Loss Of Freshwater Biodiversity Research Articles

Bending the curve of global freshwater biodiversity loss: what are the prospects?

Freshwater biodiversity conservation has received substantial attention in the scientific literature and is finally being recognized in policy frameworks such as the Global Biodiversity Framework and its associated targets for 2030. This is important progress. Nonetheless, freshwater species continue to be confronted with high levels of imperilment and widespread ecosystem degradation. An Emergency Recovery Plan (ERP) proposed in 2020 comprises six measures intended to "bend the curve" of freshwater biodiversity loss, if they are widely adopted and adequately supported. We review evidence suggesting that the combined intensity of persistent and emerging threats to freshwater biodiversity has become so serious that current and projected efforts to preserve, protect and restore inland-water ecosystems may be insufficient to avert substantial biodiversity losses in the coming decades. In particular, climate change, with its complex and harmful impacts, will frustrate attempts to prevent biodiversity losses from freshwater ecosystems already affected by multiple threats. Interactions among these threats will limit recovery of populations and exacerbate declines resulting in local or even global extinctions, especially among low-viability populations in degraded or fragmented ecosystems. In addition to impediments represented by climate change, we identify several other areas where the absolute scarcity of fresh water, inadequate scientific information or predictive capacity, and a widespread failure to mitigate anthropogenic stressors, are liable to set limits on the recovery of freshwater biodiversity. Implementation of the ERP rapidly and at scale through many widely dispersed local actions focused on regions of high freshwater biodiversity and intense threat, together with an intensification of ex-situ conservation efforts, will be necessary to preserve native freshwater biodiversity during an increasingly uncertain climatic future in which poorly understood, emergent and interacting threats have become more influential. But implementation of the ERP must be accompanied by measures that will improve water, energy and food security for humans - without further compromising the condition of freshwater ecosystems. Unfortunately, the inadequate political implementation of policies to arrest widely recognized environmental challenges such as climate change do not inspire confidence about the possible success of the ERP. In many parts of the world, the Anthropocene future seems certain to include extended periods with an absolute scarcity of uncontaminated surface runoff that will inevitably be appropriated by humans. Unless there is a step-change in societal awareness of - and commitment to - the conservation of freshwater biodiversity, together with necessary actions to arrest climate change, implementation of established methods for protecting freshwater biodiversity may not bend the curve enough to prevent continued ecosystem degradation and species loss.

Evaluating the eDNA spatial signal in natural populations and its application for the monitoring of the threatened Harttiella (Siluriformes, Loricariidae)

AbstractTo face the current downward trajectory of freshwater biodiversity loss, the implementation of effective biodiversity monitoring programs is of utmost importance. Environmental DNA offers unprecedented opportunities for this aim but several challenges still need to be addressed before implementing efficient species monitoring using eDNA. One of them is optimizing the eDNA sampling scheme to maximize the eDNA detection probability. For instance, in flowing freshwaters, the transport of eDNA downstream from its source can impact the eDNA detection probability, and blur the link between eDNA detection and the local occurrence of the species. Here, we investigated the eDNA spatial range of Harttiella lucifer (Siluriformes, Loricariidae), a threatened neotropical siluriform fish inhabiting French Guianese mountain streams, and confined to waterfalls and fast‐flowing environments. Environmental samples were collected at 11 sites from the H. lucifer population to 2000 m downstream. A species‐specific dPCR approach was applied to quantify the amount of DNA present in each sample and evaluate the eDNA detection probability of H. lucifer according to the distance from its source. Results showed an accumulation of eDNA at 50 and 100 m downstream from H. lucifer population. The evaluation of detection probabilities revealed that 300 m downstream from H. lucifer population, the probability of detection drops to 50%. This study suggests that eDNA drift in neotropical small streams is limited to a few tens meters downstream. These findings demonstrate that in neotropical small streams, eDNA provides a picture of the local fish fauna rather than integrating information over large spatial scales.

