Small dams need consideration in riverscape conservation assessments

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Aquatic areas of ecological importance as inputs into surface water resource protection areas in Zambia

1. Although the network of national parks in Zambia offers a degree of protection for freshwater diversity, the protection status of numerous systems outside of these parks requires further action. The biodiversity associated with its freshwater systems, both lotic and lentic, is unique, covering a climatic gradient from tropical to subtropical across the Zambezi and Congo basins. Recent Zambian legislation allows for the delineation of water resource protection areas (WRPAs), with one of the criteria being that they include aquatic areas of ecological importance (AEIs).
2. In this study, a systematic conservation planning approach was used to identify aquatic AEIs objectively. Importantly, the approach included a rigorous and iterative stakeholder engagement and review process.
3. The conservation planning software marxan was chosen because of its ability to integrate upstream–downstream connectivity. In total, 5,671 planning units (sub-catchments with an average area of approx. 14,000 ha) were populated with 77 biodiversity features: data were drawn from a wide range of sources, and included fishes, semi-aquatic mammals, molluscs, amphibians, and ecotonal physiographic features, such as waterfalls. Sub-catchments were preferentially chosen using a combination of area- and distance-weighted boundary costs.
4. The final solution highlights critical clusters in each of the major freshwater ecoregions in Zambia, with all conservation targets being met. Results show that although the existing protected area network also coincides with identified aquatic AEIs, approximately 80% of all aquatic AEIs fall outside of formally protected areas.
5. The outcomes of this process serve as one of three prioritization layers (the other two being water provision and sensitivity to human impacts) that are integrated in a larger study to select and prioritize WRPAs.

     

Integrating freshwater wetland science into planning for Great Barrier Reef sustainability

1. The paper ‘Biodiversity values of remnant freshwater floodplain lagoons in agricultural catchments: evidence for fish of the Wet Tropics bioregion, northern Australia’, published in Aquatic Conservation: Marine and Freshwater Ecosystems in 2015, has contributed in several ways to the integration of freshwater wetland science within new catchment management policies and practices for Great Barrier Reef (GBR) sustainability.
2. The Tully–Murray biodiversity study developed novel protocols to sample larval, juvenile, and adult fish life‐history stages in floodplain lagoons using a combination of boat‐based backpack electrofishing and fyke netting. In addition, hydrological and hydrodynamic models were applied in a completely new way to quantify the timing, extent, and duration of water connectivity across floodplain streams, cane drains, and wetlands. Combining the two novel approaches enabled an analysis of lagoon fish assemblage patterns in relation to environmental gradients, especially floodplain hydrology, connectivity patterns, and measures related to agricultural land use.
3. In demonstrating the importance of different levels of connectivity for different biodiversity outcomes in freshwater floodplain lagoons of the Tully–Murray catchment, the subject paper established that floodplain connectivity needs to be taken into consideration in wetland management practices.
4. The timing of the subject publication was fortuitous. It coincided with the preparation of the evidence‐based 2017 Scientific Consensus Statement on land‐based water quality impacts on the GBR. As one of the few freshwater wetland ecology publications for the catchments of the GBR at that time, this paper played an important role in demonstrating freshwater wetland values, fish conservation options, and management imperatives to sustain wetland ecological health and services in GBR catchments.
5. By advancing the understanding of factors driving biodiversity patterns, and the importance of connectivity and ecohydrological processes in freshwater floodplain wetlands of the GBR catchment, the Tully–Murray study helped to drive new policy directives for the protection and restoration of catchment, floodplain, and estuary functions, and connectivity, now embedded in the Reef 2050 Long‐Term Sustainability Plan 2018, an overarching strategy for managing the GBR over the next 35 years, and complementary Queensland environmental legislation.

