## 1 Introduction  
Mangrove forests are widely located in the intertidal zone with an estimated area of 152,361,000 ha in tropical and sub-tropical shorelines of the world [1; 2; 3]. The mangrove ecosystem is significant as an ecological service in coastal neighborhoods through providing natural resources to local livelihoods (i.e., provision of fuel, food, timber, and construction materials) [4; 5], and being a habitat for diversity of flora and fauna [6]. Moreover, mangrove forests also play crucial roles in coastal stabilization and protection [7] by contributing to the reduction of greenhouse gas emission, and mitigating the negative effects of global warming by a considerable extent [8]. However, the mangrove ecosystem has been severely degraded due to the negative impacts of population growth, industrialization, urban expansion, and agricultural activities [2; 9; 10]. Therefore, the need to map and monitor mangrove forest patterns and dynamics is both necessary and urgent. The Can Gio Mangrove Biosphere Reserve, which covers an area of 750 square kilometers, is considered as a \"green lung\" of Ho Chi Minh City (HCMC) [8; 11]. During the Vietnam War period from 1954 to 1975, the mangrove forest in the study area was destroyed, however, a large scale of reforestation has been implemented by the HCMC Forestry Department since after 1977 [11; 12]. The effort for forest recovery was resolved in the year 2000, when United Nations Educational Scientific and Cultural Organization (UNESCO) recognized the Can Gio mangrove forest as a World Biosphere Reserve, making it the first biosphere reserve region in Vietnam [13]. However, under high demands for economic development (i.e., construction of apartments and tourism facilities, and shrimp farming activities), mangrove sustainability around buffer and transition zones has been crucially influenced by anthropogenic activities in recent years [14]. The expansion of built-up areas and an increase in tourism development in coastal areas in Ho Chi Minh City [15; 16; 17] have exerted negative impacts on vegetation cover. Moreover, an enlargement of sea-encroached urban-tourism zones in Can Gio in 2025 based on Decision No. 3800 by the People's Committee of Ho Chi Minh City might cause critical damage on the mangrove area [18]. Therefore, it is necessary to implement an assessment of mangrove change following the conversion of land use purposes in the Can Gio district. The advantages of remote sensing have been reported as a practiced database resource by a large number of studies in mapping mangroves with lower cost, faster speed, and a larger scale, compared to traditional field investigations [2; 6; 19; 20]. Additionally, following remotely sensed data, there is a variety of multispectral satellite imagery techniques for spectral indices performance and the determination of mangrove conditions, such as Landsat [21; 22], Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) [23; 24], Moderate Resolution Imaging Spectroradiometer (MODIS) [25], and Pleiades [26]. Recently, several studies have applied Landsat [27], ALOS PALSAR-2 [28], and Satellite Pour I'Observation de la Terre (SPOT) [8] combined with field observation to characterize mangrove species in the study area. Compared to other digital resource databases, Sentinel-2 provides a greater extent of the distribution of vegetation over the coastal region [29] with a high spatial resolution of 10 m, a high temporal resolution, a five day re-visit interval, and it is free of charge. These benefits make Sentinel-2 an efficient data source when examining the spatiotemporal aspects of a mangrove forest, and it is especially valuable in the context of developing countries, where the budget for this kind of work is limited. Major methods for monitoring mangrove forests include visual interpretation, supervised classification, unsupervised classification, neural network classification, and the object-based classification method [8; 20; 30].