A new paleoclimate reconstruction from central China has exposed a thousand year sequence of rainfall instability that coincided with the rise, transformation and disappearance of the Shijiahe culture. The record comes from a stalagmite known as HS4 inside Heshang Cave above the Middle Yangtze Valley. Its growth layers contain variations in calcium isotopes, trace elements and carbon signatures that correspond to rainfall levels between 4.6 and 3.5 thousand years before present. During this span the region experienced repetitive cycles of drought and intense rainfall. These cycles affected river levels, lake expansion, vegetation patterns and the suitability of floodplain land for settlement. The Shijiahe occupied this landscape through the early part of the sequence and abandoned it after multi decade wet periods created sustained flooding across the plains.
The Middle Yangtze Valley remains one of China’s major agricultural zones. In the Neolithic period it supported dense populations with fortified settlements, craft industries and extensive food production. HS4 formed on the western edge of this region while water moved through limestone and deposited calcite inside the cave. Each band of calcite contains a chemical imprint of the hydrological conditions at the time of deposition. Calcium isotopes shift depending on how much prior calcite precipitation occurs above the cave. When rainfall is low the water remains longer in the karst and more calcite precipitates before reaching the stalagmite. This produces higher isotope values. When rainfall is high the water flows more rapidly and the isotope values move lower. By measuring these variations along with magnesium, strontium, barium and carbon ratios the researchers created a timeline of changing moisture over more than a millennium.
The earliest part of the record contains dry conditions. Two intervals fall below 700 millimeters of annual rainfall. These occur between 4.36 and 4.33 thousand years before present and between 4.23 and 4.10 thousand years before present. Archaeological evidence from the same era shows that the Shijiahe adjusted their cultivation methods during these dry intervals. Millet becomes more common, reflecting a shift toward crops that withstand low rainfall. Pollen assemblages from ancient settlements show an increase in xerophytic plants. There is no widespread abandonment of settlements during these dry spans. Population levels remain high at this stage. The Shijiahe maintain their presence across the plains and continue expanding their cultural network.
A major shift appears later in the record. After the early dry spans there is a long interval with rainfall near the average of roughly 850 millimeters per year for the period studied. The pottery, jade production and settlement layout of the early middle Shijiahe phase belong to this zone of relative stability. That stability ends when the first major wet interval begins around 3.95 thousand years before present. Rainfall exceeds 1000 millimeters per year for multi decade spans. This wet interval lasts approximately 140 years. Archaeological data show a rapid drop in population at the same time. Settlements shrink or are abandoned. Flood deposits appear in multiple sites across the region. Pollen samples from the Shijiahe ancient city area show increased wetland species. Lake levels rise on the Jianghan Dongting plain and the landscape shifts into marsh dominated conditions.
Sediment profiles from Neolithic sites across the Middle Yangtze show thick flood layers that align with the stalagmite’s wet intervals. These layers sit above cultural deposits that show no signs of reoccupation. Some sites display overbank flood deposits between occupation horizons, indicating repeated flooding. Others show a final flood layer marking the last human use of the area. The pattern is consistent with long term inundation rather than short lived events. With farmland submerged and settlement platforms saturated, the plain would have been unsuitable for sustained habitation. Once the wet interval became entrenched the agricultural system of the Shijiahe could not be restored.
After the 140 year wet interval there is a brief return to moderate conditions. Then a second wet interval begins around 3.70 thousand years before present and continues for roughly 80 years. Rainfall again exceeds 1000 millimeters per year for multi decade spans. By this point the archaeological record shows that the Shijiahe are absent from the core plains. The post Shijiahe phase represents scattered remnants rather than a coherent system. The long series of wet decades removes the possibility of reoccupation. The plains remain too waterlogged to support the settlement density seen earlier in the millennium.
The hydrological instability over the full 1100 year span includes a third dry interval around 3.57 to 3.55 thousand years before present. This coincides with the establishment of a Shang related site at Panlongcheng. Archaeology at Panlongcheng indicates lower water levels in the surrounding rivers and lakes. The site’s construction during a dry window underscores how sensitive the region is to rainfall oscillations. When water retreats the plains open for new occupation. When water advances they cannot be maintained. The thousand year stalagmite record contains multiple shifts in both directions, but the most intense and persistent changes are the wet intervals that arrived during the final centuries of Shijiahe occupation.
Across the record the stalagmite also shows smaller fluctuations that correspond to variations in trace element ratios. Magnesium, strontium and barium concentrations all change alongside the calcium isotope signals. Stable carbon isotopes reflect shifts in vegetation density and soil gas processes. Together these indicators form a detailed picture of the environmental conditions above the cave at any given time. The uranium thorium dating provides chronological anchors that tie the geochemical variations to specific decades. Annual layer counting inside the stalagmite refines the duration of each interval, confirming that the major wet episodes lasted long enough to reshape the landscape for generations.
