Southeast Asia harbours the world’s most diverse and extensive mangroves, and northern Vietnam hosts a large proportion of the region’s mangrove plants. These habitats can act as buffers along coastlines to mitigate the impacts of natural disasters; they act as nurseries for an array of animal species; and they provide important resources for local human communities. Anthropogenic activity is the most significant threat to mangrove ecosystems globally. In Vietnam, a 50-80% reduction in the extent of mangroves has been recorded in some areas since the Vietnam/American War due to the use of defoliants in that war and the later establishment of shrimp aquaculture ponds in these habitats.
Predicted future rises in sea-level in the Song Hong delta will further restructure coastal ecosystems, and the human communities that depend on their resources are particularly vulnerable to associated changes. Understanding how the region has adapted to both environmental and anthropogenic impacts in the past is essential to guide modern responses to the effects of climate change.
Recent multidisciplinary research by the SUNDASIA project published in Quaternary Science Reviews has identified that mangrove habitats were present in the dolines of the limestone karst landscape of the Tràng An World Heritage property in northern Vietnam as early as 8,000 years ago and these persisted until around 1700 CE despite a significant drop in sea-level. An opening in the structure of limestone vegetation was also observed and this coincided with the establishment of the ancient capital of Hoa Lu and the onset of the Medieval Climate Anomaly suggesting that one or both of these factors could have contributed to the opening up of the vegetation.
Video abstract produced for this research by Rachael Holmes
By combining palaeoenvironmental, archaeological and historical research, the authors argue that the relict mangrove habitats within Tràng An were resilient to change, only disappearing very recently. They suggest that sheltered sub-coastal karst settings may provide suitable areas for future mangrove restoration projects in northern Vietnam.
Reference: Shawn O’Donnell, Thi Mai Huong Nguyen, Christopher Stimpson, Rachael Holmes, Thorsten Kahlert, Evan Hill, Thuy Vo, Ryan Rabett. 2020. Holocene development and human use of mangroves and limestone forest at an ancient hong lagoon in the Tràng An karst, Ninh Binh, Vietnam. Quaternary Science Reviews. 242: 106416
SUNDASIA Project Team Members