Search

The Sustainable Development Goals aim to improve access to resources and services, reduce environmental degradation, eradicate poverty and reduce inequality. However, the magnitude of the environmental burden that would arise from meeting the needs of the poorest is under debate—especially when compared to much larger burdens from the rich. We show that the ‘Great Acceleration’ of human impacts was characterized by a ‘Great Inequality’ in using and damaging the environment. We then operationalize ‘just access’ to minimum energy, water, food and infrastructure. We show that achieving just access in 2018, with existing inequalities, technologies and behaviours, would have produced 2–26% additional impacts on the Earth’s natural systems of climate, water, land and nutrients—thus further crossing planetary boundaries. These hypothetical impacts, caused by about a third of humanity, equalled those caused by the wealthiest 1–4%. Technological and behavioural changes thus far, while important, did not deliver just access within a stable Earth system. Achieving these goals therefore calls for a radical redistribution of resources.

Safe and just Earth System Boundaries (ESBs) for surface and groundwater (blue water) have been defined for sustainable water management in the Anthropocene. We evaluate where minimum human needs can be met within the surface water ESB and, where this is not possible, identify how much groundwater is required. 2.6 billion people live in catchments where groundwater is needed because they are already outside the surface water ESB or have insufficient surface water to meet human needs and the ESB. Approximately 1.4 billion people live in catchments where demand side transformations are required as they either exceed the surface water ESB or face a decline in groundwater recharge and cannot meet minimum needs within the ESB. A further 1.5 billion people live in catchments outside the ESB with insufficient surface water to meet needs, requiring both supply and demand-side transformations. These results highlight the challenges and opportunities of meeting even basic human access needs to water and protecting aquatic ecosystems.

Around 36,000 km3 of freshwater flows through rivers and estuarine ecosystems and enter the world’s coastal fishing regions every year. The flow of freshwater and sediments creates regional changes in coastal circulation, stimulates marine productivity and helps define the hydrologic properties of estuarine and oceanic waters. These processes can affect different life stages of marine species either directly, through variations in salinity and temperature, or indirectly, due to changes in the availability of food and habitat. This paper reviews the relationship between freshwater flowing through estuarine and coastal ecosystems, and the variable productivity associated with global marine capture fisheries. The results of a global synthesis revealed that 72% of species representing 77% of the total catch (43 million tonnes) were linked to river flows for at least some part of their life cycle. Insights into how the relationship between flow and fishery production varies globally indicates wild capture fisheries and freshwater resources would benefit from an integrated planning and management approach.

Living within planetary limits requires attention to justice as biophysical boundaries are not inherently just. Through collaboration between natural and social scientists, the Earth Commission defines and operationalizes Earth system justice to ensure that boundaries reduce harm, increase well-being, and reflect substantive and procedural justice. Such stringent boundaries may also affect ‘just access’ to food, water, energy and infrastructure. We show how boundaries may need to be adjusted to reduce harm and increase access, and challenge inequality to ensure a safe and just future for people, other species and the planet. Earth system justice may enable living justly within boundaries.

Many species of tilapia (a collection of fish species from the cichlidae family) have biological traits that make them successful invaders. While widespread herbivory has been observed in many tilapia species, knowledge on habitat preferences and tilapia interactions with native fish food webs is limited. This study used stomach contents and stable isotope analysis of spotted tilapia (Pelmatolapia mariae) and Mozambique tilapia (Oreochromis mossambicus), and stable isotopes of common native fish species to explore relationships between habitat and diet for fish food webs in the Mitchell River, northern Australia, three years after tilapia were detected in the catchment. While plant material was the most abundant item in tilapia stomachs, some also contained other items in small quantities, such as fish eggs, small shrimp, and bivalves. Macrohabitat type (in-channel (no tilapia), off-channel (no tilapia), weir (tilapia present)) was related to native fish food web structure, with weir food webs showing similarities to off-channel food webs. In-channel food webs were more constrained than weir or off-channel food webs, reflecting a more limited range of available food sources. Off-channel habitats including creeks and wetlands were most similar to weir habitats and may therefore be most at risk of colonization as tilapia spread throughout the catchment. This study clearly demonstrated that the successful rapid invasion of these two tilapia species is linked to suitable habitat with abundant food that fuels growth and reproduction. These findings increase understanding of diet related habitat use during new tilapia invasions and trophic interactions with native species.

Ecologists are interested in modeling the population growth of species in various ecosystems. Specifically, logistic growth arises as a common model for population growth. Studying such growth can assist environmental managers in making better decisions when collecting data. Traditionally, ecological data is recorded on a regular time frequency and is very well-documented. However, sampling can be an expensive process due to available resources, money and time. Limiting sampling makes it challenging to properly track the growth of a population. Thus, this design study proposes an approach to sampling based on the dynamics associated with logistic growth. The proposed method is demonstrated via a simulation study across various theoretical scenarios to evaluate its performance in identifying optimal designs that best estimate the curves. Markov Chain Monte Carlo sampling techniques are implemented to predict the probability of the model parameters using Bayesian inference. The intention of this study is to demonstrate a method that can minimize the amount of time ecologists spend in the field, while maximizing the information provided by the data.

