Landscape Burning Research Articles

Hadza Landscape Burning.

We present the first published ethnographic description of landscape burning by Hadza hunter-gatherers of northern Tanzania and identify environmental, social, and cultural influences on Hadza landscape burning, thereby broadening the ethnographic record of anthropogenic burning practices described for hunter-gatherer communities. We report interview data collected in 2022 and 2023, describing their practices and attitudes regarding the causes and consequences of burning. We provide context by comparing our observations with those recorded for hunting and gathering populations in Africa, Australia, and North America. Hadza landscape burning is generally a solitary and male-dominated activity, contrary to ethnographic accounts of Indigenous landscape burning from North America and Australia. The primary goals stated by Hadza for landscape burning were improved hunting, reduced hazards from dangerous animals, and to reduce the density of livestock. Firsthand observations suggest that landscape burning has decreased over the past 20 years, and this historical trend is supported by interviews. Satellite imagery also suggests an overall decrease in burning activity in the region from 2001 to 2022. Among the Hadza, landscape burning is a culturally influenced and strongly gender-biased activity that is rapidly disappearing. Because burning can radically transform landscapes, these practices often generate or amplify conflicts of interest between groups with different land use strategies. Hadza report serious social conflict with pastoralists over landscape burning, and our study suggests this tension has constrained the practice in the past two decades.

Seed dispersal by Martu peoples promotes the distribution of native plants in arid Australia

Commensal relationships between wild plants and their dispersers play a key ecological and evolutionary role in community structure and function. While non-human dispersers are often considered critical to plant recruitment, human dispersers have received much less attention, especially when it comes to non-domesticated plants. Australia, as a continent historically characterized by economies reliant on non-domesticated plants, is thus a key system for exploring the ecological role of people as seed dispersers in the absence of agriculture. Here, we utilize a controlled observation research design, employing ecological surveys and ethnographic observations to examine how seed dispersal and landscape burning by Martu Aboriginal people affects the distribution of three preferred plants and one (edible, but non-preferred) control species. Using an information theoretic approach, we find that the three preferred plants show evidence of human dispersal, with the strongest evidence supporting anthropogenic dispersal for the wild bush tomato, Solanum diversiflorum.

Wildfire smoke impacts lake ecosystems.

Wildfire activity is increasing globally. The resulting smoke plumes can travel hundreds to thousands of kilometers, reflecting or scattering sunlight and depositing particles within ecosystems. Several key physical, chemical, and biological processes in lakes are controlled by factors affected by smoke. The spatial and temporal scales of lake exposure to smoke are extensive and under-recognized. We introduce the concept of the lake smoke-day, or the number of days any given lake is exposed to smoke in any given fire season, and quantify the total lake smoke-day exposure in North America from 2019 to 2021. Because smoke can be transported at continental to intercontinental scales, even regions that may not typically experience direct burning of landscapes by wildfire are at risk of smoke exposure. We found that 99.3% of North America was covered by smoke, affecting a total of 1,333,687 lakes ≥10 ha. An incredible 98.9% of lakes experienced at least 10 smoke-days a year, with 89.6% of lakes receiving over 30 lake smoke-days, and lakes in some regions experiencing up to 4 months of cumulative smoke-days. Herein we review the mechanisms through which smoke and ash can affect lakes by altering the amount and spectral composition of incoming solar radiation and depositing carbon, nutrients, or toxic compounds that could alter chemical conditions and impact biota. We develop a conceptual framework that synthesizes known and theoretical impacts of smoke on lakes to guide future research. Finally, we identify emerging research priorities that can help us better understand how lakes will be affected by smoke as wildfire activity increases due to climate change and other anthropogenic activities.

