Mangroves in Gabon's Nyonié region, south of the capital Libreville. Vigna Christian, Wikimedia Commons

Gabon’s mangroves stand among the world’s tallest but face threats

Studies show links between height and carbon storage, but development and climate change risks survival

On the northern coast of Gabon, the rumble of chainsaws has now joined the usual buzz of insects in the mangrove forests fronting the Atlantic. The chainsaws are just one sign of increased human encroachment into undeveloped areas near the country’s capital, Libreville, leading to calls for conservation action as the importance of Gabon’s mangroves has come into sharper focus.

“Gabon’s mangrove trees are really critical forest biomass because the mangroves store so much carbon,” says Liza Goldberg, a NASA Goddard Flight Center researcher. In the past decade, scientists at the NASA Goddard Flight Center determined that mangroves in Gabon and other Central African nations are among the world’s tallest, with freshwater key to their growth. In Gabon, an abundance of freshwater has enabled mangroves to grow up to 63 meters in height and provide an important brake on climate change.

As part of their research, the NASA scientists created the first map of mangrove heights and learned that the above-ground carbon stored in the tall mangrove trees of Gabon averaged about 244 metric tons per hectare. By comparison, shorter mangrove trees in Nigeria and Brazil sequestered roughly 100 per hectare.

“The amount of freshwater that mangroves have access to either from rivers or precipitation is one of the most important drivers of canopy height and growth in mangrove trees, which has a direct influence on how much carbon they are able to store in the trees,” says Temilola Fatoyinbo, a physical scientist who led NASA’s measuring study.

Women gathering mollusks from the mangroves in Cap Estérias. David Stanley, Flickr
Women gathering mollusks from the mangroves in Cap Estérias. David Stanley, Flickr

However, these mangroves are increasingly threatened by the country’s urban growth. Just outside Libreville, property developers have torn out mangroves on Cap Estérias to build hotels and housing. At the same time, the city’s growing population has pushed into protected and semi-protected places areas in a belt known as the ‘Emerald Arc.’ The removal of the mangroves has been linked to increased flooding in Libreville and created concern among fishing communities about lost livelihoods.

Also at risk are protections for coastal communities and for marine life. As extreme weather linked to climate change increases, the mangrove forests serve as a buffer against strong waves and storm surges. Freshwater flowing to the ocean helps with this barrier, bringing with it sediment that accumulates on the boggy soil and adds to the shoreline protection. At the brackish water level, the trees have thick and twisted root systems that slow wave energy and support fish, crabs, shrimp and other sea life.

“There are many benefits of mangroves: the provision of food, protection from storms, prevention of sediment erosion, ecotourism, and other forms of ecosystem services,” explains Camille Rivera, a marine conservationist working in Filipino mangroves facing similar challenges. “Recent studies show mangroves store four to five times more carbon than terrestrial [tropical] forest.”

These studies underscore what is at risk of being lost if more of Gabon’s mangrove forests are removed.

NASA Earth Observatory's map of global mangrove habitat loss between 2000 and 2016. Courtesy of NASA Earth Observatory
NASA Earth Observatory’s map of global mangrove habitat loss between 2000 and 2016. Courtesy of NASA Earth Observatory

The measuring and mapping of the world’s mangroves also gives countries crucial information on their sequestered carbon as they work towards meeting climate goals established by the Paris climate agreements.

For now, mangrove clearing in Gabon has mostly taken place on the northern coast. With forests covering roughly 90 percent of the small nation of 2 million people, Gabon has a record of success in protecting its environment and rich biodiversity. Since 2002, the country has created 13 national parks and 20 protected marine zones. But Gabon’s lack of regulations and allegations of development-enabling corruption are new challenges. Climate change adds another threat, though the mangroves provide a natural, ready-made remedy so long as they are protected.

Globally, conservation programs and improved government oversight have slowed mangrove loss in the past 20 years after widespread destruction due to large-scale aquaculture, agriculture and logging. But this trend could be upended by sea-level rise, erosion and soaring populations in Asia and Africa re-enforcing the need for continued conservation efforts in Gabon elsewhere. The Global Mangrove Alliance, for instance, has set a goal of boosting mangrove cover by 20 percent by 2030.

To help reach this target, Rivera said integrating mangrove protection into public policy and implementing community-based conservation management programs is key. “Having the communities involved will multiply the efforts of the government, plus these communities will protect it because they get the food from this habitat,” she says.

Fatoyinbo also stressed the importance of a balanced approach. “It is important to have well thought out strategies that protect natural ecosystems as well as allow for some local use,” she says. “Access to water is an important factor in mangroves’ conservation status and highlights the need to enable conservation and restoration that takes into account the hydrology, geology, biodiversity and other drivers that impact the health of the ecosystem.”

In Gabon, activists are calling for the creation of a wildlife sanctuary and a protected area to conserve the vulnerable mangroves at Cap-Estérias.

In an interview with AfricaNews, the head of Citizen Actions for Local Development, Paul Kopedina Itanguino, said, “What is at risk through the destruction of the mangroves in the Idolo area is our environment, our coasts. These mangroves serve as a water watch for bad marine weather and in relation to climate change, they play the role of the biofilter. Therefore, [their conservation] is very important.”



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