Geoffrey Hope

Late Quaternary climates of Australia and New Guinea

Abstract Between 60,000 and 40,000 B.P., northeastern Queensland, south New South Wales, and southeastern South Australia were drier than at present. From 40,000–30,000 B.P. a colder climate than at present is indicated from one New Guinea area. Dryness became even more accentuated in northeastern Queensland, whereas many lakes filled up in the southern mainland, probably because of increasing precipitation effectiveness there. Before the end of this period colder conditions than now were already giving rise to slope instability in the Snowy Mountains of New South Wales. The period of 25,000–15,000 B.P. saw the greatest lowering of the New Guinea treeline, reaching an extreme at 17,000 B.P. when glaciers also achieved their maximum extent. This was the time of extensive glaciation in Tasmania and small glaciers formed in the Snowy Mountains. Estimates of the lowering of mean annual temperature range from 6°–10°C. Northeastern Queensland experienced its driest Late Quaternary climate; lakes were contracting throughout the southern mainland and the final phase of substantial desert dune building took place before the period ended. In the Snowy Mountains ice retreat began before 20,000 B.P., as did the construction of clay dunes in the southern semi-arid belt, a process demanding higher temperatures. However, in New Guinea and Tasmania ice retreat and treeline rise did not begin till after 15,000 B.P. Temperatures rose rapidly and everywhere most of the ice had gone by 10,000 B.P., when some lakes filled up in southern Australia, implying an increase in absolute precipitation. In the last 10,000 years climate has been relatively stable although there are some indications that temperature and rainfall were marginally higher than now between 8000 and 5000 B.P. Since then, lake levels have oscillated; a brief, limited resumption of periglacial activity took place in the Snowy Mountains and there were small glacier advances in New Guinea.

History of vegetation and habitat change in the Austral-Asian region

Over 1000 marine and terrestrial pollen diagrams and Some hundreds of vertebrate faunal sequences have been studied in the Austral-Asian region bisected by the PEPII transect, from the Russian arctic extending south through east Asia, Indochina, southern Asia, insular Southeast Asia (Sunda), Melanesia, Australasia (Sahul) and the western south Pacific. The majority of these records are Holocene but sufficient data exist to allow the reconstruction of the changing biomes over at least the past 200,000 years. The PEPII transect is free of the effects of large northern ice caps yet exhibits vegetational change in glacial cycles of a similar scale to North America. Major processes that can be discerned are the response of tropical forests in both lowlands and uplands to glacial cycles, the expansion of humid vegetation at the Pleistocene-Holocene transition and the change in faunal and vegetational controls as humans occupy the region. There is evidence for major changes in the intensity of monsoon and El Nino-Southern oscillation variability both on glacial-interglacial and longer time scales with much of the region experiencing a long-term trend towards more variable and/or drier climatic conditions. Temperature variation is most marked in high latitudes and high altitudes with precipitation providing the major climate control in lower latitude, lowland areas. At least some boundary shifts may be the response of vegetation to changing CO2 levels in the atmosphere. Numerous questions of detail remain, however, and current resolution is too coarse to examine the degree of synchroneity of millennial scale change along the transect

Predictability of biomass burning in response to climate changes

Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo- fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming.

A long vegetation history from lowland Irian Jaya, Indonesia

Abstract This paper reports the pollen analysis of a 10 m core from a mire at 780 m altitude and 2°S latitude on ultrabasic soils on a northern coastal range of New Guinea. The area is almost undisturbed by humans and the record is believed to cover about 60,000 yr B.P. The results show that montane forest grew around the site continously through the Late Pleistocene with a distinct increases in higher-altitude taxa from 25,000 to 10,500 yr B.P., the time of glacial maxima elsewhere. The invasion of the site by lower-altitude forest, which commenced at 10,500 yr B.P., was reversed after a few hundred years, and was not finally completed until about 7000 yr B.P. The results show that vegetation in the region has been sensitive to climatic change, the Pleistocene ecology being consistent with a temperature change of about 3–4°C. Times of change agree with other tropical areas even though the site climate was probably affected by changing sea levels. However, the tropical forest demonstrates overall long-term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity. A distinctive record of fine charcoal occurs after 10,900 yr B.P. but not at any level prior to that time. This shows that the forest was continously fire free for a very long time. the charcoal is probably an indication of anthropogenic disturbance which may correlate with the spread of agricultural innovation in lowland New Guinea. An increase in secondary species after 7000 yr B.P. may be a result of minor anthropogenic activity or the result of warmer conditions and shorter tree life in the lower-altitude forests.