Promoting Optimal Habitat Availability by Maintaining Fine-Grained Burn Mosaics: A Modelling Study in an Australian Semi-Arid Temperate Woodland

The pyrodiversity–biodiversity (P–B) hypothesis posits that spatiotemporally variable fire regimes increase wildlife habitat diversity, and that the fine-grained mosaics resulting from small patchy fires enhance biodiversity. This logic underpins the patch mosaic burning (PMB) paradigm and reinforces the benefits of Indigenous fire management, which tends to promote pyrodiversity. However, tests of the P–B hypothesis and PMB paradigm are few. One of the most comprehensive field evaluations—a snapshot study of pre-existing fire mosaics in south-east Australian semi-arid mallee eucalypt woodlands—found little support. To explore the longer-term effects of fire mosaic grain size on habitat availability and biodiversity, we combined published data from the mallee study with a simple fire simulation. We simulated 500 years of landscape burning under different fire sizes. In the resulting mosaics, we assessed the proportional mixture and patch configuration of successional habitat states, then summarised habitat availability through time using a composite index based on the published fire history responses of 22 vertebrate taxa from the mallee study. Small fires formed fine-grained mosaics with a stable habitat mixture and with habitat diversity occurring at fine scales. Large fires formed coarse-grained mosaics with the opposite properties. The fine-grained mosaics maintained optimal habitat availability for vertebrate diversity over 500 years, while the fluctuating habitat mixture in the coarse-grained mosaics was unlikely to maintain maximum vertebrate diversity. Broadly, our results support the P–B hypothesis and justify further field-testing and evaluation of PMB programs to manage both pyrodiversity and biodiversity in the mallee and other flammable landscapes.

Restoring landscape burning is compatible with conservation and livestock production in a southeast Australian grassland fragment

Abstract Lowland grassland fragments in southeast Australia are valued for both sheep grazing and conservation. Many fragments are now rarely burnt, despite being shaped by millennia of Aboriginal fire‐use. Restoring fire could potentially reduce fuels, control exotic plant species, promote native species and renew Aboriginal cultural burning. However, this requires understanding of how fire and large herbivores, both native and exotic, are coupled and influence vegetation. We implemented a single round of low‐intensity experimental burns in an area of remnant grassland and patchy eucalypt woodlands in Tasmania that is managed for conservation, albeit intermittently grazed by sheep, as well as by native and exotic wild herbivores. We compared herbivore activity between burnt and unburnt areas over 2 years using cameras and scat transects, and assessed how fire and herbivory influenced herbaceous biomass and the cover of broad vegetation classes with and without herbivore exclusion. Contrary to expectations, burnt areas did not disproportionately attract the main herbivores: domestic sheep, introduced deer and native wallabies. In the predominant grassy sward, grazing and fire both reduced herbaceous biomass but we found no support for our hypothesis that grazing reduces biomass more strongly after burning. This contrasts with isolated patches of Poa tussock grassland, where fire reduced biomass much more strongly than grazing, and grazing effects on biomass were more pronounced following burning. The cover of broad vegetation classes was little affected by burning, but excluding herbivores increased exotic grass cover in both burnt and unburnt plots. Practical implication. In degraded fragments of lowland native grassland, burning and grazing do not necessarily act as strongly synergistic disturbances. Grazing by sheep and wild herbivores can help to control exotic grasses and reduce herbaceous biomass, although burning is much more effective than grazing for reducing biomass of unpalatable Poa tussock grassland. Our results suggest that returning occasional low‐intensity fires to our study system, and other degraded grassland‐woodland fragments, can be compatible with livestock production and conservation goals, but this requires caution and adaptive management.

On the timing of megafaunal extinction and associated floristic consequences in Australia through the lens of functional palaeoecology

