From around 150,000 to 130,000 years ago, Australasia experienced colder and more arid than present conditions. About 130,000 years ago, a warm phase began, and this lasted until about 115,000 years ago, with climates fairly similar to the present, or possibly somewhat moister. Subsequent cooling and drying of the climate led to a cold, arid maximum about 70,000 years ago, followed by a slight moderation of climate with a second aridity maximum around 22,000-13,000 14C years ago. Conditions then quickly became warmer and moister, and similar to the present.
Australasia present-potential vegetation
Australasia present-potential vegetation
This is much how the region would have looked before Europeans arrived. A semi-desert zone (light red/brown) dominates the central regions of Australia (this map should probably show more semi-desert in the south-centre; different published atlas map sources disagree markedly on the extent of semi-desert in Australia). Most of the rest of the continent is scrub (lightest green) and grassland (yellow). A fringe of open woodland (medium green) occurs closer to the coasts where the rainfall is highest. In the south-eastern coastal regions, dense temperate forest occurs (dark green). Small areas of tropical rainforest (dark green) also occur in the extreme northeast, and the more open monsoon forest (lavender colour) occurs in a broken-up belt close to the northern coasts.
New Guinea is mostly covered with tropical rainforest, except in the highlands where the cooler-climate montaine forest predominates, and on the southern peninsula where a dry climate gives woodland vegetation. New Zealand is mainly covered with temperate forest.
At three pollen-bearing sites in south-eastern Australia, the period after 30,000 years ago up until 10,000 14C y.a. is dominated by herbaceous vegetation, indicating that the present forest cover did not exist (Kershaw et al. 1990). However, at Ulugra Springs (also in SE Australia) the forest/tree vegetation was still present around 25,000 14C y.a. (Dodson & Wright 1989). In contrast with other sources of evidence, lake levels from the south-east of Australia were still generally higher than today at 28,000-25,000 14C y.a. (Harrison 1993).
For Tasmania, several pollen cores show that presently forested areas were reduced to cold-climate scrub and herbland, under conditions cooler than present but still quite moist (Colhoun et al. 1994).
In the northern-most peninsula of New Zealand, conditions seem to have been cooler but wetter than at present. Forest was still present at this stage (Newnham et al. 1993).
LGM-Late Glacial; 18,000-12,000 14C y.a. The Australian continent seems to have been much more arid than present up until about 12,000 14C years ago, with some early moistening suggested by a reduction in dust flux to the Tasman Sea around 14,000 14C y.a. (Bowler 1978). Mean annual temperatures also appear to have been at least several degrees cooler throughout the region. Dune activity seems to have been very widespread, indicating that most of the continent was occupied by extreme desert conditions (Bowler 1978). Pollen diagrams and lake levels also suggest greater aridity than at present (Harrison 1993), with arid and semi-arid vegetation more widespread and forest much more restricted in area than during the Holocene. The evidence for the LGM-Late Glacial is reviewed more extensively in the main QEN review text. Here, the LGM vegetation reconstruction for northern Australia, north of 20S, is derived from maps in the doctoral thesis of W.A. Van der Kaars (University of Amsterdam, 1990), and from maps of G. Hope (pers. comm. 1990). For Australia south of 20S, the maps are derived from those of G. Hope and also from J. Dodson (March 1990), a map published by Dodson et al. (1988), and a map for the whole of Australia published in Markgraf et al. (1992).
Australasia during the Last Glacial Maximum and Late Glacial - 18,000-12,000 14C ya
(ERRATUM; The LGM line map above here shows the numbering code for montane forest in the highlands of New Guinea. In fact, it should be montane tundra and grassland).
Australasia Glacial Maximum vegetation
Aridity caused a large area of extreme desert with drifting sand dunes to appear in central Australia. The temperate forests of the south-east were also eliminated, their place being taken by scrub (light green), woodland (darker green) and semi-desert (light red). A land bridge connected Australia and New Guinea; this was apparently covered in open grasslands (yellow) or scrub. In New Guinea, some rainforest (dark green) seems to have survived, though reduced in area. In New Zealand, forest was almost eliminated and its place taken by scrub and grasslands.
12,000 to 10,000 14C y.a. to present. Pollen, dune and lake level evidence generally suggest a moistening in climate around 12,000 14C y.a. In Tasmania, pollen cores suggest that forest had returned by about 12,000 14C y.a. (Colhoun et al. 1994). However, the recovery in woody vegetation cover in many areas may have lagged behind climate, with forests in both the north-east (Harrison 1993) and the south-east (Dodson & Wright 1989, Kershaw et al. 1991) of Australia taking until about 10,000 14C y.a. to return fully. In the tropical rainforests in the north, there may have been a lag of several thousand years in some areas, and possibly continuing up to the present, due to time taken for the rainforest to encroach on periodically burnt savannas and woodlands (Hopkins et al. 1996). The Younger Dryas cold and arid event which affected so many other parts of the world may also have affected parts of the Australasian region; there was a substantial ice advance in the New Zealand Alps, around half-way to the previous LGM state (Denton & Hendy 1994, Anderson 1997).
A slight temporary cooling and/or increase in aridity may have occurred in New Zealand at around 2,600 14C y.a. (2,600 y.a.) (van Geel et al. 1996).
Australasia after the onset of interglacial conditions - since 10,000 14C ya
Australasia 10,000 14C ya to present-potential vegetation