Alligator Rivers Region Research Articles

Codesigned Archaeological Research in the Alligator Rivers Region, Northern Territory, Australia

ABSTRACTIn much of the Western world, collaborative research undertaken by settler archaeologists readily lends itself, at least in part, to a continuation of the colonial project. Yet, against this backdrop, Australia's First Nations’ peoples continue to work with researchers and to drive systemic change in research practice. Community-engaged archaeology, defined here as codeveloped studies of ancestral places (following Schaepe et al. 2017), is directed to improving relationships between Indigenous peoples and archaeologists. Even so, the practice of archaeology with and for nonsettler communities remains underdeveloped with regard to institutional priorities and funding agency bureaucracies. Here, we (Mirarr Traditional Owners, Mirarr employees, and settler archaeologist researchers) reflect on these issues as part of our ongoing research on the ochres and bim (rock art) of the well-known Madjedbebe rockshelter in the Alligator Rivers region, Northern Territory, Australia.

Fishhooks, fishing spears, and weaving: The bone technology of Madjedbebe, Northern Australia

AbstractArcheological assemblages of osseous material culture are rare in the Australian context, especially in the north where environmental conditions are not usually conducive to organic preservation. Nevertheless, more than 230 bone artifacts were recovered from the site of Madjedbebe, located in the Mirarr clan estate of the Alligator Rivers region of the Northern Territory. Of these artifacts, 199 have been identified to tool type. Here, we present the analysis of this exceptional assemblage, including the recovery of one‐piece jabbing fishhooks, numerous fishing‐spear tips, fragments of weaving tools, and possible osseous elements originating from ornamental pieces. The size and diversity of the Madjedbebe osseous technology assemblage is unique in the north and provides new insights into the lives of Mirarr peoples over the past 7,000 years.

The first record of Caenis Stephens, 1835 in Australia (Ephemeroptera: Caenidae) with descriptions of two new species

Two species of Caenis with straight forceps with a terminal tuft of spines are described from northern Australia. Male imagoes and nymphs of C. hanleyi n. sp. are described from reared material from the Alligator Rivers Region in the Northern Territory and C. binda n. sp. is described only from male imagoes collected from streams in the Wet Tropics of Queensland. C. hanleyi differs from C. binda by the structure of the forceps with C. binda being longer and narrower with longer apical spines. These are the first records of the genus Caenis in Australia.

Controlling feral ruminants to reduce greenhouse gas emissions: a case study of buffalo in northern Australia

Context The bourgeoning carbon economy is creating novel ways to incentivise conservation management activities that have the co-benefits of reducing greenhouse gas (GHG) emissions and social inequality. Aim To estimate the monetary value of carbon credits that landowners could generate by reducing ecologically destructive feral populations of the Asian water buffalo (Bubalus bubalis) in northern Australia. Methods First, we estimated buffalo enteric emissions based on the population structure of feral buffalo in northern Australia, and discounted the reduction of fire emissions due to the consumption of grassy fuel by feral buffalo. We then predicted the change in buffalo population size across the South Alligator River region of Kakadu National Park under four buffalo management scenarios: (1) no buffalo control; (2) low-intensity buffalo control; (3) moderate-intensity buffalo control; and (4) high-intensity buffalo control. We quantified the reduction of GHG emissions under the three buffalo control scenarios, relative to the scenario of no buffalo control, while discounting the GHG emissions that directly result from buffalo control actions (e.g. helicopter emissions). Key results All three buffalo control scenarios substantially reduced the estimated GHG emissions that would otherwise have been produced. The low-intensity buffalo control scenario was predicted to abate 790 513 t CO2-e over the 20-year simulation, worth USD15 076 085 (or USD753 804 year−1). Our high-intensity buffalo control scenario had the greatest reduction in GHG emissions, with a total net abatement of 913 231 t CO2-e, worth USD17 176 437 (or USD858 822 year−1). Conclusions The potential value of carbon credits generated by controlling feral buffalo populations in northern Australian savannas far exceeds the management costs. Implications The management of feral ruminants could be incentivised by the generation of carbon credits. Such management could simultaneously avoid GHG emissions, generate income for landowners and offer significant ecological benefits.

