Estado de conservação e simulação de cenários futuros nos ecossistemas costeiros da Ilha de Benguerra – Arquipélago de Bazaruto

Abstract

Benguerra Island, located in the Bazaruto Archipelago, is recognised for its ecological and socio-economic importance, hosting fragile coastal ecosystems with high biodiversity. However, in recent decades, the island has been under pressure from natural and anthropogenic processes that affect the balance of its ecosystems, particularly the expansion of urbanisation, the degradation of dunes and sedimentary banks (sandbanks and submerged banks), as well as changes associated with sea-level rise. The present study aimed to assess the conservation status of the island between 1990 and 2024 and to simulate future scenarios of coastal transformation up to 2100. To this end, Landsat 5-TM and Landsat 8/9 OLI_TIRS satellite images (1990 to 2024), wind data from the U and V components (ERA5), sea-level data (INoM and APDRC), and field surveys with GPS for supervised land-cover classification were used. The simulation of future scenarios was carried out with the Sea Level Affecting Marshes Model (SLAMM) version 6.7, integrating SRTM DEM (30 m), slope, NWI categories, and sea-level rise series (SSP1, SSP2 and SSP5). The results showed that the island is undergoing a progressive degradation process: between 1990 and 2024 there was a marked increase in exposed soil, a retreat of dense vegetation, and the disappearance of the sandbank in the southern sector, reducing coastal resilience. The sectional analysis revealed greater vulnerability in the northern part of the island (Section A), where dunes were fragmented and ocean intrusion into Lake Nhanombe was projected for 2100 under SSP5, while the southern part of the island (Section B) showed relative resilience, despite the partial submersion of coastal plains. The simulations confirmed that, even under optimistic scenarios, there will be a significant retreat of dunes and wetlands, which will intensify under SSP2 and culminate, under SSP5, in widespread submersion and the near-total loss of the coastal strip. Overall, Benguerra Island is in a compromised state of conservation, with high vulnerability to sea-level rise and the anthropogenic pressure exerted on its ecosystems. The results presented in this study reinforce the urgent need to implement coastal management strategies, such as dune protection and restoration, urbanisation control, and the conservation of inland lagoons, in addition to continuous monitoring and regional comparative studies.