Floodplain wetlands are among the most productive and biodiverse ecosystems on Earth and provide a major subsidy of food resources for consumers in river systems. The basal energy source for those ...

Defining a safe and just biosphere space requires a synthetic scaleable measure of biosphere functional integrity to secure Nature’s Contributions to People (NCP). Using a systematic review of 153 peer-reviewed studies we estimated the minimum level of functional integrity needed to secure multiple critical NCP, including pollination, pest and disease control, water quality regulation, soil protection, recreation and natural hazards mitigation in human-modified landscapes. We characterise functional integrity by the quantity, quality and spatial configuration of (semi-)natural habitat within any landscape. We find that at least 20-25% of structurally complex and biologically diverse (semi-)natural habitat in each 1 km2of land area is needed to maintain the supply of multiple NCP simultaneously. Exact quantity, quality and spatial configuration required is dependent on local context, and may differ for individual NCP. Today, about 50-60% of human-modified lands have less than 10% and 20% (semi-)natural habitat per 1 km2respectively. These areas require immediate attention to regenerate functional integrity in order to secure ecological functioning in those landscapes.

Environmental assessments increasingly call for just transformations, yet do not offer concrete visions of what these might be. This paper conceptualizes and operationalizes Earth system justice (ESJ) through articulating just ends which minimize significant harm to humans from Earth system change while ensuring access to needed resources for all and just means which involve reallocation of resources, responsibilities, and risks. We argue that Earth system justice is underpinned by recognition and epistemic justice, inclusivity and procedural justice, and corrective and distributive justice with a scope that encompasses intragenerational, intergenerational, and interspecies justice concerns. This Earth system justice framework provides the theoretical underpinning for assessing proposals for international environmental policy based on Earth System Boundaries (ESBs) and for proposing just approaches to sustainability transformations.

Hydrological connectivity in river systems facilitates the movement of animals, nutrients, and energy across riverine landscapes but is threatened by climate change and water resource developments. These anthropogenic disturbances are expected to alter connectivity patterns in wet-dry tropical river systems that are driven by a highly variable seasonal flow regime. We studied the composition and functional diversity of fish assemblages across a large wet-dry tropical river system in northern Australia that is under consideration for new agricultural and water resource developments. We explored changes in the environment, species turnover, and relationships between environmental characteristics and fish species composition, quantifying how they were influenced by hydrological connectivity, to identify species and habitats at risk of impacts of reduced connectivity. Characteristics of the aquatic environment were significantly different between low connectivity, high connectivity, and off-channel sites, and these environmental characteristics were associated with changes in fish community composition. Fish species turnover occurred across the catchment, with unique assemblages in headwater sites. High turnover between adjacent sites of low connectivity suggested that reduced movement opportunity creates localized populations, and these differences in species presence/absence are likely to be exacerbated by reduced connectivity from water resource developments. Species turnover was also related to functional diversity, which itself varied across connectivity levels. Habitat specialists and species with functional traits that depend on hydrological connectivity, such as diadromous species, are most at risk from anthropogenic change. Protection of the flow regime and environmental characteristics that support these species is important for maintaining biodiversity.

Accurately accounting for flows of energy through food webs is challenging because of the spatial and temporal variability associated with energy production and consumption. Wet–dry tropical rivers have a highly seasonal discharge regime where wet season flows allow access to energy sources (inundated wetlands) that are not available during the dry season when aquatic consumers are confined to disconnected waterholes. We combined measures of fish community biomass with previously published feeding guild specific stable isotope analyses to explore how opposing wet- and dry-season habitat templates influence spatial and temporal trends in the sources of energy supporting fish biomass throughout a river network in the wet–dry tropics of northern Australia. Accounting for the relative contribution of each feeding guild to fish community biomass was a critical component of our analyses, as a single feeding guild (invertivore/piscivore) influenced spatial and temporal patterns in the sources of energy supporting overall fish biomass. During the early dry season, the reliance of fish communities on autochthonous sources of energy (periphyton) decreased from the upper to lower reaches of the river network, which correlates with increasing floodplain area and wet season inundation times. These patterns disappeared by the late dry season as fish in both upper and lower reaches became increasingly reliant on autochthonous sources produced within waterholes over the course of the dry season, indicating that the large wet-season gains in fish biomass are maintained through the dry season by energy produced within waterhole refuges. Collectively these results indicate that a combination of autochthonous and allochthonous sources of energy work in unison to support fish community biomass throughout the Mitchell River catchment and that access to these sources of energy is dictated by seasonal patterns in discharge interacting with spatial variability in river geomorphology (channel geometry and floodplain area). Many rivers are experiencing decreased flows due to water resource development and more frequent and severe droughts. Thus, we suggest our study provides insight into how changes in discharge regime could influence food web energetics throughout river networks.