The return of the kinga (saltwater crocodile): Population ‘bust then boom’ shapes shifting baselines in Indigenous biocultural knowledge in northern Australia

The saltwater crocodile (Crocodylus porosus) can be regarded as a cultural keystone species for many Indigenous societies around the world, including for many Aboriginal clans in northern Australia. Here the regional population of Crocodylus porosus suffered a decline, almost to extinction, with unregulated commercial hunting between the 1940s to the early 1970s. Following protected status, saltwater crocodile populations made a rapid recovery. This research documents the perceptions and experiences of this rapid (within living memory) ‘bust then boom’ saltwater crocodile population change, among a regional group of Indigenous Australians (comprising several clans) from the Alligator Rivers Region of western Arnhem Land and Kakadu National Park in the Northern Territory. Using semi-structured interviews, archival work and on-Country (place-based) learning, significant influences on the continuity of Aboriginal people's contemporary engagement with freshwater Country were identified. In particular, the loss of access to freshwater customary harvesting sites and to key harvested species, and as a driver of adaptive changes in harvesting methods and consumption preferences for saltwater crocodile meat and eggs. Importantly, the experiential losses from restricted access to waterbodies were found to have significant impact on opportunities for inter-generational knowledge transmission, according with more recent applications of the Shifting Baseline Syndrome to Indigenous Ecological Knowledge. Findings demonstrate the need for monitoring and management programs of cultural keystone species, like the saltwater crocodile, to include Indigenous-led biocultural knowledge programs as a means of supporting local and Indigenous Knowledge systems. This is particularly critical in cross-cultural, First Nations, and joint-management contexts.

Elevated Magnesium Concentrations Altered Freshwater Assemblage Structures in a Mesocosm Experiment.

Magnesium (Mg) is a mining-related contaminant in the Alligators Rivers Region of tropical northern Australia. A mesocosm experiment was used to assess Mg toxicity to aquatic freshwater assemblages. Twenty-five 2700-L tubs were arranged, stratified randomly, on the bed of Magela Creek, a seasonally flowing, sandy stream channel in the Alligator Rivers Region of northern Australia. The experiment comprised 5 replicates of 4 nominal Mg treatments, 2.5, 7.5, 23, and 68 mg L-1 , and a control. Phytoplankton biomass, and diatom, zooplankton, and macroinvertebrate assemblages present in the treatment tubs were sampled before and after Mg addition. A significant negative relationship between phytoplankton biomass and Mg was observed 4 wk after Mg addition as measured by chlorophyll a concentrations (r2 = 0.97, p = 0.01). This result was supported by reductions in some major phytoplankton groups in response to increasing Mg concentrations, in the same experiment and from independent field studies. There was a significant negative relationship between zooplankton assemblage similarity (to control) and Mg concentrations (r2 = 0.96, p = 0.002). Seven weeks after Mg addition, macroinvertebrate assemblages were dominated by 3 microcrustacean groups (Ostracoda, Cladocera, and Copepoda), each reaching maximum abundance at intermediate Mg concentrations (i.e., unimodal responses). The responses of phytoplankton and zooplankton were used to derive assemblage effect concentrations (Mg concentrations resulting in x% of the assemblage change [ECx]). Magnesium concentrations resulting in assemblage EC01 values were <3 mg L-1 . Together with candidate guideline values from other laboratory- and field-based lines of evidence, the mesocosm EC01 values were incorporated into a weight-of-evidence framework for a robust regulatory approach to environmental protection. Environ Toxicol Chem 2020;39:1973-1987. © 2020 Commonwealth of Australia. Published by Wiley Periodicals LLC on behalf of SETAC.

