In the western world, rice has joined the beloved potato and pasta as a diet staple; providing an alternative source of carbohydrate. The history of rice and rice cultivation, however, stretches much further back than its appearance in Europe and other westernised areas. Asian rice (Oryza sativa L.) is one of the world’s most important crops and is said to be amongst the earliest cultigens.
The lower Yangtze in eastern China is acknowledged as one of the original areas of early rice-based agriculture, with the earliest evidence of exploitation of rice in the area dated to ca. 10,000 cal yr BP (on the Shangshan archaeological site (Fig. 1)). However, details of the early history of rice-based agriculture in the area remain obscure, and this is partly due to lack of understanding of how early societies who possessed the technique of rice-based agriculture and the environment they inhabited interacted. A project carried out by TCD geographers, in cooperation with researchers from China and Australia, was designed to test a hypothesis that environmental changes, in particular changes in hydrology, have had an impact upon prehistoric and historic communities in the lower Yangtze. The project is currently focusing on the Chuodun site, in the heart of the lower Yangtze, close to an archaeological site that carries the same name.
Fig. 1: map of the lower Yangtze
Palaeoecological techniques provide a means to assess the possible interaction between humans and environmental changes over the Holocene scale. Sediments were collected from a trench excavated close to the Chuodun archaeological site (Fig. 1) in the lower Yangtze. Pollen and spores, diatoms, phytoliths, and charcoal contents in the sediments were extracted and analysed. Also useful were measurements on other physical proxies that enabled a reconstruction of site hydrology, in particular particle size analysis.
Results suggest that palaeohydrology was one of the most important environmental factors influencing early rice-based agriculture on the site over the Holocene scale, based on correlation of various sorts of microfossil evidence (Fig. 2). For example, expansions of water bodies in the lower Yangtze at ca. 2,500 cal yr BP, are suggested to have been associated with a disruption of rice-based agriculture on the site. However, little evidence of marine intrusion during this period, based on results of diatom and dinoflagellate cysts analyses, was found in the sediments. It is inferred that inundation during this period was freshwater in origin, possibly due to impeded drainage as a result of changes in geomorphology and unstable climatic conditions.
Fig. 2: a selection of microfossils found in the research (1-5: pollen grains; 6-9: diatom frustules) 1. Chenopodiaceae; 2. Fagaceae Quercus; 3. Poaceae (≤40 μm); 4. Poaceae (>40 μm); 5. Typhaceae; 6. Diadesmis confervacea; 7. Caloneis bacillum; 8. Luticola mutica; 9. Rhopalodia gibba.
This disruption provides an example of the vulnerability of early food production systems to environmental changes in the lower Yangtze. However, early communities also had strategies for coping with environmental change. Archaeological evidence suggests migration away from and reoccupation of the site, the latter having occurred when people possessed more advanced technologies, including early forms of hydraulic engineering such as construction of canals and of embankment along lakes. These flood protection schemes seem to have had the additional benefits of converting a dense network of rivers and lakes, which accounted for the aforementioned floods, into an efficient transportation system that underpinned the boosting economy of the lower Yangtze in historic China. Therefore, palaeohydrology is exemplified as both a constraint and an impetus to development of early agriculturalists in the lower Yangtze.