Mining is an environmentally destructive human activity. Consequently, community expectations and legislation require minimisation of impacts and rehabilitation once mining ceases. Rehabilitation standards now include restoration of structural and functional attributes of pre-disturbed landscapes. However, insufficient baseline data before, and during, mining often makes it difficult to assess impacts and develop rehabilitation objectives. Techniques that retrospectively document the pre-impact condition and environmental history of wetlands affected by mines can provide this information. We demonstrate how this can be achieved using data from palaeoecology and remote sensing, to understand mine impact on Fishermans Wetland, North Stradbroke Island (Minjerribah), by inferring its environmental history from formation to present. Fishermans Wetland is a small, clear, open water, wetland with extensive macrophyte growth. A lack of information about the wetland's pre-mine condition created uncertainty about the effects of upstream sand mining. Contrary to local community concerns that Fishermans Wetland was ancient and hydrologically modified by mining, it only formed in the 1950s. Moreover, changes to site hydrology predated mining. Consequently, ongoing supplementation of water is unnecessary for maintaining the wetland's ecological character. Similar techniques could be used elsewhere where mine impacts are poorly understood or contested.

More than half of the world's rivers dry up periodically, but our understanding of the biological communities in dry riverbeds remains limited. Specifically, the roles of dispersal, environmental filtering and biotic interactions in driving biodiversity in dry rivers are poorly understood. Here, we conduct a large-scale coordinated survey of patterns and drivers of biodiversity in dry riverbeds. We focus on eight major taxa, including microorganisms, invertebrates and plants: Algae, Archaea, Bacteria, Fungi, Protozoa, Arthropods, Nematodes and Streptophyta. We use environmental DNA metabarcoding to assess biodiversity in dry sediments collected over a 1-year period from 84 non-perennial rivers across 19 countries on four continents. Both direct factors, such as nutrient and carbon availability, and indirect factors such as climate influence the local biodiversity of most taxa. Limited resource availability and prolonged dry phases favor oligotrophic microbial taxa. Co-variation among taxa, particularly Bacteria, Fungi, Algae and Protozoa, explain more spatial variation in community composition than dispersal or environmental gradients. This finding suggests that biotic interactions or unmeasured ecological and evolutionary factors may strongly influence communities during dry phases, altering biodiversity responses to global changes.

In dryland areas, wetland refugia that provide permanent wetted habitats are important for the persistence of obligate aquatic species. Situated in Australia's arid and semiarid regions, Great Artesian Basin discharge springs contain high biodiversity and many endemic species and are believed to provide the only permanent wetted habitat. However, conflicting information indicates that hydroperiods in these springs can be variable. The aim of this study was to use palaeoenvironmental information to assess millennial-scale variability in one large spring wetland and provide an initial assessment on the long-term presence of wetted habitat. A sediment core was collected from Big Spring at Byarri (Edgbaston Station) in central Queensland, Australia, and the sedimentary layers were analysed using radiocarbon dating, geochemistry, and palynology. An age model developed on the radiocarbon dates indicated that changes in the rate of sediment deposition are likely associated with the last glacial maximum but with no disruption in the sediment accumulation, or therefore wetland development. Variable wetland and landscape conditions over similar to 43 000 years are supported by the geochemistry and palynological sedimentary records, including a change from a lacustrine to palustrine wetland and more recent changes, likely due to an anthropogenic presence in the landscape. The lack of a hiatus in available wetted habitat throughout the period of sediment development corroborates that Great Artesian Basin discharge springs represent a permanent wetted refugia in Australia's drylands.

