LATE HOLOCENE ANTHROPOGENIC IMPACTS ON TROPICAL ECOSYSTEMS OF NORTHERN VIETNAM

Northern Vietnam has a long history of human occupation (>4000 years), warfare, and agriculture. An ongoing project is examining anthropogenic factors influencing Northern Vietnam tropical ecosystems during the late Holocene. The results of pollen and macroscopic charcoal from two sediment cores, one from a mainland estuary at the Red River Delta and another from Quan Lan Island 75 km east in Halong Bay, suggest that periods of instability, namely warfare and trade, significantly influenced tropical forests and agricultural practices. At the mainland site a 4000 year paleoenvironmental record suggests periods of political stability were associated with increased agriculture (growing of rice) and burning, while periods of instability (warfare and political unrest) resulted in a return of native vegetation and decreased burning. The findings are contrary to prior research found just 75 km south that inferred warfare and political instability resulted in higher rates burning in northern Vietnam (Li et al., PNAS, 2009). At the island location, the 2500 year paleoenvironmental record suggests that agriculture and low-level burning ceased after the establishment of the major Van Don trading port (1149-1397 AD; 900-550 cal yr BP) on Quan Lan Island. During the trading period native vegetation also expanded. When the mainland capital near present day Hanoi shifted south ~1397 AD, the port ceased operation and rice agriculture and burning returned. Charcoal levels were significantly higher than before, native species declined to low levels, and rice pollen increased after trading ceased, likely reflecting intensive rice agriculture and the establishment of Quan Lan Commune on the island. Future work will focus on the historical port of Van Don and island locations that were not historically population centers to examine the extent of human impact across the region. The research has implications for understanding the maintenance of tropical biodiversity amidst long-term human occupation and political unrest.