An update on the status of mangrove forests in the western coast of Unguja Island, Tanzania: a rural vs peri-urban comparison.

The status of mangrove forests was assessed in the western coast of Unguja Island, Tanzania along a rural-peri-urban gradient. Employing a systematic random sampling, we specifically compared the structural composition and rates of deforestation and forest regeneration. Sampling was carried out within 179 sample plots (10 x 10 m) established along line transects set across the shores. A total of six mangrove species were encountered. Tree density averaged 2134 trees ha(-1). Spatial variation in species composition, stand density, species importance, and forest structural complexities were observed among the mangrove forests. High levels of forest degradation and deforestation were also observed, with averages of 854.0 and 314.4 stumps and partially-cut trees per hectare, respectively. Although the rate of regeneration was high (37,600 juveniles ha(-1)) and far above the recommended minimum for natural forest restocking, the actual regeneration potential is questionable, as the majority (> 60%) of the juveniles were of the lowest regeneration class (RCI), with little or no chance to recruit into higher classes and eventually adulthood under the current levels of exploitative pressure. This study has revealed higher intensity of anthropogenic pressure within the peri-urban mangroves, compared to their rural counterparts. Unless appropriate measures are undertaken, within the framework of the newly established Marine Conservation Areas (MCAs) in the western coast of the Island, this trend may irreversibly impair the capacity of these vital habitats to offer the ecological services upon which coastal livelihoods are dependent.