Abstract Debate about the nature of climate and the magnitude of ecological change across Australia during the last glacial maximum (LGM; 26.5–19 ka) persists despite considerable research into the late Pleistocene. This is partly due to a lack of detailed paleoenvironmental records and reliable chronological frameworks. Geochemical and geochronological analyses of a 60 ka sedimentary record from Brown Lake, subtropical Queensland, are presented and considered in the context of climate-controlled environmental change. Optically stimulated luminescence dating of dune crests adjacent to prominent wetlands across North Stradbroke Island (Minjerribah) returned a mean age of 119.9 ± 10.6 ka; indicating relative dune stability soon after formation in Marine Isotope Stage 5. Synthesis of wetland sediment geochemistry across the island was used to identify dust accumulation and applied as an aridification proxy over the last glacial-interglacial cycle. A positive trend of dust deposition from ca. 50 ka was found with highest influx occurring leading into the LGM. Complexities of comparing sedimentary records and the need for robust age models are highlighted with local variation influencing the accumulation of exogenic material. An inter-site comparison suggests enhanced moisture stress regionally during the last glaciation and throughout the LGM, returning to a more positive moisture balance ca. 8 ka.

Quaternary Research is an international journal devoted to the advancement of the interdisciplinary understanding of the Quaternary Period.We aim to publish articles of broad interest with relevance to more than one discipline

Since their introduction in 1935, cane toads (Rhinella marina (Linnaeus, 1758)) have established and spread throughout north and north-eastern Australia. Cane toad impacts to terrestrial ecosystems are well documented, but impacts to aquatic ecosystems are less well known. We investigated the diet of cane toads collected from warm Great Artesian Basin-fed springs on Edgbaston Reserve in Central Queensland, Australia. A higher proportion of aquatic invertebrates to terrestrial invertebrates were found amongst their alimentary canal contents. Aquatic taxa consumed included molluscs (Gastropoda), insects (Coleoptera) and crustaceans (Amphipoda). Given this diet, the presence of cane toads at Edgbaston Springs, and the high endemicity of the aquatic biota of these springs, we conclude that R. marina present a threat to the conservation of desert spring ecosystems.

Ecosystem monitoring often fails to provide the right information to evaluate and guide environmental stewardship due to a lack of diagnostic capacity, long-term operational resources, explicit monitoring objectives and rigorous sampling designs. Our objective is to describe a monitoring framework that addresses these failures by including causative conceptual models and the concepts of adaptive monitoring and management. Resources are rarely available to monitor all ecosystem components, so identifying priorities is vital for the success of a monitoring program. An ecological risk assessment combining available information and expert opinion on threats and their consequences to the ecosystem can be used to prioritise monitoring and identify explicit objectives. A Pressure-Stressor-Response conceptual model forms the causative understanding of the ecosystem and the model components underpin the factors in the risk assessment. In this way, field sampling can validate the priority of ecosystem threats; provide information for refinement of conceptual understandings and guide efficient management activity. Repeated risk assessments using updated data and information can identify successful management and the increase and establishment of threats. Updated risk assessments can change threat priorities and therefore monitoring and assessment hypotheses and objectives can change. This ability to change underlies the concepts of adaptive monitoring and management.

1. Feral pigs (Sus scrofa) are widespread and cause significant damage to the ecological and cultural values of wetlands through their rooting, pugging, and wallowing behaviour. 2. The impacts of feral pigs on the epigeic (ground surface) invertebrates of exposed wetland sediments were investigated using 48 composite pitfall samples collected from 21 sites over three occasions in the Archer River catchment, north Queensland, Australia. Feral pig damage was quantified in transects along the margins of the wetlands. We tested the prediction that invertebrate assemblages would demonstrate reduced taxon richness and abundance, and altered assemblage composition, with an increasing intensity of pig damage. 3. Pig damage to exposed wetland sediments was a stressor to epigeic invertebrates in this environment, where there was a diverse invertebrate fauna. As expected, both taxon richness and abundance were significantly limited by pig damage, as was variability in multivariate assemblage composition. Thirty-one epigeic invertebrate taxa (66%) showed a decrease in their frequency of occurrence, mean abundance, or both, at sites with high levels of pig damage, relative to sites with low levels of pig damage. Certain families of spiders, beetles, snails, and freshwater crabs were among the taxa more prevalent when pig damage was low, whereas none of those taxa was more prevalent when pig damage was high. 4. There are biodiversity conservation ramifications from these results as pigs threaten elements of this fauna and thus wetland biodiversity, but the taxonomy, ecology, and distributions of epigeic invertebrates of exposed wetland sediments are poorly known. 5. The intensity of pig damage and the richness and abundance of epigeic invertebrates, as measured here, provide useful monitoring indicators to evaluate the effectiveness of pig control measures wherever pigs damage wetlands.

