How do typhoons affect coral reefs?

Posted on 19 November 2013    
Tubbataha Reefs Natural Park lagoon looking bleached caused by infestation of crown-of-thorn starfish (Acanthaster planci). Tubbataha,
© Jürgen Freund / WWF
By Gregg Yan, WWF-Philippines Communications and Media Manager 

Storms and typhoons continuously shape the composition, distribution, and range of the world's coral reef systems. Strong waves and currents spurred by typhoons can break off delicate coral branches, overturn even large coral heads and smother entire reef systems in whirlwinds of sand. Massive corals like Favia or Porites are far more resilient to storm effects than branched corals like Acropora or Pocillopora. The end result is that hard coral cover plummets, the dead coral skeletons eventually coated by faster-growing species of algae or seaweed.

A valuable resource in peril

Already the Philippines is seeing more powerful storms. Typhoons Milenyo, Ondoy, Pablo, Pepeng, and now Yolanda (international name Haiyan) have ploughed through the country - exacting a toll in both Pesos and in lives. Because coral reefs lie beneath the blue, reef damage is often overlooked, highly significant in a country which needs to produce more food to feed a burgeoning population.

Healthy Philippine coral reefs annually produce about 30 to 40 metric tonnes of seafood (scientifically termed fish biomass) per square kilometer yearly. Unfortunately, only 1 per cent of Philippine coral reefs remain in excellent condition, meaning hard coral cover is at 75 percent or higher. The annual population growth rate of the country is about 2 percent, with a population estimated at 100 million. Philippine reefs are of course threatened by overfishing, sedimentation, and pollution. However, storms pose an enormous threat.

The Apo Reef example

Situated off Occidental Mindoro, Apo Reef is the largest atoll-like reef in the Philippines and the second largest non-contiguous reef on earth. It covers 34 square kilometers and boasts of two impressive lagoon systems. After Tubbataha, Apo Reef became the country’s second Marine Protected Area (MPA) where fishing in all its forms is completely banned.

With the reclassification of Apo Reef National Park as a strict protection zone in 2007, illegal fishing activities have been dramatically reduced. Fish biomass per square kilometer has soared to over 75 tonnes – easily twice the levels seen in a typical healthy Philippine reef. However, even after full protection, Apo Reef suffered extensive damage from Typhoon Caloy in 2006.

In 2006, WWF pegged Apo Reef's hard coral cover at 51 percent. After Typhoon Caloy, it dropped to a paltry 18 percent. Each large storm dramatically erodes the capacity of coral reefs to provide people with seafood.

The Yolanda effect

While WWF has no data on Leyte’s coral reefs (one of the most affected coastal areas hit by this typhoon), it is almost certain that Typhoon Yolanda devastated its reefs and will have long-term effects on the country’s fisheries resources.

Tubbataha Reefs Natural Park lagoon looking bleached caused by infestation of crown-of-thorn starfish (Acanthaster planci). Tubbataha,
© Jürgen Freund / WWF Enlarge

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