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As efforts to restore coastal habitats accelerate, it is critical that investments are targeted to most effectively mitigate and reverse habitat loss and its impacts on biodiversity. One likely but largely overlooked impediment to effective restoration of habitat-forming organisms is failing to explicitly consider non-habitat-forming animals in restoration planning, implementation, and monitoring. These animals can greatly enhance or degrade ecosystem function, persistence, and resilience. Bivalves, for instance, can reduce sulfide stress in seagrass habitats and increase drought tolerance of saltmarsh vegetation, whereas megaherbivores can detrimentally overgraze seagrass or improve seagrass seed germination, depending on the context. Therefore, understanding when, why, and how to directly manipulate or support animals can enhance coastal restoration outcomes. In support of this expanded restoration approach, we provide a conceptual framework, incorporating lessons from structured decision-making, and describe potential actions that could lead to better restoration outcomes using case studies to illustrate practical approaches.

Mangroves have among the highest carbon densities of any tropical forest. These ‘blue carbon’ ecosystems can store large amounts of carbon for long periods, and their protection reduces greenhouse gas emissions and supports climate change mitigation. Incorporating mangroves into Nationally Determined Contributions to the Paris Agreement and their valuation on carbon markets requires predicting how the management of different land‐uses can prevent future greenhouse gas emissions and increase CO2 sequestration. We integrated comprehensive global datasets for carbon stocks, mangrove distribution, deforestation rates, and land‐use change drivers into a predictive model of mangrove carbon emissions. We project emissions and foregone soil carbon sequestration potential under ‘business as usual’ rates of mangrove loss. Emissions from mangrove loss could reach 2391 Tg CO2 eq by the end of the century, or 3392 Tg CO2 eq when considering foregone soil carbon sequestration. The highest emissions were predicted in southeast and south Asia (West Coral Triangle, Sunda Shelf, and the Bay of Bengal) due to conversion to aquaculture or agriculture, followed by the Caribbean (Tropical Northwest Atlantic) due to clearing and erosion, and the Andaman coast (West Myanmar) and north Brazil due to erosion. Together, these six regions accounted for 90% of the total potential CO2 eq future emissions. Mangrove loss has been slowing, and global emissions could be more than halved if reduced loss rates remain in the future. Notably, the location of global emission hotspots was consistent with every dataset used to calculate deforestation rates or with alternative assumptions about carbon storage and emissions. Our results indicate the regions in need of policy actions to address emissions arising from mangrove loss and the drivers that could be managed to prevent them., Business as usual for mangroves by the end of the century could result in emissions of over 2300 Tg of CO2 from agriculture in southeast and south Asia, and from clearing and erosion in the Caribbean, Myanmar, and north Brazil.

Physiological traits are key determinants of species success in any given environment. Competing metabolic demands can influence success by limiting the available scope for aerobically-demanding activities, including reproduction and dispersal. The present study investigated whether the aerobic performance of Gambusia holbrooki, one of the most invasive species in the world, was affected by the embryonic demands of pregnancy and whether these demands were compounded in a hypoxic environment. To quantify these effects, we measured the resting metabolic rate (RMR) and critical swimming speed (Ucrit) of wild-caught adult mosquitofish in saturated oxygen conditions, and following chronic exposure to hypoxic or hyperoxic water. Contrary to expectations, the RMR and Ucrit of gravid females was equal to that of non-gravid females and males, once the significant effects of body mass on these traits was accounted for. Whilst the exposure studies demonstrated that RMR changes subject to oxygen availability, overall aerobic performance does not. These findings suggest that mosquitofish metabolism is adapted for continued reproductive function and dispersal in low oxygen environments, which are essential for establishing and replenishment of populations. The ability of this species to tolerate hypoxia may confer a competitive advantage relative to native species, especially in disturbed lentic environments where prolonged periods of hypoxia are more common. Given their live-bearing mode of reproduction and resilience to the metabolic demands of reproduction, even in low oxygen conditions, we suggest that the physiology of female mosquitofish is a significant contributor to the invasion success and persistence of the species.

