Environmental Engineering Reference
In-Depth Information
Carbon Budget as a Tool for Assessing
Mangrove Forests Degradation
in the Western, Coastal Wetlands Complex
(Ramsar Site 1017) of Southern Benin, West
Africa
Gordon N. Ajonina, Expedit Evariste Ago, Gautier Amoussou, Eugene
Diyouke Mibog, Is Deen Akambi, and Eunice Dossa
Abstract
Carbon budgets were established for pockets of mangrove forests within the western coastal
wetland complex of southern Benin (Ramsar site 1017) using standard methods. We assessed
carbon stocks in four (0.1 ha) transects in sites with different levels of degradation of
mangrove vegetation from non-forested, very degraded, degraded, to non-degraded
mangroves in Kpétou, Djègbadji, Adounko (1), and Adounko (2) sites, respectively. Species
encountered were typical of the west-central African region: Avicennia germinans,
Rhizophora racemosa, Acrosticum aureum (fern), and Paspalum vaginatum. The maximum
diameter was 24.8 and 20.3 cm for Avicennia and Rhizophora, respectively, in non-degraded
mangrove sites, at a maximum height of 21 m. Standing volumes varied from 6.55 m 3 /ha in
degraded mangroves to 50.42 m 3 /ha in the non-degraded mangrove sites. The total annual
carbon stock, to a soil depth of one meter, varied from 179.39 t/ha in the non-forested site, to
288.77 t/ha in degraded mangroves and 184.01 t/ha for non-degraded mangroves.
Aboveground biomass carbon in non-degraded sites was on average 35.07 t/ha, more than
five times that in degraded mangrove sites. The distribution of total ecosystem carbon stocks
for the aboveground component for the mangrove sites ranged from 0.82 % for non-forested
sites, 2.94 % for degraded to 16.01 % for non-degraded mangrove forests. The belowground
carbon stocks component ranged from 179.39 to 288.77 t/ha, being the highest in degraded
mangrove sites due to leached organic matter following degradation. Potential annual net
CO 2 e emissions from up to 30 cm soil depth (compared to non-wooded mangrove
vegetation) is estimated to increase from 10.28 to 99.64 t CO 2 e (22 % of non-wooded
 
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