Human responses to the late Holocene freshwater transition on the northern coastal plains of the Alligator Rivers region in western Arnhem Land

Little is known about cultural change on the inlets of the northern subcoastal plains of the Alligator Rivers region during the transition period between sea-level highstand c.8,000 BP and the establishment of freshwater wetlands (c.2,000 BP to present). The research presented here begins to fill this gap by illustrating differences in Indigenous land-use at two sites only a few kilometres apart and both dating to c.1,000 years ago. Located on the lower reaches of the South Alligator River within what is now Kakadu National Park, the earth mound Myaranji 1 and the shell midden Djindibi 1 provide a snapshot of settlement and subsistence strategies practiced on the floodplains in the late Holocene. This paper presents the analyses of the cultural materials recovered from these two open sites, including those of invertebrate and vertebrate faunal remains, shell and stone artefacts, and pigment on artefacts. Interpretation of the data suggests that occupation was relatively short-lived. Differential representation of food resources indicates that each site was occupied in different seasons. Both local manufacture and regional connectivity are suggested by ochre use and stone artefact working. Evidence from other regional sites implies a subsequent focus for settlement to the south and east.

A review of revegetation at mine sites in the Alligator Rivers Region, Northern Territory, and the development of a state and transition model for ecological restoration at Ranger uranium mine

Abstract Society’s expectations for mining operations are that they are undertaken using the principles of sustainable development. Numerous mines have been ‘rehabilitated’ in past decades without clear closure criteria or regulatory oversight and are characterised by less than desirable environmental outcomes. These sites provide us with information and data (in some instances) to inform future mine site restoration efforts and the sustainable development of mining resources. However, this information and data are often contained in inaccessible grey literature or have been lost over time. We used records and data on revegetation efforts and outcomes at mine sites in and around the Alligator Rivers Region (ARR) of the Northern Territory, Australia, to demonstrate the extent and currency of rehabilitation knowledge. There have been 20 mines in the region since 1950 and we found that these sites are in various deviated ecological states and that data for these mines were generally unavailable or unable to be located. A number of studies have been conducted at the largest operation, Ranger uranium mine, and there is also information from Nabarlek and South Alligator River Valley mines. We furthered the understanding of the system using available information to develop a preliminary state and transition model for eucalypt-dominated ecosystems in the region. The identification of likely desired and undesired ecological states and management requirements developed in this model could be used to actively guide future restoration and research efforts, particularly at Ranger uranium mine. Based on the lessons learned from the mine sites in the ARR, we provide recommendations for monitoring revegetation in the future.

Application of 3D seismic in the delineation of U bearing structures at Ranger 3 Deeps

Energy Resources of Australia Ltd (ERA) own and operate the world class Ranger Uranium Mine located in the East Alligator Rivers Region of the Northern Territory. Over the past four years ERA has been undertaking extensive exploration in the area which in 2008 resulted in the discovery of a very significant uranium resource, called Ranger 3 Deeps (R3D), down-dip but separate from the existing Ranger #3 orebody. Evaluation drilling work highlighted the complex structural setting of the mineralisation and detailed pit mapping together with reinterpretation of historical data provided a new perspective on the importance of structural controls to the formation of the Ranger orebodies

Water hardness determines 226Ra uptake in the tropical freshwater mussel

Chemical data for freshwater mussels (Velesunio spp.) and water from 15 sampling sites in the Alligator Rivers Region and Rum Jungle uranium provinces in tropical Northern Australia were analysed to develop a predictive model of radium-226 (226Ra) bioaccumulation for variable water calcium (Ca) and magnesium (Mg) concentrations. Application of the model as a 226Ra screening approach for freshwater mussels in tropical waterbodies potentially impacted by operational or remediated uranium mine sites is discussed in relation to Mudginberri Billabong, located approximately 12 km downstream of Ranger uranium mine in the Alligator Rivers Region.

A Lift for Lichens.

The article discusses research which aims to physically relocate entire communities of lichens at the swamp forests of the Alligator River region in North Carolina. It references a study by James Lendemer et al, published in the October 2016 issue of "Biological Conservation." Topics covered include the biodiversity of lichens stretching from southern New Jersey through South Carolina and their study of the ways to transplant lichen communities from imperiled habitat.