Freshwater ecosystems are highly vulnerable to global warming because 1) their chief drivers, water quality and flow regimes, are highly sensitive to atmospheric warming, and 2) they are already extremely threatened by a wide range of interacting anthropogenic pressures. Even relatively modest global warming of 1.5°C poses a considerable threat to freshwater ecosystems and the many critical services these provide to people. Shifts in the composition and function of freshwater ecosystems are widely anticipated with adverse consequences for ecosystem services, including those underpinning water and food security. While the extent and severity of effects is likely to be significantly reduced if global warming is limited to 1.5°C, concerted efforts to implement widely recognised priorities for policy and management are required to mitigate unavoidable impacts and reduce the likelihood of perverse outcomes of climate mitigation and adaptation efforts in other sectors—all of which rely on fresh water supply. Freshwater ecosystems and their services, including provision of fresh water, must therefore be considered first and foremost when developing and implementing any climate action.

Water resource development can lead to the significant alteration of natural flow regimes, which can have impacts on the many aquatic species that rely on both freshwater and estuarine environments to successfully complete their lifecycles. In tropical northern Australia, annual catches of commercially harvested white banana prawns (WBP) are highly variable in response to environmental conditions, namely rainfall and subsequent riverine flow. However, little is known about the spatial extent to which flow from individual rivers influences offshore WBP catch. In this study, we quantify how the relationship between WBP catch in the Gulf of Carpentaria is influenced by flow from the Mitchell River, Queensland Australia. We used a Bayesian framework to model both prawn presence and catch per unit effort, and found evidence that multiple components of the flow regime contribute to fishery catch. We also found evidence to suggest that the relationships between prawn presence and flow were spatially structured across the fishing ground. Our results suggest that attributing fishery catch to a single river remains challenging, though highlights the importance of maintaining natural flow regimes to support a highly valuable commercial fishery species in the face of potential water resource development.

In many parts of the world, conditions for small scale agriculture are worsening, creating challenges in achieving consistent yields. The use of automated decision support tools, such as Bayesian Belief Networks (BBNs), can assist producers to respond to these factors. This paper describes a decision support system developed to assist farmers on the Mekong Delta, Vietnam, who grow both rice and shrimp crops in the same pond, based on an existing BBN. The BBN was previously developed in collaboration with local farmers and extension officers to represent their collective perceptions and understanding of their farming system and the risks to production that they face. This BBN can be used to provide insight into the probable consequences of farming decisions, given prevailing environmental conditions, however, it does not provide direct guidance on the optimal decision given those decisions. In this paper, the BBN is analysed using a novel, temporally-inspired data mining approach to systematically determine the agricultural decisions that farmers perceive as optimal at distinct periods in the growing and harvesting cycle, given the prevailing agricultural conditions. Using a novel form of data mining that combines with visual analytics, the results of this analysis allow the farmer to input the environmental conditions in a given growing period. They then receive recommendations that represent the collective view of the expert knowledge encoded in the BBN allowing them to maximise the probability of successful crops. Encoding the results of the data mining/inspection approach into the mobile Decision Support System helps farmers access explicit recommendations from the collective local farming community as to the optimal farming decisions, given the prevailing environmental conditions.

1. Predator–prey interactions are an inherently local-scale phenomenon, but the intensity of these interactions can be mediated by abiotic conditions that can exert a multi-scaled influence through space and time. Understanding how multi-scale abiotic factors may influence local-scale biotic processes has proven challenging; however, the hierarchical nature of riverine flow regimes makes these environments an ideal setting to test how predator–prey relationships may vary with multi-scaled flow variation. 2. We developed a series of Bayesian hierarchical models to explore how predator–prey relationships between barramundi Lates calcarifer and their prey may be influenced by multi-scaled flow variables in the Daly River, northern Australia. 3. We found that spatio-temporal variation in barramundi abundance was strongly related to both antecedent flow and the abundance of prey fishes (predictive r2 = 0.57), and that barramundi abundance is more likely to be influenced by bottom-up, rather than top-down predator–prey dynamics. We also found that the strength and direction of these relationships varied across the catchment and between seasons. We found stronger, positive relationships between barramundi abundance and prey abundance in the most downstream sites with higher mean annual flows, compared to upstream sites. 4. These results indicate that the abundance of predatory fishes can be related to both recent abiotic (flow) conditions and the abundance of prey (biotic conditions), and provides strong support for the importance of bottom-up trophic dynamics. Management of iconic predators such as barramundi should therefore consider both flow management and other key factors such as habitat maintenance to support their prey.

Data collection for fresh-water regions of The Ecosystem Health Monitoring Program (EHMP), in southeast Queensland, Australia, involves the sampling of over 130 sites among 19 catchments twice per year and has been ongoing for over ten years. The sampling design was derived following an exhaustive process of indicator and site selection to develop a composite indicator that represented aquatic ecosystem health. After 13 years of implementation, there was an interest in identifying redundancies in sampling to reduce sampling costs without making a substantial impact on the integrity of the program and its capacity to report on ecosystem health. This paper focuses on identifying a subset of sites and times that could be removed from sampling with a minimal impact on the subsequent ecosystem health scores. Herein, Mixed models are employed to assess a variance structure from which optimality criteria are utilized to identify the scheme. Integer programs are then used to ensure specific practical constraints are observed.