Hot springs are characterised by water temperatures above 36.7 °C. Temperature decreases with distance in flow away from spring vents; this natural gradient provides a unique opportunity to investigate the influence of water temperature on aquatic biota. This study investigated the relationship between water temperature and the aquatic invertebrates and benthic diatoms in outflows from a hot spring complex in tropical north Queensland, Australia. Water temperature ranged from 62.7 °C at the vents to 26.0 °C at the location furthest downstream. Richness of benthic diatoms and aquatic invertebrates increased linearly in response to decreasing temperature, with no species present in the hot vents. Multivariate analysis showed that both community assemblages had a response to the temperature gradient. A drop in aquatic invertebrate richness and a change in assemblage composition occurred between 40 °C and 42 °C, indicating a threshold at this temperature. The nearby Einasleigh River has experienced several contemporary peaks in water temperature over 40 °C, which corresponds to this threshold level. The relationships indicate that consistent increases in water temperature expected under climate change could decrease biological richness and precipitate changes in the aquatic invertebrate and benthic diatom taxa of tropical aquatic ecosystems.

River health assessment and the science to support it have evolved and expanded over recent decades so that it is now a common component of water resource management throughout the world. The broad-scale application of such assessments began as audits of the current condition and trend (i.e., how condition changed over time) using general health indicators considered to be sensitive to a broad suite of anthropogenic stressors. These broad-scale audits provide an overall evaluation of the success of environmental management in protecting river health. However, water managers are increasingly interested in assessments that not only document health, but also go further by both diagnosing the causes of degradation and identifying the priorities for mitigation measures. We outline such an approach developed by the Queensland Government in Australia and provide a case study of its application. This approach identifies multiple stressors in river health within defined assessment regions, then quantifies both the likelihood of exposure to each and the impacts (consequences) to the ecosystem condition. This is done using cause-effect conceptual models that link human pressures to stressors and stressors to ecosystem responses. Specific regional information on the likelihood and consequence is derived from literature, interrogation of available data, and expert elicitation, along with associated estimates of confidence. Risk is calculated as the product of consequence and likelihood and used to rank stressors, with those posing high and moderate risks to the ecosystem condition selected for field measurement within resourcing constraints. Metrics of stressor intensity and relevant ecosystem responses are selected according to conceptual models and their operational efficacy, then applied to a spatially balanced statistical sampling design. The resulting assessments compare and combine results of the initial risk assessment with those from field samplings to give an overall picture of river health, and importantly along with the diagnosis of the stressors responsible for the degradation. Finally, recommendations are made for management priorities to restore river health or prevent further degradation. This approach has been successfully applied to many rivers in Queensland, Australia.

Invasive carp are widely reported to harm ecosystems. In Australia, carp are a serious pest and, consequently, investigations of biocontrol options are under way. Best practice biocontrol requires cost/risk:benefit evaluation. To assist this, the impacts of carp on aquatic ecosystems have been summarized. To aid the evaluation of benefits, general predictions were tested by comparing dryland river ecosystems with and without carp, and ecosystem responses to a gradient in local carp density. Expectations were that in the presence of carp, and with increasing density, there would be increasing turbidity, decreasing densities of macrophytes and macroinvertebrates, and associated changes in assemblage composition, resulting in decreasing native fish density. Not all expected responses were found, indicating that the general understanding of carp impact requires modification for dryland rivers. Notably, carp did not increase turbidity or reduce macroinvertebrate density or composition, probably because of key attributes of dryland rivers. In contrast, there were large impacts on native fish biomass, not from the mechanisms expected, but from food resource monopolization by carp. Macrophyte occurrence was reduced, but macrophytes are naturally rare in these rivers. It is likely that the extirpation of an endangered river snail resulted from carp predation. Impacts on native fish may be reversible by carp control, but reversal of impacts on the snail may require carp elimination and snail reintroduction. Modelling is necessary to predict the probability of beneficial versus undesirable outcomes from carp control, and complementary measures to control other stressors may be needed. Benefits of carp control on dryland river ecosystems are fewer than generally predicted. This reinforces the point that ecological understanding cannot always be transferred between diverse settings and highlights the need to understand system characteristics relevant to causal impact pathways when applying generic carp impact models to specific settings. This has global relevance to future carp control efforts.

