2000 years of lake-level fluctuations and human adaptation around China's largest freshwater lake

The human society is facing growing flood risks due to the rapidly-changing global climate. Understanding how early human coped with flooding will shed light on the increase of contemporary social resilience to projected intensified extreme climate change. However, assessment of such ancient human response to hydrological changes remains difficult due to the paucity of records for flood risk coupled with ancient human activities. Here, we present a two-millennium continuous reconstruction of water level changes for Poyang Lake, China's largest freshwater body, using microbial tetraethers extracted from a well-dated sedimentary core. The rising trend of lake water level over the past 2000 years indicates an increase in flood risks for this fertile region that has long been populated by ancient human settlements. A comparison with spatial-temporal distribution of ancient cities and towns in the lake basin reveals that, during the first millennium, human settlements passively retreated outwards and upwards away from the lake to minimize flood risk due to the rising lake water. However, a reversal pattern occurred at ∼1000 CE, witnessing human settlements to moving closer to lakeshore during the second millennium despite of the high water table. The strategic shift, accompanied by a booming economy in southern China during the Song Dynasty, was possibly facilitated by technology innovations, such as intensified water conservancy construction and enhanced shipbuilding, in and around the lake basin. Such an enhanced social resilience in responding to flood risks as early as 1000 years ago remains as a common practice today although the unprecedented scale of anthropogenic climate change in the near future may post additional and unexpected challenges.