A new study which estimates the amount of carbon stored in Madagascar’s mangrove forests, shows their true value as being amongst the most carbon-rich forests on earth. Mangroves are the world’s only marine forest ecosystem and have been estimated to contain up to 12 times more carbon than undisturbed Amazonian rainforests, meaning that their conservation is vital for mitigating climate change.
Mangroves are found in more than 120 countries throughout the tropics, and provide critical resources to coastal communities, from fishing to coastal protection, as well as supporting rich marine biodiversity. Despite their enormous value, as much as half of the world’s mangrove forests have been lost since 1960, with an estimated ongoing deforestation rate of 1-2% a year.
The research, carried out by scientists from Blue Ventures and the University of Antananarivo’s Department of Forestry (ESSA-Forêts), assessed carbon stocks and quantified long-term changes in mangrove forest cover. The study highlighted Madagascar’s northwestern Ambanja and Ambaro bays as hotspots of deforestation, with more than 20% of the region’s mangroves being lost between 1990 and 2010.
Driven by poverty in a country where 92% of the population live on less than two dollars per day, forest cutting for charcoal production is the main cause of mangrove loss, threatening the livelihoods of Madagascar’s coastal communities as well as endangering the unique biodiversity of these critical ecosystems.
“Our socioeconomic research shows that the main driver of mangrove loss in Madagascar’s northwest is exploitation for charcoal production by local communities.” said Dr Harifidy Rakoto Ratsimba, researcher at the University of Antananarivo and co-author of the study, “This research is not just ‘science for science’ but also shows evidence of the link between mangroves and livelihoods. This will help us to implement conservation initiatives not just for the forest but also for people.”
Of all the atmospheric carbon captured on earth, 55% is sequestered by marine ‘blue carbon’ ecosystems like mangroves, seagrass beds and salt marshes. The deep muddy soils of mangrove forests, rich in organic material, contain most of the forests’ carbon stocks.
The study highlights the very high levels of organic carbon held in mangroves and their underlying sediments, showing that high-stature closed-canopy mangroves in Ambanja and Ambaro bays support on average 147 Mg/ha of carbon in their vegetation, as well as a further 446 Mg/ha within their underlying soil. Disturbance to these soil layers can lead to substantial emissions of greenhouse gases to the atmosphere. Although mangroves comprise only 3% of global forest cover, the loss of these habitats accounts for up to 19% of global emissions from deforestation. Their destruction equates to economic losses of US $6-42 billion annually.