The timing and cause of megafaunal extinctions are an enduring focus of research interest and debate. Despite the developments in the analysis of coprophilous fungal spores (CFS), the proxy for reconstructing past megaherbivore changes, the environmental consequences of this fauna loss remain understudied. This is partly due to the general obscurity of such a signal in pollen records, as well as limitations in disentangling human and extinction ecological impact, and the lack of spatial information of megafauna changes in site-level sedimentary records. In Australia, the debate centres on the possibility that habitat loss through climate change, vegetation-fire change, human intervention, or a combination of these factors led to the extinction of some large animals during the Late Pleistocene. Pollen and plant isotope studies have also demonstrated that vegetation-fire responses following the Late Pleistocene megafaunal extinctions were characterized by increased vegetation density and fire activity due to reduced grazing/browsing pressure. Here, we use a well-dated marine sedimentary core record from the Murray Darling Basin in southern Australia and apply palynological and functional palaeoecological approaches to reconstruct the Late Pleistocene megafaunal abundance changes, the timing and potential cause of extinction across the basin and investigate if extinction was associated with any signal of trait-based vegetation changes. We infer megafaunal abundance changes from the abundance of CFS and compare this with climatic proxies from the same core. We then link modern observations of fruit, seed and fire response traits of plant genera within the basin to the fossil pollen record to reconstruct palaeo vegetation community traits and determine if extinction was associated with any changes in plant community trait composition. Closely-spaced 14C dates obtained from planktonic foraminifera and δ18O tie points place a major decline in CFS, and thus the timing of extinction, within the basin at ∼43.3 ka. While climate-driven environmental changes largely controlled megafaunal presence, human arrival and frequent landscape burning are considered the most likely primary cause of extinction or, at the very least, megafauna decline in the Murray Darling Basin. We also found that the proposed period of megafaunal decline was also accompanied and followed by a decline in the prevalence of plants with larger seeds and fruits that were likely to have been once dispersed by megaherbivores. Our study supports the idea of a human-driven megafaunal extinction in mainland Australia and that the extinction caused changes in vegetation due to reduced plant dispersal and herbivory. However, high fire activity primarily linked to these vegetation changes was not observed, as humans were already practicing landscape burning before the period of megafaunal extinction and likely continued to do so afterward.

Exploration of the Burning Question: A Long History of Fire in Eastern Australia with and without People

Ethnographic observations suggest that Indigenous peoples employed a distinct regime of frequent, low-intensity fires in the Australian landscape in the past. However, the timing of this behaviour and its ecological impact remain uncertain. Here, we present detailed analysis of charcoal, including a novel measure of fire severity using Fourier transform infrared (FTIR) spectroscopy, at a site in eastern Australia that spans the last two glacial/interglacial transitions between 135–104 ka and 18–0.5 ka BP (broadly equivalent to Marine Isotope Stage (MIS) 6-5 and 2-1, respectively). The accumulation of charcoal and vegetation composition was similar across both periods, correlating closely with Antarctic ice core records, and suggesting that climate is the main driver of fire regimes. Fire severity was lower over the past 18,000 years compared to the penultimate glacial/interglacial period and suggests increasing anthropogenic influence over the landscape during this time. Together with local archaeological records, our data therefore imply that Indigenous peoples have been undertaking cultural burning since the beginning of the Holocene, and potentially the end of the Last Glacial Maximum. We highlight the fact that this signal is not easily discernible in the other proxies examined, including widely used charcoal techniques, and propose that any anthropogenic signal will be subtle in the palaeo-environmental record. While early Indigenous people’s reasons for landscape burning were different from those today, our findings nonetheless suggest that the current land management directions are based on a substantive history and could result in a reduction in extreme fire events.

Особенности формирования и реализации пожароопасных обстановок в Урало-Каспийском регионе в аномально жаркие и засушливые годы

The results of the analysis of the relationship between meteorological indicators of fire hazard and the actual development of wildfires are presented. The relevance of the study is due to the need to form a reliable understanding of the prerequisites and trends in the development of fires against the background of changes in the regional climate, accompanied by an increase in its anomaly. The main methodological approach to solving the tasks was to identify the features of the occurrence and spread of wildfires in some abnormally hot and dry years observed in the Ural-Caspian region – 2010 and 2021. The data obtained, reflecting the degree of fire danger and the vastness of the spread of fires, were compared with the average long-term (2001-2021) indicators and with longer data series. The study revealed the features of the seasonal development of fires during the firehazardous periods of the years under consideration in the whole region and taking into account its natural-zonal heterogeneity. Despite the fact that the occurrence of fires in general is stochastic in nature, some data indicate a predominantly agricultural nature of fires. Abnormally hot and dry years were not significantly distinguished by the degree of burning of steppe and desert landscapes; the exception was the extensive spread of fires in the forest and forest-steppe lowlands of the Southern Urals in 2021. The absence of statistically significant relationships between the indicators is evidence that weather conditions, although they form fire hazard conditions, are not decisive for their implementation. The occurrence and spread of fires depend on a complex combination and interaction of many natural and anthropogenic factors. In this regard, we believe that the introduction of effective methods of environmental management can minimize the level of pyrogenic impacts on steppe ecosystems, reduce the threat of damage and ensure the safety of the population.

