Text and Photos by Henrylito D. Tacio
Mangroves store up to times the carbon of tropical forests. Such was the finding of a new study in New Guinea which highlights the value of Indonesia’s mangrove forests, both on the global carbon market and for local communities.
“Threatened mangroves and marine ecosystems in general get far less attention than tropical rainforests in climate negotiations, despite the many useful ecosystem services they provide,” wrote Johnny Langenheim in article which appeared in the website of The Coral Triangle. “Mangroves are highly efficient carbon sinks, absorbing up to 10 times as much carbon dioxide as terrestrial forests.”
This was supported by a study conducted by a team of U.S. Forest Service and university scientists. Coastal mangrove forests store more carbon than almost any other forest on Earth, surmised the findings which was published online in the journal Nature Geoscience.
“Mangroves have long been known as extremely productive ecosystems that cycle carbon quickly, but until now there had been no estimate of how much carbon resides in these systems. That’s essential information because when land-use change occurs, much of that standing carbon stock can be released to the atmosphere,” says Daniel Donato, a postdoctoral research ecologist at the Pacific Southwest Research Station in Hilo, Hawaii.
The research team examined the carbon content of 25 mangrove forests across the Indo-Pacific region and found that mangrove forests, per hectare, store “up to four times more carbon than most other tropical forests around the world.”
The Science Daily gives this bit of information: “The mangrove forest’s ability to store such large amounts of carbon can be attributed, in part, to the deep organic-rich soils in which it thrives. Mangrove-sediment carbon stores were on average five times larger than those typically observed in temperate, boreal and tropical terrestrial forests, on a per-unit-area basis.
It further explains: “The mangrove forest’s complex root systems, which anchor the plants into underwater sediment, slow down incoming tidal waters allowing organic and inorganic material to settle into the sediment surface. Low oxygen conditions slow decay rates, resulting in much of the carbon accumulating in the soil. In fact, mangroves have more carbon in their soil alone than most tropical forests have in all their biomass and soil combined.”
Mangroves are a “very efficient living system in terms of sequestering carbon dioxide,” says Daniel Murdiyarso, a climate change expert at the Center for International Forestry Research (CIFOR) in Bogor, Indonesia. The carbon dioxide, he continues, is “stored in the leaves, and the leaves will be consumed by the feeders, including crabs and all those microorganisms below the ground.”
According to the Science Daily, the high-carbon storage suggests mangroves may play an important role in climate change management. Aside from the main greenhouse gas contributor of fossil-fuel burning, the forestry sector can play a part — especially carbon-rich forests that are being cleared rapidly on a global scale, such as mangroves.
“When we did the math, we were surprised to see just how much carbon is likely being released from mangrove clearing,” Donato was quoted as saying. This suggests, according to Donato, that where consistent with local management objectives, mangroves may be strong candidates for programs aiming to mitigate climate change by reducing deforestation rates.
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 Fortes, a professor of Marine Science Institute at the College of Science of University of the Philippines in Diliman.
Dr. Theresa Mundita Lim, Biodiversity Management Bureau, says its agency has identified 42 species of mangroves in the country. None of them are facing extinction yet. But the International Union for Conservation of Nature (IUCN) is considering of putting 11 out of 70 mangrove species assessed on the IUCN Red List of Threatened Species.
“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, who led the first-ever global assessment on the conservation status of mangroves.
Mangroves are very important to marine life, says Dr. Rafael Guerrero III, former director of the Philippine Council for Aquatic and Marine Research and Development. 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,” a World Bank report on environment adds. “Fry that gather in mangrove areas are very important for aquaculture.”
But still, mangrove forests are being denuded. “Despite legislation and programs to protect mangroves, the country has lost most of its mangroves due largely to fishpond development, charcoal production, industrial conversion, reclamation, and pollution,” deplores Dr. Fortes.
Studies have shown the country’s original 500,000 hectares of mangroves has whittled down to 100,000 hectares or less.
To think of, mangroves are considered as the best hope of the Philippines for mitigating climate change, according to a news item carried by the Rappler.
“Mangroves in general are one of nature’s best ways for combatting global warming,” Dr. Filiberto Pollisco, policy and research specialist of ASEAN Centre for Biodiversity (ACB), told participants of the panel discussion on the relationship between biodiversity and climate change.
But on the other hand, mangroves also act as “a ticking carbon time bomb.” The Rappler report explained that “when a mangrove forest is uprooted and deforested, the enormous amount of carbon stored in its roots are released into the atmosphere as carbon emissions.”
According to Dr. Pollisco, digging up only two meters of soil in a mangrove forest for conversion into, say, a shrimp pond, already releases 1,400 tons of carbon per hectare per year.
CIFOR’s Murdiyarso says mangroves account for less than 1 percent of the world’s tropical forest area, but their destruction produces 10 percent of all carbon emissions from deforestation. Deforestation, meanwhile, is the second-largest source of carbon emissions after the burning of fossil fuels.
