The international push to protect blue carbon started around 2009, when the United Nations published a report pointing out that coastal ecosystems capture and store carbon far more efficiently than their drier counterparts. Mangroves and coastal wetlands, for instance, suck up about 10 times more carbon dioxide per acre per year than rainforests do, and store three to five times as much over the long term, mostly in the soil that extends deep beneath their roots. They are also disappearing much faster than rainforests due to coastal development, pollution, aquaculture, and overuse. Globally, scientists estimate that up to half of all mangroves have been lost in the last 50 years. When the mangrove forests go, they release centuries or even millennia of stored carbon back into the atmosphere.
“They’re small areas, but very intensely important for carbon emissions,” said Emily Pidgeon, senior director of Conservation International’s oceans and climate program. Five years ago, she helped launch a joint initiativewith the International Union for Conservation of Nature and UNESCO to develop science and policy related to blue carbon. Since then, scientists have been investigating exactly how coastal carbon cycles work so they can be incorporated into conservation schemes such as REDD+, the United Nations framework for mitigating climate change by preventing deforestation. A handful of blue-carbon pilot projects have gotten underway around the world.
The project in Senegal is among the first and largest of these. It began in 2006 when a Senagalese non-profit called Oceanium started mobilizing villagers to plant mangroves along the sinuous channels of the Casamance Delta, in the southern part of the country. The work was desperately needed. Up and down Senegal’s coast, dense thickets of mangroves had once divided land from sea, protecting villages from waves, wind, and salt and sheltering a riot of birds, fish, monkeys, marsh mongoose, and other animals. When drought struck West Africa in the 1970s and 1980s, however, the amount of freshwater flowing into the deltas declined, and the soil became too saline for even mangroves to thrive. Road building and woodcutting worsened the problem, and a quarter of Senegal’s mangroves gave way to barren salt flats.
Oceanium took a more systematic, large-scale approach to reviving the mangroves than previous grassroots efforts. Led by the charismatic environmentalist Haidar El Ali, its work soon drew the attention of Danone, a French multinational corporation looking to offset its greenhouse gas emissions. The company began investing in 2008 and continued through 2012, during which time it opened its carbon investment fund to other companies and renamed it Livelihoods. (Livelihoods did not respond to requests for an interview, but according to one estimate the total investment by Danone and the other companies was about $4.5 million.)
The new stream of funds allowed for coastal restoration on a scale Senegal had never seen before: Nearly 300,000 local participants (mostly women) planted 150 million mangrove trees on 12,000 hectares, according to Oceanium. Riding this wave of success and recognition, Haidar was appointed Senegal’s Minister of Ecology in 2012.
The impacts of these new plantations on biodiversity and soil quality have not yet been studied. Whereas natural mangrove forests are usually made up of several different species adapted to varying levels of salinity, rainfall, and tidal movement, the man-made forests include just one species, chosen for its ease of planting. According to Bienvenue Sambou, who directs the Institute of Environmental Science at Cheikh Anta Diop University in Dakar, that puts them at greater risk of dying from disease or environmental change over the long term. Octavio Fleury, who oversees Oceanium’s mangrove reforestation program, said about 20 percent of the trees have died so far.