One-third of Taiwan's corals dying due to bleaching: researchers

Taipei, Jan. 12 (CNA) At least 31 percent of the coral reefs in waters around Taiwan are dying as a result of bleaching, which is now the worst in the country's recorded history, researchers said Tuesday.

According to the Taiwan Coral Bleaching Observation Network (TCBON), 52 percent of the coral in Taiwan is under different levels of heat stress, while 31 percent is in an irreversible process of dying due to high water temperatures.

Having entered that process, the coral reefs will not recover, even if the water temperatures fall, said Kuo Chao-yang (郭兆揚), a postdoctoral research associate at the Biodiversity Research Center at Academia Sinica and a member of TCBON.

The coral bleaching, the worst since Taiwan began keeping such records in the 1980s, was a result of both global warming and a low incidence of typhoons in the country last summer, he said.

Average sea temperatures around Taiwan rose in 2020 to the highest in two decades, Kuo said, citing an average 30.5 degrees Celsius in waters off the north coast last summer, about 1 degree above normal.

The optimal water temperature for coral growth is 23-28 degrees, and in unfavorable conditions, most corals will expel their symbiotic algae, causing bleaching or even death, according to Kuo.

The areas around Taiwan where the worst bleaching occurred in 2020 were Liuqiu Island off the southwest coast, Kenting on the southern tip of Taiwan, northeast coastal areas, and the outlying islands of Penghu and Green Island, he said.

Mingo Lee (李世明), a diver who helps document the condition of Taiwan's coral, said the underwater temperature near the uninhabited island of Sijiyu in Penghu County was about 34 degrees when he went diving there last year.

"It was white everywhere, like snow," he said, describing the coral. "I had never seen anything like that in my 20 years as diver."

The massive coral bleaching in Taiwan is worrisome because it threatens biodiversity, said Allen Chen (陳昭倫), an Academia Sinica researcher and one of the founders of TCBON.

Chen said a more aggressive approach to reducing greenhouse gas emissions is needed.

If carbon emissions could be halved by 2030 to the 2016 level, carbon neutrality may be achieved by 2050, he said. As a result, global warming will be limited by 1.5 degrees, which will save 30 percent of coral reefs worldwide, he said.

According to the international environmental organization Greenpeace, coral reef communities around Taiwan make up less than one-thousandth of the world's in terms of scale, but they account for one-third of the various species globally.

Of the 700 species of stony corals worldwide, 250 can be found along the coast of Taiwan, Greenpeace said.