Regional climate comparisons place the Middle Yangtze in a zone that experienced distinct rainfall behavior relative to northern and southern China. At several points in the record Central China is wet while areas to the north and south are dry. At other points the opposite occurs. Modern meteorological studies show similar patterns driven by shifts in the East Asian summer monsoon. Large scale pressure systems in the western Pacific, oscillations in Pacific and Atlantic sea surface temperatures and the position of monsoon fronts influence these rainfall patterns. The stalagmite record corresponds to a time when ENSO variability was changing and when the Intertropical Convergence Zone was likely shifting southward. These larger scale atmospheric movements would alter the distribution of moisture across East Asia and produce the alternating wet and dry phases recorded in HS4.
Within the Middle Yangtze region the effect of these shifts was cumulative. The early dry intervals strained but did not displace the Shijiahe. The later wet intervals reshaped the rivers and floodplains in ways that prevented recovery. The total sequence lasts more than a thousand years. This sequence includes stable decades, unstable decades, droughts and prolonged periods of excessive rainfall. The settlement patterns follow this progression. Early growth and expansion take place before the strong wet pulses. The population peak around 4.4 to 4.1 thousand years before present aligns with the end of the dry phases. Once the wet interval begins around 3.95 thousand years before present the decline is rapid. During the second wet interval almost no Shijiahe presence remains in the plains.
The archaeological record shows the collapse in real time. Large settlements shrink to smaller clusters. Jade workshops cease production. Defensive structures fall out of use. Pottery traditions shift as populations disperse into higher ground. There is no evidence of a return to the scale or complexity seen before the wet intervals. The landscape that once supported them had turned into a network of lakes and marshes. Flood layers in excavation sites record the physical outcome of multi decade rainfall surges.
Carbon, oxygen and trace element measurements from HS4 reinforce the picture of fluctuating moisture. Oxygen isotopes shift with changes in precipitation amount and moisture source. Carbon isotopes change with vegetation and water flow through the soil. Magnesium, strontium and barium ratios reflect the degree of prior calcite precipitation and variations in water chemistry. Each component contributes to the reconstruction of annual to decadal hydrological patterns. These patterns align with both archaeological data and sedimentary evidence across the region.
Throughout the sequence the stalagmite’s calcium isotope values produce a continuous rainfall reconstruction. The lowest values in the early record correspond to drier phases. The highest deviations correspond to the wettest conditions. The overall average for the millennium is lower than modern rainfall, but average values conceal the severity of the extremes. The periods above 1000 millimeters were long enough to transform the entire landscape. The periods below 700 millimeters were long enough to alter vegetation and crop selection. The alternation between them created a dynamic environment with frequent adjustments required for survival.
The geological setting of Heshang Cave allows the stalagmite to serve as a precise recorder of these changes. The cave sits near the Qing River which feeds into the Yangtze system. Water entering the karst above the cave carries chemical signatures that reflect rainfall intensity and frequency. As this water precipitates calcite the chemical record becomes trapped. Over centuries the stalagmite preserves a continuous profile. By sampling 343 micro drilled sections and extracting calcium, carbon, oxygen and trace element data, the researchers resolved the hydrological pattern with a level of detail not previously available for the region.
The thousand year hydrological sequence has direct parallels in nearby archaeological sites. Lake expansion in the Jianghan Dongting plain took place during the same period. Flood deposits at Zhongba, Zhongqiao, Tanjialing and other sites correspond with the wet intervals. Phytolith and macroremains from cultural layers show shifts in crop composition and land use. Radiocarbon dates from paleoflood layers align with the stalagmite chronology. Together these sources form a coherent timeline in which natural hydrological instability intersects with human settlement patterns.
The Shijiahe collapse aligns with the most intense and persistent part of the instability. Their rise and early development occur during the dry and moderate phases of the sequence. Their disappearance follows the two major wet intervals. After these wet spans the cultural landscape changes. Populations do not return to the central plains. Later groups occupy new areas under different hydrological conditions. The plains themselves take on different roles as river and lake levels recalibrate.
Across the thousand year record the Middle Yangtze region moves repeatedly between drought, moderate rainfall and flood conditions. Each phase leaves a clear imprint in both the stalagmite and the archaeological remains. The sequence begins with water scarce years that encourage crop diversification. It ends with water saturated decades that permanently inundate the plains. The combined evidence indicates that the Shijiahe were exposed to a long series of hydrological shifts that culminated in conditions that made their core territory uninhabitable. The thousand year span of environmental change defines the context in which their civilisation expanded, adapted and eventually dissolved.
Source:
Liao, J., Day, C. C., Hu, C., Liu, Y., & Henderson, G. M. (2026).
Precise chronology of hydrological changes at ∼4.2 kyr in Central China to assess the impact of flooding on Neolithic societies.
National Science Review, 13, nwaf567.
https://doi.org/10.1093/nsr/nwaf567
