The mangrove forests in the Guyanas (French Guiana, Surinam and Guyana), which spread across the Orinoco and Amazon deltas, are among the most extensive in the world. (Credit: © IRD / C. Proisy)

Feb. 1, 2013 — The mangrove forests in the Guyanas (French Guiana, Surinam and Guyana), which spread across the Orinoco and Amazon deltas, are among the most extensive in the world. This particular ecosystem, between the earth and the sea, plays a major role in protecting the particularly unstable muddy coastline (2) against erosion. However, most of the Guyana mangroves have been destroyed to develop the coastal plain. The retreating mangrove wall will result in large-scale coastal erosion, threatening populations and their economic activities, as demonstrated in a study conducted by researchers from IRD and the University of Aix-Marseille.

Gaining ground on the sea

Although the French Guiana coastline remains protected by human developments for the time being, that of Guyana is already highly disrupted. The entire coastal strip is now inhabited. In order to conquer this space and subsequently develop the aquaculture and agriculture — mainly rice cultivation — the coastal swamp areas have been transformed into polders (3). To this end, dikes have been built, reducing the 1km mangrove strip to just a few dozen metres wide.

Less protective dikes

More than three quarters of Guyana's 450 km of coastline along the Atlantic are currently diked up. Coastal stability now depends on these earthen dikes. However, these dikes do not provide the same level of protection as mangroves against the swell, which is the main cause of erosion. Moreover, they would not withstand the strength of the waves if the mangroves were to disappear completely. Yet, they prevent the sedimentation of mud coming from the Amazon, which enables forest regeneration.

Coastal stability in danger

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