Factors influencing coastal land cover change and corresponding impact on habitat quality in the North-western Coastline of Guinea-Bissau (NC-GB)

Abstract

Coastal zones are transitional and inter-connected areas between marine and terrestrial ecosystems. Changes in coastal zones will inevitably have implications on coastal habitat quality which provide appropriate conditions for individual and population to live. Habitat quality is degraded either directly or indirectly as a result of land use increases and the intensification of natural hazards. Moreover, quantitative assessment studies to clarify the impact of coastal land cover change on habitat quality have rarely been implemented. Therefore, we first combined the Habitat Quality Model (HQM) with Digital Shoreline Analysis System (DSAS), to investigate the main factors influencing coastal habitat quality change and estimate the habitat degradation index over the four decades in the NC-GB. The results indicated that, between 1979 and 2020 a complicated series of land cover change occurred in the study area, affecting a total area of nearly 377 km2. All the coastal land cover displayed geomorphological alteration of 12.52% erosion, 39.61% accretion and moderate changes of 47.74%. The conversion of saltmarsh, coastal forest and mangroves into cultivated, residential and sand dune were the main responsible for coastal habitat quality change. Saltmarsh was the most degraded with 38% in 1979 to 51% in 2020, followed by coastal forests 25%–37% degraded. Mangroves showed significant improvement of 12%–5% degraded, respectively. The study concluded that anthropogenic factors were the main processes driving change in the quality of coastal habitats. Therefore, measures should be taken to control the two main land conversion such as cultivation and residential. These findings support the clear definition of priorities for sustainable coastal zone management, in order to decrease vulnerability and increase resilience of the coastal communities.