What Happened to Kangaroo Grass? Human Agents and Endemic Grassy Ecosystems in South-Western Australia

Early colonists encountered extensive grassed areas in south-western Australia. While important in colonial agriculture, they declined and are almost forgotten today. In this study, focused on the Goorbilyup (Blackwood River) catchment, their remnants were surveyed and their distribution related to historical commentary. We argue the grassy ecosystems in higher rainfall zones in this catchment were derived through landscape burning by Wadandi/Pibulmun, the Indigenous people of this part of the south-west, and that fire was used across all zones. Colonists drew upon this knowledge to manage these grassy ecosystems for fifty years before adopting more intensive agriculture. The extent of these grassy ecosystems is established and proposals for preserving the remnants are discussed.

Population collapse of a Gondwanan conifer follows the loss of Indigenous fire regimes in a northern Australian savanna

Colonialism has disrupted Indigenous socioecological systems around the globe, including those supported by intentional landscape burning. Because most disruptions happened centuries ago, our understanding of Indigenous fire management is largely inferential and open to debate. Here, we investigate the ecological consequences of the loss of traditional Aboriginal fire management on fire-exposed savannas on the Arnhem Plateau, northern Australia, using the fire-sensitive conifer Callitris intratropica as a bio-indicator. We contrast Kakadu National Park, where traditional Aboriginal fire management was severely disrupted during the early twentieth century following Aboriginal relocation to surrounding settlements, and an adjacent Aboriginal estate where traditional Aboriginal fire management endures. Since 2006, traditional Aboriginal fire management at this site has been overlaid by a program of broad-scale institutionalized burning in the early dry season, designed to reduce greenhouse emissions. Using remote sensing, field survey, and dendrochronology, we show that on the Aboriginal estate, C. intratropica populations depend on the creation of a shifting patch mosaic of long unburned areas necessary for the recruitment of C. intratropica. However, the imposition of broad-scale fire management is disrupting this population patch dynamic. In Kakadu, there have been extreme declines of C. intratropica associated with widespread fires since the mid twentieth century and consequent proliferation of grass fuels. Fire management in Kakadu since 2007, designed to increase the size and abundance of patches of unburned vegetation, has not been able to reverse the population collapse of C. intratropica. Our study demonstrates that colonial processes including relocation of Indigenous people and institutional fire management can have deleterious consequences that are nearly irreversible because of hysteresis in C. intratropica population dynamics.

Stakeholders' Perceptions of the Outcomes of Translocated Eland in Nyae Nyae Conservancy, Namibia

Translocation of wildlife species from one area to another is a conservation tool that contributes to the restoration of depleted populations, augments declining populations, or establishes of new populations. This paper documents one of the first studies examining in detail stakeholders' perceptions of the factors influencing the outcomes of translocations of wildlife into a community conservation area, using the case of eland (Taurotragus oryx) translocations into the Nyae Nyae Conservancy in Namibia. The translocations took place between 2000 and 2005 as part of the national community-based natural resource management programme and were monitored through annual waterpoint counts. These data on perceptions were collected through a household survey and focused group discussions involving community members and leaders and key informant interviews with external stakeholders. Community members' perceptions could not confirm that the translocated eland decreased or increased, however, reflected that eland individuals moved away from the release site soon after translocation to more distant locations further away from human settlements. The outcomes of the translocations were perceived to be most strongly associated with anthropogenic factors compared to habitat or environmental factors. However, stakeholders exhibited divergent perceptions regarding which of the anthropogenic factors was of most importance, particularly with respect to the roles of the different types of hunting, and to a lesser degree, the role of traditional burning of landscapes on translocation outcomes. The paper illustrates the complexities associated with translocations of wildlife into community conservation areas compared to state protected areas, given the strong influence of human disturbances on translocation success. It highlights the importance of understanding the social factors influencing how and why translocated individuals may adapt well or poorly to their new environment. Building this understanding is essential to improving the outcomes of similar translocations in the future.