Background: Studying and quantifying fish behaviour is important to understand how fish interact with their environments. Yet much of fish behaviour in aquatic ecosystems remains hard to observe and time-consuming to manually document. Automated tracking through computer vision techniques can provide fine-scale movement data of many individuals across spatial and temporal scales. When used alongside statistical methodologies such as structural equation models (SEMs), these data can be used to infer underlying latent behavioural events of an animal without direct observations. However, interpreting the main modes of fish behaviour when presented with large datasets remains a challenge. Methods: We developed a cross-validation routine to evaluate methods for accurately predicting behaviour from a large field dataset. We created SEM behavioural models using different combinations of temporal buffers in training data and evaluated them against a fixed evaluation dataset for three common fish species (Moses perch, southern herring and yellowfin bream). We then used the SEM model with the lowest error for each species to translate movement data into ecologically relevant behavioural events. Results: The temporal buffer generating the SEM models with the best predictive capacity varied among species, from 1 min for Moses perch and southern herring, to 45 min for yellowfin bream. Models were able to accurately predict behavioural events such as foraging (slow, sinuous movement near the substrate) and fine-scale diurnal migration (fast, directional movement near the surface).Conclusions: We developed a framework to optimise temporal partitioning in computer vision tracking data using SEMs. We demonstrate how data can be translated into ecologically relevant behavioural events such as foraging and fine-scale migrations. This is a step towards bridging the gap between development and application of new technologies to monitor behaviour of animals in aquatic ecosystems.

Global-scale conservation initiatives and policy instruments rely on ecosystem indicators to track progress towards targets and objectives. A deeper understanding of indicator interrelationships would benefit these efforts and help characterize ecosystem status. We study interrelationships among 34 indicators for mangroves, saltmarsh, and seagrass ecosystems, and develop data-driven, spatially explicit typologies of coastal wetland status at a global scale. After accounting for environmental covariates and gap-filling missing data, we obtained two levels of clustering at 5 and 18 typologies, providing outputs at different scales for different end users. We generated 2,845 cells (1° (lat) × 1° (long)) globally, of which 29.7% were characterized by high land- and marine-based impacts and a high proportion of threatened species, 13.5% by high climate-based impacts, and 9.6% were refuges with lower impacts, high fish density and a low proportion of threatened species. We identify instances where specific actions could have positive outcomes for coastal wetlands across regions facing similar issues. For example, land- and marine-based threats to coastal wetlands were associated with ecological structure and function indicators, suggesting that reducing these threats may reduce habitat degradation and threats to species persistence. However, several interdimensional relationships might be affected by temporal or spatial mismatches in data. Weak relationships mean that global biodiversity maps that categorize areas by single indicators (such as threats or trends in habitat size) may not be representative of changes in other indicators (e.g., ecosystem function). By simplifying the complex global mosaic of coastal wetland status and identifying regions with similar issues that could benefit from knowledge exchange across national boundaries, we help set the scene for globally and regionally coordinated conservation.

Significance Seagrasses are important for ecosystem services, including climate regulation and fisheries production. But they are threatened by multiple pressures including poor water quality and coastal development. Seagrass extent is not monitored in many places, so areas at most risk of decline and the management actions needed in these places are largely unknown. We examine associations between change in seagrass meadow area and key pressures globally, helping predict the trajectory of meadows in unmonitored regions. We find rapidly shrinking seagrass meadows in areas where water quality is poor and destructive fishing occurs. Trajectories of change also vary with seagrass life-history strategy. Finally, we identify several unmonitored locations at risk of decline, highlighting where urgent monitoring and management are required., Seagrass meadows are threatened by multiple pressures, jeopardizing the many benefits they provide to humanity and biodiversity, including climate regulation and food provision through fisheries production. Conservation of seagrass requires identification of the main pressures contributing to loss and the regions most at risk of ongoing loss. Here, we model trajectories of seagrass change at the global scale and show they are related to multiple anthropogenic pressures but that trajectories vary widely with seagrass life-history strategies. Rapidly declining trajectories of seagrass meadow extent (>25% loss from 2000 to 2010) were most strongly associated with high pressures from destructive demersal fishing and poor water quality. Conversely, seagrass meadow extent was more likely to be increasing when these two pressures were low. Meadows dominated by seagrasses with persistent life-history strategies tended to have slowly changing or stable trajectories, while those with opportunistic species were more variable, with a higher probability of either rapidly declining or rapidly increasing. Global predictions of regions most at risk for decline show high-risk areas in Europe, North America, Japan, and southeast Asia, including places where comprehensive long-term monitoring data are lacking. Our results highlight where seagrass loss may be occurring unnoticed and where urgent conservation interventions are required to reverse loss and sustain their essential services.

