Impacts of urbanization and land transitions on seagrass beds in tropical lagoon in central Vietnam

Abstract

Socio-economic development activities have significantly affected biodiversity of seagrass beds in the coastal lagoon areas in central Vietnam. This study was carried out to investigate the major past and potential impacts on seagrass changes in Lang Co lagoon. In this study, historical satellite remote sensing data and GIS technology were used to evaluate the variation of seagrass beds during the period of 1998 to 2020. Bottom Reflectance Index (BRI) was employed with the correlation coefficient between the band pairs and the depth, which fluctuated between 0.76 and 0.90 with the bottom reflectance of the bands including bands 1, 2 and 3 ranging between 0.59 to 3.10, 0.66 to 2.35 and 0.45 to 1.95, respectively. Two coefficients were used to evaluate the accuracy of underwater objects including Kappa coefficient (K) and overall accuracy (OA) which ranged from 0.78 to 0.88 and 83.78 to 91.22, respectively. The classification results of terrestrial layers recorded Kappa coefficients and overall accuracies ranging from 0.76 to 0.90 and 85.35 to 99.27, respectively. The change in the area of seagrass beds and other land use types around Lang Co lagoon was studied during the period of 22 years. In the period of 1998–2004, seagrass was not clearly affected by socio-economic development activities, while the period of 2006–2012 witnessed significant impacts of socio-economic activities on seagrass beds. The period of 2014–2020 revealed the most apparent impacts of economic development on seagrass beds. The results of analyzing land use transitions indicated that while water, sand and artificial layers were stable over time; bare soil, forest and agricultural soil layers combined with plantation areas tended to change continuously over the years. The study results provide a scientific database for sustainable management of the Lang Co lagoon ecosystem in particular and coastal area in central Vietnam in general.