Evidence of a Holocene and continuing recent expansion of lowland rain forest in humid, tropical North Queensland

Abstract. The identification and radiocarbon dating of charcoal collected under tropical rain forest indicated that sclerophyll forests dominated by Eucalyptus occupied parts of the wet tropical lowlands in the Daintree region of North Queensland at least intermittently from 12,000 yr bp until very recently. The results extend the late Pleistocene expansion of pyrophytic, sclerophyll forests which occurred in the upland rain forests to a humid, megathermic coastal lowlands region. Unlike the early Holocene re-expansion of rain forests which occurred generally on the uplands, the sclerophyll forests in the lowland study area were present until at least 1400 yr bp. Changes in coastal geomorphology and coastline positions during the late Quaternary were examined in the study area by superimposing sea levels derived from published curves on sea-bed contours. The results indicate that a very rapid decrease in the extent of the coastal plain occurred during the late Pleistocene. Between 12,000 and 9000 yr bp, 26 km of the coastal plain was submerged and this would have inevitably resulted in concentrations of Aboriginal populations in the area of the present coastline. It is suggested that burning activities by Aborigines in the coastal lowlands were sufficient to reestablish sclerophyll forests during the latter part of the Holocene from approximately 4000 yr bp following a wanner and wetter period which would have been conducive to rain forest re-expansion. Although the evidence suggests that the most recent rain forest recolonization occurred in the study area more than 1000 years ago, the process is still continuing elsewhere in the wet tropical lowlands in North Queensland. The process of eucalypt forest replacement by rain forest may have accelerated since the arrival of Europeans and the concomitant decrease in Aboriginal management.