     

Approaches to the selection of a network of freshwater ecosystems within New Zealand for conservation

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Freshwater biodiversity conservation through source water protection: Quantifying the potential and addressing the challenges

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Connectivity between lentic and lotic freshwater habitats identified as a conservation priority for coho salmon

1. Juvenile Pacific salmon exhibit diverse habitat use and migration strategies to navigate high environmental variability and predation risk during freshwater residency. Increasingly, urbanization and climate-driven hydrological alterations are affecting the availability and quality of aquatic habitats in salmon catchments. Thus, conservation of freshwater habitat integrity has emerged as an important challenge in supporting salmon life-history diversity as a buffer against continuing ecosystem changes.
2. To inform catchment management for salmon, information on the distribution and movement dynamics of juvenile fish throughout the annual seasonal cycle is needed. A number of studies have assessed the ecology of juvenile coho salmon (Oncorhynchus kisutch) during summer and autumn seasons; catchment use by this species throughout the annual cycle is less well characterized, particularly in high-latitude systems.
3. Here, n = 3,792 tagged juvenile coho salmon were tracked throughout two complete annual cycles to assess basin-wide distribution and movement behaviour of this species in a subarctic, ice-bearing catchment.
4. Juvenile coho salmon in the Big Lake basin, Alaska, exhibited multiple habitat use and movement strategies across seasons; however, summer rearing in lotic mainstem environments followed by migration to lentic overwinter habitats was identified as a prominent behaviour, with two-thirds of tracked fish migrating en masse to concentrate in a small subset of upper catchment lakes for the winter. In contrast, the most significant tributary overwintering site (8% of tracked fish) occurred below a culvert and dam, blocking juvenile fish passage to a headwater lake, indicating that these fish may have been restricted from reaching preferred lentic overwinter habitats.
5. These findings emphasize the importance of maintaining aquatic connectivity to lentic habitats as a conservation priority for coho salmon during freshwater residency.

     

Stewardship and management of freshwater ecosystems: From Leopold's land ethic to a freshwater ethic

1. In 1949, Aldo Leopold formalized the concept of the ‘land ethic’, in what emerged as a foundational and transformational way of thinking about natural resource management, biodiversity conservation, and stewardship in terrestrial systems. Yet, the land ethic has inherent linkages to aquatic ecosystems; Leopold himself conducted research on rivers and lakes, and freshwater ecosystems figured widely in his writing.
2. We reflect on the land ethic and other aspects of Leopold's scholarship to identify key messages that provide insight into the stewardship and management of freshwater ecosystems around the globe. We also frame what we call the ‘freshwater ethic’ around Leopold's legacy. Although Leopold could not have envisaged the stressors affecting modern aquatic ecosystems, his core principles remain salient. These apply not only to ecosystem protection, but also to the ethics of modern conservation economics, sustainability, and the protection of natural capital, in which lakes, rivers, and wetlands now figure prominently.
3. We identify key ‘Aldo-inspired’ recommendations for protecting and restoring freshwater ecosystems in the Anthropocene that emanate directly from his writings (e.g. adopt an ecosystem approach, identify win–win–win scenarios, recognize the irreplaceability of wild waters, and strive for freshwater optimism).
4. In an epoch where links between people and nature are becoming more explicit in environmental management, policy, and governance, we suggest that Aldo Leopold's work illustrates how inspirational, seminal thinkers have offered leadership in this domain. We contend that today there is still much that can be learned from Leopold, especially by the next generation of environmental practitioners, to ensure the effective stewardship of our aquatic ecosystems.
5. We submit that the adoption of a freshwater ethic in parallel with Leopold's land ethic will enhance the stewardship of the world's increasingly threatened fresh waters by raising the profile of the plight of fresh waters and identifying enduring actions that, if embraced, will help conserve and restore biodiversity.

     

Assessing the societal benefits of mahseer (Tor spp.) fishes to strengthen the basis for their conservation

1. Mahseer (Tor spp., Cyprinidae) are iconic, large-bodied, migratory freshwater fishes of Asian rivers. Long valued as a food source and serving other societal roles, these fishes are severely threatened by a broad range of interacting and escalating human impacts, including dam construction, water pollution, over-exploitation, and habitat destruction. Mahseer fishes are therefore beneficial to people, both directly and as indicators of ecosystem functionality and the associated ecosystem service benefits provided by the rivers that they inhabit.
2. A literature review demonstrated that wild mahseer populations have a direct role in 11 of the 36 ecosystem services assessed and are indicative of a further 18 ecosystem services provided by the habitats that support them.
3. Recognition of this range of ecosystem service benefits is helpful in describing to non-specialist public and policy-making communities the diversity of values provided by mahseer fishes and their supporting habitats, and hence the importance of their conservation.
4. Assessment of the broad range of ecosystem services to which mahseer contribute is an approach that could usefully be applied to promote the benefits of conserving other ‘umbrella’ taxa and the habitats that support them.