Unraveling fish diversity and assembly patterns in a temperate river: Evidence from environmental DNA metabarcoding and morphological data

The loss of freshwater biodiversity has drawn greater attention to fish diversity and community assembly patterns. However, traditional survey methods, such as ground cages and electrofishing, may cause damage to fish communities and have become increasingly unsuitable for frequent and large-scale fish diversity surveys. In this study, environmental DNA (eDNA) metabarcoding and morphological data were both used to investigate the distribution and diversity of fish communities in the Taizi River basin, a temperate river in Northeast China, and the fish diversity and assembly patterns were investigated by using the null model. The results showed that a total of 7 orders, 17 families, 49 genera and 56 species were detected by the eDNA metabarcoding (6 orders, 15 families, 40 genera and 45 species) and morphological method (6 orders, 10 families, 31 genera and 34 species), and the eDNA method had a higher detection probability. Cypriniformes was detected most frequently, followed by Perciformes. Principal coordinate analysis revealed that fish communities in the Taizi River exhibited different spatial structures between the upper and lower reaches, with fish sensitive to environmental changes mostly found in the upper reaches and higher fish richness in the same area. The beta diversity in the upper reaches was higher than that in the lower reaches. The null model results showed the main factor that affected the distribution of fish in the Taizi River is the stochastic processes. Among the deterministic processes, the main environmental filter factors affecting fish community structure include total phosphorus, biochemical oxygen demand and temperature. We also confirm that eDNA metabarcoding has a higher detection rate compared to traditional survey methods, so it is feasible for freshwater ecosystem and fish resource monitoring. Therefore, the utilization of eDNA metabarcoding can effectively enhance monitoring efficiency and minimize interference with water bodies.

Freshwater biodiversity loss in urbanised rivers

Since the second half of the 20th century, when monitoring programmes were implemented as a measure to improve the water quality of rivers, numerous advantages have been achieved. one of the most remarkable advances was the integration of bioindicators as a suitable and quick tool to complement the assessment based on the evaluation of physical and chemical parameters. This paper evaluated which of the already used water quality indices based on macroinvertebrates would be more suitable to assess the ecological status of 6 rivers (Barxas, Deva, Tea, Manco, Louro and Furnia rivers) within the Miño River international basin (NW Spain and N Portugal) applying the methodology proposed by the Water Framework Directive (WFD). In addition, the relationship between the water quality and the land uses within a buffer zone of 100 along the watershed of each river was studied. Our findings demonstrate that the IBMWP (Iberian Biomonitoring Working Party) is the most suitable index to evaluate the water quality of rivers from this geographical zone. Nevertheless it is necessary to use other more sensitive index like EPT and PT indices to identify any potential pressures that might be concealed by IBMWP. The tributaries of the Miño River generally presented a good ecological status according to the IBMWP. Nevertheless, the Louro River had the lowest score for all the indices being the worst preserved among all within the basin. On the contrary Barxas, Deva and Furnia rivers showed the higher values. The results indicated that the most urbanised river was the Louro River (13 %) followed, to a lesser extent, by Manco River (7 %) and Tea River (2 %). Consequently, the Louro River had the worst water quality (poor quality) and a less diverse benthic macroinvertebrate community, in which more generalist taxa such as Chironomids, Ceratopogonids, or Crustaceans were found. On the other hand, the rivers with the best water quality were the Barxas, Deva, and Furnia, all of them with a negligible proportion of artificial cover surface (<1 %) within the delimited buffer zone. This would suggest a negative influence of the proportion of artificial areas over diversity and quality indices.