Macropod Bone Apatite Isotopic Analysis as Evidence for Recent Environmental Change at Bandicoot Bay Pearling Camp, Barrow Island, Australia

Stable isotope analysis of bone apatite oxygen (δ18O) and carbon (δ13C) was undertaken for modern and archaeological spectacled hare wallaby (Lagorchestes conspicillatus) bone collected from an 1880s indentured labor confinement camp on Barrow Island in Western Australia. δ18O results and historical climate data indicate decreased annual precipitation during occupation of the site and provide insight into the conditions experienced by Aboriginal pearling laborers incarcerated on the offshore island. δ13C values may reflect variation in water availability or a short-term vegetation change resulting from landscape burning. This study is the first application of macropod bone apatite isotopic analysis in an Australian historical context and demonstrates its significant potential for identifying recent environmental changes to a high level of sensitivity.

Анализ горимости пойменных ландшафтов нижней Волги по данным информационных продуктов спутникового детектирования активного горения и выгоревших площадей

Landscape fires have significantly intensified in the last two decades. A lot of research is devoted to forest fires, while much less attention is paid to the analysis of the burning of non-forest lands. The floodplain landscapes of the arid zone, which include the Volga-Akhtuba floodplain with the Volga delta, are practically not covered by studies of the fire regime. The aim of the work is to establish the spatio-temporal regularities of the burning of the floodplain landscapes of the Volga in its lower reaches according to the detection of active burning and burnt areas based on Earth remote sensing technologies. The work used MCD14ML (FIRMS), MCD64A1, FireCCI51 and GABAM data for 2001–2020, the first three of which are based on MODIS data, the last one is based on Landsat data. Each of the products has both omissions and false definitions and artifacts. Nevertheless, a joint analysis of all the data makes it possible to obtain a fairly reliable assessment of the flammability. In total, during the study period, the total area of burned areas ranged from 2.9 million hectares to 4.8 million, according to estimates of different products. The average long-term flammability is 9.2 % of the study area. The maximum burning rate was noted in 2019 (15.4 %), and the minimum—in 2016 (2.8 %). These years are characterized by the shortest and longest duration of periods of maximum flood flow, respectively. The influence of the hydrological situation on the burning of floodplain landscapes is confirmed by the correlation analysis. A significant correlation between the fire rate and the flood level and its duration has been established. The higher the maximum flood level of the floodplain and the longer the water stays on the floodplain, the lower the flammability. This is especially pronounced in the Volga delta, where, due to the reduction in flood costs and the drop in the level of the Caspian Sea, the drying of floodplain landscapes is intensifying. This leads to the intensification of fires. In addition to the hydrological situation, the weather affects the flammability. At the same time, the main climatic factor is atmospheric moisture. The more rainfall, the less fire. The air temperature does not affect the size of the burnt area, since the temperatures remain quite high throughout the entire warm period. Trends in hydrological changes are aimed at reducing the water content of the flood, which will lead to the drying of the floodplain against the backdrop of a continuing drop in the level of the Caspian Sea. With the existing system of fire prevention, we should expect a further increase in the burning of landscapes.