Coastal freshwater supply and demand systems are expected to be significantly affected by changes to both climatic and non-climatic drivers over coming decades. Adapting to these changes to secure adequate freshwater to meet the rising demands of socio-economic development has become a critical task for decision-makers. Whilst a range of adaptation options may be available, the complexity and interconnectedness of water resource systems make it challenging to identify which options are likely to be most feasible and effective. Here, we present a Bayesian decision network (BDN) that was co-developed with local experts to identify appropriate adaptation options for freshwater management under both current and likely future conditions in the Da Do Basin of coastal Vietnam. Potential adaptation options were prioritised according to cost-effectiveness based on relative costs incurred and relative utilities delivered across a range of future scenarios. The BDN model indicated that cost-effectiveness of adaptation options varied between future scenarios. Constructing pumping stations was the most cost-effective option under climate change scenarios, whilst a higher water price was the most cost-effective option under non-climatic changes. Under combined climatic and non-climatic changes, constructing pumping stations in combination with increasing water prices provided the most cost-effective option. The model affords an opportunity for decision-makers in the Da Do Basin to prioritise and evaluate appropriate and feasible adaptation actions under different scenarios with respect to multiple drivers.

The growing demand for freshwater resources has led to dam construction and water diversions in a majority of the world's large rivers. With an increasing demand for freshwater, trade‐offs between water allocations and the preservation of ecological connections between terrestrial and marine ecosystems are inevitable. The ecological links formed by rivers flowing into the ocean benefit many commercially fished species. The degree to which different species and the livelihoods of fishers are negatively impacted by changes in river flows due to water extraction or diversion is important for management across terrestrial and marine boundaries. Our objective was to predict how changes in freshwater flows from three wet–dry tropical rivers in northern Australia, that is, the Mitchell, Gilbert, and Flinders rivers, affect the commercial banana prawn (Penaeus merguiensis) catch. We used a novel spatiotemporal Bayesian approach to model the effects of river flows and key climate drivers on banana prawn catch. We then predicted how the loss of flow due to water extraction or diversion affected prawn catch. Our analyses of three water development scenarios found that catch was most impacted by water extraction during low flows. The impact of water extraction was greatest for a scenario with dams on the Mitchell River, where we predicted catch would decline by 53% during a year with low flow. Overall, our results imply that maintenance of low‐level flows is a crucial requirement for sustained fishery yields. We suggest that water managers must balance agricultural demand for water during drier years against the impact of water extraction on prawn fisheries during low‐flow years. Protecting low‐level flows during drier years is a priority for maintaining terrestrial–marine linkages for adjacent marine fisheries.

Aquatic ecosystems are used for extensive rice-shrimp culture where the available water alternates seasonally between fresh and saline. Poor water quality has been implicated as a risk factor for shrimp survival; however, links between shrimp, water quality and their main food source, the natural aquatic biota inhabiting these ponds, are less well understood. We examined the aquatic biota and water quality of three ponds over an entire year in the Mekong Delta, Vietnam, where the growing season for the marine shrimp Penaeus monodon has been extended into the wet season, when waters freshen. The survival (30–41%) and total areal biomass (350–531 kg ha−1) of shrimp was constrained by poor water quality, with water temperatures, salinity and dissolved oxygen concentrations falling outside known optimal ranges for several weeks. Declines in dissolved oxygen concentration were matched by declines in both shrimp growth rates and lipid content, the latter being indicative of nutritional condition. Furthermore, as the dry season transitioned into the wet, shifts in the taxonomic composition of phytoplankton and zooplankton were accompanied by declines in the biomass of benthic algae, an important basal food source in these systems. Densities of the benthic invertebrates directly consumed by shrimp also varied substantially throughout the year. Overall, our findings suggest that the survival, condition and growth of shrimp in extensive rice-shrimp ecosystems will be constrained when poor water quality and alternating high and low salinity negatively affect the physiology, growth and composition of the natural aquatic biota. Changes in management practices, such as restricting shrimp inhabiting ponds to the dry season, may help to address these issues and improve the sustainable productivity and overall condition of these important aquatic ecosystems.

Adaptation to drought is particularly challenging on remote island atolls, such as those found in the Republic of the Marshall Islands (RMI), a nation of 58,000 populating 29 low-lying coral atolls spread over >2 million km2. Exposure to consecutive atmospheric hazards, such as meteorological floods and droughts diminish scarce water resources and erode the resilience of island communities. Drought impact mitigation measures must supply emergency drinking water to stricken communities, while simultaneously conserving natural sources in order to reduce their vulnerability to subsequent events. Household surveys (n = 298) and focus group discussions (n = 16) in eight RMI communities revealed that 86% of households have experienced drought and 88% reported using multiple water sources to meet normal household needs. With no surface water and a thin freshwater lens (FWL), rainwater collected from rooftops is the most common household water source. The traditional use of carved hollows in the base of coconut trees to collect rainwater (“Mammaks”) appears to have been displaced by large rainwater tanks. However, rationing of rainwater for consumption only during drought was widely reported, with private wells supporting non-consumptive uses. Reverse osmosis (RO) desalination units have provided relief during drought emergencies but concerns have been raised around dependency, maintenance challenges, and loss of traditional water practices. Most notably, RO use has the potential to change the anthroposhpere by adversely affecting the FWL; 86% of RO units were installed at island-centre where excessive pumping can cause upconing, making the FWL brackish. Balancing the introduction of desalination technology to mitigate water shortages with maintenance of traditional water conservation practices to preserve the quantity and quality of the FWL is a promising strategy on island atolls that requires further investigation.

