Mangrove forests (MFs), which occur along tropical and subtropical coastal zone, are among the most productive and richest carbon-rich ecosystems in the world. However, MFs have experienced great losses worldwide due to the impacts of intensive human activities and relative sea level rise. Here, the recent dynamic changes in the MFs of the Red River Delta (RRD), the second largest delta in Vietnam, were quantified using the random forest algorithm based on 328 remote images obtained by Landsat TM/ETM+/OLI during 1986–2019. The results show obvious increasing trends in the MF area with a change rate of 39 ha/y from 1,655 ha in 1986 to 2,944 ha in 2019. The change rates in the northern RRD (NP) and southern RRD (SP) were 8.44 ha/y and 30.62 ha/y, respectively, even though MFs in the tropics worldwide encountered significant losses. Further, approximately 1,091 ha of MF was converted into aquaculture ponds during 2000–2006 in the interior of the RRD, while the shoreline of MFs in the NP and SP continually expanded seaward to the northeast and southwest at average rates of 38.9 m/y and 17.9 m/y, respectively. Moreover, although the fluvial sediment supply declined dramatically from 199.57 to 16.41 mt/y during 1986–2017, the sediment supply was not responsible for the present seaward expansion of MFs. Wave action drove sediments to overwash barriers, and tidal dynamics carried this sediment into tidal channels, depositing sediments behind the barriers and on both sides of tidal channels with continuing MF growth. In addition, the conversion of MFs into aquaculture ponds by human activities was responsible for the massive losses of MFs in 2000–2006, but these impacts were alleviated as conservation policies were implemented by local governments in subsequent years. This study indicates that the growth, loss and recovery of MFs are affected by various factors, and it is vital to map the variations in MFs to better implement regional ecological restoration programs for coastal MFs.

沿热带和亚热带沿海地区生长的红树林（MFs）是世界上生产力最高，碳含量最高的生态系统之一。但是，由于人类密集的活动和相对海平面上升的影响，MF在全球范围内遭受了巨大损失。在这里，越南随机应变算法基于1986-2019年Landsat TM / ETM + / OLI获得的328幅远程图像，对越南第二大三角洲红河三角洲（RRD）MF的近期动态变化进行了量化。结果表明，中频区的增长趋势明显，从1986年的1655公顷到2019年的2944公顷，年变化率为39公顷/年。北部RRD（NP）和南部RRD（SP）的变化率为8.44 ha / y y和30.62 ha / y，尽管全世界热带地区的MF遭受了重大损失。进一步，在2000–2006年期间，RRD内部约有1,091公顷的MF被转换为水产养殖池塘，而NP和SP的MF海岸线不断向海扩展至东北和西南，平均速率为38.9 m / y和17.9 m / y。此外，尽管在1986年至2017年期间，河流沉积物供应量从199.57吨/年急剧下降至16.41公吨/年，但沉积物的供应量并不构成当前MF向海扩张的原因。波浪作用驱使沉积物冲刷障碍物，潮汐动力将这种沉积物带入潮汐通道，在障碍物后面和潮汐通道的两侧沉积沉积物，从而使MF持续生长。此外，由于人类活动，MFs转化为水产养殖池塘是2000-2006年MFs大量损失的原因，但是随着随后几年地方政府实施保护政策，这些影响得以缓解。这项研究表明，MF的生长，损失和恢复受到多种因素的影响，因此，绘制MF的变化图对于更好地实施沿海MF的区域生态恢复计划至关重要。