Mangrove Biodiversity, GIS Weighted Overlay Analysis, and Mapping of Suitable Areas in Alabel, Sarangani Province, Philippines

Abstract

The utility of Geographic Information System (GIS) has been adopted in mapping and predicting sites for mangrove suitability in Alabel, Sarangani Province, Province. Biodiversity assessment of coastal mangroves in Alabel, Sarangani Province, Philippines was performed in purposive manner using sampling quadrats. There were 13 observed mangrove species in sand-dominated (51.48%) soil. The sampled field data points are scattered irregularly, showing slight curvature on the east-west trendline but a flatter surface on the north-south trendline. The abundance and soil data were converted into shapefiles and subjected to inverse distance weighted (IDW) interpolation. The rasterized and reclassified thematic map layers were assigned with factor influence consisting of mangrove abundance (40%), land cover (30%), sand composition (20%), and slope (10%) for suitability analysis. The suitable mangrove areas were computed using weighted overlay suitability analysis, and the final score for the suitability index was converted into suitability classes. Prediction of mangrove suitable areas was performed under the ModelBuilder workflow tool in ArcMap. The mangrove suitability classes were extracted using a zonal geometry tool depicting three suitability classes. The predicted mangrove high suitability areas covered 463.37 km², the low suitability areas covered 573.02 km², and the unsuitable areas covered 9,403.77 km². The study utilized a combination of field gathering and available online data for GIS analysis which local government units could perform. The results could be used to plan and manage mangrove resources in the area effectively.