In the age of climate change, increasing populations and more limited resources, efficient agricultural production is being sought by farmers across the world. In the case of smallholder farms with limited capacity to cope with years of low production, this is even more important. To help to achieve this aim, data analytics and decision support systems are being used to an ever greater extent. For rice/shrimp farmers in the Mekong Delta, Vietnam, trying to tune the conditions so that both crops can be successfully grown simultaneously is an ongoing challenge. In this paper, the design and development of a smartphone app, from a well researched Bayesian Belief Network, is described. This now gives farmers the ability to make better informed planting and harvesting decisions. The app has been initially well received by water management practitioners and farmers alike.

Aim: Springs in the Australian arid zone are distinct from other waterways because they house a large number of endemic species. We aimed to assess spatial patterns in endemic diversity at a basin-wide scale and whether environmental features can help to explain them. In doing so, we take the opportunity to summarize the current state of conservation in the system.Location: Great Artesian Basin (GAB), arid and semiarid regions of eastern AustraliaMethods: We combine data regarding the location of springs with published GIS layers regarding environmental characteristics and a literature review of all species and subspecies documented in the published literature to be endemic to GAB springs.Results: We found evidence of 96 species and subspecies of fishes, molluscs, crustaceans and plants endemic to these springs. The majority of endemic species are invertebrates with geographical distributions limited to a single spring complex (

Longitudinal and lateral connectivity is important for mobile aquatic species in rivers for reproductive migrations, recruitment, gene flow and access to food resources across habitat types. Water resource developments such as dams and levees may disrupt these connections, causing river fragmentation and loss of access to highly productive habitats such as floodplain wetlands. We used sulfur stable isotopes as a tracer to estimate patterns of fish movement in an unregulated river in tropical northern Australia, taking advantage of observed spatial variation in sulfur isotope values of their food resources across the catchment. We also modelled the flow and barrier related impacts of potential dam development scenarios on fish movement. Fish with isotope values significantly different from local prey values were determined to be migrants. In the ‘no dams’ scenario, movement varied among fish species (0–44% migrant fish within species where n > 5) and sites (0–40% migrant fish within sites where n > 5), and immigration was higher in more connected sites. Impacts of water resource development on fish movement varied between dam scenarios, with predictions that a dam on the main channel of the Mitchell River would have the highest impact of the three individual dam scenarios. This study provides critical information on how flow-mediated connectivity supports patterns of fish community movement in an unregulated river system. The generic quantitative approach of combining tracers of fish movement with connectivity modelling provides a powerful predictive tool. While we used sulfur stable isotopes to estimate fish movement, our approach can be used with other tracers of movement such as otoliths and acoustic telemetry, making it widely applicable to guide sustainable development in other river systems.

Freshwater ecosystems and their associated biota are under increasing threats from multiple stressors including climate and land-use change. The conservation of these ecosystems must be based on an integration of data including species physiological tolerances, the biotic and abiotic drivers of the distribution of populations, and demographic processes, to provide the comprehensive ecological information necessary for management. This study used a Bayesian belief network (BBN) to synthesize research on northern river blackfish, a threatened species in the upper Condamine River, Australia, into a probabilistic framework capable of predicting the complex relationships that exist between environmental conditions and population success. This study tested how predicted air temperature scenarios for the years 2050 and 2080, and catchment restoration scenarios, would be expected to affect three indices of population success: adult abundance, juvenile abundance, and juvenile recruitment. Compared with current climatic conditions, climate warming scenarios reduced the probability of future population success by between 0.4% and 1.6%. These shifts were almost completely offset, and even improved, when riparian zones were restored at the catchment scale, where changes ranged from an overall decrease of 0.2% to an increase of 1%. To achieve the highest probability of population success, the impacts of warming stream temperatures and the degradation of riparian zones must be mitigated. However, the model showed that there is still a possibility of complete population failure under a wide range of conditions, even when conditions appear to be suitable. To maximize the future population success of river blackfish we recommend targeting the restoration of hydrologically active catchment areas where grazing strongly influences stream biota. The use of a BBN allowed the combination of multiple sources of information to solve complex ecological problems, including how multiple stressors may affect threatened freshwater species.

A large proportion of the uncertainty surrounding catchment sediment budget modelling has been attributed to sediment supplied from riverbank erosion. Some of the variables influencing riverbank erosion are bend curvature, specific streampower, riparian vegetation, and in some instances sand and gravel extraction. The empirical relationship between these variables and observed riverbank erosion across 78 km of the Upper Brisbane River, Australia was investigated. No significant relationship was found between curvature, specific streampower and riverbank erosion. The role of riparian vegetation relative to sediment supply from riverbank erosion varied with spatial location, susceptibility of a reach to erosion, and human disturbance such as sand and gravel extraction. Despite not having data on substrate type the model described approximately 37% of the variation in observed riverbank erosion. It appears that inclusion of a management practice factor in riverbank erosion models is justified, where appropriate, and may improve model performance.