     

Beyond catchment considerations in the conservation of lotic biodiversity

• 1. The history of river conservation has largely focused on preservation of the physical and structural properties of lotic ecosystems in an attempt to ensure safe and potable water supplies for human consumption. Such strategies are increasingly being implemented at the catchment or basin scale.
• 2. Although these reflect positive developments in the conceptualization of conservation issues pertaining to lotic systems and provide the logical economic, sociological and/or political units for management, we question whether they represent the appropriate scale for the protection of lotic biodiversity and biological processes. We argue that this requires considerations that extend beyond the protection of physical habitat to ensure protection of population processes.
• 3. Although many species can be successfully conserved using the catchment as the basic management unit, many others cannot. We review evidence from genetic studies of aquatic populations to examine movement in relation to catchments, recognizing that organisms with poor dispersal characteristics during their life cycles exhibit a high degree of genetic structure, whilst organisms with robust dispersal characteristics typically exhibit a homogeneous genetic structure.
• 4. Species with poor dispersal characteristics are more easily conserved at the catchment level, whereas those with high dispersal characteristics can only be safely conserved at bio‐regional supra‐catchment levels.
• 5. Modern technological advances aimed at redistributing water from areas with perceived surpluses to those with perceived deficits (inter‐basin water transfers), demonstrated to transfer organisms between historically isolated catchments, pose a potential threat to the conservation of biodiversity by mixing genetically distinct populations and hence altering evolutionary processes and pathways.
• 6. If our arguments hold, then it appears that conservation authorities need to reappraise the current dominant paradigm of the catchment as the basic unit for conservation and management, and incorporate broader, strategic landscape planning in water resource management.

Copyright © 2003 John Wiley & Sons, Ltd.     

Re‐introduction of structurally complex wood jams promotes channel and habitat recovery from overwidening: Implications for river conservation

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The local responses of aquatic ecosystems to adjacent grassland conservation: Can streams of dreams exist in a degraded riverscape?

1. Landscape homogenization and the removal of riparian areas have altered stream ecosystems worldwide. Numerous conservation programmes attempt to improve water quality and increase instream habitat heterogeneity to elicit desired biological responses. However, the effectiveness of many conservation efforts on isolated stream fragments remains unknown, especially in grassland regions.
2. The effects of grassland conservation practices and the re-establishment of riparian corridors in the James River basin, South Dakota (USA) on stream water quality, habitat availability and aquatic macroinvertebrate and fish assemblages were studied in an agriculturally dominated prairie landscape.
3. Grassland conservation efforts may have repaired riparian condition, reduced turbidity and created more diverse instream habitat complexes at conservation sites based on comparisons with paired reference reaches. Reference sites were relatively homogeneous, with prevalent siltation, bank erosion and disturbances to the riparian vegetation. Owing to significant riparian vegetation development, overhanging and aquatic vegetation, benthic detritus and woody materials were significantly more common at conservation reaches.
4. Restoration efforts that assume ‘if you (re-)build it, they will come’ (i.e. the ‘field of dreams’ hypothesis) underestimate other important barriers to biodiversity restoration in dynamic, grassland riverscapes. Although aquatic organisms in grassland ecosystems are adapted to rapidly inhabit available habitats, the development of niche space at conservation reaches did not directly result in colonization by aquatic life.
5. Grassland management actions did not address stream connectivity issues or overcome land use influences elsewhere in the riverscape that may govern the responses of aquatic macroinvertebrates and fish. Stream fragmentation and continuing, damaging land use patterns seemed to exceed the positive effects of restoring isolated stream reaches in these heavily degraded catchments. Catchment-scale management strategies that combine reach-level restoration actions with efforts to improve connectivity are likely to be more successful in degraded riverscapes.

