Fast facts

Mangroves grow along tidal mud flats and shallow water coastal areas, extending inland along rivers, streams and their tributaries where the water is generally brackish, or having less salinity than seawater.

Forty-six out of 70 mangrove species in the world can be found in various parts of the Philippines, according to the Department of Environment and Natural Resources (DENR).

In 1918, the country had some 450,000 hectares but the total area shrank to 310,531 hectares by 2010, data from the 2012 Philippine Forestry Statistics showed. The latest figure represents 5 percent of the total land forest area of 6.84 million hectares.

Ecological benefits

Mangroves provide economic and ecological benefits, such as the following:

• Support aquaculture by providing nursery grounds for fish, prawns and crabs, and support fisheries production in coastal waters;

• Protect coastal areas and communities as they serve as barriers to storm surges, tidal currents and typhoons;

• Produce leaf litter and detrital matter (sediments), which are valuable sources of food for animals in estuaries and coastal waters;

• Produce organic biomass (carbon) and reduce organic pollution in nearshore areas by trapping or absorption;

• Serve as recreational grounds for bird watching and observation of other wildlife as they provide shelter for local and migratory wildlife;

• Provide housing materials, such as wood, timber and nipa shingles, firewood and charcoal, and poles for fish traps; and

• Stabilize coastline by reducing soil erosion.

Direct threats

Destruction of mangrove forests can be attributed to direct (man-made) or indirect (natural phenomenon) threats.

Direct or human threats, which the DENR regards as the common causes, include:

* Conversion of mangroves to fishponds and salt beds;

* Reclamation and industrial developments;

* Pollution and siltation;

* Overexploitation;

* Disturbance due to fish landing; and

* Dike construction obstructing waterways and tidal inundation, thus affecting nutrient distribution, salinity and temperature gradients, accumulation of biogas and other products of decomposition.

Indirect threats

Indirect threats include typhoons, rising sea levels due to global warming, and pests and diseases.

Some pests that destroy mangroves are barnacles, which envelope stems of young  “bakawan,” causing roots to rot; tiny beetles (Phoecilips fallax), which attack propagules, preventing germination; worm-like Diopatra cuprea, which defoliate leaves and seedlings; and crabs, which girdle newly planted propagules and seedlings.

Inquirer Research

Sources: denr.gov.ph, Mangrove Management Handbook, 2012 Philippine Forestry Statistics