Landscape sensitivity to rapid environmental change—a Quaternary perspective with examples from tropical areas

A millennial scale of ‘rapid’ change during the Quaternary is recorded in GRIP and GISP2 ice-core records, and is also found in tropical oceans. Rapid warming episodes followed by gradual cooling, associated with sub-Milankovich cycles implies an asymmetry in the behaviour of climate that is likely to be reflected in landscape responses. Slope failures, floods, colluvial/alluvial sedimentation may reflect short-term changes in the record, but reorganisation of slope and fluvial systems involves significant time lags or delays, often on a millennial scale, and requiring changes to the vegetation cover. While some records of sedimentation indicate major landscape instability during last 20 ky, or in the early Holocene, others indicate pulses of activity throughout the Last Glacial Cycle (LGC). These differences may reflect regional patterns of climate change, but also illustrate the importance of landscape sensitivity to our understanding of the impacts of rapid environmental change. Methodological problems arise in attempting correlations between site-specific records of sedimentation and integrated signals of hydrologic change found in deltaic and off-shore fans.