Biodiversity in Replanted Mangrove Forests : A Study in the Southern Viti Levu Island Mangrove Ecosystem in Fiji

The biodiversity level of mollusks and environmental conditions in replanted as well as natural mangrove forests were investigated to determine the restoration level in replanted mangroves. This study was performed in 2 replanted and 2 natural mangrove forests in 2003 and 2004 in Viti Levu Island, Fiji. The ages of the trees in each replanted mangrove were 1-3 and 7 years old. The main mangrove tree species replanted in both areas was Rhizophora stylosa. The mangrove trees in the natural forest were between 5 m and 20 m in height. However, those in the forests replanted 1-3- and 7 years previously were from 1 m to 1.5 m and from 3 m to 4 m in height, respectively. Trees near the landside were taller than those on the seaside in all of the mangrove forests examined. Salinity in the regions of the replanted mangroves was about 3% but that in natural mangrove forests was from 0.2 to 3%. The older mangrove forests had neutral pH but younger forests were alkaline. About 10 mollusks were counted in natural forests but the replanted mangrove forests contained only 2 to 3 mollusks. Each quadrate showed a different frequency of observed mollusks. Littorina scabra was the dominant species in the 1-3-year-old mangrove forest. Nerita planospira and Littorina scabra were the dominant species near the landside but only Littorina scabra were dominant near sea side in the 7-year-old replanted mangrove. Environmental conditions and biodiversity levels in replanted mangrove forests were different from those in natural mangrove forests. However, the 7-year-old mangrove forest showed a slightly higher biodiversity level than 1-3-year-old forest and environmental conditions similar to those of the natural forest