Bridging gaps in the Indian freshwater biodiversity conservation through science-based and policy-backed recommendations

India's freshwater biological resources are threatened by multiple stressors and ongoing conservation efforts are insufficient to tackle these challenges. We therefore propose 14 recommendations to halt India's freshwater biodiversity loss. i) Set up a separate ministry on biodiversity to develop and monitor policies. ii) Collection of comprehensive ecological data and sharing with the global scientific community for better assessment. iii) Assessment of data reliability and relevance towards conservation and sustainable management. iv) Integrating terrestrial-freshwater ecosystem management to effectively conserve freshwater biota. v) Implementation of environmental flow regulations for maintaining hydrological connectivity. vi) Augmentation of Protected Areas to protect freshwater biota. vii) Implementation of regulatory frameworks for trade in exotic species to reduce invasiveness. viii) Avoiding fish seed ranching programs in rivers to evade contamination of natural stocks and disease outbreaks from aquaculture. ix) Increasing collaboration between neighboring states and countries on shared freshwater ecosystem for global and regional sustainability. x) Inclusion of compulsory curriculum on biodiversity at different educational stages for developing responsibility towards protecting biodiversity. xi) Building trust among all stakeholders for better management plans through their active participation. xii) Providing alternative livelihood options to improve the socio-economic status of local people to reduce their direct dependency on freshwater ecosystems. xiii) Promotion of citizen science approach on remuneration basis in conserving freshwater biodiversity. xiv) Enabling better use of digital technologies for freshwater biodiversity monitoring. Inclusion of these timely science-based and policy-backed aquatic ecosystems protection guidelines will therefore help to achieve freshwater biodiversity conservation goals successfully in India.

Accelerating environmental flow implementation to bend the curve of global freshwater biodiversity loss

Environmental flows (e-flows) aim to mitigate the threat of altered hydrological regimes in river systems and connected waterbodies and are an important component of integrated strategies to address multiple threats to freshwater biodiversity. Expanding and accelerating implementation of e-flows can support river conservation and help to restore the biodiversity and resilience of hydrologically altered and water-stressed rivers and connected freshwater ecosystems. While there have been significant developments in e-flow science, assessment, and societal acceptance, implementation of e-flows within water resource management has been slower than required and geographically uneven. This review explores critical factors that enable successful e-flow implementation and biodiversity outcomes in particular, drawing on 13 case studies and the literature. It presents e-flow implementation as an adaptive management cycle enabled by 10 factors: legislation and governance, financial and human resourcing, stakeholder engagement and co-production of knowledge, collaborative monitoring of ecological and social-economic outcomes, capacity training and research, exploration of trade-offs among water users, removing or retrofitting water infrastructure to facilitate e-flows and connectivity, and adaptation to climate change. Recognising that there may be barriers and limitations to the full and effective enablement of each factor, the authors have identified corresponding options and generalizable recommendations for actions to overcome prominent constraints, drawing on the case studies and wider literature. The urgency of addressing flow-related freshwater biodiversity loss demands collaborative networks to train and empower a new generation of e-flow practitioners equipped with the latest tools and insights to lead adaptive environmental water management globally. Mainstreaming e-flows within conservation planning, integrated water resource management, river restoration strategies, and adaptations to climate change is imperative. The policy drivers and associated funding commitments of the Kunming–Montreal Global Biodiversity Framework offer crucial opportunities to achieve the human benefits contributed by e-flows as nature-based solutions, such as flood risk management, floodplain fisheries restoration, and increased river resilience to climate change.

Future-proofing the emergency recovery plan for freshwater biodiversity

Freshwater biodiversity loss is accelerating globally, but humanity can change this trajectory through actions that enable recovery. To be successful, these actions require coordination and planning at a global scale. The Emergency Recovery Plan for global freshwater biodiversity aims to reduce the risk for freshwater biodiversity loss through six priority actions: (1) accelerate implementation of environmental flows; (2) improve water quality to sustain aquatic life; (3) protect and restore critical habitats; (4) manage exploitation of freshwater species and riverine aggregates; (5) prevent and control nonnative species invasions in freshwater habitats; and (6) safeguard and restore freshwater connectivity. These actions can be implemented using future-proofing approaches that anticipate future risks (e.g., emerging pollutants, new invaders, and synergistic effects) and minimize likely stressors to make conservation of freshwater biodiversity more resilient to climate change and other global environmental challenges. While uncertainty with respect to past observations is not a new concern for freshwater biodiversity, future-proofing has the distinction of accounting for the uncertainty of future conditions that have no historical baseline. The level of uncertainty with respect to future conditions is unprecedented. Future-proofing of the Emergency Recovery Plan for freshwater biodiversity will require anticipating future changes and developing and implementing actions to address those future changes. Here, we showcase future-proofing approaches likely to be successful using local case studies and examples. Ensuring that response options within the Emergency Recovery Plan are future-proofed will provide decision makers with science-informed choices, even in the face of uncertain and potentially new future conditions. We are at an inflection point for global freshwater biodiversity loss; learning from defeats and successes can support improved actions toward a sustainable future.