Wetlands of Melaleuca spp. in Australia form large forests that are highly threatened by deforestation and degradation. In America, Melaleuca has invaded large areas of native wetlands causing extensive damage. Despite their status as an endangered native ecosystem and as a highly invasive one, little is known about their C and N dynamics. In this study, we sampled five Melaleuca wetlands and measured their C and N ecosystem stocks (aboveground biomass and soil), tree accumulation rates, sedimentation rates, and soil stability. Melaleuca wetlands were highly heterogeneous, but most have large ecosystem C [mean ± SE (range); 360 ± 100 (80–670) Mg C ha−1] and N [8100 ± 1900 (1600–13,000) kg N ha−1] stocks. Tree accumulation rates were 5.0 ± 2.1 Mg C y−1 and 26 ± 14 kg N y−1, and surface soil accumulation rates were 0.6 ± 0.2 Mg C ha−1 y−1 and 39 ± 1 kg N y−1. We found evidence of long-term C and N accumulation in the soil, but also of some level of organic decomposition. Overall, we found that Melaleuca wetlands store and accumulate large amounts of C, especially in their trees, and large amounts of N in their soils, suggesting an important role in coastal biogeochemical cycles.

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.

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.

As human impacts increase in coastal regions, there is concern that critical habitats that provide the foundation of entire ecosystems are in decline. Seagrass meadows face growing threats such as poor water quality and coastal development. To determine the status of seagrass meadows over time, we reconstructed time series of meadow area from 175 studies that surveyed 547 sites around the world. We found an overall trajectory of decline in all seven bioregions with a global net loss of 5602 km2 (19.1% of surveyed meadow area) occurring since 1880. Declines have typically been non-linear, with rapid and historical losses observed in several bioregions. The greatest net losses of area occurred in four bioregions (Tropical Atlantic, Temperate North Atlantic East, Temperate Southern Oceans and Tropical Indo-Pacific), with declining trends being the slowest and most consistent in the latter two bioregions. In some bioregions, trends have recently stabilised or reversed. Losses, however, still outweigh gains. Despite consistent global declines, meadows show high variability in trajectories, within and across bioregions, highlighting the importance of local context. Studies identified 12 different drivers of meadow area change, with coastal development and water quality as the most commonly cited. Overall, however, attributions were primarily descriptive and only 10% of studies used inferential attributions. Although ours is the most comprehensive dataset to date, it still represents only one-tenth of known global seagrass extent, with conspicuous historical and geographic biases in sampling. It therefore remains unclear whether the bioregional patterns of change documented here reflect changes in the world's unmonitored seagrass meadows. The variability in seagrass meadow trajectories, and the attribution of change to numerous drivers, suggest we urgently need to improve understanding of the causes of seagrass meadow loss if we are to improve local-scale management.

Coronavirus disease 2019 (COVID-19) is a global crisis. Severe interruptions to international trade and travel are crippling economies and forcing reevaluation of economic, health, and environmental trajectories. Given that COVID-19 has triggered widespread changes in human behavior and reductions in pollution (1, 2), it presents opportunities for further positive change. Lockdowns have spurred households to rethink consumer needs, making now an opportune time to promote sustainable consumer choices that will become more engrained with prolonged exposure (1). How we emerge from the state of lockdowns will drive a new world economy with lasting effects on global biodiversity and supply chains (3, 4).

