Paleolimnology, 2007 vol. 40 no 1 pp. 3-31
Abstract: A 6.48 m sediment core sequence from
Erhai lake, Yunnan Province, provides a multi-proxy
record of Holocene environmental evolution and
human activity in southwest China. These sedimentary
records provide proxy time series for catchment
vegetation, flooding, soil erosion, sediment sources
and metal workings. They are complemented by
independent regional climate time-series from speleothems,
archaeological records of human habitation,
and a detailed documented environmental history.
The article attempts to integrate these data sources to
provide a Holocene scale record of environmental
change and human–environment interactions. These
interactions are analysed in order to identify the roles
of climate and social drivers on environmental
change, and the lessons that may be learned about
the future sustainability of the landscape. The main
conclusions are: lake sediment evidence for human
impacts from at least 7,500 cal year BP is supported
by a terrestrial record of cultural horizons that may
extend back to *9,000 cal year BP. A major shift in
the pollen assemblage, defined by detrended correspondence
analysis, at *4,800 cal year BP marks the
transition from a ‘nature-dominated’ to a ‘humandominated’
landscape. From 4,300 cal year BP, a
change in river discharge responses may signal the
beginning of hydraulic modification through drainage
and irrigation. Major increases in disturbed land taxa
and loss of forest taxa from 2,200 cal year BP
onward, also associated with the start of significant
topsoil erosion, register the expansion of agriculture
by Han peoples. It is also the start of silver smelting
linked to trade along the SW Silk Road with Dali
becoming a regional centre. Peak levels of disturbed
land taxa, topsoil and gully erosion are associated
with the rise and fall of the Nanzhao (CE 738–902)
and Dali (CE 937–1253) Kingdoms, and the documented
environmental crisis that occurred in the late
Ming and Qing dynasties (CE 1644–1911). The crisis
coincides with a stronger summer monsoon, but
exploitation of marginal agricultural land is the main
driver. These historical perspectives provide insight
into the resilience and sustainability of the modern
agricultural system. The largest threat comes from
high magnitude-low frequency flooding of lower dry
farmed terraces and irrigated valley plains. A sustainable
future depends on reducing the use of high
altitude and steep slopes for grazing and cultivation,
maintaining engineered flood defences and terraces,
and anticipating the behaviour of the summer
monsoon.