Mangrove Response to Environmental Change in Kakadu National Park

The responses of mangroves to climate-related phenomena are difficult to decipher in many areas as human activities also influence changes in their extent and biophysical properties. In Kakadu National Park (KNP) in Australia's Northern Territory, human disturbance of mangroves is minimal and hence observed changes are more likely to indicate a natural environmental change, including that associated with climatic fluctuation. Using fine (<;2 m) resolution aerial photography, hyperspectral, and light detection and ranging data from 1991, 2002, and 2011, respectively, maps of mangroves were generated for four catchments in the Alligator Rivers Region, the Wildman, West, South and East Alligator Rivers, and Field Island. The net change in mangrove for all areas where data intersected were 1.29 km 2 , but redistributions approximating 18.5 km 2 occurred with both losses and gains toward the coast and inland intrusion along many smaller creeks. A close correspondence between the planimetric canopy cover (PCC; %) within 25-m cells, as determined from aerial sensor data, and Landsat-derived foliage projected cover (FPC) was observed. A FPC threshold of ≥30% (~50% PCC) best captured mangrove extent and was used to quantify annual changes in the area for all catchments and Field Island from 1987-2012 Landsat sensor data. Over the period of the time-series, fluctuations in extent above this threshold were observed with these corresponding to changes in sea level and, to a lesser extent, river discharge. The study concludes that changes in mangrove extent and cover in KNP are indicating a changing climate, as manifested by fluctuations (and a general) rise in sea level and changes in rainfall amounts. Such changes are anticipated to lead to alterations of the hydrological regime, with these further affecting mangroves and potentially impacting on the internationally important wetlands of KNP.

Radiocarbon age constraints for a Pleistocene–Holocene transition rock art style: The Northern Running Figures of the East Alligator River region, western Arnhem Land, Australia

In this article we present nine radiocarbon age determinations producing a minimum age and a minimum age range for a regionally distinct rock art style known as the Northern Running Figures from Red Lily Lagoon, western Arnhem Land Australia. These radiocarbon determinations provide age constraints for both Pleistocene and early Holocene rock art in western Arnhem Land. The radiocarbon age determinations are produced from extracting calcium oxalate contained within mineral crusts associated with the rock art. Significantly this study employs a novel separation technique, designed to effectively isolate the oxalate compounds from the mineral crust sample using chemical pre-treatment, and demonstrates significant time offsets between radiocarbon age determinations for the calcium oxalates and other carbon inclusions contained within mineral crusts.

Seasonal spatial dynamics of floodplain macrophyte and periphyton abundance in the Alligator Rivers region (Kakadu) of northern Australia

AbstractIsotope studies of freshwater aquatic habitats have shown that epiphytic algae in the form of periphyton provides much of the source material for the biomass of secondary aquatic producers. Consequently, methods that can quantify the seasonal abundance of periphyton are important spatial inputs for wetland management and conservation planning processes for tropical floodplains. In this study, estimation of the seasonal spatial variability in floodplain macrophyte and periphyton abundance was made for the floodplains of the Kakadu region in northern Australia. Statistical modelling, using remotely sensed information, was applied to predict the seasonal distributions of macrophyte structural types, which were then combined with the field measurements of periphyton biomass to produce seasonal distributions of floodplain periphyton biomass per unit area. The seasonal spatial distribution of periphyton was strongly influenced by the seasonal variation in macrophyte abundance. Vertical emergent macrophytes (mainly aquatic grasses), covering 70% of the floodplain in May, had the lowest periphyton abundance. Submerged macrophytes, covering 10–15% of the floodplains, had the greatest periphyton abundance. The submerged macrophytes occupied open water areas, mainly in the deeper backswamp areas on the edges of the floodplains, and these areas maintained high periphyton abundance into the dry season. This study provides explicit spatial representation of the seasonal dynamics of tropical floodplain macrophyte and periphyton abundance and presents an approach that can be applied to map ‘hotspots’ of floodplain periphyton abundance. Copyright © 2016 John Wiley &amp; Sons, Ltd.