Climate change, biodiversity conservation, and the role of protected areas: An Australian perspective

Abstract The reality of human-forced rapid climate change presents an unprecedented challenge to the conservation of biodiversity in Australia. In this paper we consider the role of Australias current protected area network in mitigating biodiversity loss across the continent. We do this by first examining the evolutionary history of Australias extant fauna and flora and, specifically, the reasons why species have persisted through major changes in climate during repeated glacial cycles, and through the massive climatic changes that occurred during the Miocene and Pliocene climate change events. We then review the current major threats to Australian native species, including inappropriate fire regimes, feral mammalian predators and herbivores, invasive plants, and habitat loss, fragmentation and degradation by land use activities (especially commercial logging, water impoundment and diversion, agricultural expansion, and the intensification of pastoralism). We argue that these current threats are interfering with the natural responses to climate change that native species have relied upon in the past, thereby undermining their resilience in the face of current, human-forced climate change. We predict that the current approach to conservation planning based on accumulating small amounts of protected lands across the continent, using a set of arbitrary conservation ‘targets’, will not be effective in mitigating the impacts of human-forced climate change on Australias biodiversity. We argue that an Australia-wide conservation strategy is needed that incorporates a larger adaptation agenda- one that recognizes the importance of protecting and restoring those natural processes and responses that have enabled species to persist through past environmental change. The following key elements are a crucial component of an effective conservation plan: identifying and protecting important climate refugia (both ecological and evolutionary); conserving the large-scale migration and connectivity corridors that operate at continent scales (including regional networks of habitat patches and habitat ‘stepping stones’); maintaining viable populations of all extant species to maximize intra-species genetic diversity and thus options for local adaptation; reducing all current threatening processes at the landscape scale across the continent; and protecting and restoring key large scale ecological processes (especially hydro-ecology and ecological fire regimes). Finally, underpinning climatic adaptation responses must be a thorough understanding of the special role Australias extensive intact landscapes will play in the future protection of Australias native biodiversity.

Late Quaternary vegetation history

At every geographical scale and taxonomic level, the vegetation pattern of New Guinea presents problems, the solutions to which must have substantial historical components. Some of the processes involved doubtless began millions of years ago while some may be only a few centuries, perhaps decades, old. Ideally, explanations of the courses of vegetational change and the forces which have determined them should be based on substantial fossil records and related geological and archaeological phenomena. For the greater part of New Guinea and most of its geological history, however, information of these kinds is entirely lacking. Particularly for explanations of grosser patterns, therefore, recourse must be had to arguments from present day distributions beyond New Guinea, and notions about changing shapes and positions of land masses in the distant past.

Pleistocene occupation of New Guinea's highland and subalpine environments

Abstract New Guineas mountains provide an important case study for understanding early modern human environmental adaptability and early developments leading to agriculture. Evidence is presented showing that human colonization pre-dated 35ka (ka = thousands of uncalibrated radiocarbon years before present) and was accompanied by landscape modification using fire. Sorties into the subalpine zone may have occurred before the Late Glacial Maximum (LGM), and perhaps contributed to megafaunal extinction. Humans persisted in the intermontane valleys through the LGM and expanded rapidly into the subalpine on climatic warming, when burning and clearance may have retarded vegetation re-colonization. Plant food use dates from at least 31ka, confirming that some of New Guineas distinctive agricultural practices date to the earliest millennia of human presence.