Feral pigs damage the significant ecological and cultural values of tropical Australian wetlands. Control measures such as culling, baiting, and trapping can reduce overall pig populations, but do not eliminate the substantial physical damage to wetlands that can occur from just a few individuals. Exclusion fences have been adopted as a potential technique to prevent damage to selected wetlands. To test the effectiveness of exclusion fences we measured the physical damage caused by pigs to multiple wetlands in the Archer River catchment of tropical northern Australia. Wetlands were fenced using a typical cattle exclusion fence, a specific pig exclusion fence or had no fence. Initial analyses of these fence treatments showed no significant difference in the intensity of physical pig damage to exposed wetland sediments and fringing vegetation. However, several of the pig exclusion fences were found to have been compromised. Reanalysis indicated wetlands with functioning pig exclusion fences had no physical pig damage and this was significantly less damage than in all other treatments. In contrast, wetlands with compromised pig exclusion fences had damage that was statistically equivalent to sites without fences or with cattle exclusion fences, but in individual cases had the worst damage recorded in any of the treatments. Compromised pig exclusion fencing of wetlands can thus be worse than having no fencing at all. This suggests that the successful prevention of pig damage to wetlands by exclusion fences requires ongoing and effective fence monitoring and maintenance regimes.

Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico-chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%-98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events.

Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO 2 ) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO 2 . We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32‐fold to 66‐fold upon sediment rewetting. Structural equation modeling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use, and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO 2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2–0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting‐drying cycles on respiration and CO 2 emissions in stream networks.

Contemporary benthic diatom assemblages were examined from 52 riverine and palustrine wetlands on Cape York Peninsula, Australia, to determine their environmental sensitivities and develop inference models. Multivariate analyses identified strong relationships between nine environmental variables and the diatom assemblage composition, with the aim to select variables for developing models. Total alkalinity, bicarbonate concentration, pH, electrical conductivity (EC) and latitude were most consistently and strongly correlated with diatom composition. The river basins sampled generally have an east–west orientation, so latitude potentially represents biogeographic differences between basins. Comparison of diatom assemblages between river basins showed significant differences, but substantial overlap in species. Diatom-based transfer functions were developed for each environmental variable and tested using the relationships between measured values and values predicted by the transfer functions. These were significant, and had low root mean square errors. An independent validation dataset for EC was analysed and applied to the EC transfer function. Results showed good predictions, giving confidence in its relevance beyond the training dataset. These understandings and models of the environmental effects on diatom assemblages allow for their application to future monitoring programs and reconstruction of past water quality conditions using fossilised diatoms in layered aquatic sediments of Cape York.

