Scott Mooney

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.

Climate change frames debate over the extinction of megafauna in Sahul (Pleistocene Australia-New Guinea)

Around 88 large vertebrate taxa disappeared from Sahul sometime during the Pleistocene, with the majority of losses (54 taxa) clearly taking place within the last 400,000 years. The largest was the 2.8-ton browsing Diprotodon optatum, whereas the ∼100- to 130-kg marsupial lion, Thylacoleo carnifex, the world’s most specialized mammalian carnivore, and Varanus priscus, the largest lizard known, were formidable predators. Explanations for these extinctions have centered on climatic change or human activities. Here, we review the evidence and arguments for both. Human involvement in the disappearance of some species remains possible but unproven. Mounting evidence points to the loss of most species before the peopling of Sahul (circa 50–45 ka) and a significant role for climate change in the disappearance of the continent’s megafauna.

The Use of Mineral Magnetic Parameters to Characterize Archaeological Ochres

The application of several magnetic parameters to ochre samples has found that they can be used to characterize samples from known ochre quarries. This technique also allows the sourcing of ochre found in archaeological contexts and provides an alternative to geochemical methods of provenancing ochres. Simple magnetic parameters (susceptibility and isothermal remanence) are effective in discriminating between ochre sourced from various quarries, however, more sophisticated parameters are required to ascribe unknown samples to specific sources.

Implications of a 14 200 year contiguous fire record for understanding human—climate relationships at Goochs Swamp, New South Wales, Australia

This paper interprets macroscopic charcoal (>250 μm), humification and loss-on-ignition over the last ~14200 cal. BP from Goochs Swamp, located to the west of Sydney in the Greater Blue Mountains World Heritage Area. This study aimed to investigate relationships between humans, climate and fire through time, primarily by comparison of these palaeoenvironmental indices with archaeological evidence from the region. Climatic forcing can explain all periods of change in the history of fire at Goochs Swamp: fire activity was variable during the Lateglacial—Holocene transition, low during the relatively stable climate of the early Holocene, and high but variable after the onset of modern El Niño from the mid Holocene. Although the dominant control on fire in this environment during the Holocene appears to be climate, fluctuations in the late Holocene may reflect anthropogenic fire or human responses to climate change. The archaeological record of the Blue Mountains and other parts of the Sydney Basin illustrates that Aboriginal people altered subsistence, resource and land-use patterns in the late Holocene. We propose that these cultural measures were adopted to overcome new risks as the frequency of ENSO events increased, and the natural fire regime and resource reliability changed. These strategies perhaps included a more systematic use of fire. The most parsimonious interpretation of the evidence for changes in fire activity at Goochs Swamp in the light of nearby archaeological evidence is that Aboriginal people used fire within a changing climatic framework.

The fire, human and climate nexus in the Sydney Basin, Eastern Australia

It is widely believed that Australian Aborigines utilized fire to manage many landscapes; however, to what extent this use of fire impacted on Australias ecosystems remains uncertain. The late Pleistocene/ Holocene fire history from three sites within the Sydney Basin (Gooches Swamp, Lake Baraba and Kings Waterhole) were compared with archaeological and palaeoclimatic data. The Gooches Swamp record appeared to be most influenced by climate and there was an abrupt increase in fire activity from the mid Holocene perhaps associated with the onset of modern El Niño-dominated conditions. The Kings Waterhole site also displayed an abrupt increase at this time, however there was a marked decrease in charcoal from ~3 ka. Similarly Lake Baraba displayed low levels of charcoal in the late Holocene. At both Kings Waterhole and Lake Baraba archaeological evidence suggests intensified human activity in the late Holocene during this period of lower and less variable charcoal. It is hence possible that Aboriginal people strongly influenced fire activity in some areas of the Sydney Basin during the late Holocene perhaps in response to the increased risk of large intense fires as an ENSO-dominated climate became more prevalent. The fire history within the Sydney Basin varies both temporally and spatially and therefore it is inappropriate to apply a single fire regime to the entire region for landscape management. This work also has implications for future fire incidence associated with climatic variability under an enhanced Greenhouse effect.

Natural hazards in Australia: extreme bushfire

Bushfires are one of the most frequent natural hazards experienced in Australia. Fires play an important role in shaping the landscape and its ecological dynamics, but may also have devastating effects that cause human injuries and fatalities, as well as broad-scale environmental damage. While there has been considerable effort to quantify changes in the occurrence of bushfire in Australia, a comprehensive assessment of the most extreme bushfire cases, which exact the greatest economic and environmental impacts, is lacking. In this paper we reflect upon recently developed understanding of bushfire dynamics to consider (i) historical changes in the occurrence of extreme bushfires, and (ii) the potential for increasing frequency in the future under climate change projections. The science of extreme bushfires is still a developing area, thus our conclusions about emerging patterns in their occurrence should be considered tentative. Nonetheless, historical information on noteworthy bushfire events suggests an increased occurrence in recent decades. Based on our best current understanding of how extreme bushfires develop, there is strong potential for them to increase in frequency in the future. As such there is a pressing need for a greater understanding of these powerful and often destructive phenomena.