Preventing and controlling nonnative species invasions to bend the curve of global freshwater biodiversity loss

The Emergency Recovery Plan for freshwater biodiversity recognizes that addressing nonnative species is one of six principal actions needed to bend the curve in freshwater biodiversity loss. This is because introduction rates of nonnative species continue to accelerate globally and where these species develop invasive populations, they can have severe impacts on freshwater biodiversity. The most effective management measure to protect freshwater biodiversity is to prevent introductions of nonnative species. Should a nonnative species be introduced, however, then its early detection and the implementation of rapid reaction measures can avoid it establishing and dispersing. If these measures are unsuccessful and the species becomes invasive, then control and containment measures can minimize its further spread and impact. Minimizing further spread and impact includes control methods to reduce invader abundance and containment methods such as screening of invaded sites and strict biosecurity to avoid the invader dispersing to neighbouring basins. These management actions have benefitted from developments in invasion risk assessment that can prioritize species according to their invasion risk and, for species already invasive, ensure that management actions are commensurate with assessed risk. The successful management of freshwater nonnative species still requires the overcoming of some implementation challenges, including nonnative species often being a symptom of degraded habitats rather than the main driver of ecological change, and eradication methods often being nonspecies specific. Given the multiple anthropogenic stressors in freshwaters, nonnative species management must work with other restoration strategies if it is to deliver the Emergency Recovery Plan for freshwater biodiversity.

Documenting the impacts of increasing salinity in freshwater and coastal ecosystems: Introduction to the special issue

Documenting the impacts of increasing salinity in freshwater and coastal ecosystems: Introduction to the special issue

Using biodiversity indicators to identify priority areas for freshwater conservation in the African “Mediterranean Basin” biodiversity hotspot

The conservation of freshwater biodiversity is a global challenge for conservation biologists. The loss of freshwater biodiversity in the Mediterranean basin is particularly concerning given its biodiversity hotspot status and that its landscapes have been subject to anthropogenic modification and pressures for millennia. Most research on this region has focused on the conservation of the European region of the hotspot while knowledge regarding the north African part of the basin is much more limited. Recent research on aquatic insects has indicated that considering the combined richness of mayflies (Ephemeroptera) and aquatic beetles (Coleoptera) at the genus level is an effective surrogate for wider freshwater biodiversity within Mediterranean areas. For the first time, we use Ephemeroptera and aquatic Coleoptera biodiversity (using richness, rarity complementarity and irreplaceability) to identify freshwater biodiversity conservation priority areas in the African sector of the Mediterranean Basin global biodiversity hotspot. In addition, we undertake a gap analysis to determine how effective protected areas are in conserving the areas identified. Freshwater biodiversity conservation priority areas were mainly located in mountainous areas in the north of Morocco, Algeria and Tunisia, close to the Mediterranean Sea. Surprisingly, almost 80 % of these areas are currently unprotected. These results indicate the urgent need for policies and international agreements to protected North African freshwater biodiversity.

