The world's only marine forest ecosystem, mangroves contain up to 12 times more carbon than undisturbed Amazonian rainforests, meaning that their conservation is vital for mitigating dangerous 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."
The study highlights the very high levels of organic carbon held in mangroves and their underlying sediments, showing that high-stature closed-canopymangroves 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.
A comparison of above- and below ground carbon stocks for three types of mangroves in Ambanja and Ambaro bays with other forest types. Carbon stocks for other forest types are taken from here
This research was funded by grants from the Western Indian Ocean Marine Science Association and the John D. and Catherine T. MacArthur Foundation.
The paper, 'Ecological variability and carbon stock estimates of mangrove ecosystems in Northwestern, Madagascar' can be found here.
Notes for editors:
Blue Ventures is transforming how coastal communities in Madagascar relate to their marine environment by catalysing a sea change in sustainable fisheries management; undertaking pioneering research in blue carbon science, nurturing lucrative aquaculture businesses, and creating some of the largest locally managed marine protected areas in the Indian Ocean.
ESSA-Forêts is one of five departments attached to the School of Agricultural Sciences, University of Antananarivo. ESSA-Forêts undertakes research oriented towards the management of natural resources (including forest and water).