GIS-based integration of interdisciplinary ecological data to detect land-cover changes in Creek Mangroves at Gazi Bay, Kenya

Historic environmental, faunal, floral and socioeconomic data of Gazi Bay in coastal Kenya were collated and integrated into a GIS environment and data of impacts due to various factors were then related to remotely sensed data. Rhizophora mucronata, a valuable mangrove species, was investigated. Very low values of basal area (7.7 m²/ha and 4.9 m²/ha) and complexity indices (1.86 and 1.12) at Makongeni and Kinondo 1, respectively, reflected intense human pressure in these areas. Areas that were easily accessible or close to human settlements appeared more vulnerable. Accrued information from a socioeconomic survey carried out over the same period corroborates the hypothesis that human influence was a major contributor to these changes. Historic aerial photographs together with satellite imagery indicate less than 20% decrease in coverage of R. mucronata between 1965 and 1992, but an increase of almost 35% in sand cover over the same period. The approach that was used in this study, one largely unprecedented in the East African region, was useful in drawing the conclusion that human influence was the most probable trigger of the observed changes.