A national fish passage barrier inventory to support fish passage policy implementation and estimate river connectivity in New Zealand

Fragmentation of river systems is a key driver of freshwater biodiversity loss. Instream structure inventories are an essential component of delivering a strategic approach to restoring river connectivity. We used a range of data sources to collate the best available information on fish passage barriers and instream structures across the whole of New Zealand. To support implementation of new national policy objectives to maintain and improve river connectivity, the structure inventory has been integrated with a new fish passage assessment mobile application that allows river managers and asset owners to ground-truth, update and add records to the database. The data are provided open access and are being used for environmental reporting and to support strategic prioritisation of barrier mitigation actions. We used these data to quantify river connectivity at regional and national scales and demonstrated that at least half of New Zealand's river network is upstream of fish migration barriers. Limitations to our calculation of upstream river connectivity included the unknown influence of unrecorded structures, particularly on private land, missing information within recorded data, the large number of instream structures that have been identified but not yet assessed for their risk to fish passage, and spatial errors in the automated pairing of structures to a digital river network. A critical challenge for river managers is understanding the consequences of these uncertainties in the data for prioritisation and decision-making regarding barrier removal or mitigation.

Road effects on benthic macroinvertebrate assemblages in boreal headwater streams

Roads constitute a worldwide network of ecological barriers traversing countless streams and rivers. A large fraction of the land area lies in close proximity to roads. Ecological effects of roads likely extend well beyond the road network, suggesting wide ranging impacts on lotic ecosystems. Road impacts are multifaceted including fragmentation, changing hydrology, sedimentation and pollution. Yet, the ecological impacts are incompletely documented. We examined the effects of roads traversing lotic ecosystems on the structure and function of benthic macroinvertebrates in small temperate headwater streams. Ecological effects differed between reaches upstream and downstream of roads compared to upstream and downstream reaches in control streams. Total macroinvertebrate density and mayfly density were lower downstream of roads than upstream of roads, but they were similar at downstream and upstream reaches of control streams. Species density, but not species richness, tended to be lower downstream than upstream of roads, likely due to the lower macroinvertebrate densities at downstream sites. There were no comparable effects in control streams. Species composition and species abundances differed between road impacted streams and control streams likely because streams that were traversed by roads selected for a different set of species compared to control streams as indicated by checkerboard distribution of species in streams that were traversed by roads. Functional impacts included a greater prevalence of predators in control streams, and a higher proportion of grazers and shredders in streams that were traversed by roads. The study is inconclusive regarding the mechanisms mediating the ecological impact of roads. The ecological effects are likely caused by a combination of factors including fragmentation, pollution and hydrological change among others. Given the vast global road network, the quantitative significance of road effects driving freshwater biodiversity loss may be highly underestimated especially in smaller headwater streams comprising the major part of fluvial ecosystems.

Effects of land use and environmental gradients on the taxonomic and functional diversity of rotifer assemblages in lakes along the Yangtze River, China

Anthropogenic pressures are the main drivers of freshwater biodiversity loss. Lakes can act as sentinels of both local and regional changes and experience increased anthropogenic disturbances. Functional traits have been developed to elucidate the consequential functional progression of community changes, yet only a few studies on rotifer functional approaches exist compared with other biotic community attributes. Here, we investigate the responses of rotifer taxonomic and functional diversity metrics to an environmental gradient representing changing lake morphology, land use and physicochemical conditions in 30 lakes along the Yangtze River, China. Based on the distinct lake morphological gradient, land use patterns and environmental conditions, the 30 lakes were clustered into three groups with decreasing anthropogenic stress from Group 1 to Group 3. Our findings indicated that both species and functional richness decreased from Group 1 to Group 3 and that functional richness exhibited better correspondence with multiple stressors than did taxonomic richness. Moreover, we found that the rotifer assemblages varied significantly among the three lake groups along land use and environmental gradients, and the community-weighted means (CWM) of trait expression of the corresponding communities changed simultaneously. Types of trophi and corona were considered as the most variable traits among the three lake groups. We highlight that trait-based approaches are more sensitive, responsive and informative than taxonomic approaches in indicating human-induced environmental alterations in freshwater ecosystems.

