As the world warms, certain species of animals, like the hard corals that help sustain sea communities, tend to feel the heat more than others.

Recognising the vulnerability of these reef builders, the National Parks Board (NParks) has moved to add 10 hard coral species to its species recovery programme, to ensure they continue to thrive.

At the annual Festival of Biodiversity outreach event yesterday at the Singapore Botanic Gardens, NParks said that fragments of these coral species will be nurtured in a nursery on St John's Island, to be "planted" off Sisters' Islands Marine Park when ready.

Among the 10 species are: Micromussa amakusensis, a new species recorded in Singapore in 2019, and Trachyphyllia geoffroyi, a unique coral shaped like the figure "8".

Hard corals consist of an outermost layer of live tissue and a calcium carbonate skeleton, and are the builders of coral reefs, which help to sustain communities and grow economies through supporting fisheries and eco-tourism.

Their calcium carbonate skeleton provides nooks and crannies for other marine life such as baby fish, crabs and sea slugs to find shelter in. But hard corals are also sensitive to slight increases in sea surface temperature - making them the canaries in the coal mine of a warming ocean.

When it gets too hot, they expel the symbiotic algae that live in their folds and are deprived of a key source of nutrition, causing them to turn white, in a phenomenon known as coral bleaching.

Ocean acidification - which can result from carbon dioxide dissolving in ocean waters - could also affect the formation of their calcium carbonate skeletons and reduce growth.

"Further research and conservation efforts focused on these reef-building hard corals will enhance the resilience of Singapore's reefs and benefit the marine life that inhabit them," said NParks, the custodian of Singapore's native biodiversity.

Besides the 10 species of hard corals, NParks will also add another three animal species to its recovery programme: the straw-headed bulbul - a critically endangered song bird - the muff river prawn and the Inger's dwarf toadlet.

Another 13 plant species, including the Nervilia singaporensis, an orchid found only in Singapore, will also be added.

The species recovery programme was introduced by NParks in 2015 to conserve native flora and fauna that are endemic - found only in Singapore - rare or threatened. Some species in the programme are found in only small populations or in only a few places.

The programme aims to increase the populations of these species and help them survive adverse environmental changes.

NParks initially aimed to have 90 plant and 40 animal species under the programme by 2030, but will now increase its target to 100 plant and 60 animal species.

The 13 new plant and 13 new animal species added to the programme yesterday will join the 67 plant and 10 animal species currently under the initiative.

They include the Singapore freshwater crab and the harlequin butterfly, both of which have benefited from a captive breeding and translocation programme, as well as the Sunda slow loris.