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How to Help Corals Survive Climate Change?

Climate change — the impacts are widespread and affect all kinds of habitats, from deserts to forests to oceans.

What is The Nature Conservancy doing to address the threats of climate change in the world's center of coral reef biodiversity, the Coral Triangle? Can coral reefs learn to adapt to rising sea temperatures, mass bleaching and ocean acidification?

These are the questions for Nature Conservancy scientist Rod Salm, an expert on coral reef resiliency and director of our marine conservation work in Asia Pacific.
Brad Carlson of South Haven, MI, asks:

“Concerning the Coral Triangle, your site mentions the following: "Our scientists are pioneering strategies to boost the ability of coral reefs to survive the impacts of climate change." From what I have heard, oceanic acidity due to anthropogenic carbon is the greatest risk to the shell forming organisms. Are there breakthroughs with regards to this problem? What other issues are considered primary objectives in making this area resilient to climate change?"


Rod Salm:

Brad Carlson hit the nail on the head when he singled out ocean acidity and asked what we can do about it and other climate impacts in the Coral Triangle.

Ocean acidification is a huge challenge for us. It is a slow, creeping, insidious weakening of corals and the reef structure, and consequently hard to detect. It has been likened to osteoporosis of the reef. Other climate impacts like mass coral bleaching linked to rising sea water temperatures or flooding and coastal erosion caused by sea level rise are very obvious, in fact near impossible to miss.

In the Coral Triangle, The Nature Conservancy focused first on heat stress and mass coral bleaching. After the 1998 mass bleaching event that caused huge mortality of corals around the world, with some shallower reefs losing up to 99 percent of their corals, many coral reef scientists and managers despaired of the prospects for reef survival and focused on studying the death and dying process. However, we noticed that bleaching was patchy and, reasoning that if we could understand why some parts of reefs do survive, we would have the key to ensuring long-term reef survival.

Corals bleach in response to a range of stressors — including pollution, excessive flooding with freshwater, siltation, disease and elevated seawater temperatures. The latter is what causes mass bleaching over hundreds of square miles, such as we saw in 1998 around the world. Heating events are usually accompanied by calm, still, cloudless conditions and intense solar radiation. The heat stresses the corals, causing them to bleach and the intense radiation kills them off.

We found that anything that can reduce the heat stress — like localized upwelling of cooler water from the depths, or light stress, like shading beside high islands or screening by natural cloudy inshore waters — would moderate the bleaching and greatly reduce the related mortality. Based on these observations we developed simple scientific principles to build resilience to heat stress into the way coral reef conservation areas are selected for protection, zoned and managed.

These resilience principles were developed by our scientists in the Coral Triangle and first applied in Kimbe Bay, Papua New Guinea. The principles are now being applied around the world by a range of partners.

Now that a response to coral bleaching is firmly embedded in our work in the Coral Triangle, The Nature Conservancy is moving ahead to address sea level rise and ocean acidification. We have started with modeling sea level rise impacts on coastal people and wetlands (including the highly vulnerable mangrove habitats) over the whole Coral Triangle. This is ongoing.

However, of more value is our proposed work in the large Berau coastal and marine protected area in Northeast Kalimantan (the Indonesian part of Borneo). Here we are planning to model sea level rise impacts on green turtle nesting beaches (the most important in SE Asia), mangroves and coastal people and to identify appropriate ecosystem-based responses.

This means what actions need to be taken now to safeguard the future of all three:

  • Which beaches are likely to persist and provide habitat for nesting turtles and what needs to be done to secure these as future nesting habitat;
  • Which parts of the extensive mangrove system will have the ability to march inland as sea levels rise and what needs to be done to secure these areas for future mangrove expansion; and
  • Which lands will be flooded so that areas can be set aside now for people to relocate to when their villages, freshwater sources and agricultural lands become flooded.

In August last year we convened a small meeting of world experts in ocean acidification from Australia and the United States as well as senior coral reef managers concerned about the challenge. Our objective was to seek their help to think through the science and come up with possible responses as we had done for coral bleaching. The meeting produced the Honolulu Declaration on Ocean Acidification and Reef Management.

We are attempting to use the recommendations of this declaration to guide us with the design of a marine protected in Indonesia. More importantly, the Great Barrier Reef Marine Park Authority and NOAA have embraced the outputs of the Honolulu Declaration and will be addressing the issue in their programs.

While we still have much more to learn about the science underlying ocean acidification and possible responses, it is heartening to know that we have been joined in this endeavor by two very influential partners.

Listen to Rod Salm narrate a photo slideshow about coral reefs and the threats they're facing.

Originally posted in July 2009.


About the Conservationist

Rod Salm is The Nature Conservancy's director of our marine conservation programs in Asia Pacific.

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