Mangroves sequester large amounts of carbon (C) and they are increasingly recognized for their potential role in climate change mitigation programs. However, there is uncertainty in the C content of many mangrove forests because the amount of C stored in the roots is usually estimated from allometric equations and not from direct field measurements. There are only a handful of allometric equations in mangroves that are used worldwide to estimate root biomass, however, root biomass can vary from the allometric relationship if the environmental conditions are different from those where the equation was developed. In this study, we compiled recent information on how mangrove roots are affected by environmental conditions. Then, we explored the effect of sampling methodology on root biomass estimations. Finally, we compared published values of root biomass from field measurements against our estimations from allometric equations. The goal was to calculate the uncertainty associated with the estimation of root biomass and thus, the belowground C content of mangroves. The results showed that sampling methodology has a significant effect on root biomass estimations. The highest biomass estimations are reported where both live and dead roots are measured and when the roots are sampled by digging trenches. When comparing measured values against estimations from allometric equations, on average the general allometric equation provided root biomass values that were 40 ± 12% larger than those obtained from field measurements with cores. The result suggests that either: (a) sampling with cores largely underestimates root biomass, or (b) allometric equations overestimate root biomass when used outside the region where they were developed. The uncertainty in root biomass estimates from allometric equations corresponds to 4–15% of the ecosystem C stock (trees + soil), with higher uncertainties in forests with low tree density and low interstitial salinity. We provide a statistical model that includes salinity, forest density and root biomass to correct for this systematic bias. The estimated uncertainty is important to consider when quantifying C budgets at large spatial scales and to validate methodological approaches to C stock estimations.

In recent years, across tropical regions of the world, there has been an expansion of integrated farming systems that combine rice and shrimp production. While these systems were developed as a form of crop-rotation – growing rice in the wet season and shrimp in the dry season – some farmers grow both rice and brackish-water shrimp simultaneously during the wet season. Climatic variability has resulted in considerable crop losses in this system across many regions. Research has yet to identify the complete array of key risk factors, and their potential interactions, for integrated rice-shrimp farming. Consequently, different farming practices and environmental factors that may affect crop production need to be clarified to guide research efforts. We applied a staged, iterative process to develop a probabilistic Bayesian belief network based on expert knowledge that describes the relationships that contribute to the risk of failure of both crops in integrated rice-shrimp farming systems during the wet season. We applied the approach in the Southern Mekong Delta, Vietnam, in the context of a broader research program into the sustainability of the rice-shrimp farming system. The resulting network represents the experts' perceptions of the key risk factors to production and the interactions among them. While both farmers and extension officers contributed to the identification of the processes included in the network, the farmers alone provided estimates of the probability of the relationships among them. The network identified the challenges to minimise the risk of failure for both crops, and the steps farmers can take to mitigate some of them. Overall, farmers perceived they have a better chance to minimise risk of failure for shrimp rather than rice crops, and limited opportunities appear to exist for successful production of both. By engaging the farmers in this process of model development, we were able to identify additional research questions for the broader research team and to identify simple steps the farmers could take to reduce the risk of crop failure. Integrating additional empirical data into this network, as it becomes available, will help identify clear opportunities for improvements in farming practices which should reduce the risk of crop failure into the future.

The Mekong Delta is the most important rice- and shrimp-producing region for food and economic security in Vietnam. Rice-shrimp farming is practised where salinity fluctuates substantially between wet and dry seasons. Research points to several potential risk factors for rotational systems, but how these link directly to both rice and shrimp production remains poorly quantified for systems that stock and harvest animals year-round. We examined water and soil quality of 18 rice-shrimp-crab ponds, in which shrimp and crab are grown in both wet and dry seasons, in the Ca Mau Province of Vietnam. Multiple lines of evidence indicated that environmental conditions experienced by both rice and shrimp were suboptimal and contributed to low yields and survival. Year-round cropping of shrimp and crab was associated with sustained suboptimal salinity, intensified by drought, for the wet-season cultivation of rice. Although rice seedlings were sown in all 18 ponds, only three had a harvestable crop. Low shrimp production and survival was associated with sustained suboptimal water temperatures (too high), salinity (too high in the dry season and too low in the wet season) and dissolved oxygen concentrations (too low). Food availability and quality may also have affected shrimp production. Improving productivity of rice-shrimp-crab ponds in the study region may require (1) separation of rice and shrimp crops and improving efficiency of soil washing practices such that salinity conditions are more suitable for each when grown, and (2) management intervention to increase oxygenation of water, and the availability and quality of food for shrimp.

