Mangroves: going, going, gone?

Posted: 15 October 2010

Author: Henrylito Tacio

More than one in six mangrove species worldwide are in danger of extinction due to coastal development and other factors, including climate change, logging and agriculture.

According to the first-ever global assessment on the conservation status of mangroves for the IUCN Red List of Threatened Species, 11 out of 70 mangrove species (16 per cent) which were assessed will be placed on the IUCN Red List.

Mangroves in Colombia
Women and men from local community inside the mangrove gathering piangua (shells) near La Plata, Colombia. © CI/ photo by Haroldo Castro

 The Atlantic and Pacific coasts of Central America, where as many as 40 per cent of mangrove species are considered threatened, are particularly affected.

“Mangroves form one of the most important tropical habitats that support many species, and their loss can affect marine and terrestrial biodiversity much more widely,” pointed out Beth Polidoro, principal author of the study.

Mangrove forests grow where saltwater meets the shore in tropical and subtropical regions, thus serving as an interface between terrestrial, fresh-water and marine ecosystems. These forests provide at least US$1.6 billion each year in ecosystem services.

“The loss of mangroves will have devastating economic and environmental consequences,” says Greg Stone, Senior Vice President of Marine Programs at the Washington-based Conservation International. “These ecosystems are not only a vital component in efforts to fight climate change, but they also protect some of the world’s most vulnerable people from extreme weather and provide them with a source of food and income.”

In the Philippines, mangroves are fast vanishing.  In 1981, there were an estimated 450,000 hectares of mangrove areas in the country.  Since then, there has been a decreasing trend from 375,000 hectares in 1950 to about 120,000 hectares in 1995.

Mangroves in the Philippines
Mangroves in the Philippines. Photo credit: Henrylito Tacio


At that time, one environmentalist wrote: “All over the country, whatever coastal province you visit, you see the same plight – desolate stretches of shoreline completely stripped of mangrove cover and now totally exposed to the pounding of the ocean’s waves.”

To prevent further losses of mangroves, lawmakers enacted Republic Act 8550 otherwise known as Philippine Fisheries Code of 1988 whose section 94 stated that the conversion of mangroves into fishponds or any other purpose is prohibited.

Although a World Bank report released in 2005 stated that mangrove cover in the country was “now relatively stable” – particularly those around Bohol and Siquijor islands – Dr. Rafael D. Guerrero III said that mangroves are still in peril.

“Notwithstanding, our mangroves are disappearing due to unabated deforestation in some parts of the country, poor management practices and sea level rise as a result of climate change,” informs Dr. Guerrero, former director of the Philippine Council for Aquatic and Marine Research and Development.  The current rate of mangrove deforestation ranges from 2,000 to 3,000 hectares per year.

Mangroves are communities of trees in the tidal flats in coastal waters, extending inland along rivers where the water is tidal, saline, or brackish.  “There are 25 to 30 species of true mangrove trees and an equal number of associated species,” says Dr. Miguel D. Fortes, a marine science professor and technical consultant to various national and international institutions.

Mangroves in Madagascar
Mangroves at Baie D'Ambodi-Vahibe, Madagascar. More than one in six mangrove species worldwide are in danger of extinction due to coastal development and other factors. © CI/ photo by Sterling Zumbrunn

 Mangroves are very important to marine life, Dr. Guerrero points out.  They serve as sanctuaries and feeding grounds for fish that nibble on detritus (fallen and decaying leaves) trapped in the vegetation, and on the bark and leaves of living trees.

“(Mangroves) are important feeding sites for many commercially important fish species (mullet, tilapia, eel, and especially milkfish), shrimps, prawns, mollusks, crabs, and sea cucumbers,” the World Bank report adds.  “Fry that gather in mangrove areas are very important for aquaculture.”

Mangroves also provide protection from storm surges and high winds associated with tropical typhoons.  “This is very important in a country that is hit by an average of 20 typhoons a year,” says Dr. Fortes.

Mangrove forests also serve as protection against soil erosion.  Other important benefits from mangroves include: land builder through soil accretion; coastal pollutants trapper; and wildlife sanctuary. 

Despite the economic and ecological benefits they provide, mangroves are on the verge of disappearance.  “Mangrove forests have been converted to aquaculture, salt production, and human settlement,” the World Bank report notes.

The construction of tourism infrastructures like hotels and restaurants has also contributed to the destruction of mangroves.  Equally destructive are the saltpond operations and mining activities.

Pollution has also taken its toll.  The mangrove areas have been used as disposal for solid and liquid domestic wastes, oil, garbage, and pesticides.

The destruction of mangroves is detrimental to those living near the coastal areas.  “Research in some areas of the world, as well as in this country, show that where mangroves have been protected, yields of fish have been high; where they have been destroyed, yields have been low,” reminds Dr. Angel C. Alcala, former head of the Department of Environment and Natural Resources.

There is good news, though.  In Tinambac, Camarines Sur, it has been reported that mangrove reforestation has improved the local fish catch.  The new mangrove forest brought back red snapper fish species that had previously disappeared due to lack of habitat.

In Pangangan Island off Calape, Bohol, people have found in mangroves a natural ally to protect their island’s only road link to the mainland from typhoon damage.  The four-kilometre long causeway is protected by mangroves planted in recent decades by local school children.

Henrylito Tacio is a Contributing Editor of this website, covering South East Asia


World Mangrove Atlas highlights the importance of and threats to mangroves

The first global assessment of mangroves in over a decade has revealed that rare and critically important mangrove forests continue to be lost at a rate three to four times higher than land-based global forests, despite positive restoration efforts by some countries.

About one fifth of all mangroves are thought to have been lost since 1980. Although losses are slowing at 0.7 per cent a year, the authors warn that any further destruction due to shrimp farming and coastal development will cause significant economic and ecological decline.

Economic assessments provide some of the most powerful arguments in favour of mangrove management, protection or restoration. Studies estimate that mangroves generate between US$2,000-9,000 per hectare annually, considerably more than alternative uses such as aquaculture, agriculture or insensitive tourism.

The World Atlas of Mangroves has been published by Earthscan (20% off all Earthscan books with the voucher code p&p20) as an output of a joint project implemented since 2005 by ITTO, the International Society of Mangrove Ecosystems (ISME – project implementing agency), the Food and Agriculture Organization of the United Nations (FAO), UNEP-World Conservation Monitoring Centre (UNEP-WCMC), UNESCO-Man and Biosphere (UNESCO-MAB), UNU-Institute for Water Environment and Health (UNU-INWEH) and The Nature Conservancy (TNC).