Human arrival and landscape dynamics in the northern Bahamas

The first Caribbean settlers were Amerindians from South America. Great Abaco and Grand Bahama, the final islands colonized in the northernmost Bahamas, were inhabited by the Lucayans when Europeans arrived. The timing of Lucayan arrival in the northern Bahamas has been uncertain because direct archaeological evidence is limited. We document Lucayan arrival on Great Abaco Island through a detailed record of vegetation, fire, and landscape dynamics based on proxy data from Blackwood Sinkhole. From about 3,000 to 1,000 y ago, forests dominated by hardwoods and palms were resilient to the effects of hurricanes and cooling sea surface temperatures. The arrival of Lucayans by about 830 CE (2σ range: 720 to 920 CE) is demarcated by increased burning and followed by landscape disturbance and a time-transgressive shift from hardwoods and palms to the modern pine forest. Considering that Lucayan settlements in the southern Bahamian archipelago are dated to about 750 CE (2σ range: 600 to 900 CE), these results demonstrate that Lucayans spread rapidly through the archipelago in less than 100 y. Although precontact landscapes would have been influenced by storms and climatic trends, the most pronounced changes follow more directly from landscape burning and ecosystem shifts after Lucayan arrival. The pine forests of Abaco declined substantially between 1500 and 1670 CE, a period of increased regional hurricane activity, coupled with fires on an already human-impacted landscape. Any future intensification of hurricane activity in the tropical North Atlantic Ocean threatens the sustainability of modern pine forests in the northern Bahamas.

Population collapse and retreat to fire refugia of the Tasmanian endemic conifer Athrotaxis selaginoides following the transition from Aboriginal to European fire management.

Untangling the nuanced relationships between landscape, fire disturbance, human agency, and climate is key to understanding rapid population declines of fire-sensitive plant species. Using multiple lines of evidence across temporal and spatial scales (vegetation survey, stand structure analysis, dendrochronology, and fire history reconstruction), we document landscape-scale population collapse of the long-lived, endemic Tasmanian conifer Athrotaxis selaginoides in remote montane catchments in southern Tasmania. We contextualized the findings of this field-based study with a Tasmanian-wide geospatial analysis of fire-killed and unburned populations of the species. Population declines followed European colonization commencing in 1802ad that disrupted Aboriginal landscape burning. Prior to European colonization, fire events were infrequent but frequency sharply increased afterwards. Dendrochronological analysis revealed that reconstructed fire years were associated with abnormally warm/dry conditions, with below-average streamflow, and were strongly teleconnected to the Southern Annular Mode. The multiple fires that followed European colonization caused near total mortality of A. selaginoides and resulted in pronounced floristic, structural vegetation, and fuel load changes. Burned stands have very few regenerating A. selaginoides juveniles yet tree-establishment reconstruction of fire-killed adults exhibited persistent recruitment in the period prior to European colonization. Collectively, our findings indicate that this fire-sensitive Gondwanan conifer was able to persist with burning by Aboriginal Tasmanians, despite episodic widespread forest fires. By contrast, European burning led to the restriction of A. selaginoides to prime topographic fire refugia. Increasingly, frequent fires caused by regional dry and warming trends and increased ignitions by humans and lightning are breaching fire refugia; hence, the survival Tasmanian Gondwanan species demands sustained and targeted fire management.

How Australian Aborigines Shaped and Maintained Fire Regimes and the Biota

People proliferated across Australia, which was then a part of Sahul, from about 40 000 years ago when megafauna finally disappeared long before the Last Glacial Maximum. The so called ‘blitzkrieg’ hypothesis proposes that megafauna were extinguished by Aboriginal hunting. It is argued, either that there were some changes in vegetation and fire regimes as a consequence, or that fire regimes and vegetation were largely unaffected by human arrival. However, there is an alternative view that Aboriginal burning changed the vegetation so that megafauna had insufficient food resources to sustain them. We aimed to resolve this debate by examining the published palaeological and historical evidence. This evidence indicates that Aboriginal burning initially turned much biomass into charcoal, reducing browse, changing vegetation and causing megafaunal extinctions. It created ecosystems whose health and safety depend on constant human input of mild fire. Mild burning of these anthropogenic landscapes consumes relatively little biomass and produces relatively little charcoal. Although burning by people has typically been regarded as an ecological disturbance, the historical evidence, together with traditional Aboriginal knowledge, suggests that it is actually maintenance, essential to sustain our natural environment. We conclude that people can reinstate resilient, healthy and safe landscapes irrespective of climate change.