A database of radionuclide activity and metal concentrations for the Alligator Rivers Region uranium province

This paper presents a database of radionuclide activity and metal concentrations for the Alligator Rivers Region (ARR) uranium province in the Australian wet-dry tropics. The database contains 5060 sample records and 57,473 concentration values. The data are for animal, plant, soil, sediment and water samples collected by the Environmental Research Institute of the Supervising Scientist (ERISS) as part of its statutory role to undertake research and monitoring into the impacts of uranium mining on the environment of the ARR. Concentration values are provided in the database for 11 radionuclides (227Ac, 40K, 210Pb, 210Po, 226Ra, 228Ra, 228Th, 230Th, 232Th, 234U, 238U) and 26 metals (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Rb, S, Sb, Se, Sr, Th, U, V, Zn). Potential uses of the database are discussed.

Influence of group II metals on Radium-226 concentration ratios in the native green plum (Buchanania obovata) from the Alligator Rivers Region, Northern Territory, Australia

In this study, uptake of Ra from soil, and the influence of group II metals on Ra uptake, into the stones and edible flesh of the fruit of the wild green plum, Buchanania obovata, was investigated. Selective extraction of the exchangeable fraction of the soil samples was undertaken but was not shown to more reliably predict Ra uptake than total soil Ra activity concentration. Comparison of the group II metal to Ca ratios (i.e. Sr/Ca, Ba/Ca, Ra/Ca) in the flesh with exchangeable Ca shows that Ca outcompetes group II metals for root uptake and that the uptake pathway discriminated against group II metals relative to ionic radius, with uptake of Ca > Sr > Ba >> Ra. Flesh and stone analysis showed that movement of group II metals to these components of the plant, after root uptake, was strongly related. This supports the hypothesis that Sr, Ba and Ra are being taken up as analogue elements, and follow the same uptake and translocation pathways, with Ca. Comparison with previously reported data from a native passion fruit supports the use of total soil CRs on natural, undisturbed sites. As exchangeable CRs for Ra reach a saturation value it may be possible to make more precise predictions using selective extraction techniques for contaminated or disturbed sites.

Floodplain inundation and vegetation dynamics in the Alligator Rivers region (Kakadu) of northern Australia assessed using optical and radar remote sensing

The Alligator Rivers region is located in the wet–dry tropics along the coastal zone of northern Australia and contains Kakadu National Park, which is recognized under the Ramsar Convention on Wetlands and is a World Heritage listed site. Multiple anthropogenic stressors increasingly affect the floodplains of this region, and baseline information on floodplain inundation dynamics is necessary to manage these threats and develop adaption strategies for sea level rise. This study uses classification tree modeling to combine microwave (ALOS L-band Synthetic Aperture Radar) and optical (Landsat Thematic Mapper, TM 5) satellite data with field-sampled aquatic vegetation and depth logger data to predict the seasonal and inter-annual dynamics of aquatic plant cover and extent of inundation in the region. The USGS Landsat TM 5 image archive was sampled between 1985 and 2011 using three seasonal samples per year to create a comprehensive long-term time series of seasonal and inter-annual floodplain inundation extents. Classification accuracy for the inundation mapping was estimated at 86% based on seasonal depth logger data. The mean extent of inundation at the end of the wet season (March/April) was 1784km2 (range 2283–1309km2), receding on average to approximately 25% of its extent by August/September. Seasonal inundation patterns exhibit an exponential recession of inundation into ‘backswamp’ areas on the fringes of the floodplains with hydro-periods on the order of 5months. The findings of this work significantly improve our understanding of dynamics in this environmentally and culturally unique area and provide a basis for application in other seasonally flooded environments.

Radium concentration factors in passionfruit (Passiflora foetida) from the Alligator Rivers Region, Northern Territory, Australia

In this study, uptake of Ra from soil into the edible fruit of the wild passionfruit species Passiflora foetida was investigated, using selective extraction from the soil samples. A wide range of environmental exposure conditions were represented by the locations that were sampled, including both natural soils, and soils influenced by past and present uranium mining activities. The bioavailable 226Ra fraction in soils was found to be a better predictor of 226Ra fruit activity concentrations than the total soil activity concentration, or any of the other fractions studied. Concentration Factors (CFs) derived using the bioavailable fraction varied by only a factor of 7 between different locations, whereas CFs derived using other fractions and total soil varied by up to two orders of magnitude. CFs were highest for those soils containing the lowest concentrations of Mg, Ca and Ba, and approached a saturation value at higher soil concentrations. This finding suggests that group II elements influence radium uptake, most likely the result of increased pressure on the plant to take up essential nutrient group II elements from soil with the lower concentrations, with Ra being taken up as an analogue element. It is also possible that at higher concentrations of bioavailable Ca and Mg in the soil, these ions will outcompete Ra for adsorption sites in the soil and/or on the root surfaces. The study also shows that 228Ra can potentially be a significant contributor to ingestion doses and should also be considered when assessing committed effective doses from the ingestion of fruits.

