On top of its expertise in reforestation of Rhizophora, Oceanium developed expertise in the restoration of Avicennia, another species of mangrove, which is found mostly in the regions of Sine Saloum, Casamance and Saint-Louis.

Strong resistance to salinity

These trees typically grow three to six metres high in a zone between Rhizophora mangroves and paddy fields and forests of the hinterland. It adapts easily to silty soil with a lack of oxygen (asphyxiation) as well as to high levels of salinity. Avicennia africana is characterised by its elevated roots called pneumatophores. Those roots present a special inverse geotropism as they grow above the surface instead of penetrating deeper into the ground.

Better known as "white mangrove", Avicennia can be identified with its salty excretions which are found on its leaves. In effect, the leaves work as secretion glands that allow for the elimination of the surplus of salt in the soil which is absorbed through the roots, thereby mitigating the harmful effects of strong salinity. Finally, unlike Rhizophora, Avicennia can survive many days without water.

Our methodology

Utilising traditional knowledge, our teams successfully planted Avicennia, on top of traditional irrigation embankments experimenting with different sowing methods such as broadcasting, direct and semi-direct sowing and transplanting of young plants (Copyright: Maxime Le Hégarat).

In Tobor since 2008 and in Niambaang since January 2010, our teams have been testing a lot in the field: The method that brings about the best results is to plant the trees on top of traditional irrigation embankments (billon irrigué) by broadcasting, direct sowing an transplanting young plants. Consequently, it responds perfectly to the criteria we require, namely:

• a simple method, applicable and repeatable everywhere (most suitable relationship between cost of planting and results) ;
• the participation and mobilisation of the population ;
• the utilisation of local knowledge (utilisation of traditional tools, knowledge about the local situation, etc.) ;
• a survival ratio of more than 80 per cent.

Up to date, our teams, together with local villagers, have planted more than 100 hectares of Avicennia in the Casamance region.