Editorial | Bleached coral adds to signs of global warming

If Hongkongers were given a quiz on species found locally, few would probably check off coral as an answer. While the city has nothing like Australia’s Great Barrier Reef or Southeast Asia’s marine paradise, our waters are home to as many as 84 species of coral. As with other components of our rich and delicate biodiversity, better conservation efforts are needed or these species may eventually disappear.

It is sad to learn that the local coral is also under threat because of global warming and this year’s unusually heavy rainfall. According to a local marine biologist, mass coral bleaching was found in the protected waters off Sharp Island last month, with some sites recording levels of bleaching at more than 70 per cent of the “coral communities”. In another survey, international conservation group WWF Hong Kong also found more than half of the coral was bleached at a site in Hoi Ha Wan Marine Park.

The problem is nothing new. In a study by the Agriculture, Fisheries and Conservation Department, Baptist University and the Chinese University of Hong Kong in 2022, coral bleaching was also observed at 18 of 19 sites. Among them, 13 per cent and 33 per cent of coral had turned pale near Tung Ping Chau and northern Sharp Island respectively. But the recent pace and scale of bleaching has been described by local conservationists as alarming.

With local sea temperatures hitting 30.7 degrees Celsius in some areas this summer, considerably higher than the optimal range for coral growth of 26 to 28 degrees, bleaching is to be expected. The prolonged rainfall that started in March was also an aggravating factor as run-off had decreased the salinity of the seawater. But authorities sought to play down the problem, saying coral was resilient and the situation would improve when the temperature returned to normal.

We may think there is not much we can do about seawater temperatures or rainfall. But the aggravating problem of coral bleaching is yet another reminder that the negative impact of global warming and extreme weather will only increase if we sit back and do nothing. Unless more concerted and resolute efforts are taken to better protect the environment, the price to pay could be more than disappearing coral reefs and other marine life.