A late Quaternary record of environmental change and human impact from NewCaledonia

A late Quaternary vegetation record is presented from a lowland site on the leeward southwest coast of New Caledonia. Plum Swamp is a backswamp on the Plum River at around 10 m a.s.l., just within the ultramafic terrain that dominates the southern third of New Caledonia. Pollen analysis, charcoal an alysis, radiocarbon dating and stratigraphic analysis are employed to recon struct the vegetation and sedimentary history of the valley. The vegetation record commences at around 20,000 yr BP and shows that from this time up u ntil the late Holocene the valley was forested. The greater representation of taxa more prevalent at higher altitudes during the late glacial suggests a response to cooling and an enrichment of the lowland forest with more mo ntane elements. The late glacial transition between 14,000 and 9000 yr BP i s a period of instability within the valley when vegetation is disturbed by fire. Forest recovers after this and there is increasing stability until t he arrival of people in the late Holocene at around 3000 yr BP. The initial colonisers of New Caledonia had a profound effect upon the vegetation of t he valley, converting the lowland forest to a stunted and species poor maqu is on the ultramafic sediments and Melaleuca woodland on the non-ultramafic substrates. However, sedimentary processes are relatively unchanged during this time. Dramatic geomorphic change does occur in the catchment though, during the latter part of the 20th Century as a consequence of mining. (C) 2001 Elsevier Science B.V. All rights reserved.