The Response of Aboriginal Burning Practices to Population Levels and El Niño–Southern Oscillation Events during the mid- to late-Holocene: a case study from the Sydney Basin using charcoal and pollen analysis

Abstract Pollen and macroscopic charcoal have been analysed from a sedimentary sequence representing approximately 6100 years from a site within Wollemi National Park. This is located to the north-west of Sydney and forms a part of the Greater Blue Mountains World Heritage Area. The overall aim of the work was to examine the prehistoric interrelationships between vegetation, fire and human activity. There were relatively minor changes in the vegetation over the last ∼6000 years, perhaps reflecting the climate- and fire-resilient nature of the sclerophyllous vegetation found on Hawkesbury Sandstone throughout the Sydney Basin. Casuarinaceae declined in the late Holocene, a trend that has been detected in numerous palaeoecological studies throughout south-eastern Australia. This decline was unrelated to fire, which has been a persistent feature at the site over the entire analysed sequence. The fire regime at the site changed from 5.7 ka, which is interpreted as reflecting the onset of increased climatic variability associated with El Niño-Southern Oscillation (ENSO) events. Another dramatic change in the fire regime occurred at 3 ka, which was coeval with archaeological changes in the region. It is possible that the change in fire activity from 3 ka represented an alteration to Aboriginal management strategies associated with an increasing population and/or the increased risk of conflagrations in an ENSO-dominated climate.

A Comparison of Charcoal and Archaeological Information to Address the Influences on Holocene Fire Activity in the Sydney Basin

Abstract The influence of Aboriginal people on fire activity and hence the vegetation of Australia has long been debated. This study aimed to document the local fire activity of the Holocene in the catchment of a small freshwater reed swamp located in the Sydney Basin and to compare this with nearby archaeological evidence; including artefact discard rates and the number of base camps and activity locations used through time. This archaeological evidence was used as an index of human activity through time to assess anthropogenic influences on fire activity. Charcoal (>250 µm) was quantified in a radiocarbon-dated sediment core from Griffith Swamp covering ∼6000 calibrated years BP. A substantial increase in fire activity was found from ∼3000 years BP and a lesser increase approximately 700 years ago. The change in fire activity at ∼3000 years BP was approximately coeval with changes in archaeological evidence from Upper Mangrove Creek, suggesting either greater human presence in the landscape or altered subsistence and land-use strategies. Fire frequency in the catchment of Griffith Swamp peaked at about eight episodes per century, perhaps in response to environmental change that promoted both increased human activity and a higher natural fire frequency. This study provides an extended temporal perspective on fire and humans in this landscape, demonstrating how palaeoecology can provide practical information for the contemporary management of such fire-prone ecosystems.

A Comparison of the Environmental Changes of the Post-European Period with those of the Preceding 2000 Years at Lake Keilambete, South-western Victoria

Several parameters representing aspects of vegetation, fire, erosion and lacustrine productivity are investigated to compare the environmental changes of the historic period against those of the last 2000 years at Lake Keilambete in south-western Victoria. The average sedimentation rate post-dating European settlement was found to be c .2.5 times that of the analysed pre-European period and the nature of this sediment is distinctly different. Pollen representation was generally stable prior to the European period, but instability increased subsequently, reflecting the influence of pastoralism and the increase in exotic plant species. An increased concentration (and variability) of carbonised particles in the historic period, despite the faster rate of sedimentation, suggests a complex change in the fire regime of the region. The productivity of Lake Keilambete has varied in the past (e.g. it was elevated between c .1750 and 1250 years BP) but the response to European land use was diminutive. The expression of the quantified sedimentary parameters as average accumulation rates suggests a marked difference in the rate of landscape processes between the pre- and post-contact periods. The environmental change of the post-European period suggests that this landscape was particularly susceptible to the land-use strategies of the European settlers.

Rising waters: New geoarchaeological evidence of inundation and early agriculture from former settlement sites on the southern Yangtze Delta, China

New pollen, phytolith, charcoal and diatom data from 14C AMS-dated sediments from three clusters of former occupation sites on the southern Yangtze Delta – Liangzhu, Majiabang and Chuodun – reveal that hydrological conditions were a key factor influencing early food production on the southern Yangtze Delta. At least two episodes of inundation are recognized, the first occurring at c. 7200–5700 cal. yr BP and a second from c. 4700 cal. yr BP. The first involved increasing salinity of surface waters, likely associated with marine intrusion linked to post-glacial sea-level change (meltwater pulse (MWP) 2). The second appears to have been freshwater in nature and driven at least in part by extreme meteorological events of high levels of precipitation in combination with impeded drainage. These two episodes had profound impacts on Neolithic settlement and farming. Further hydrological changes, presumably linked to changes in sedimentary regime, geomorphology and drainage of the Taihu depression, recorded at the Chuodun site after c. 3000 cal. yr BP, appear to have had a major effect on technologically relatively advanced food production systems. While environmental pressures appear to have played an important role in shaping human activities and settlement on the southern Yangtze Delta, people responded by adopting strategies that included an increased reliance on food production, migration to more clement locations and implementation of new technologies, which possibly included the construction of flood defence works.