Mangrove Forest Landcover Changes in Coastal Vietnam: A Case Study from 1973 to 2020 in Thanh Hoa and Nghe An Provinces

Abstract

Mangrove forests can ameliorate the impacts of typhoons and storms, but their extent is threatened by coastal development. The northern coast of Vietnam is especially vulnerable as typhoons frequently hit it during the monsoon season. However, temporal change information in mangrove cover distribution in this region is incomplete. Therefore, this study was undertaken to detect change in the spatial distribution of mangroves in Thanh Hoa and Nghe An provinces and identify reasons for the cover change. Landsat satellite images from 1973 to 2020 were analyzed using the NDVI method combined with visual interpretation to detect mangrove area change. Six LULC classes were categorized: mangrove forest, other forests, aquaculture, other land use, mudflat, and water. The mangrove cover in Nghe An province was estimated to be 66.5 ha in 1973 and increased to 323.0 ha in 2020. Mangrove cover in Thanh Hoa province was 366.1 ha in 1973, decreased to 61.7 ha in 1995, and rose to 791.1 ha in 2020. Aquaculture was the main reason for the loss of mangroves in both provinces. Overall, the percentage of mangrove loss from aquaculture was 42.5% for Nghe An province and 60.1% for Thanh Hoa province. Mangrove restoration efforts have contributed significantly to mangrove cover, with more than 1300 ha being planted by 2020. This study reveals that improving mangrove restoration success remains a challenge for these provinces, and further refinement of engineering techniques is needed to improve restoration outcomes.

New and Emerging Insect Pest and Disease Threats to Forest Plantations in Vietnam

“…The remaining 1,158,000 ha includes mangroves, other bamboo species, small monocultures of other native species, and some mixed forests. At present, there is no national strategy to investigate the health of these forests even though tree mortality has been observed [102,103]. These planted forests in Vietnam have potential pests and diseases, some of which may become invasive and damage new production forests in the future.…”

Mangrove Dieback and Leaf Disease in Sonneratia apetala and Sonneratia caseolaris in Vietnam

“…Thanh Hoa Province in north-central Vietnam was chosen because afforestation trials had been established in 2015, and remote sensing imagery showed that many plantings had been unsuccessful [47]. Thanh Hoa city (20.0 • N, 105.5 • E) has a tropical climate with intermittent rainfall concentrated in the summer (1447 mm/year), and the average annual temperature is 27.3 • C. Preliminary health surveys were randomly conducted in mangroves in two geographical areas (Table 2) to assess canopy conditions in 2018.…”

“…Large gaps remain in the documentation of mangrove diseases for most parts of northern Vietnam. As the average rate of success of mangrove restoration in northern Vietnam is approximately 30% [47], understanding whether mangrove diseases are a contributing factor could help improve the management of mangroves in future projects. Therefore, this study was undertaken to document the extent and impact of disease problems on afforested mangroves in Thanh Hoa Province.…”

Coastal forest cover change detection using satellite images and convolutional neural networks in Vietnam

“…Coastal forests are an important part of tropical biodiversity. They provide a lot of important services for our ecosystem, such as extreme weather protection, erosion prevention, environments for different species, and storage of blue carbon, which allow to mitigate climate change [1]. However, these forests are increasingly vulnerable to degradation as a result of climate change, sea-level rise or anthropogenic processes such as deforestation [2].…”