Geospatial assessment of ecosystem health of coastal urban wetlands in Ghana

Abstract

This study employed geospatial techniques to assess the ecosystem health of some coastal urban wetlands in Ghana over 32-year period and predicted changes that will occur in the next 15 years. Landsat satellite images of 1985, 2002 and 2017 were obtained for this study. The study was carried out in three coastal urban wetlands; Muni-Pomadze, Densu Delta and Sakumo II Ramsar Sites. The ecosystem health of the wetlands was assessed using structure, function and resilience indicators. The results indicated that between 1985 and 2002 about 21 percent of the total area of the wetlands were subjected to land use land cover (LULC) changes and almost half of the total area (48%) experienced changes in 2002-2017 period. The annual change rate in 1985-2002 was relatively slow whereas the annual change rate in 2002-2017 was relatively fast due to increasing anthropogenic activities. The natural LULC classes progressively became more fragmented over the study period due to the expansion of built-up areas. It was estimated that about 30 percent of the total area of the wetlands in 2017 will be subjected to LULC changes as result of built-up expansion in 2032. In 2002, ecosystem health of Densu Delta experienced the least decline (12%) from the 1985 state among all the three wetlands and Sakumo II recorded the highest deterioration (38%). Contrary to 2002, in 2017 the health of Densu Delta experienced the worse deterioration (46.3%) whereas Sakumo II recorded the least decline (26.2%). Ecosystem health of Muni Pomadze Ramsar Site deteriorated at a similar magnitude, 27 percent and 29.1 percent for 2002 and 2017 respectively. An urgent pragmatic intervention is needed to protect the coastal urban wetlands in Ghana to save them from being wiped out completely.