## 3 Results and Discussion
### Spatiotemporal Variations of Mangrove Forests in the Study Area  
There was a considerable change in the NDVI patterns and its influence on types of land cover during the 2015-2019 period in the study area, as shown in Figure 4. It is clear that the land cover dynamics occurred mainly in the transition zone and part of the buffer zone, while this pattern around the core area was more constant, with a greenness response. In addition, the study also focused on the other types of land use patterns in the study area (i.e., built-up, crop land, and residential area). Regarding the variations of mangrove areas in the ecological zones, a downward trend in total area was observed with 705 ha, while an upward trend was observed with 1248 ha between 2015 and 2019 (presented in Table 6). In particular, an increased area of 669 ha and 579 ha was observed at the buffer and core zones respectively, while this trend was constant in the transition zone from 2015 to 2019. On the other hand, the largest decline in mangrove area was investigated at the buffer zone, followed by the transition zone, at 350 ha and 314 ha, respectively. The spatial trend of mangrove patterns are also illustrated in Figure 5. The value of the factor increased most across the core and buffer zones with a Z value greater than zero in the central zone, whereas this pattern mainly decreased gradually from the buffer zone to the transition zone, where most socio-economic activities are practiced and are highly concentrated. Therefore, this demonstrates that activities of the local residents created influences on the mangrove area in the Mangrove Biosphere Reserve around the transition and buffer zones, despite the fact that the stable diversity of the mangrove coverage provides a large amount of ecosystem services (i.e., environment, economy, and society) to local residents [64]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Water Bodies** & **Non-Mangrove** & **Mangrove** & **User Acc** \\ \hline Water Bodies & **74** & 14 & 2 & 90 \\ Non-Mangrove & 3 & **26** & 4 & 33 \\ Mangrove & 4 & 24 & **149** & 177 \\ Producer Acc & 81 & 64 & 155 & **300** \\
**Overall Accuracy** & & & **83\%** & \\
**Kappa** & & & **0.7** & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Confusion matrix of classification accuracy in 2015. Figure 4: The change in types of land cover based on the annual NDVI classifications from 2015 to 2019. Can Gio experienced war in 1965, destroying the mangrove vegetation over three ecological zones [12; 40]. It was rehabilitated by the city government in 1977 [65], however, the mangrove species were still used for energy consumption, economic purposes, and construction. Until June 1999, the HCMC People's Committee issued a conservation letter--Decision No. 3172/QD-UB-CNN--to safeguard the forest, and the use of mangrove species for fuel purposes was totally prohibited [66]. The rehabilitated area of the Can Gio mangrove forest, until present, has accounted for 6.6 percent of the total core area. Therefore, most of the gathering activities in the forest have been completely prohibited for conservation purposes. However, the daily activities (mainly focusing on tourism, built-up areas, and shrimp farming) have exerted an impact on the mangrove variations in recent years. For instance, the number of visitors, demonstrated by [PERSON] et al. (2018) [13], showed that 3.4 million tourists visited, with huge increases from 2011 to 2016. The conversion in land use patterns is shown in Figure 6, and an analysis for each sector conversion is presented in Table 7. Most of the transformation in land use land cover (LULC) took place in the transition zone, apart from the buffer (mainly in Thanh An), focusing on the process between forests and other land. In addition, there was an area of 7.75 ha converted from forest to water bodies, while no