American Association for the Advancement of Science (AAAS)—Fire activity by the Han army around 221 to 111 BCE sparked the devastation of an ancient Chinese swamp cypress forest, according to new research*. Today, traces of this ancient forest lurk beneath the water in the Pearl River Delta. The research also indicates that human agricultural activity related to the invasion introduced new plants, such as rice, to the swamp – bringing the cypress closer to extinction. Between 2 and 6 thousand years ago, the Chinese swamp cypress (Glyptostrobus pensilis) grew abundantly throughout the Pearl River Delta in modern China. Then, its population rapidly dropped almost to the point of extinction, leaving behind peat- and water-covered stumps from the ancient forest. Researchers have put forth many theories to explain the forest’s collapse, but none have yet solved the mystery. Now, Ning Wang and colleagues suggest that fire from the Han army’s attacks around 2100 years ago caused this forest’s destruction. Radiocarbon analysis of preserved underwater cypress stumps dates the burn damage to the Han Empire’s invasion of the Nanyue Realm. Many historical documents establish the Han army’s use of fire during this conquest, further supporting a causal relationship between warfare and the cypress’s decline. Wang et al. studied pollen records and observed an increase in Poaceae (grasses) including rice and other cereals, indicating agricultural activity assumed to provide food for the army. They also found higher metal concentrations tied to human use.
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Distribution of extant and buried G. pensilis in Asia and the PRD. (A) Distribution
of buried forests (brown circles) and those identified as ancient G. pensilis forests
(orange diamonds) in the PRD. Yellow diamonds indicated the study sites of
Gaoyao and Sihui (14, 71). (B) Distribution of extant and buried G. pensilis within
ecoregions based on Ecogions2017. Yellow triangles indicate the locations of paleoclimate records mentioned in the text. Wang et al., Sci. Adv. 11, eadt1736 (2025)
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Article Source: AAAS news release.
*Collapse of fragile Chinese Swamp Cypress forest, Science Advances, 23-Apr-2025. 10.1126/sciadv.adt1736
