by Gina Mapua
Last October 21, the Biodiversity Management Bureau of the DENR invited WBCP President Gina Mapua to a seminar on “Ecosystem Services, Dynamics and Threats to the Shoreline and Intertidal Areas of Manila Bay”. There were several speakers and she summarizes their talks in this article.
Coastal and Offshore Sedimentation in Manila Bay
Dr. Fernando Siringan – The Marine Science Institute, UP Diliman
Dr. Siringan described the sedimentation patterns found in the Manila Bay basin. Clearly the rivers that flow into Manila Bay carry a large load of sediment and deposit these, heaviest particles closest to the mouth of the river and lightest particles further on. Wind-driven currents, depending on the season, drive these sediments back toward the shore. Heaviest sedimentation has been recorded along the mouths of the rivers of Bulacan and Pampanga in the northwestern corner of the bay and along the southeastern corner which is the shoreline of Cavite.
Siringan also described how the Cavite spit formed through longshore currents. Then he showed a bathymetric reading of the areas off Cavite. There were many mysterious deep spots that could not be explained geologically. He went on to reveal that the filling material used for the reclamation of what is now the Cultural Center complex came off this area!
Finally, Dr. Siringan described the detrimental effects of installing hard structures along the shoreline. Because of wave action, solid piers along shorelines cause massive erosion on the shoreline where the waves impact and depositions on the leeward side. Piers have to be constantly readjusted so boats can use them. It would have been better to have built piers that allow waves to pass through them. Many beach resorts, believing they are preventing beach erosion by building retaining walls, actually worsen the situation. Dr. Siringan gave a prime example of a resort where the beach was so wide people could play baseball on it. When a wall was installed, wave action scoured the sand off the beach, leaving only the remains of an extinct coral reef.
In Dr. Siringan’s words, “Any structure placed along the coast will cause rapid modifications in the movement of water. Changes in water movement, direction or velocity, will have an impact on sedimentation.
Foreshore Management in Manila Bay
Erma Quirimit – Foreshore Area Management Unit, Land Management Bureau, DENR
Foreshore management is critical because almost 60% of the country’s total population reside in the coastal zone. A foreshore is defined as a string of land margining a body of water; the part of a seashore between the low-water line usually at the seaward margin of a low tide terrace and the upper limit of wave wash at the high tide usually marked by a beach scarp or berm. (Section 4 [48] of Republic Act No. 8550 The Philippine Fisheries Code of 1998)
In more concise words, DENR Administrative Order No. 2004-24, August 24, 2004, refers to foreshore as that part of the shore, which is alternately covered and uncovered by the ebb and flow of the tide.
Foreshores are considered lands of public domain and the DENR exercises exclusive jurisdiction of the management and disposition of all lands of public domain.
Common uses of Foreshore lands
- Wharves, piers, ports, docking or dockyard
- Fish canneries, ice plants, warehouse, fixed industrial machineries and other related structures
- Beach resorts, including hotels, rest houses and restaurants
- Recreational places, parks
- Residential, commercial and industrial estates developed by cities, municipalities and lately by the PRA
- Fishponds in bays along the shores of navigable lakes and rivers
One activity performed by the DENR regarding foreshore areas is the survey and mapping of foreshore land and the issuance of Foreshore Lease Permits.
At this point, a lightbulb lit in Arne’s mind. (He was sitting beside me.) Anyone who has the permit from DENR to a foreshore area, can pretty much do what they want on that tract of shoreline! Certainly, no government agency will object if permit-holder simply does nothing to the foreshore but let it be.
Biological Diversity in Manila Bay: the Status of Macrobenthic Communities
Dr. Benjamin Vallejo – Institute of Environmental Science and Management, UP Diliman
The Manila Bay is a semi-enclosed estuary, 16.7 kilometers wide at the mouth with 190 kilometers of shoreline. The bay area comprises of 1,800 square kilometers with a gentle slope of a generally 1 meter per kilometer gradient and average depth of 17 meters. Manila bay drains 17,000 cubic meters from 26 catchment areas. Major habitats found within the bay are seagrass areas, mangroves, mudflats, coastal lagoons and sandy beaches.