Tallis, Heather; Kreis, Katharine; Olander, Lydia; Ringler, Claudia; Ameyaw, David; Borsuk, Mark E.; Fletschner, Diana; Game, Edward; Gilligan, Daniel O.; Jeuland, Marc; Kennedy, Gina; Masuda, Yuta J.; Mehta, Sumi; Miller, Nicholas; Parker, Megan; Pollino, Carmel; Rajaratnam, Julie; Wilkie, David; Zhang, Wei; Ahmed, Selena; Ajayi, Oluyede C.; Alderman, Harold; Arhonditsis, George; Azevedo, Ines; Badola, Ruchi; Bailis, Rob; Balvanera, Patricia; Barbour, Emily; Bardini, Mark; Barton, David Nicholas; Baumgartner, Jill; Benton, Tim G.; Bobrow, Emily; Bossio, Deborah; Bostrom, Ann; Braimoh, Ademola; Brondizio, Eduardo; Brown, Joe; Bryant, Benjamin P.; Calder, Ryan S.D.; Chaplin-Kramer, Becky; Cullen, Alison; DeMello, Nicole; Dickinson, Katherine L.; Ebi, Kristie L.; Eves, Heather E.; Fanzo, Jessica; Ferraro, Paul J.; Fisher, Brendan; Frongillo, Edward A.; Galford, Gillian; Garrity, Dennis; Gatere, Lydiah; Grieshop, Andrew P.; Grigg, Nicola J.; Groves, Craig; Gugerty, Mary Kay; Hamm, Michael; Hou, Xiaoyue; Huang, Cindy; Imhoff, Marc; Jack, Darby; Jones, Andrew D.; Kelsey, Rodd; Kothari, Monica; Kumar, Ritesh; Lachat, Carl; Larsen, Ashley; Lawrence, Mark; DeClerck, Fabrice; Levin, Phillip S.; Mabaya, Edward; Gibson, Jacqueline MacDonald; McDonald, Robert I.; Mace, Georgina; Maertens, Ricardo; Mangale, Dorothy I.; Martino, Robin; Mason, Sara; Mehta, Lyla; Meinzen-Dick, Ruth; Merz, Barbara; Msangi, Siwa; Murray, Grant; Murray, Kris A.; Naude, Celeste E.; Newlands, Nathaniel K.; Nkonya, Ephraim; Peterman, Amber; Petruney, Tricia; Possingham, Hugh; Puri, Jyotsna; Remans, Roseline; Remlinger, Lisa; Ricketts, Taylor H.; Reta, Bedilu; Robinson, Brian E.; Roe, Dilys; Rosenthal, Joshua; Shen, Guofeng; Shindell, Drew; Stewart-Koster, Ben; Sunderland, Terry; Sutherland, William J.; Tewksbury, Josh; Wasser, Heather; Wear, Stephanie; Webb, Chris; Whittington, Dale; Wilkerson, Marit; Wittmer, Heidi; Wood, Benjamin D.K.; Wood, Stephen; Wu, Joyce; Yadama, Gautam; Zobrist, Stephanie. Aligning evidence generation and use across health, development, and environment. Current Opinion in Environmental Sustainability 2019 ;Volum 39. s. 81-93

It is a substantial challenge to quantify the benefits which ecosystems provide to water supply at scales large enough to support policy making. This study tested the hypothesis that vegetation could reduce riverbank erosion, and therefore contribute to reducing turbidity and the cost of water supply, during a large magnitude flood along a 62 km riparian corridor where land cover differed substantially from natural conditions. Several lines of evidence were used to establish the benefits that vegetation provided to reducing eleven riverbank erosion processes over 1688 observations. The data and analyses confirmed that vegetation significantly reduced the magnitude of the riverbank erosion process which was the largest contributor to total erosion volume. For this process, a 1% increase in canopy cover of trees higher than five metres reduced erosion magnitude by between 2 and 3%. Results also indicate that riverbank erosion was likely to be affected by direct changes to the riparian corridor which influenced longitudinal coarse sediment connectivity. When comparing the impact of these direct changes on a relative basis, sand and gravel extraction was likely to be the dominant contributor to changed erosion rates. The locations where erosion rates had substantially increased were of limited spatial extent and in general substantial change in river form had not occurred. This suggests that the trajectory of river condition and increasing turbidity are potentially reversible if the drivers of river degradation are addressed through an ecosystem restoration policy.

Summary 1.Connectivity is regarded globally as a guiding principle for conservation planning, but due to difficulties in quantifying connectivity empirical data remain scarce. Lack of meaningful connectivity metrics are likely leading to inadequate representation of important biological connections in reserve networks. Identifying patterns in landscape connectivity can, theoretically, improve the design of conservation areas. 2.We used a network model to estimate seascape connectivity for coral reef-associated fishes in a subtropical bay in Australia. The model accounted for two scales of connectivity: i) within mosaics at a local scale and ii) among these mosaics at a regional scale. Connections among mosaics were modelled using estimations of post-larval small and intermediate movement distances represented by home ranges of two fish species. 3.Modelled connectivity patterns were assessed with existing data on fish diversity. For fishes with intermediate home ranges (0 to 6 km), connectivity (quantified by the index Probability of Connectivity (dPC)) explained 51– 60% of species diversity. At smaller home ranges (0 to 1 km) species diversity was associated closely with intra-mosaic connectivity quantified by the index dPCintra. 4.Mosaics and their region-wide connections were ranked for their contribution to overall seascape connectivity, and compared against current positions and boundaries of reserves. Our matching shows that only three of the ten most important mosaics are at least partly encompassed within a reserve, and only a single important regional connection lies within a reserve. 5.Synthesis and applications. Notwithstanding its formal recognition in reserve planning, connectivity is rarely accounted for in practice, mainly because suitable metrics of connectivity are not available in planning phases. Here, we show how a network analysis can be effectively used in conservation planning by identifying biological connectivity inside and outside present reserve networks. Our results demonstrate clearly that connectivity is insufficiently represented within a reserve network. We also provide evidence of key pathways in need of protection to avoid nullifying the benefits of protecting key reefs. The guiding principle of protecting connections among habitats can be achieved more effectively in future, by formally incorporating our findings into the decision framework. This article is protected by copyright. All rights reserved.

