GIS-based Integration of Interdisciplinary Ecological Data to Detect Land-cover Changes in Creek Mangroves at Gazi Bay, Kenya

  • PT Obade Kenya Marine and Fisheries Research Institute, P. O. Box 1843, Naivasha, Kenya and Laboratory of General Botany and Nature Management, Mangrove Management Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
  • F Dahdouh-Guebas Laboratory of General Botany and Nature Management, Mangrove Management Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium;
  • N Koedam Laboratory of General Botany and Nature Management, Mangrove Management Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium;
  • R De Wulf Laboratory of Forest Management and Spatial Information Techniques, Universiteit Gent, Coupure 653, B-9000 Gent, Belgium
  • J Tack Biodiversity Platform Belgium, c/o Institute for Nature Conservation, Kliniekstraat 25, B-1070, Brussels, Belgium; Laboratory of Ecology and Systematics (ECOL), Mangrove Management Group, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
Keywords: mangrove, satellite imagery, environment, aerial photography, GIS, Kenya

Abstract

Key words: mangrove, satellite imagery, environment, aerial photography, GIS, 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.
Western Indian Ocean Journal of Marine Science Vol.3(1) 2004:11-27

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eISSN: 0856-860X
print ISSN: 0856-860X