Mangroves are the rainforests by the sea, found at the boundary where land meets ocean. They serve a wide range of ecological functions, providing economically valuable products and services. Mangroves, once estimated to cover an area of over 36 million hectares, dominated large stretches of tropical coastline. However, due to ongoing development pressures, mangroves are degraded and their area substantially diminished relative to their historic range, less than 15 million hectares remain.
Mangrove forests are vital for healthy coastal ecosystems. The shallow inter-tidal reaches that characterize mangrove wetlands offer refuge and nursery grounds for juvenile fish, crabs, shrimps, and molluscs, and are prime nesting and migratory sites for hundreds of bird species. Additionally, manatees, crab-eating monkeys, monitor lizards, Bengal tigers, sea turtles and mudskipper fish utilize the mangrove wetlands.
Mangroves play a vital role in protecting sea grasses and coral reefs from sediments and pollution, filtering out heavy metals and halting shoreline erosion. Mangroves buffer against hurricane winds, storm surges and tsunamis, saving thousands of lives, while protecting infrastructure. Mangroves are also invaluable in combating climate change!
Mangroves, tidal marshes and seagrass beds remove massive amounts of carbon from the atmosphere and fix it in mangrove soils, where it can remain for millennia. Unlike terrestrial forests, marine wetlands are constantly building carbon pools, storing large amounts of so-called "blue carbon" in highly organic sediments, storing up to 5-times more carbon per unit area than tropical rainforests. Their carbon sequestration potential is significant in helping to reduce atmospheric carbon dioxide. Including the carbon stored in soils, mangrove forests store the most carbon per hectare of any other forest type.
Deforestation and land-use change currently account for 8-20% of global anthropogenic carbon dioxide (CO2) emissions, second only to fossil fuel combustion. Destruction of mangroves accounts for around 10% of emissions from deforestation globally, despite accounting for just 0.7% of tropical forest area. Moreover, if left undisturbed, the carbon storage by mangroves currently continues to expand through biological sequestration of CO2 and carbon burial. If current trends in conversion continue, however, much of the carbon stored in mangroves along with its future accumulation could be lost.
Mangroves are among the most threatened and rapidly disappearing natural environments worldwide, with a much higher rate of loss than other tropical rainforests. One of the greatest threats to mangroves today is the rapacious shrimp aquaculture industry, which has caused massive mangrove losses in Asia and Latin America. With the current 0.7% rate of loss, most of the world’s mangroves may disappear by the end of this century. Conversion for agriculture or aquaculture, results in massive emissions of greenhouse gases into the atmosphere, as mangroves change from a sink for carbon to a massive source. This greatly exacerbates the problems of global warming.
Restoring mangrove forests would deliver significant benefits in reducing net greenhouse gas emissions, improving food security and livelihoods of coastal communities, increasing resilience in the face of sea level rise and extreme weather events, and improving habitat for many vulnerable species along extremely biodiverse tropical coastlines.
Alfredo Quarto is the Executive Director and co-founder of the Mangrove Action Project. You can follow Alfredo on Twitter @mangroveap. For more information visit MAP’s website www.mangroveactionproject.org.