Palaeoecology and prehistory in New Guinea

Marked differences in climate during the last 30,000 years are reflected in significant changes in vegetational distribution in New Guinea, with the treeline varying from 400–1200 m below the present level. There have been minor fluctuations in climate during the Holocene period and it is probable that rainfall increased in lowland areas following the flooding of the Arafura shelf. Savannah and grassland areas have been maintained over the last 12,000 years in some areas by burning, but more subtle changes produced by human activity still remain to be explored. At the height of the last glaciation, the grassland areas were more than ten times their present area, and the extensive forest-grassland area presented a potential resource for Pleistocene man. Several archaeological sites in highland areas give evidence of exploitation at various times back to 30,000 years B.P. Sites occupied toward the end of the Pleistocene age indicate that mid-montane forest was more attractive than the forest-alpine ecotone. There is now strong evidence for the appearance of agriculture in the highlands about 9000 years ago. About 6000 years ago taro appears to have been cultivated, associated with roughly contemporaneous introduction of the pig. As human exploitation of the land intensified, resources of the bush declined and the gap was filled by increased use of the domesticated economy, including intensification of pig husbandry. This, in turn, led to the pig becoming an item of currency exchange and to the development of the role of big-men in New Guinea society. The introduction of the sweet potato, a few hundred years ago, resulted in intensification of agriculture and extension of the cultivated areas and further development of pig husbandry. The islands and lowland areas present quite different environments to that of the highlands and no sites have been excavated in these areas so far of Pleistocene age. But the lower levels of Balof shelter and Kukuba Cave were occupied by people who did not make pottery. The latter probably was introduced by speakers of Austronesian languages, although pottery did not appear in Balof Shelter until about 2000 year B.P. Between 3500 and 2500 years B.P. a distinctive Lapita-ware pottery has been found in sites from Manus Island across into the central Pacific, but only a single Lapita sherd has been found on the New Guinea mainland. About 2500 years ago Lapita pottery disappeared at the time when a number of localized cultural groups were developing and evidence suggests a “Melanization” of the Lapita people. On the mainland New Guinea pottery sites date to only 2000 years ago and on the south coast the last 1200 years is characterized by long-distance trading. Study of skeletal remains from Nebira and Motupore, on the south coast, dated from 1000 and 300 B.P. has enabled estimates of life expectancy to be made and also shows the presence of anaemia, yaws and leprosy. The two populations also show a striking difference in incidence of dental disease.

The contribution of humans to past biomass burning in the tropics

Tropical ecosystems, particularly savannas, contribute substantially to global biomass burning which influences the composition of the atmosphere as well as the nature and stability of soils, hydrology and vegetation. The history of burning in the tropics is constructed mainly from the analysis of charcoal preserved in accumulated sediments and within soils derived from a range of tropical environments. There is evidence for burning from the mid Tertiary associated with the development of savannas and drier or more seasonal rainforest types under global drying. The trend towards increased burning appears to have accelerated in more recent geological times due to the activities of people. Some separation of human from natural burning has been possible from a comparison of past burning patterns in areas with different human histories, and particularly from rainforest which is unlikely to experience frequent fires in the absence of people. Although there is evidence that Homo erectus used fire as long ago as 1.5 my, it is not until the time of evolution of H. sapiens that any relationship between people and biomass burning can be demonstrated. The earliest proposed anthropogenic burning is from at least 40 ky and possibly up to 140 ky BP in Australia where the environment may have been extremely sensitive to impact from an additional ignition source. Dates for increased burning within the rainforests of New Guinea also extend back to about 40 ky. Further increases in tropical burning are recorded by sites in Central and South America from the early Holocene, presumably with the arrival of people, and in most parts of the tropical region from the mid Holocene with the development and spread of agriculture and with the colonization of oceanic islands. Charcoal peaks are frequently associated with times of climate change and it is likely that, regardless of the nature of future fire management strategies, biomass burning will continue to increase in the near future because of the predicted period of climate change.

Populating PEP II: the dispersal of humans and agriculture through Austral-Asia and Oceania

Abstract This paper examines the history of Homo erectus and Homo sapiens in the Austral-Asian region bisected by the PEP II (Pole–Equator–Pole) transect, from Siberian Russia, south through Asia, insular Southeast Asia, Australasia and Oceania. Current evidence is reviewed for the timing of the arrival of humans along PEP II, their subsequent expansion through the region and their concurrent development or acquisition of increasingly sophisticated technologies for resource exploitation. Particular emphasis is placed on assessing the role of environmental change in the observed trajectories of human dispersal and technological development. It is concluded that rapid environmental change events may have influenced at least some of these trajectories.