     

Influences of in-stream habitat and upstream land-use on site occupancy of the Kanawha darter (Etheostoma kanawhae): A narrowly distributed species from the New River (Upper Kanawha Basin)

1. Freshwater communities are threatened by the conversion of natural landscapes for urban and agricultural purposes. Changes to land use may disrupt stream nutrient and geomorphological processes and reduce water quality, increase sedimentation, and decrease habitat heterogeneity eventually leading to species loss and decreases in ecosystem productivity. Endemic species are frequently at greater risk of habitat-mediated fragmentation and extirpation due to their constrained distributions.
2. The Kanawha darter (Etheostoma kanawhae) is an understudied fish endemic to the New River Drainage in North Carolina and Virginia, USA. To investigate the potential effect(s) of land-use change on Kanawha darters, naïve occupancy was modelled using instream habitat characteristics and upstream forest cover.
3. Generalized linear models revealed that instream habitat and forest cover are reliable predictors of Kanawha darter site occupancy. Specifically, models demonstrated that occupancy increased in reaches with reduced stream width, velocity, and bedrock substrate but higher concentrations of coarse woody material. Kanawha darter occupancy was also positively associated with the extent of forest cover in upstream catchments.
4. Although Kanawha darters are not currently considered imperilled, most populations occurred in isolated reaches separated by large sections of unoccupied habitat. Continuing ex-urban development in riparian zones is likely to be the primary threat to Kanawha darters and other endemic species in this catchment. Resource managers and stakeholders should preserve forest cover in headwaters and occupied tributaries and protect or restore riparian zones along the main-stem South and North Forks of the New River to preserve high-quality habitat and enhance connectivity among isolated Kanawha darter populations.
5. As human populations in montane regions continue to grow, there is a need to understand how land-use change affects endemic freshwater species. This study further supports the importance of retaining forest cover as an effective strategy for protecting and restoring populations of endemic fishes in high-gradient streams.

     

Conservation of Amazonian aquatic mammals

1. Aquatic mammals worldwide are highly threatened in freshwater ecosystems where they are affected by direct human activities (e.g. hunting) as well as indirect human alteration of freshwater ecosystems (e.g. dams, mining activity). Although aquatic mammals of the Amazon Basin are experiencing many growing threats, little is known about the escalating impacts on them, current limitations in protection mechanisms, and possible strategies to ensure their conservation. This study synthesizes the available information on Amazonian aquatic mammals, including the ecological characteristics of these species, key threats, population status and conservation prospects.
2. Amazonian aquatic mammals comprise seven species – Inia geoffrensis, Inia boliviensis, Inia araguaiaensis, Sotalia fluviatilis, Trichechus inunguis, Pteronura brasiliensis and Lontra longicaudis – which are characterized by low reproductive rates and keystone ecosystem roles. These species are endangered mainly by biological resource use, natural ecosystem modifications, energy production and mining, and climate change. Although information is sparse, there is evidence that these threats are inducing population declines of Inia spp., and hindering the recovery of populations of P. brasiliensis.
3. Protection mechanisms for these species mostly include national and international laws and agreements, legislation governing environmental licensing and protected areas. Each of these protection mechanisms, however, has limited capacity to protect Amazonian aquatic mammals, largely because they are poorly enforced, lack transnational coordination or require population trend data that do not exist.
4. Reversing the current state of affairs for Amazonian aquatic mammals requires an integrated research and policy approach that, at a minimum, substantially increases the present capacity to monitor their population responses to human impacts, establishes effective enforcement of existing legislation and prevents further impacts from hydropower development. To implement such an approach, information on the ecology of these species is necessary to create public and scientific awareness.

     

Geospatial genetics: Integrating genetics into marine protection and spatial planning

