Reef Revelations: Saving Corals from Hotter Oceans

Written by Rod Salm
Published on August 4th, 2010
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In 1990, I was living a conservationist’s dream.

While developing conservation plans along the coast of Oman, I found a place with great reefs and no people. It looked like protecting the reefs was going to be easy… until the waters heated, and heated, and heated.

This year, things are once again heating up, and we fear that we may witness the worst global coral bleaching event since 1998. But back in 1990, temperatures reached 95°F, hovering there for over a month and killing 95% of the corals through a process called bleaching. It raised a worrying question: how could we conserve coral reefs in the face of climate change?

This dilemma challenged me for a decade. I was based in East Africa when the 1997-’98 El Niño—and the following 1998-’99 La Niña—caused the greatest mass coral bleaching in recorded history, killing off 16% of the world’s coral reefs.

When I joined the Conservancy in 1999, I suddenly had access to a new range of project sites where I could study how climate change hastened coral bleaching. And the clear patterns in bleaching resistance and coral mortality in Palau helped me piece together a possible solution that could reduce bleaching caused by the current warming.

Bleaching is a stress response in corals caused by a number of factors, particularly hotter water temperatures and intense sunshine. So, it stands to reason that reducing the heat or light stress on corals will diminish the intensity of bleaching and reduce mortality.

The importance of this conclusion finally struck me when I was snorkeling around Palau’s Rock Islands. As I swam into the shade provided by one of the island’s rocky overhangs, I noticed live corals under my facemask of the same species that were dead under my swim fins. It all fell together: corals were alive and healthy when protected by cooler water or by shade.


Coral reef scientists were at their wits’ end about what to do regarding coral bleaching. But our observations of factors that help corals survive—and our knowledge of how to design networks of marine protected areas (MPAs) to protect and expand natural refuges—resonated with people around the world and prepared us for the impending bleaching event.

We have waited more than 10 years for another mass bleaching event to be able to test and refine the resilience hypotheses and the principles that Stephanie Wear and our Global Marine team have helped popularize. So, we are mobilizing our field teams and partners to track the current bleaching event in Indonesia and Palau as well as the Caribbean. This new information will allow us to better design MPA networks and ensure that they protect the most resilient corals that will repopulate and heal more vulnerable reefs.

While it’s tragic to witness another major bleaching event, this one can help us improve our methods and the prospects for global coral reef survival. Reefs provide fish, diving and coastal protection: hopefully, we can ensure that enough of them remain to fulfill any conservationist’s dream.

Rod Salm is the Conservancy’s director of marine conservation programs in the Asia Pacific.

(Image 1: Shaded corals with no bleaching. Credit: Rod Salm/TNC. Image 2: Fantasy Reef pale corals with early heat stress. Credit: Rod Salm/TNC.)
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