There is an urgent need to halt and reverse loss of mangroves and seagrass to protect and increase the ecosystem services they provide to coastal communities, such as enhancing coastal resilience and contributing to climate stability.

At the crux of the debate over the global sustainability of fisheries is what society must do to prevent over‐exploitation and aid recovery of fisheries that have historically been over‐exploited. The focus of debates has been on controlling fishing pressure, and assessments have not considered that stock production may be affected by changes in fish habitat. Fish habitats are being modified by climate change, built infrastructure, destructive fishing practices and pollution. We conceptualize how the classification of stock status can be biased by habitat change. Habitat loss and degradation can result in either overly optimistic or overly conservative assessment of stock status. The classification of stock status depends on how habitat affects fish demography and what reference points management uses to assess status. Nearly half of the 418 stocks in a global stock assessment database use seagrass, mangroves, coral reefs and macroalgae habitats that have well‐documented trends. There is also considerable circumstantial evidence that habitat change has contributed to over‐exploitation or enhanced production of data‐poor fisheries, like inland and subsistence fisheries. Globally many habitats are in decline, so the role of habitat should be considered when assessing the global status of fisheries. New methods and global databases of habitat trends and use of habitats by fishery species are required to properly attribute causes of decline in fisheries and are likely to raise the profile of habitat protection as an important complementary aim for fisheries management.

Submerged aquatic vegetation (SAV; e.g. seagrasses, macroalgae), forms key habitats in shallow coastal systems that provide a plethora of ecosystem services, including coastal protection, climate mitigation and supporting fisheries production. Light limitation is a critical factor influencing the growth and survival of SAV, thus it is important to understand how much light SAV needs, and receives, to effectively assess the risk that light limitation poses. Light monitoring is commonly used to inform environmental decision making to minimise loss of SAV habitat, but the temporal and spatial extent of monitoring is often limited by cost and logistical difficulties. An ability to remotely estimate light across different locations can therefore improve the conservation and management of SAV habitats. Here we combine an extensive monitoring program with publicly available data and machine learning to develop a model that estimates the light reaching submerged seagrasses in a shallow subtropical embayment in southern Queensland, Australia. Our model accurately predicts the intensity of photosynthetically active radiation (PAR) reaching the canopy of SAV from entirely remotely available data. The best performing model predicted light intensity with >99% at the management relevant daily, and 14-day rolling average time resolutions. This model enables monitoring of light available to SAV without an ongoing need for in-water instruments, minimising cost and risk to personnel, and improving assessment speed. The technique can be applied to SAV management plans in shallow waters throughout the world, where suitable remote public data is available.

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.

Our lack of knowledge on the spatiotemporal drivers of the distribution of many freshwater fishes, particularly as they differ among life-history stages, is a challenge to conservation of these species. We used 2-stage hurdle models to investigate drivers of occurrence and abundance of locally threatened adult and juvenile Northern River Blackfish in the upper Condamine River, Queensland, Australia. Different processes drive occurrence and abundance between the 2 life-history stages. Both adult and juvenile occurrences were negatively associated with high-magnitude, extended warming events, suggesting Northern River Blackfish are thermally restricted to cooler headwaters. Juveniles had greater sensitivity than adults to high stream temperatures. In contrast, drivers of abundance differed between life-history stages. Adult fish were negatively associated with increased fine-sediment loads, whereas juveniles were negatively associated with a hydrologically active inverse-distance-weighted grazing metric that accounted for the greater influence of grazed land close to the stream or in areas of high overland flow. Teasing apart environmental drivers affecting multiple life-history stages of a locally threatened headwater species enabled us to provide direct management recommendations for conserving this species and ecologically similar headwater fishes and their associated habitats.

