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Can coral reefs keep up with a warming planet?

“Assisted Evolution” offers hope for the future of corals.



The oceans are warming and scientists are unsure if coral reefs can survive without intervention. 

Coral reefs have the highest biodiversity and economic value of any ecosystem on the planet, rivalling only tropical rainforests. While coral reefs cover only two percent of the world’s oceans, almost a quarter of all marine life rely on them for survival. They protect coastlines from erosion and storms and provide habitat and nursery for fish and other marine life. They provide food and livelihood from fishing, tourism and recreation for 500 million people in coastal areas and islands around the world, including the Maldives, a low-lying island nation built on coral reefs that would not have been formed without them. 

Though corals are living organisms, they do not have to die of old age. Theoretically, they could continue to live and grow as long as the surrounding environment would allow. There are corals alive today that are more than 4,000-years-old, and it is possible that even older corals exist. Corals require very specific conditions to survive, which is why they only occur where they do. Yet throughout natural cycles of the earth warming and cooling, corals have adapted and survived for millions of years. 

Climate Change and its Effects on Coral Reefs

Since the industrial revolution, humans have driven global climate change, releasing increasing amounts of Carbon Dioxide (CO2) into the earth’s atmosphere. This has resulted in shifts in ocean temperature, ocean chemistry and sea level, as well as increased frequency of storms and changes in weather patterns around the world. Even in the Maldives, the usually predictable monsoon patterns have shifted and become increasingly unpredictable. 

These changes to the climate have a profound impact on marine ecosystems, especially coral reefs. Increased CO2 in the atmosphere causes the ocean to become more acidic, and reduces the corals’ ability to grow. Corals have a mutual relationship with a micro-alga called zooxanthellae, which live in the coral and provides its food. Warm water stresses the coral and disrupts the symbiotic relationship. This causes the coral to expel the zooxanthellae and turn white, a process known as coral bleaching. Without its source of food, bleached coral can starve and die.  

Reef in Baa Atoll showing healthy coral in April 2015, bleached coral in April 2016, dying coral in May 2016 and dead coral in May 2017, with most of the surrounding reef reduced to rubble. Photos: Hussein Didi

In the past few decades, the earth has been experiencing mass bleaching events, which coincide with El Nino periods, a global weather phenomenon which causes already rising ocean temperatures to spike even higher. These mass bleaching events were first recorded in modern history in the 1980s and has since increased in frequency five-fold, largely driven by climate change. Between then and now, we have lost 40 percent of the world’s coral reefs. The most recent events which occurred from 2014-2016, caused extreme bleaching in reefs around the world. A study conducted by the Maldives Marine Research Centre and Environmental Protection Agency, in partnership with the International Union for Conservation of Nature (IUCN), revealed that 60 percent of the corals in the Maldives bleached during this event. The oceans are warming at a rate not experienced by life on earth for at least 50 and possibly even hundreds of millions of years. 

“Assisted Evolution” as a Solution for Reef Restoration

Scientists believe that corals are dying at this rate because our oceans are warming and acidifying faster than corals can evolve and adapt. Researchers from the Australian Institute of Marine Science (AIMS) and the Hawaii Institute of Marine Biology have been working together to study how “Assisted Evolution” may help some corals adapt faster to climate change. Assisted Evolution is the speeding up of natural evolutionary processes to enhance certain traits. This idea has been widely used in commercial species, including crops, wood trees and livestock. 

“Today we are facing the potential loss or massive degradation of all of our reefs by 2050. If we don’t have coral reefs, we’ll have people who don’t have food, who will have to move, whose lands and entire islands will be eroded, and the tourist economies of these places will be completely obliterated,” Ruth Gates, Director of the Hawaii Institute of Marine Biology explained in an interview with Al Jazeera.

“If you could get a coral to acclimate or adapt at the same rate at which the climate is changing, you could get the corals to keep up with that”. 

To test whether they can achieve this, they are simulating ocean conditions of today, as well as conditions predicted for the years 2050 and 2100 by the IPCC. They aim to find out whether corals can be conditioned, or trained, to withstand future conditions, as well as whether those corals can pass on those traits to their future generations. The approaches they use include cross-breeding to allow natural selection to pick the individuals who do better in higher temperatures and acidity, as well as pre-conditioning the larvae and adults to these conditions to see if their offspring can withstand the same stress. 

Sea Simulator Lab in Queensland, Australia. Photo: Christian Miller. Source:

What the Future May Hold

Few places in the world are as dependent on coral reefs as the Maldives. We depend on reefs for food, livelihood, and for the very existence of our islands. Predictions based on latest Inter-Governmental Panel on Climate Change (IPCC) data indicate that at current rates, all coral reefs could be dead in as early as 40 years. When we talk about how climate change will affect Maldives, it is usually about sea level rise and the threat of our islands becoming submerged.

The Maldives is on average 1.5m above sea level. Current IPCC data predicts sea levels to rise between 0.26-0.77m by the year 2100. Given the statistics on the current status and the predictions for the status of the world’s coral reefs for this century, the threat to the survival of corals may well be a more pressing concern. What would we do without fish or tourists? What would our islands do without protection? And if our islands were to wash away, what would the Maldives be without islands?

Scientists acknowledge that Assisted Evolution approach in corals are still at a proof-of-concept stage, and current experiments will have to be scaled up both spatially and across a wider range of species and functional groups before it can be used in major coral reef restoration efforts. With research ongoing, we will soon be able to answer the question as to whether we can help coral evolve so that they have a better chance of adapting to the conditions we created. So that they have a chance to exist.

Written by Aya M R Naseem.

Aya Naseem is a marine biologist with a BSc in Marine Biology and Zoology and a BSc (Hons) in Marine Biology from the University of Queensland.  

Cover photo by Joseph Litt.

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