Factors Determining the Abundance of Red Swamp Crayfish (Procambarus clarkii) in a Large Lake Connected to the Yangzte River

Invasive species and habitat degradation are the main reasons for freshwater biodiversity loss. Reports on the habitat degradation and invasion ecology of Red Swamp crayfish (Procambarus clarkii) are few, although it is one of the most devastating invasive species in freshwater ecosystems. Based on a three-year investigation during 2017–2019 in West Dongting Lake, this study used Principal Component Analysis (PCA), Generalized Linear Model (GLM) and Bayesian model to analyze the relationships of P. clarkii stocks and environment factors in natural and modified wetlands. The results showed that the abundance of P. clarkii was positively correlated with total nitrogen, total phosphorus, water temperature, pH, water depth, and water transparency; while it was negatively correlated with dissolved oxygen and redox potential. The difference between P. clarkii stocks in natural and modified wetlands was nonsignificant. The P. clarkii stock decreased yearly, as levels in both 2018 and 2019 were significantly lower than in 2017. We concluded that inter-annual variation of the hydrological regime plays an important role in P. clarkii dynamics, and thus it is of great importance to ensure that the water level and flow velocity in summer to control the invasive P. clarkii.

Linking pollution to biodiversity and ecosystem multifunctionality across benthic-pelagic habitats of a large eutrophic lake: A whole-ecosystem perspective

Biodiversity loss is often an important driver of the deterioration of ecosystem functioning in freshwater ecosystems. However, it is far from clear how multiple ecosystem functions (i.e., ecosystem multifunctionality, EMF) relate to biodiversity across the benthic-pelagic habitats of entire ecosystems or how environmental stress such as eutrophication and heavy metals enrichment might regulate the biodiversity-EMF relationships. Here, we explored the biodiversity and EMF across benthic-pelagic habitats of the large eutrophic Lake Taihu in China, and further examined abiotic factors underlying the spatial variations in EMF and its relationships with biodiversity. In our results, EMF consistently showed positive relationships to the biodiversity of multiple taxonomic groups, such as benthic bacteria, bacterioplankton and phytoplankton. Both sediment heavy metals and total phosphorus significantly explained the spatial variations in the EMF, whereas the former were more important than the latter. Further, sediment heavy metals mediated EMF through the diversity of benthic bacteria and bacterioplankton, while nutrients such as phosphorus in both the sediments and overlaying water altered EMF via phytoplankton diversity. This indicates the importance of pollution in regulating the relationships between biodiversity and EMF in freshwater environments. Our findings provide evidence that freshwater biodiversity loss among phytoplankton and bacteria will likely weaken ecosystem functioning. Our results further suggest that abiotic factors such as heavy metals, beyond nutrient enrichment, may provide relatively earlier signals of impaired ecosystem functioning during eutrophication process.

Patterns of Spatial Overlap between Non-Indigenous and Critically Endangered Freshwater Fishes from a Mediterranean Biodiversity Hotspot

Non-indigenous fish species (NIFS) can cause severe ecological impacts on the invaded ecosystems and are considered as one of the leading factors of freshwater biodiversity loss. Unraveling the spatial overlap between NIFS and critically endangered (CR) fish species can contribute to targeted conservation actions to minimize the potential negative effects. In this study, we applied geostatistical analyses to investigate the spatial overlap of NIFS against fish species that are designated under the CR status according to the IUCN and the Hellenic Zoological Society (HZS) Red Lists. Distributional data (presence–absence) from 800 records of 52 NIFS were compiled for both lentic and lotic ecosystems of Greece. Our results indicate that freshwater ecosystems under high NIFS richness were located mainly in lowland areas and often near large cities and ecosystems with well-developed commercial and recreational fisheries. On the contrary, low NIFS richness was observed in mountainous regions and in relatively small river basins. Overlapping areas of CR species with moderate to high NIFS richness (1.5–4.3 NIFS per 1 km2) were relatively high (~50%). A quarter of the overlapping areas (24.8%) fall within NATURA 2000 network, where legal management bodies could implement specialized programs to minimize the negative impacts. However, the majority of CR fish species’ distribution remains in unprotected areas indicating that protected areas should be re-designed to include areas containing freshwater species under the highest threatened category. Our findings demonstrate that whole assemblages of fishes are rapidly changing as NIFS spread into Greece and many freshwater ecosystems of outstanding biodiversity conservation value are under significant invasion pressure.

