Growth, Dynamics And Distribution Of Mangrove Forests In Mozambique

The worldwide degradation of mangrove forests and the coinciding loss in the ecosystem services they provide has affected both coastal processes and peoples’ livelihoods. Despite the recognized importance of mangroves as coastal buffers, carbon source to the oceans and habitat for many species, the growth and dynamics of these forests are still poorly understood. This dissertation analyses the growth, community composition, structure and dynamics of mangrove forests on Inhaca Island and in the Maputo Bay in detail, and the structure, biomass and distribution of mangroves in Mozambique on a larger scale.

In total, five species of mangrove were recorded on Inhaca Island. The field data was used to classify Landsat images of the Maputo Bay from 1991 and 2001. The classifications showed that while total mangrove area in the Maputo Bay has decreased by 28 % since 1991, healthy mangrove area has increased by 88% while scrub mangrove area has decreased by 43%. Tree ring analysis and cambial wounding measurements of Avicennia marina were carried out on Inhaca Island. The cambial wounding experiments showed that A. marina produces one full ring per year. Dendrometric measurements of cross sections showed that average ring width was 1.6 mm (+/- 0.4 mm) and that there is a significant correlation between the number of rings and the diameter at breast height. Based on field surveys of the mangrove forests, stand age was calculated and it was determined that over 50% of trees were under 20 years old. The remote sensing study of mangroves across Mozambique showed that mangrove forests covered a total of 2909 km2 in Mozambique, a 27% lower area than previous estimates. The SRTM calibration indicated that average tree heights were lowest in southern Mozambique, and changed with geographical setting. We did not find a relationship between latitude and biomass in Mozambique. These results confirm that geological setting has a greater influence than latitude alone on mangrove production. The results of this dissertation may have practical implications for the sustainable management of mangrove forests and as inputs into mangrove forecasting models.