Stable lead isotope ratios and metals in freshwater mussels from a uranium mining environment in Australia’s wet-dry tropics

Abstract Concentrations of Fe, Mn, Cu, Zn, U and Pb, and stable Pb isotopes 206Pb, 207Pb and 208Pb were measured via inductively coupled plasma mass spectrometry in sediments, water and freshwater mussels (Velesunio angasi) from two catchments in the Alligator Rivers Region, Australia. Sediment U and Pb concentrations were higher in Magela Creek downstream than upstream of the Ranger U mine due to the mineralised nature of the catchment and potential local input of sediment from the mine site. Water metal concentrations were highest in Georgetown Creek, which is a tributary of Magela Creek and part drains the Ranger mine site, but there was little difference in concentrations between the Magela Creek upstream and downstream sites. Metal concentrations in mussels collected immediately upstream and downstream of the mine site also showed little difference, whereas Pb isotope ratios displayed a very distinct pattern. The 206Pb/207Pb and 208Pb/207Pb isotope ratios were more uranogenic downstream than upstream of the site and also more uranogenic than ratios measured in Sandy Billabong, a reference billabong in a catchment not influenced by U mineralisation. Isotope ratios were also more uranogenic in younger mussels, potentially due to the increasing footprint of the mine site over the past decade. The most uranogenic ratios were found in mussels from Georgetown Creek and at a site approximately 2 km downstream. At Mudginberri Billabong, approximately 12 km downstream of the Ranger mine, the relative contribution of uranogenic Pb to the total Pb concentration in mussels was small and overwhelmed by the input of industrial Pb with a Broken Hill type Pb signature. Whereas metal uptake by and thus concentrations in mussel flesh are influenced by water chemistry, mussel condition and metabolic rates, Pb isotope ratios are independent of these factors and provide a powerful means of source apportionment of contaminants in mussels and waterways, in particular in an U mining environment.

Water Quality, Water Management and the Ranger Uranium Project: Guidelines, Trends and Issues

This paper explores the regulation of water quality protection downstream from the Ranger Uranium Project in the Alligator Rivers Region, an area of high conservation value which is both World Heritage- and Ramsar-listed. Available historical monitoring data for surface water quality in Magela Creek downstream of Ranger have been compiled and analysed with respect to hydrologic data and the Australian and New Zealand Environment and Conservation Council–Agricultural and Resource Management Council of Australia and New Zealand (ANZECC–ARMCANZ) regulatory guidelines, introduced in late 2000. The paper focuses on the underlying scientific basis for the current approach and examines the complex inter-relationships of minesite water management, hydrology, climate, monitoring design, implementation and interpretation which are used to differentiate between natural variability and potential mine-derived solutes. The research found that the application of the ANZECC–ARMCANZ guidelines has clearly improved the regulation of water quality protection downstream from the Ranger Uranium Project. The scientific basis is more coherent than the previous regulatory regime; however, for U (a key parameter of indigenous Mirarr-Gundjeihmi and public concern), higher downstream concentrations are permitted than those observed through natural variability, leaving open the potential for an influence of mine-derived U loads while still being within regulatory limits. Another improvement that could be made to the current regulatory regime, to provide enhanced protection of the water quality in Magela Creek downstream of Ranger, would be to explicitly link the water quality monitoring regime with hydrologic flow conditions. The paper makes a valuable case study for the application of water quality guidelines, especially for controversial projects such as uranium mining surrounded by a World Heritage- and Ramsar-listed region on indigenous land—a context of clear relevance for many places around the world.