Rivers and streams that dry up are found on every continent, and can form a large proportion of river networks. When rivers are dry, traditional indicators of river health - such as aquatic macroinvertebrates, fish or water quality - cannot be measured. Aquatic health indicators are widely used to assess wetted habitats, but currently no universally applicable indicators have been developed or applied to assess dry riverbed health. Dry riverbeds are often the 'typical' state of many intermittent rivers and streams; however, the ecological health of these habitats is rarely, if ever, assessed in monitoring programs. Resource managers have called for indicators of intermittent river health during the dry phase. The use of terrestrial invertebrate biota (e.g. ants, beetles, and spiders) as indicators in this study provides a novel solution to assessing rivers when they are dry. We developed a conceptual model of human-induced stressors (i.e. disturbance by livestock and feral mammals) on dry riverbed biota, which guided the selection of potential health indicators. Livestock and feral mammals are one of the most significant stressors on riverine ecosystems in Queensland, and impact riverbeds by altering the substrate through compaction, rooting and pugging. We trialled the use of metrics of terrestrial invertebrate assemblages as indicators of dry riverbed health in four Australian dryland catchments: Bulloo, Paroo, Warrego and Nebine. We used quantile regression and found that terrestrial invertebrate communities responded negatively (and significantly, p < 0.05) to a gradient of disturbance, defined by on-the-ground field measurements of livestock and feral mammal impacts. This response to stressors was predicted by the initial conceptual model. We conclude that terrestrial invertebrates in this study are suitable indicators of dry riverbed health, as they are impacted by disturbance from livestock and feral mammals. They can be used in the same way that indicators, such as aquatic macroinvertebrates, are traditionally used to assess river health. We also successfully combined indicators of wet and dry habitats to provide a holistic assessment of the health of intermittent river ecosystems incorporating all sections of the river network. We suggest that this approach should be adopted by other river health monitoring programs in rivers around the world.

Perennial rivers and streams make a disproportionate contribution to global carbon (C) cycling. However, the contribution of intermittent rivers and ephemeral streams (IRES), which sometimes cease to flow and can dry completely, is largely ignored although they represent over half the global river network. Substantial amounts of terrestrial plant litter (TPL) accumulate in dry riverbeds and, upon rewetting, this material can undergo rapid microbial processing. We present the results of a global research collaboration that collected and analysed TPL from 212 dry riverbeds across major environmental gradients and climate zones. We assessed litter decomposability by quantifying the litter carbon-to-nitrogen ratio and oxygen (O2) consumption in standardized assays and estimated the potential short-term CO2 emissions during rewetting events. Aridity, cover of riparian vegetation, channel width and dry-phase duration explained most variability in the quantity and decomposability of plant litter in IRES. Our estimates indicate that a single pulse of CO2 emission upon litter rewetting contributes up to 10% of the daily CO2 emission from perennial rivers and stream, particularly in temperate climates. This indicates that the contributions of IRES should be included in global C-cycling assessments. Rewetting of plant litter accumulated in dry riverbeds releases pulses of CO2, reveals a global analysis of intermittent rivers and ephemeral streams.

Protecting the ecological health of rivers relies on maintaining intact flows from source areas to downstream navigable waters (1). Yet the U.S. Environmental Protection Agency (EPA) intends to rescind legal protection of tributary rivers, streams, and wetlands that do not have year-round flows (temporary waterways) and whose surface waters contribute flow to permanent navigable waters (2). This decision would severely damage the condition and uses of many U.S. waters, both temporary and navigable.

In the version of this Article originally published, the affiliation for M. I. Arce was incorrect; it should have been: 5Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany. This has now been corrected in the online versions of the Article.

Spatial statistical stream-network models are useful for modelling physicochemical data, but to-date have not been fit to macroinvertebrate data. Spatial stream-network models were fit to three macroinvertebrate indices: percent pollution-tolerant taxa, taxa richness and the number of taxalacking out-of-network movement (in-stream dispersers). We explored patterns of spatial autocorrelation in the indices and found that the 1) relative strength of in-stream and Euclidean spatial autocorrelation varied between indices; 2) spatial models outperformed non-spatial models; and 3) the spatial-weighting scheme used to weight tributaries had a substantial impact on model performance for the in-stream dispersers; with weights based on percent stream slope, used as a surrogate for velocity because of its potential effect on dispersal and habitat heterogeneity, producing more accurate predictions than other spatial-weighting schemes. These results demonstrate the flexibility of the modelling approach and its ability to account for multi-scale patterns and processes within the aquatic and terrestrial landscape.