September 23, 2006

By Angel Alcala

MANGROVE forests, mangrove ecosystems, or simply mangroves have been in the limelight since August 13, 2006 two days after the MV Solar I carrying 2.1 million liters of bunker oil sank at a depth of 640 meters in the Panay Gulf some 24 kilometers southwest of the island of Guimaras. Why did the press focus on mangroves? The obvious reason is that, aside from sand beaches, the mangroves appeared to be the living resources on Guimaras showing unmistakable impacts of the oil spill. The evidence was clear: bunker oil was observed coating the trunks, roots and leaves of mangrove trees and contaminating water and sediments of mangrove swamps.

If this is so, why is there so much concern on the part of scientists and the public about these effects on the more than a thousand hectares of mangrove ecosystem of Guimaras Island?

Original mangrove ecosystems, which at this time constitute less than 100,000 hectares out of the estimated 500,000 hectares at the turn of the 20th century, are found mainly on Palawan Island and the Sulu Archipelago and in southeastern and southern Mindanao, rank among the most productive natural ecosystems. Mangroves, together with seagrass beds and coral reefs with which they are associated, produce no less than 30 percent of the total capture fisheries of the Philippines, 70 percent being the contribution of pelagic species such as tuna. Many species of marine organisms used as food are jointly produced by mangroves, seagrasses and coral reefs; these species move among these marine habitats, and for many of them, it is difficult to label as strictly mangrove or strictly coral reef. (Note that I am not talking about aquaculture.). Anybody can see that mangroves are very important sources of marine species exploited for food by coastal communities that make up at least 60 percent of the Filipinos.

To appreciate the foregoing statement, let me give you comparative figures on fish standing stock in the Philippines. We were able to survey fish standing stock in the strictly coral reef habitats of the Spratlys in the south China Seas and to compare this with the standing stock in the Central Visayas, where there are mangroves, seagrass beds and coral reefs adjacent to each other. We found that the Central Visayas fish standing stocks were about two to three times as great as the standing stocks in the purely reef environment of the Spratlys. However, we also found that standing stock of fish in the Tubbataha reefs very high and in some cases surpassing those in the recovering reefs in the Central Visayas, adding some unknown factors to consider.

However, if only the South China reef (which has some degree of protection by the Armed Forces stationed there) and the Central Visayas protected reefs are compared, there is a difference that can be attributed to the fact that the Central Visayas have abundant mangroves and seagrasses but the Spratlys have no mangroves and very scanty seagrasses. The presence of mangroves would tend to explain the higher fish productivity of Central Visayas protected areas.

(Click Mangroves, Sept. 23, 2006, for the entire piece.)



  1. sana lagyan nyo ng picture ng mangroves,yung talagang mangroves

  2. Francielle, you may click on the blogroll in the sidebar “About the header image” and it will take you to the Greenpeace web site which has the photos of the oil slicked mangroves. If you want photos of mangroves in their original state, you can find them all over the Internet. Google is a wonderful thing. Thanks.

  3. kaylangan ko yan…salmat sa info!! meron na ako irereport thanks

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