Accurately evaluating ecosystem status is vital for effective conservation. The Red List of Ecosystems (RLE) from the International Union for the Conservation of Nature (IUCN) is the global standard for assessing the risk of ecosystem collapse. Such tools are particularly needed for large, dynamic ecosystem complexes, such as the Indian Sundarbans mangrove forest. This ecosystem supports unique biodiversity and the livelihoods of millions, but like many mangrove forests around the world is facing substantial pressure from a range of human activities. Holistic, standardised and quantitative environment risk assessment frameworks are essential here, because previous assessments have either been qualitative in nature, or have generally considered single threats in isolation. We review these threats and utilise the RLE framework to quantitatively assess the risk of ecosystem collapse. Historical clearing and diminishing fish populations drove a status of Endangered (range: Vulnerable to Endangered), and ongoing threats including climate change and reduced freshwater supply may further impact this ecosystem. However, considering recent change, the outlook is more optimistic. Mangrove extent has stabilised, and analysis of mangrove condition highlights that only a small proportion of the forest is degraded. Using the RLE provides an authoritative avenue for further protection and recognition of the issues facing this UNESCO World Heritage Site. We also identify knowledge and data gaps in the Sundarbans that are likely common to coastal systems globally. By articulating these and presenting opportunities and recommendations, we aim to further the conservation goals of the IUCN and the implementation of its new assessment framework.

Vegetated coastal wetlands, including seagrass, saltmarsh and mangroves, are threatened globally, yet the need to avert these losses is poorly recognized in international policy, such as in the Convention on Biological Diversity and the United Nations (UN) Sustainable Development Goals. Identifying the impact of overlooking coastal wetlands in ecosystem assessment frameworks could help prioritize research efforts to fill these gaps. Here, we examine gaps in the recognition of coastal wetlands in globally applicable ecosystem assessments. We address both shortfalls in assessment frameworks when it comes to assessing wetlands, and gaps in data that limit widespread application of assessments. We examine five assessment frameworks that track fisheries, greenhouse gas emissions, ecosystem threats, and ecosystem services. We found that these assessments inform management decisions, but that the functions provided by coastal wetlands are incompletely represented. Most frameworks had sufficient complexity to measure wetland status, but limitations in data meant they were incompletely informed about wetland functions and services. Incomplete representation of coastal wetlands may lead to them being overlooked by research and management. Improving the coverage of coastal wetlands in ecosystem assessments requires improving global scale mapping of wetland trends, developing global-scale indicators of wetland function and synthesis to quantitatively link animal population dynamics to wetland trends. Filling these gaps will help ensure coastal wetland conservation is properly informed to manage them for the outstanding benefits they bring humanity.

Freshwater stream systems are under immense pressure from various anthropogenic impacts, including climate change. Stream systems are increasingly being altered by changes to the magnitude, timing, frequency, and duration of their thermal regimes, which will have profound impacts on the life-history dynamics of resident biota within their home range. Although temperature regimes have a significant influence on the biology of instream fauna, large spatio-temporal temperature datasets are often reduced to a single metric at discrete locations and used to describe the thermal regime of a system; potentially leading to a significant loss of information crucial to stream management. Models are often used to extrapolate these metrics to unsampled locations, but it is unclear whether predicting actual daily temperatures or an aggregated metric of the temperature regime best describes the complexity of the thermal regime. We fit spatial statistical stream-network models (SSNMs), random forest and non-spatial linear models to stream temperature data from the Upper Condamine River in QLD, Australia and used them to semi-continuously predict metrics describing the magnitude, duration, and frequency of the thermal regime through space and time. We compared both daily and aggregated temperature metrics and found that SSNMs always had more predictive ability than the random forest models, but both models outperformed the non-spatial linear model. For metrics describing thermal magnitude and duration, aggregated predictions were most accurate, while metrics describing the frequency of heating events were better represented by metrics based on daily predictions generated using a SSNM. A more comprehensive representation of the spatio-temporal thermal regime allows researchers to explore new spatio-temporally explicit questions about the thermal regime. It also provides the information needed to generate a suite of ecologically meaningful metrics capturing multiple aspects of the thermal regime, which will increase our scientific understanding of how organisms respond to thermal cues and provide much-needed information for more effective management actions.

