat restoration works once the proposed reclamation is completed by 2028, said the Housing Board on Jan 26.

About 31.1ha of land – the size of 43 football fields – will be reclaimed on the eastern part of the island, which has been gazetted for military use since the 1970s. This is so that the emergency runway can be upgraded, which will improve flight safety, especially during bad weather, HDB said in response to queries from The Straits Times. 

A new sea-wall revetment, or retaining wall, will also be constructed around the periphery of the reclaimed area.

An environmental impact assessment report completed by environmental consultant DHI for the authorities quantified the potential habitat losses from the proposed reclamation, and recommended a number of measures to mitigate its impact. 

The reclamation works will result in habitat loss – including 2ha of coral reefs, or about 1.8 per cent of Singapore’s overall coral reef cover; about 17.28ha of intertidal habitat; and 71.91ha of soft seabed habitat, where marine worms, crabs and marine snails typically reside, the report noted.

The intertidal zone – which includes rocky shores, seagrass meadows, sandy beaches and mangroves – is home to a wide diversity of marine species, some of which are vulnerable or rare in Singapore. 

Also to be lost in the process are some 229 mangrove trees, or 1.46ha of mangrove forest, which are home to mangrove species like the Rhizophora stylosa and the Ceriops tagal, the report said.

The seed dispersal abilities of the surviving mangroves could also be affected, underlining the need for the remaining species to be well-protected, the report noted. 

Through surveys that were conducted from 2016 to 2017, and from December 2022 to January 2023, 83 different species of marine fauna were recorded across the affected intertidal areas, a number of which have been listed as vulnerable, according to the report.

These include the blue-spotted fantail ray, the white-spotted bamboo shark, and the tomato anemonefish. Rare hard coral species were also recorded, like the open brain coral (Trachyphyllia geoffroyi), the mole mushroom coral (Polphyllia talpina) and the ten ray star coral (Madracis kirbyi).

While the loss of seagrass habitats and small marine creatures could have an indirect impact on animals like dolphins and dugongs, there were no sightings of these marine animals when the surveys were conducted.

HDB said a range of mitigation measures will be implemented to minimise the impact on the ecology and biodiversity in the area.

To mitigate the environmental impact of the reclamation works, rare and uncommon coral species are recommended to be transplanted to surrounding islands such as Pulau Hantu, Pulau Semakau and Sisters’ Islands, said the report.

Threatened fauna residing in the intertidal zone can be relocated to the northern lagoon of Pulau Sudong, which is unaffected by the reclamation works, or to surrounding islands. 

To save the mangroves, the report recommended that the remaining mangrove propagules, or seeds, be collected and transplanted to suitable nature areas like the Sungei Buloh Wetland Reserve or Pulau Ubin.

A more detailed biodiversity management plan will be drawn up in consultation with the National Parks Board (NParks) before reclamation works begin. Once construction works are completed, key coral fragments can then be transplanted onto the sea walls, while mangrove saplings and seagrass can be transplanted to the eastern lagoon of the island as part of habitat restoration efforts. 

To better support biodiversity and hasten nature’s recolonisation, bio-tiles can be installed for the sea walls, which better help to support marine life. Bio-tiles are usually made with environmentally friendly materials, and typically have small holes or crevices to encourage biodiversity to accrete.

Environmental monitoring has been recommended to track the health and survival of the corals in their new habitats.

Associate Professor Huang Danwei, from the National University of Singapore’s Tropical Marine Science Institute, said studies on the marine ecosystems of Pulau Sudong have been very limited since it has been out of bounds for years to researchers and the public. 

However, some of the vulnerable species found on the island are similar to the ones found around Raffles Lighthouse – an area also left untouched by development, and which continues to host some of the healthiest coral reefs in Singapore, he added. 

Research collections of coral specimens on Pulau Sudong since the 1960s suggest that the reefs host high biodiversity, and have a relatively high representation of staghorn corals, which are much less common on most other offshore islands in Singapore. 

These stony coral species have been wiped out over the years amid reclamation and development, and should therefore be prioritised for transplantation and rehabilitation; otherwise, they could potentially become locally extinct, Prof Huang added. 

In the 1970s, about 242.82ha of land was reclaimed around Pulau Sudong, drastically expanding the size of the island. 

Its inhabitants were made to move to the mainland as the island was earmarked for redevelopment, with Pulau Semakau and Pulau Seking facing a similar fate. 

Since then, Pulau Sudong has become a military live-firing zone, while Pulau Semakau and Pulau Seking were connected to form Semakau Landfill.

Mr Muhammad Nasry, executive director of the Singapore Youth Voices for Biodiversity, said many military live-firing areas serve a secondary function of conservation, so any loss in habitat will naturally be major.

But he noted that the Changi beach intertidal area, for instance, is now a thriving spot for biodiversity featuring seagrass meadows, despite its relatively recent reclamation.

“Trialling innovative strategies, like different types of textured biodiversity tiles, can help NParks to better determine ideal structures to promote habitat restoration. This would be extremely useful for planning larger-scale reclamation projects like the upcoming Long Island,” he said.

He added that it will take time for replanted mangroves to serve the same ecological functions as the original ones, as mangrove saplings take years to grow.

Meanwhile, seagrasses need certain conditions such as having clear water for effective photosynthesis and suitable sediment to grow well, he said.

As these critical habitats are relatively understudied, long-term changes to the hydrology of the site should be carefully considered to ensure conditions are ideal for their recolonisation, he added.