Enclosed basins (glacial and nonglacia) of Tasmania contain the most comprehensive record in Australia of trends in a regional vegetation and climate since the late Pleistocene. Seven pollen sequences, each continuous and extending back at least 10,000 years, are used to reconstruct the history of postglacial vegetation and climate in Southern Tasmania (42°S–43°30′S). Interpretations are supported by a study of the modern pollen rain. Postglacial climates in Tasmania were characterized by a strong west-to-east decrease in precipitation. During the late Pleistocene, climates were markedly colder and drier than at present, and the vegetation was largely devoid of trees. A major rise in temperature between ca. 11,500 and 9500 yr B.P., accompanied by rising effective precipitation, resulted in the expansion of Eucalyptus, then other trees, across Tasmania. This warming trend may have been temporarily reversed during the early postglacial. Dry climates delayed the development of forest in inland eastern Tasmania until after ca. 9500 yr B.P. There is no evidence for a major change in climate since this temperature rise. Two broad phases of development have occurred within the postglacial forests. The first was an early Holocene phase during which Nothofagus cunninghamii cool temperate rain forest developed in western Tasmania and on the slopes of mountains in central and southeastern Tasmania. Eucalyptus sclerophyll forests developed in eastern Tasmania and have remained dominant there since. By ca. 7800 yr B.P. rain-forest communities were established beyond present-day limits. The second phase was a mid to late Holocene phase during which forests and alpine vegetation became more open in structure, leading to the re-expansion of Eucalyptus and shade-intolerant species. During the early to mid Holocene, climates in Southern Tasmania were wetter and (? then) warmer than at present. Maximum and minimum dates for this “optimum” are 8000 and 5000 yr B.P. Since then, climates have become increasingly rigorous, possibly through an increased incidence of inequable “weather types” leading to an increase in the frequency of drought and frost. Structural changes in the postglacial vegetation of Southern Tasmania closely parallel those at equivalent latitudes in New Zealand and Chilean South America, hence are likely to reflect the same primary cause.

Aim This paper documents reconstructions of the vegetation patterns in Australia, Southeast Asia and the Pacific (SEAPAC region) in the midHolocene and at the last glacial maximum (LGM).

To date, the only published comprehensive zonation for dating and correlating late Tertiary non-

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Australian sites that are claimed to preserve evidence of fossil spores and pollen for Late Neogene (Late Miocene, Pliocene) climates, mostly lack one or both of the prerequisites, i.e. accurate dating and continuous preservation of plant microfossils. Nevertheless, the available data confirm that climatic gradients closely parallelled those of the present day in direction although not in strength: broad-scale vegetation successions are ecologically consistent with long-term cooling and (middle to high latitudes) drying trends in global climate. Although it is rarely possible to establish precise meteorological values for the individual sites along these gradients, climatic envelopes can be estimated for many localities. For example, during the Late Miocene-Pliocene, mean annual precipitation along the northern margin appear to range from 600 mm to 1500 mm in the Kimberley region of north-western Western Australia to above 2000-3000 mm on the Atherton Tableland, north-eastern Queensland. If these and other estimates are correct, then environments along the northern margin show only gradual (unidirectional?) change or did not fall below biologically critical thresholds during the Late Miocene and Early Pliocene but began to approach modern values during Late Pliocene time. Whether the observation implies that meteorological controls at this time were similar to modern synoptic scale systems is unknown. Climates along the southern margin were more labile. For example, there is unequivocal evidence that Early Pliocene climates in the Bass Strait region were effectively more humid and warmer than at present, possibly resembling conditions now found on the northern New South Wales and southern Queensland coast. This phase was preceded (weak evidence) and succeeded (strong evidence) by less temperate conditions during the Late Miocene and Late Pliocene respectively. Forcing factors appear to include changes in relative sea level, orographic effects and, speculatively, remote events such as the isolation and reconnection of the Mediterranean Sea to the world ocean. One promising direction for future research is provided by a recently located onshore basin in Western Australia which preserves an extraordinarily long (100 m), detailed sequence of Late Neogene palynofloras.