Mangroves are one of the few woody ecosystems that grow in hot-arid climates. They can survive extreme conditions of low precipitation, high solar radiation, wide temperature fluctuations and hypersalinity. These unique mangroves have distinct geomorphology, hydrology, forest structure, tree physiology, and soil biogeochemistry. In this review, supported by field data from Australia and Mexico, we explore the characteristics of mangroves in arid climates of the world. These mangroves are mostly tide-dominated with freshwater flows restricted to groundwater and sporadic tropical storms. They form dense forests with stunted growth dominated mainly by trees of the genus Avicennia that co-occur with salt marshes in the high intertidal. Their soils have low nutrient and carbon concentrations, and high soil δ15 N and δ13C values compared to subhumid and humid mangroves. Mangroves in arid climates have relatively low human pressure due to sparse human settlements. Key threats to these mangroves, which often persist at the edge of their physiological tolerances, include extreme drought, reductions in groundwater inputs, altered hydrology, sea-level fluctuations and increases in nutrient loading. Restoration of mangroves in arid climates should focus on restoring their hydrology. Mangroves in arid zones are under-represented in global maps and assessment programs, as they may not be consistent with countries’ definition of “forests”. Improved global representation and understanding of the ecology of mangroves in arid climates could help sustain their valuable ecosystem services.

Human-induced habitat clearing and pollution are leading drivers of biodiversity loss. Ecosystem assessments are required to identify ecosystems at risk of collapse, but they should account for cross-system linkages and dynamics where necessary. This is particularly true for coastal wetlands (e.g. seagrass, mangroves and saltmarsh), which exhibit high ecological connectivity and have individually suffered global declines over the last century. We use the coastal wetlands of Moreton Bay, Queensland, Australia, as a model system to examine how integrating outcomes of multiple, simultaneously conducted, ecosystem assessments can assist in identifying appropriate management and conservation strategies. We simultaneously conducted separate assessments of seagrass, mangrove and saltmarsh ecosystems against the IUCN Red List of Ecosystems criteria. Despite substantial human population growth in the region, seagrass and mangroves were assessed as Least Concern. Mangroves were found to be rapidly encroaching on saltmarsh. This process, together with past clearing, were the major drivers behind saltmarsh being assessed as Endangered. Given the importance of connectivity among these connected ecosystems, collapse in any one ecosystem can have seascape-wide consequences, highlighting the benefit of conducting multi-ecosystem assessments. Consequently, a fully integrated assessment of the coastal wetlands as a single entity would miss key processes, such as mangrove encroachment, potentially underestimating overall risks. Our study highlights the plight of saltmarsh and the value of conducting simultaneous RLE assessments for multiple ecosystems comprising seascapes. We recommend that connectivity be accounted for explicitly in assessments of other connected, high-risk ecosystems.

Human activities that threaten ecosystems often vary across small spatial scales, though they can be driven by large-scale factors like national governance. Here, we use two decades of data on global mangrove deforestation to assess whether landscape-scale indirect pressures – cumulative impacts, population density, mangrove forest fragmentation, the global human footprint – and management responses (protected areas) are related to rates of mangrove loss, and whether the impacts of these activities vary by nation. By integrating rates of loss at different spatial scales into a Bayesian hierarchical model, we also assess whether national-scale patterns in mangrove loss are predicted by national regulatory quality. Globally, less fragmented forests had lower rates of mangrove loss. We observed variability among nations in the effect of pressures and management responses on mangrove loss. National regulatory quality mediated how pressures and management interact to influence mangrove loss. Protected areas had a greater benefit for slowing mangrove loss rates in countries with low, rather than high, regulatory quality, ostensibly because countries with higher regulatory quality have greater protection of mangroves outside of protected areas. High population densities were also associated with greater mangrove loss, but only in nations with low regulatory quality. We suggest that efforts to protect mangrove forests will benefit from developing solutions that consider national context and address differences in the effect of pressures and cumulative impacts. Our model can also be applied to other globally threatened ecosystems to understand how variation in local context can affect national-scale conservation outcomes.

