Geochemical approach to evaluate deforest of mangroves

Processes of mangrove deforest related human activities were examined. To evaluate changes of soil feature, multielements geochemical compositions of mangrove muds and soils of deforest were analyzed. To describe present situation of the mangrove, Conakry in Guinea, Dar es Salaam in Tanzania, Sundarbans of Bangladesh and Nago in Okinawa of Japan were selected. Soil samples of the forests were evaluated enrichment of biologically concentrated heavy metals such as Zn, Cu and Fe, and TS (total sulfur) and phosphate. Mangrove soils of dominant biome are normally dark colored and enriched in organic matter and element concentrations indicated above compared to those of deforest soils. On the other hand, Ca contents became higher in deforest soils due to inflow of marine carbonate matter by the disappearance of mangrove barrier. Deforest and degradation of soils were related to the land use and agriculture practices; namely development of paddy field and logging in Guinea, salt farm development in Tanzania, red soil inflow and development of constructions in Okinawa. Although the observations were limited in small area, geological and geographical examination can reveal mechanism of the degradation of the forest in relation to environmental change. These observations and geochemical data set would be useful for planning of conservation of mangrove.