STUDY OF CHANGES IN MANGROVE FOREST COVER IN THREE AREAS LOCATED ON THE EAST COAST OF NORTH SUMATRA PROVINCE BETWEEN 1990 AND 2020

Abstract

Monitoring mangrove distribution is essential to ensure appropriate and efficient management of mangrove forests, as an effort to minimise the damage that potentially occurs in the ecosystem, including preventing human-induced activities that could lower the quantity and quality of mangroves. On the other hand, monitoring activities are also important for mangrove forest rehabilitation programmes. The use of high- and medium-resolution satellite imageries, especially free Landsat images, is very popular for mapping mangrove forests. As a unique wetland ecosystem, mangroves are mapped by applying unsupervised and supervised classification techniques. The specific objective of this study was to examine the rate of change in mangrove forest cover in two regencies and one city located on the east coast of North Sumatra province over a period of three decades. It was found that mangrove forests have lost 34,063.12 ha over three decades between 1990 and 2020, with the main drivers of mangrove deforestation being conversion to agricultural lands (~20,961.27 ha) and ponds (~8,584.39 ha). The normalised difference vegetation index showed that the current extent of mangroves in North Sumatra Province in 2020 were: very poor (344.91 ha), poor (244,78 ha), moderate (844.98 ha), healthy (5,692.58 ha) and very healthy (12,989.71 ha).