Stressors to marine ecosystems are increasing, driven by human activities in the sea and on land, and climate change. Cumulative impact maps highlight regions affected by multiple human activities, but efficient conservation investment requires linking dominant pressures to management actions that best address the particular drivers of impacts. We rebuild cumulative impact maps by stressor type (climate change, marine and land) at a global scale to evaluate the expected effectiveness of various management strategies for all coastal territories. Average cumulative impact from non-marine stressors (climate and land) was double those of marine impacts at a national level. The greatest climate impacts by country were in the waters of Pacific Island and Antarctic territories; in the Caspian Sea region and East-Asia for land impacts; and in the waters of European, East-Asian and Caribbean countries for marine impacts. We developed a conservation-effectiveness indicator for the 10 worst-impacted countries in each of the three stressor categories. The indicator considered common management tools for each stressor category: ecosystem-based adaptation and disaster risk reduction (climate), marine protected areas (marine) and integrated coastal management (land). Key disparities were found between broad-scale management of marine ecosystems and the dominant stressors, with existing management in tropical island nations likely insufficient to address intense impacts from climate change. These countries also typically had low performance on governance indicators, suggesting challenges in implementing new mitigation. We highlight trade-offs in making decisions for stressor mitigation and offer strategic guidance on identifying locations to target management of marine, land, or climate impacts.

China's Belt and Road Initiative is the world's largest infrastructure development project aimed at linking Europe and East Africa with Asia. Port infrastructure development associated with the maritime component of China's Belt and Road Initiative (mBRI) could have trans-boundary environmental impacts. These impacts are likely to affect key coastal marine habitats (coral reefs, mangroves, seagrasses and saltmarshes) and threatened marine species. We used spatial analyses to quantify the potential impacts of ports and subsequent increased shipping traffic associated with the mBRI for key habitats and species. Significant areas of individual countries coastal marine habitats could be affected by port development. Over 400 threatened marine species, including mammals, could be affected by port infrastructure, while over 200 threatened species are at risk from an increase in shipping traffic and noise pollution. A project of this magnitude provides an opportunity for a central governing body to develop and implement an overarching environmental framework and policy that mitigates risks to biodiversity.

Habitat loss is accelerating a global extinction crisis. Conservation requires understanding links between species and habitats. Emerging research is revealing important associations between vegetated coastal wetlands and marine megafauna, such as cetaceans, sea turtles, and sharks. But these links have not been reviewed and the importance of these globally declining habitats is undervalued. Here, we identify associations for 102 marine megafauna species that utilize these habitats, increasing the number of species with associations based on current International Union for the Conservation of Nature (IUCN) species assessments by 59% to 174, accounting for over 13% of all marine megafauna. We conclude that coastal wetlands require greater protection to support marine megafauna, and present a simple, effective framework to improve the inclusion of habitat associations within species assessments.

It has long been hypothesised that there is a functional correlation between brain size and metabolic rate in vertebrates. The present study tested this hypothesis in wild-caught adult mosquitofish Gambusia holbrooki by testing for an intra-specific association between resting metabolic rate (RMR) and brain size while controlling for variation in body size, and through the examination of the effects of spatial enrichment and laboratory housing on body mass-independent measures of brain size and RMR. Controlling for body mass, there was no relationship between brain size and RMR in wild-caught fish. Contrary to predictions, spatial enrichment caused a decrease in mass-independent brain size, highlighting phenotypic plasticity in the adult brain. As expected, after controlling for differences in body size, wild-caught fish had relatively larger brains than fish that had been maintained in the laboratory for a minimum of six weeks, but wild-caught fish also had significantly lower mass-independent RMR. This study demonstrates that an organisms' housing environment can cause significant plastic changes to fitness related traits including brain size and RMR. We therefore conclude that current standard laboratory housing conditions may cause captive animals to be non-representative of their wild counterparts, potentially undermining the transferability of previous laboratory-based studies of aquatic ectothermic vertebrates to wild populations., Summary: The discovery of a difference in brain size between adult mosquitofish living in the wild, in spatially enriched tanks and in bare tanks has implications for the effect of environmental enrichment on transferability of data from laboratory animals to their wild counterparts.

