Comparative Evaluation of Three Mangrove Restoration Methods in Côte d’Ivoire: A Multi-Site Experimental Approach

Abstract

This study aims to identify favourable conditions for the restoration of Rhizophora racemosa. Mangroves play a major ecological role by reducing coastal erosion, capturing carbon, and supporting fisheries. In Côte d'Ivoire, they are highly threatened by urbanization, pollution, and overexploitation, resulting in the loss of more than 50% of their surface area since 1990. This study was conducted in the Grands-Ponts region, located in the south of Côte d'Ivoire. The experiments were carried out in four localities (Gboyo, Gbéhiri, Téffrédji, and Tiemien), testing three techniques: transplanting wildlings, direct sowing of propagules, and planting seedlings in nurseries. The results show that direct sowing has the best germination rate, while the nursery method offers the best survival (up to 97.5%). Seedling growth is favoured by sandy-clay soils and a moderate pH. Factors such as salinity, prolonged flooding, pests, and weed cover were major constraints. The success of reforestation also depends on the active involvement of local communities. Locations with sandy-clay and sandy-loam soils (Gbéhiri and Tiemien) recorded the best results. Finally, the physicochemical parameters of the water, notably pH and dissolved oxygen, have proven to be decisive in the success of mangrove plantations.