Diminishing mangrove forest structures in Davao City, Philippines

Abstract

The decline of mangrove coverage across the Philippines to 50% of its original coverage in present years has, led to significant reductions of ecological functions to fisheries and benefits to man. The mangrove forest in Davao City was assessed for its taxonomic list, Importance Value Index, abundance and distribution of mangrove regenerations, forest structure, and species diversity status. The study was conducted in Barangay Bunawan, Lasang, Panacan, Matina Aplaya, 76-A, and Bago Aplaya. All data were gathered by establishing sampling plots (10m x 10m) using the modified transect-plot method. Overall, a total of 34 mangrove species were listed, of which 21 were identified as true mangroves and 13 as mangrove associates. The 21 mangrove species were very low in species richness (54%). Importance Value Index showed that Avicennia marina, Rhizophora apiculata, and Sonneratia alba, respectively, as dominant mangrove species. The mangrove regenerations were in poor condition (<0.50) while relative abundances of growth stages consisted of mature stands at 46.04%, saplings with 27.78%, and seedlings with 26.18%. General diversity indices obtained a low value on the Shannon-Wiener diversity index (H'=1.42) and an average value on the species evenness index (E=0.61), all indicating stressful and unstable mangrove forests. Thus, the mangrove forest ecosystem has imbalances and eventually, only certain species would survive.