Dryland river foodwebs are thought to be largely driven by autochthonous production derived from littoral/benthic algae, particularly during extended periods of zero flow, with allochthonous production taking primacy after flooding as floodplain carbon is distributed into waterholes during flood recession. This study tested whether we could detect any influence of autochthonous production (littoral gross primary production) on fish biomass after flooding in Cooper Creek, a dryland river in the Lake Eyre Basin, Australia. It was found that the majority of fish biomass, mostly large carnivores, was not supported by benthic algal production. However, the biomass of juvenile bony bream Nematalosa erebi, the highly abundant benthivore of many Australian dryland rivers, was indeed driven by benthic algal productivity throughout the post-flood period, a finding also evident in post-flood waterholes in the nearby Warrego River (Murray-Darling Basin). With a consistently high abundance turnover of bony bream juveniles and their significant importance to dryland river food-webs this study demonstrates not only the need to protecting intact littoral zones for N. erebi, but by association, fish assemblages in general.

At the crux of the debate over the global sustainability of fisheries is what society must do prevent overexploitation of fisheries and aid recovery of fisheries that have historically been overexploited. The focus of debates has been on controlling fishing pressure and assessments have not considered that stock production may be affected by changes in fish habitat. Fish habitats are being modified by climate change, built infrastructure, destructive fishing practices and pollution. We conceptualise how the classification of stock status can be biased by habitat change. Habitat loss can result in either overly optimistic or overly conservative assessment of stock status. The classification of stock status depends on how habitat affects fish demography and what reference points management uses to assess status. Nearly half of the 418 stocks in a global stock assessment database use seagrass, mangroves, coral reefs and macroalgae, habitats that have well documented trends. There is also considerable circumstantial evidence that habitat change has contributed to overexploitation or enhanced production of data-poor fisheries, like inland and subsistence fisheries. Globally many habitats are in decline, so the role of habitat should be considered when assessing the global status of fisheries. New methods and global databases of habitat trends, and use of habitats by fishery species are required to properly attribute the causes of decline in fisheries, and are likely to raise the profile of habitat protection as an important complementary aim for fisheries management.

The distribution and population structure of organisms is governed by a broad suite of biotic and abiotic variables, interacting across multiple scales. Recruitment is a key demographic process critical to the maintenance of successful populations. Isolating and quantifying the multiscale environmental drivers of recruitment is vital for species conservation, especially for those species with traits that increase their susceptibility to local extirpation. We developed a Bayesian hierarchical model to quantify the relationship between the rate of recruitment in a locally threatened river blackfish (Gadopsis marmoratus) and environmental predictors across two spatial scales. There was a 0.99 probability that increased broad-scale stream temperature negatively affected juvenile recruitment rate. We also found that there was a 0.97 probability that the fine-scale relationship between recruitment rate and riparian foliage cover was dependent on temperature. This suggests that broad-scale thermal conditions provide the template upon which at least one local environmental variable influences recruitment rate. Understanding drivers influencing key population processes and the spatial scales at which they operate is critical to gaining an insight into likely changes in population persistence for potentially imperilled species, along with the potential future effects of habitat degradation and climate warming on freshwater fishes in general.

Excess nitrogen (N) leading to the eutrophication of water and impacts on ecosystems is a serious environmental challenge. Wetlands can remove significant amounts of N from the water, primarily through the process of denitrification. Most of our knowledge on wetland denitrification is from temperate climates; studies in natural tropical wetlands are very scarce. We measured denitrification rates during a dry and a wet season in five floodplain forests dominated by Melaleuca spp., a coastal freshwater wetland of tropical Australia. We hypothesised that the denitrification potential of these wetlands would be high throughout the year and would be limited by N and carbon (C) availability. Mean potential denitrification rates (Dt) were 5.0±1.7mgm2h–1, and were within the reported ranges for other tropical and temperate wetlands. The rates of Dt were similar between the dry and the wet seasons. From the total unamended denitrification rates (Dw, 3.1±1.7mgm2h–1), 64% was derived from NO3– of the water column and the rest from coupled nitrification–denitrification. The factor most closely associated with denitrification was background water NO3–-N concentrations. Improved management and protection of wetlands could play an important role in improving water quality in tropical catchments.