Impacts of climate change on aquatic insects in temperate alpine regions: Complementary modeling approaches applied to Swiss rivers.

Freshwater biodiversity loss is a major concern, and global warming is already playing a significant role in species extinctions. Our main goal was to predict climate change impacts on aquatic insect species distribution and richness in Swiss running waters according to two climate change scenarios (RCP2.6 and RCP8.5), using different modeling approaches, that is, species distribution models (SDMs), stacked‐SDMs (S‐SDMs) and a macroecological model (MEM). We analyzed 10,808 reaches, used as spatial units for model predictions, for a total river network length of 20,610 km. Results were assessed at both the countrywide and the biogeographic regional scales. We used incidence data of 41 species of Ephemeroptera, Plecoptera and Trichoptera (EPT) from 259 sites distributed across Switzerland. We integrated a coupled model for hydrology and glacier retreat to simulate monthly time‐step discharge from which we derived hydrological variables. These, along with thermal, land‐cover, topographic and spatially explicit data, served as predictors for our ecological models. Predictions of occurrence probabilities and EPT richness were compared among the different regions, periods and scenarios. A Shiny web application was developed to interactively explore all the models’ details, to ensure transparency and promote the sharing of information. MEM and S‐SDMs approaches consistently showed that overall, climate change is likely to reduce EPT richness. Decrease could be around 10% in the least conservative scenario, depending on the region. Global warming was shown to represent a threat to species from high elevation, but in terms of species richness, running waters from lowlands and medium elevation seemed more vulnerable. Finally, our results suggested that the effects of anthropogenic activities could overweight natural factors in shaping the future of river biodiversity.

Grand Challenges to Support the Freshwater Biodiversity Emergency Recovery Plan

The year 2021 offers a critical opportunity for concerted action to influence the future of freshwater biodiversity, ecosystem services and human well-being. The United Nations Decade on Biodiversity 2011–2020 has ended, and governments around the world are reviewing major international agreements relevant to biodiversity conservation, including the Convention on Biological Diversity (CBD)1, the Sustainable Development Goals (SDGs)2, and the UN Framework Convention on Climate Change (UNFCCC)3. A Post-2020 Global Biodiversity Framework4 is under development, with the grand mission to “Halt the loss of species, ecosystems and genetic diversity by 2030; restore and recover biodiversity to ensure a world of people “living in harmony with nature' by 2050”. Freshwater ecologists have acted quickly to draw attention to the global dimensions of the freshwater biodiversity crisis and address the lack of a comprehensive framework to guide policy responses (Bunn, 2016; Darwall et al., 2018). An Emergency Recovery Plan for freshwater biodiversity, published by 25 authors from 14 organizations (Tickner et al., 2020), sets out six major priorities for global action and policy development to “bend the curve of freshwater biodiversity loss.” It has been submitted to the working committees of the Post-2020 Global Biodiversity Framework, and further promoted as a dramatic OUPblog “Bring living waters back to our planet5” Comprehensive reviews have since enumerated many research questions, actions and policy refinements needed to “bend the curve” and protect the world's freshwater ecosystems (van Rees et al., 2020; Buxton et al., 2021; Harper et al., 2021; Maasri et al., 2021). Each review cuts across important scientific, societal, management and policy issues. The purpose of this brief challenge paper is, likewise, to strengthen and support the Emergency Recovery Plan, but in a different way, by advocating a broader package of strategic activities that too often operate in silos, with patchy coverage of the world's freshwater ecosystem types and biogeographic diversity. This package presents traditional areas of scientific and societal activity that require more strategic, integrated and collaborative global effort to deliver evidence-based freshwater conservation outcomes, conjoined with terrestrial and estuarine/marine conservation, depending on context: (i) inventory, evaluation and research; (ii) restoration and rehabilitation; (iii) protected area design and management; and (iv) socio-ecological science and governance. The paper is intended to motivate greater interest, commitment and collaboration of all stakeholders in the most urgent and ambitious conservation enterprise of the next decade—to protect and sustain freshwater biodiversity in the socio-ecological systems of the Anthropocene.