Sedimentary charcoal proxy records of fire in Alaskan tundra ecosystems

Extensive burning of Arctic tundra landscapes in recent years has contradicted the conventional view that fire is a rare, spatially limited disturbance in tundra. These fires have been identified as harbingers of climate change, despite our limited understanding of Arctic fire frequency and climatic controls. Much of this understanding relies upon sedimentary charcoal-based fire reconstructions, yet the controls on sedimentary charcoal abundance need to be rigorously tested in tundra ecoregions. We compile published charcoal-based tundra fire reconstructions in Alaska and compare them with historical, limnological, and spatial data to: (1) evaluate the spatial and temporal characteristics of tundra fires, (2) identify the primary controls of charcoal accumulation in lake sediments, (3) assess the accuracy of peak analysis in identifying local (<1 km) fire events, and (4) constrain charcoal source area. We find that tundra fires are spatially and/or temporally dichotomous in the historical (observational) period (1940–2015 CE), a characteristic which is mimicked by charcoal accumulation rates. We show that, despite methodological differences in published studies, analyses of charcoal peaks accurately identified local (<1 km) fire events in the historical period. Further, we find that lake properties (e.g. depth and surface area) have weak influences on charcoal accumulation in the tundra and that charcoal source areas in the Alaskan tundra are much broader than in forest and grassland ecosystems. We conclude that the unique nature of tundra fire regimes allows for the reliable use of total charcoal accumulation as a fire proxy.

Extinction in the Anthropocene.

Samuel Turvey and Jennifer Crees introduce the effects of humans on biodiversity.

45,610–52,160 years of site and landscape occupation at Nawarla Gabarnmang, Arnhem Land plateau (northern Australia)

We present Bayesian modelling on a long sequence of radiocarbon ages from the archaeological site of Nawarla Gabarnmang, central Arnhem Land plateau, northern Australia. A horizon of wind-borne sediments containing flaked stone artefacts and charcoal commencing >45,610 cal BP (the young end of the modelled boundary age range, which extends beyond the limit of the calibration curve), with a median modelled age of 48,500 cal BP, signals the onset of aeolian mobilisation of fine sands and silts across the landscape, and re-deposition within the site at a time synchronous with the first evidence of people. This earliest cultural horizon (Stratigraphic Unit 4) contains 509 stone artefacts, and is marked by a contemporaneous sedimentary break, from underlying culturally sterile sediments consisting of disintegrating roof-fall and in situ sandstone and quartzite to overlying culturally-rich wind-blown sand. The new radiocarbon ages and wind-blown sediments together provide evidence for the commencement of noticeable landscape burning on the Arnhem Land plateau c. 48,500 cal BP, suggesting an intensification of landscape management practices at the summit of the Arnhem Land plateau some 10,000–15,000 years after the lowest dense band of artefacts (Phase 2) at Madjedbebe on the floodplains 90 km to the north. These results have ramifications for the structure and timing of the spread of people across Australia, and the extinction of megafauna in Sahul.

A Holocene record of savanna vegetation dynamics in southern lowland Papua New Guinea

The southern lowlands of Papua New Guinea (PNG) are biogeographically distinct. Vast tracts of savanna vegetation occur there and yet most palaeoecological studies have focused on highlands and/or forest environments. Greater focus on long-term lowland environments provides a rare opportunity to understand and promote the significance of local and regional savannas, ultimately allowing non-forested and forested ecosystem dynamics to be compared. This paper examines palaeoecological and archaeological data from a lowland open savanna site situated on the south-central PNG coastline. The methods used incorporate pollen and micro-charcoal analyses, artefact recovery and sediment descriptions. We conclude with an environmental model of sedimentation and vegetation change for the past c. 5,800 years, revealing a mid to late Holocene savanna interchange between herbaceous and woody plant growth, with fluctuating fire occurrence increasing toward the present day. Increased silt deposition and modified regional hydrology are also recorded. Environmental changes correspond in timing with the start of permanent settlements and human use of fire. In particular, landscape burning for hunting and gardens for agriculture have helped create the open ecosystem still evident today.