Climate change puts pressure on world’s coral reefs

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Scientists raised the alarm on Tuesday over the accelerated rate of climate change for putting more pressure on coral reefs, one of the most biologically rich and productive ecosystems, which has served as a grocery and pharmacy for people for centuries.

The rise in seawater temperatures was blamed for coral bleaching and for the change of ocean chemistry — known as ocean acidification — which has garnered a reputation as the equally evil twin of climate change.

The impacts range from slower coral growth, changes in the behavior of fish and reducing reefs’ abilities to provide fish for millions of people who depend on the ocean for their source of livelihoods.

“Tropical coral reef waters are already significantly warmer than they were, and the rate of warming is accelerating,” Janice M. Lough of the Australian Institute of Marine Science told the media at the 12th
International Coral Reef Symposium in Cairns, Australia.

“With or without drastic curtailment of greenhouse gas emissions, we are facing, for the foreseeable future, changes in the physical environment of present-day coral reefs.”

In the past century, she said global temperatures had warmed by 0.7 degree Celsius and those of the surface tropical oceans by 0.5 degree Celsius.

The rise of baseline temperatures has already resulted in widespread coral bleaching, where corals lose their colorful symbiotic algae and expose their white skeletons, leaving them vulnerable to death and outbreaks of coral diseases.

Increasing carbon dioxide emissions are also blamed for making the world’s oceans more acidic, thereby reducing coral growth rates.

Several reefs, including Australia’s protected Great Barrier Reef, have witnessed slower massive coral growth in recent decades.

Indonesia, one of the six countries grouped under the Coral Triangle Initiative that aims to preserve the world’s richest marine biodiversity, is not free from the impacts.

Suharsono, a researcher from the Indonesian Institute of Sciences’ Research Center for Oceanography, said that climate change-triggered coral bleaching was not a chronic, but an acute problem.

“Coral bleaching does not happen continuously, but when it happens, it may significantly affect the reefs, sometimes by 80 percent,” he said.

Indonesia, the largest archipelagic country in the world, is home to 16 percent of the world’s coral reefs.

In Indonesia, Suharsono said the worst coral bleaching, blamed on a rise in seawater temperatures by 3 to 4 degrees Celsius, took place in 1982-1983. It happened again in 1997 and 2010. The latter happened only in certain parts of the country’s reef cover.

“The thing that worries me is that bleaching incidents are becoming more frequent. If the bleaching happens when the reefs are not yet fully recovered from the last incident, I’m afraid they will be gone for good,” Suharsono said.

Based on his team’s research, it took around 10 years for coral reefs to recover after suffering from bleaching.

Philip L. Munday of James Cook University said changes to the coral reef habitat caused by climate change would potentially lead to changing fish populations, with its direct impacts already occurring, such as reduced coral cover and less habitat structure for fish. “That will mean fewer species and lower fish abundance,” Munday said.

Based on his team’s research, he said that more carbon dioxide dissolved in the ocean could also cause abnormal behavior in fish, leading to reduced survival. “Like coral, there will be winners and losers, and the communities of fish we see on reefs in the future are likely to be different to those of today,” Munday said.