The Manila bay was studied during the Spanish colonial period by Jesuit priests. American scientists studied the fisheries of the bay starting in 1902. Much research to date has been focused on fisheries, aquaculture and oceanography.
Pollution became an issue are far back as 1950 and biological invasion studies began in 2005. Other environmental issues are: land reclamation, acidification of coastal water, harmful algal blooms, sea level rise, invasive marine species, shallow water hypoxia (oxygen deficiency) and natural hazards to human communities.
Manila Bay isn’t dead. It hosts 67 macroinvertebrates, of which 49% are bivalves, 43% are gastropods and 5% are crustaceans.
The Manila Ocean Park has been monitoring water quality for 3 years, collecting samples twice daily. Documented “normal” values are 32.6 psu salinity, a pH of 8.2 and a temperature of 28.2 degrees Centigrade.
Dr. Vallejo also shared research on biological invasions in Manila Bay. Most of the invaders arrive via discharged ballast water. To date, research on invasive species is being conducted at three sites in the bay – Manila Ocean Park, Philippine Navy Headquarters and Sangley Point Naval Base. Of particular concern is a small black mussel from the Mediterranean Mytilus gallopovincialsi. Ironically, it is also an object of aquaculture in France and China. Dr. Vallejo says the thickest infestation is at the piers of the Manila Ocean Park. Yum yum! Or maybe not…
Biological Diversity in Manila Bay: the Status of Migratory and Waterbirds
Dr. Arne Erik Jensen – Wetlands International
There are 9 major flyways in the world. As we all know, the Philippines is located within the East Asian-Australasian Flyway. Migratory bird populations within this flyway are crashing. The EAAF has now the highest number of threatened waterbird species.
The most important point along the EAAF is the Yellow Sea, 4000 kilometers of tidal wetland ecosystems in China and North Korea. Because of unprecedented coastal development in the Yellow Sea, 50 to 80 percent of wetlands have been lost. This is the primary cause of water bird populations crashing. But habitat loss in all their feeding grounds within the EAAF have all been affected, contributing to the massive loss of populations.
For a water bird population to stabilize, they need:
- Undisturbed roosting areas
- Healthy intertidal ecosystems producing a large amount of invertebrate and fish populations for feeding and refueling
- Undisturbed breeding areas with diverse habitats
- Habitat management to avoid vegetation overgrowth
Manila Bay hosts at least 1% of the populations of 23 bird species of the 54 migratory species. Northern Manila bay hosts an estimated 15% of the Great Egret and 20% of the Little Egret populations, as well as 10% of Black-winged Stilts and 15% of the Black-headed Gull populations. In total, the estimate for Bataan and Pampanga coastal wetlands and fishponds is up to 100,000 waterbirds during the migratory season. And among these are 6 threatened or near-threatened species.
Manila Bay hosts the following population percentages of these birds:
- Pacific Golden Plover – 2.5% of adult flyway population
- Whiskered Tern – 25% of adult flyway population
- Redshanks and Greenshanks – each 2.5% adult flyway population
- Black-winged Stilt – 2.5% of adult flyway population
- Kentish Plover – 4% of adult flyway population
- Little Egret – 15% of adult flyway population
- Great Egret – 20 of adult flyway population
- Chinese Egret – globally threatened
Of the current Ramsar sites in the Philippines, only two are coastal and of importance for migratory waterbirds – one of which is the Las Pinas-Paranaque Critical Habitat and Eco-Tourism Area or LPPCHEA. Approximately 40,000 hectares in Bataan and Pampanga qualify for protection and sustainable use. This wetland area in northern Manila Bay represents the largest congregation of waterbirds in the Philippines. This is an important waterbird site, not only in the Philippines, but also internationally. Manila Bay, not just LPPCHEA, must be protected.