Rice-shrimp culture systems occur throughout Asia where there are seasonal alterations of fresh and saltwater availability. During the dry season, black tiger shrimp are grown at low densities, and in the wet season, rice, or rice and shrimp are grown together. Previous studies point to issues with suboptimal rice and shrimp production, due, in part, to climatic conditions driving changes in water quality, and pond management practices. However, the availability of natural benthic food supplies for shrimp production is less well studied. This study used a 15N‑nitrogen stable isotope tracer added to replicated enclosures within two rice-shrimp ponds to trace shrimp feeding on benthic natural biota. This experiment was conducted in both the wet and dry seasons. The 15N-ammonium rapidly enriched the 15N signature in the particulate organic matter (POM) in the water column, indicative of significant phytoplankton uptake of nitrogen (N). In contrast there was little enrichment of the benthic algae in the same time frame. After 13 d, most of the shrimp in the replicate enclosures had little or no 15N enrichment. This result occurred across both ponds and in both seasons. This suggests that enriched N was not transferred through the benthic food web to the shrimp. The results of the 15N enclosure experiments were combined with biomass estimates of benthic algae and macrobenthos, shrimp growth data, and linked to other parallel studies of water quality and sediment biogeochemistry in the same ponds. Overall, the findings point to inadequate feed stocks for shrimp, and hence the need to consider supplemental feeding with high quality formulated feeds in order to improve growth rates and survival.

Conservation planning processes and wetland management require spatial estimations of aquatic habitats to support the maintenance of aquatic biodiversity. However, physical access to several wetlands and freshwater habitats can be restricted due to difficult topography and technological limitations associated with ground-based observations. In addition to these constraints, the distribution of some aquatic primary producers in freshwater habitats and floodplains that are difficult to reach further complicates large-scale assessment of aquatic habitats using traditional field-based techniques. The main objective of this study is to predict the spatial distribution of hot spots of primary producers (aquatic plant biomass) and assess large-scale inundation patterns in a large floodplain wetland (Flinders catchment) in the wet-dry tropics of Australia. To this end, remote sensing biophysical indicators (vegetation and inundation) were integrated with flood water depth in a classification tree model. Results indicate that in terms of floodplain total inundation, the Flinders wetland hydrology is rather restricted immediately after the summer wet season, the period when most primary production happens. While this can be attributed to the fact that much of the observed annual variability (93%) in rainfall and surface runoff (95%) occur during the wet season, post flood recession patterns are indicators that underpin the somewhat limited alimentation of the Flinders floodplain during this period. As observed in this study, post flood inundation extents in the summers of 2009 and 2019 declined by approximately 89% and 87% within fourteen and ten days, respectively. Despite having a significantly higher magnitude than the 2009 summer flood event, the 2019 extreme ‘big wet’ period did not translate to higher floodplain productivity (aquatic plant biomass and surface water distribution) immediately after summer as was the case in 2009. Furthermore, the predicted extents of aquatic plant biomass and total floodplain inundation in the downstream Flinders show substantial temporal variation and suggest the floodplain wetland hydrology is largely driven by inter-annual changes in annual rainfall. The extents of these hot spots of biomass accumulation were found to be considerably associated with total floodplain inundation extent ( r = 0.94 ), rainfall ( r = 0.81 ), and discharge ( r = 0.68 ). Furthermore, advance statistical analyses show that downstream discharge and rainfall over the Flinders are significantly correlated ( r = 0.72 ). In addition to this, observed amplitudes of discharge and rainfall in extreme wet and dry years coincided with floodplain inundation patterns and distribution of hot spots of primary producers. While these relationships emphasize the importance of flow in the nourishment of the downstream catchment, they further corroborate the composite influence of local rainfall and discharge on total floodplain inundation and hot spots of primary producers.

Aquatic ecosystems are exposed to a host of anthropogenic stressors whose combined effect can be synthesized with cumulative stress indices. The reliability of cumulative stress indices depends primarily on: 1) stressor incidence maps derived from remote sensing or modeling but rarely validated against on-the-ground observations, and 2) the weighting scheme used to combine multiple stressors into a cumulative index typically based on expert opinion. In this paper, we evaluate the exposure and weights for 13 aquatic stressor maps of the world’s rivers with a comparison against local stress reporting across 1018 inland and coastal sites from the Ramsar Wetlands of International Importance. We found that globally-mapped and locally-reported stressors are poorly aligned overall (AUC-ROC = 0.50–0.63), and that concordance did not improve when stratifying by ecosystem types or continents. Agreement varied across individual stressors, was highest for hydrological stressors and lowest for habitat disconnectivity stressors. We estimated stressor weights from the comparison and found them to be remarkably aligned well with expert-generated weights, suggesting there is convergence on a stressor hierarchy across local and global scales. Our comparison illustrates the value of integrating data across scales to inform the calculation of global stressor indices. Continued systematic stressor monitoring across environmental observation networks is central to benchmarking maps of ecosystem stress globally.