One third of the coral reefs in the world will suffer degradation by 2030 due to climate change

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According to a new study on climate change and its effects,  a group of scientists have found that the chances of saving world’s coral reef population from the ill effects of climate change is thinning day by day as the greenhouse emissions are increasing.

Great Barrier Reef
Image courtesy:  Richard Ling

The danger to coral reefs is almost impossible to be averted, indicates the study which is published in the journal Nature Climate Change. One third of the coral reefs in the world will suffer long term degradation due to climate change by 2030, finds the study even though the estimation is based on the most optimistic IPCC estimations on emissions.

“One-third (9–60%, 68% uncertainty range) of the world’s coral reefs are projected to be subject to long-term degradation under the most optimistic new IPCC emissions scenario, RCP3-PD.”, says the study

"The window of opportunity to preserve the majority of coral reefs, part of the world's natural heritage, is small," said Malte Meinshausen, a co-author of the paper to Reuters news agency. This will happen even if the emission cuts are made stricter, shows the study.

Bleaching and decalcification of corals

The scientists have assessed the impact of emissions on 2160 coral reefs in different parts of the globe, with the help of climate models. The study points out that the emission of Carbon dioxide, a greenhouse gas, has increased by more than 3 percent last year. As a result, the average temperature of the globe has also increased by 0.8 degree Celsius approximately, during the last century.

The increasing global temperature and warmer oceans will bleach the corals to death. Thus, the reefs turn pale when the warm sea surface triggers mass bleaching events across the globe, says the study.

Even if the corals survive the ill effects of bleaching, it is difficult for them to survive a prolonged period of heating up of the ocean. According to the study, when the oceans stayed hot for a prolonged period during 1998, 16 percent of corals vanished from the face of earth.

Acidification is more fatal to the survival of corals than the bleaching events. Acidification of ocean is directly proportional to the presence of Carbon dioxide in the ocean surface. With the acidification increasing, the rate of calcification - a process which is crucial to the existence of corals - gets disrupted, leaving them to corrode to death.

Location of Corals in the world

2 degree Celsius limit is no safer zone for corals

The study also points out that the present notions of safe emission levels and safe temperature rise levels may not save coral reefs. 2 degree Celsius is widely considered as a safe emission limit to avoid the devastating effects like droughts, sea level rise or failure of cultivation. However, it will not help corals to avoid the serious threats of global warming, shows the study.

According to the scientists, the chances of survival for at least half of the coral reefs in the world will remain live only if the average mean temperature rise stay below 1.2 degrees compared to that of pre-industrial period.  

Though the reefs’ ability to adapt and evolve with changing quality of the habitat may make a difference in their survival to the acidification and bleaching events. However, their ability to adapt significantly within a matter of decades (which is a very small period for evolutionary processes), in an atmosphere of continuously changing ocean temperatures is still uncertain.

Moreover, the rate and magnitude of warming, which the globe is going to face, has no equals in the past, points out the scientists. They are doubtless that the prominence of coral reefs in coastal ecosystems will plummet, if the global mean temperatures exceed 2 degree Celsius above that of the pre-industrial era.