Adaptive and transformative learning in environmental water management: Implementing the Crocodile River’s Ecological Reserve in Kruger National Park, South Africa

Freshwater biodiversity loss in the Anthropocene escalates the need for successful environmental water management to sustain human benefitting ecosystem services. Of the world’s river basins, one-third are now severely water depleted, rendering the quality and quantity of water to maintain or restore freshwater ecosystem integrity increasingly urgent. However, managing environmental water is intricate because of complexity and uncertainty in interacting social and biophysical system components, and trade-offs between costs and benefits of implementing environmental flows. Learning enabled adaptive management – embracing the uncertainty – is essential; however, practising adaptive management (worldwide) is challenging; single-, double- and triple-loop learning is required, along with social learning, to tackle complex problems. There is progressive realisation of environmental flows (Ecological Reserve) in the Crocodile River, South Africa, linked to the Kruger National Park, using Strategic Adaptive Management (SAM). In this research article, we reflected on adaptive (single- and double-loop) learning and transformative (triple-loop) learning capacity emergent in SAM between 2009 and 2019 whilst also considering social learning potentials. We found evidence of preconditions (e.g. transparency) for social learning within a burgeoning stakeholder ‘community-of-practice’, likely fostering capacities (e.g. information sharing) for sustained social learning. Adaptive and transformative learning is enabled by social learning, underpinned by ongoing nested feedbacks supporting assessment and reflection, which facilitates single-, double- and triple-loop learning. Champions exist and are vital for sustaining the adaptive management system. Executing adaptive and transformative learning aids in positive change across the range of ecological, social and economic outcomes that are essential for success in environmental water programmes, worldwide. Conservation implications: Crocodile River Ecological Reserve implementation, associated with Kruger National Park, provided an important national precedent (lessons) for protecting the ecological integrity of river systems – obligatory under the National Water Act (Act No 36 of 1998). We demonstrated the importance of ongoing stakeholder learning for successful management of the Ecological Reserve.

Freshwater mussels in Mediterranean‐climate regions: Species richness, conservation status, threats, and Conservation Actions Needed

Abstract The five global Mediterranean‐climate regions are experiencing alarming rates of freshwater biodiversity loss. Although freshwater mussels are recognized as important functional components in aquatic ecosystems, and are among the most threatened faunal groups globally, there has been no synthesis of the plight of this group within these regions. Data from the International Union for Conservation of Nature (IUCN) Red List were reviewed to compare the conservation status, threats, and conservation actions needed for freshwater mussel species occurring in Mediterranean‐climate regions (med‐mussels) with those of other freshwater mussel species globally. The first comprehensive catalogue of med‐mussel species was compiled using existing taxonomic literature. There are 41 med‐mussel species, 30 of which occur in the Mediterranean basin. Many regions have just a single species, and regions where multiple species occur generally only have between one and four species per river basin. Med‐mussel species are almost twice as likely to be ‘Imperilled’, are affected by 2.4 times more threats, and require 3.5 times more conservation actions than non‐med mussels. In many cases, the exact threats have not been identified. In combination with low species richness, this level of imperilment means that Mediterranean‐climate regions are at risk of losing the benefits that mussels provide to broader ecosystem functioning. The conservation of med‐mussels can be improved by increasing our knowledge of species distributions, including the identification of cryptic species and significant management units, through population genetic work. In addition, recognizing the potential of ‘novel’ habitats and refuge areas could augment the management of this important functional group.