1. The protection of evolutionary processes and maintenance of genetic diversity is necessary for the persistence of biodiversity and ecosystem resilience. The importance of genetic diversity has been reflected in a range of marine policy mechanisms, and the genetic ‘toolbox’ has great potential to support marine protection and marine spatial planning (MSP) at multiple scales. Despite scientific advances in the application of genetics in marine protection and management, systematic integration of genetic information has been generally lacking, primarily due to a knowledge and communication disconnect between geneticists and the marine policy and management community.
2. To meet these outstanding needs, a ‘geospatial genetics’ approach to spatially map species-specific genetic data and associated information in a way that can be readily integrated by practitioners into marine protection and MSP decisions was developed. Techniques to derive geospatial genetic data layers, which can be viewed and mapped alongside other kinds of spatial data commonly used by conservation practitioners, hold promise for increasing the accessibility of genetic data to support policy decisions more fully.
3. While applicable to many mobile and sessile taxa, an initial focus was placed on marine mammals, and the approach was developed and refined through a series of international meetings and published papers, as well as the development of interactive, expert-reviewed case studies hosted on the MSP tool SeaSketch.
4. Outcomes of the work to date are currently serving in the policy arena by informing the identification of Important Marine Mammal Areas, an initiative led by the IUCN Marine Mammal Protected Areas Task Force to apply criteria to identify marine mammal habitats across the world's ocean, seas and relevant inland waters through a standardized process.
5. It has become clear that geospatial genetics has great potential to foster increased collaboration among an intersectional community of geneticists, spatial ecologists, and practitioners. This increased opportunity for dialogue and cooperation will help ensure that evolutionary processes are factored into marine protection and MSP processes, and potentially for freshwater and terrestrial systems.

     

Assessing the role of the aquatic Natura 2000 network to protect both freshwater European species of community interest and threatened species in a Mediterranean region

1. The European Natura 2000 (N2K) network of protected areas stands out as the main conservation strategy in the European Union to preserve biodiversity under the auspices of the Convention on Biological Diversity.
2. The management of N2K sites is mainly focused on protecting the biological elements as Special Areas of Conservation for habitats or species listed in the European Habitats Directive, or as Special Protection Areas for birds listed in the European Birds Directive for which the site was designated. It seems urgent, therefore, to discriminate which N2K sites are really providing effective protection for aquatic biodiversity.
3. Although the main objective of N2K is to protect species listed in the Birds and Habitats Directives, the conservation status of threatened species included in the European Red List of the IUCN must also be a concern for the European Union.
4. Focusing on Central Spain as a case study, the aim of this work was to evaluate how far aquatic N2K (i.e. N2K sites designated for the occurrence of freshwater elements) is effective in protecting both those aquatic species in the Directives [referred to here as Species of Community Importance (SCI) and threatened species (TS)].
5. Most of the N2K sites in the study area have been designated using aquatic elements, which means that N2K could theoretically provide appropriate mechanisms to preserve aquatic biodiversity. However, N2K provides a low percentage of overlap with some of the hotspots identified for both TS and SCI. Surprisingly, TS are in general similarly or even better represented than SCI by N2K.
6. N2K may provide good coverage for aquatic biodiversity, mainly by acting as an umbrella for other species, but it could be improved by addressing some spatial gaps, thereby making it more relevant to current challenges such as climate change and other human impacts.

     

Managing threats and restoring wetlands within catchments of the Great Barrier Reef,Australia

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How does summer environmental degradation influence native mussels in Corbicula invaded rivers?

1. Droughts and heat waves are becoming more frequent, persistent, and intense in a global warming context. Although previous studies reported Corbicula mass mortality events associated with the occurrence of extreme summer conditions, knowledge of their effects lags behind ecosystem functioning.
2. The goal of this study was to determine whether summer environmental degradation (droughts, extreme temperatures, and spikes in ammonium concentration) influences the survival and behaviour of native mussels in rivers invaded by Corbicula and, in consequence, their functioning in ecosystems.
3. Unio delphinus mussels were exposed to increasing summer environmental degradation. Water column and pore water samples were collected at six sampling time-points for nutrient analysis. Environmental conditions, survival and behaviour were monitored at 12-hour intervals.
4. Mortality risk was greatest under no-flow conditions, reaching 100% of mortality after 84 ± 22 hours of exposure to anoxic (<2 mg O₂ L⁻¹) conditions. At the sub-lethal level, quiescent conditions impaired filtration activity. In addition, when facing rising temperatures, native mussels buried deeply and vertical movements were depleted.
5. There were significant differences between the water column and the pore water in physicochemical characteristics. Oxygen and nitrate concentration were generally higher in the water column. In contrast, ammonium and phosphate maximum concentrations were measured in the pore water.
6. The results suggest that environmental degradation affects the role of mussels in ecosystem functioning. For instance, prolonged valve closure under poor water quality conditions may have impacts on particle removal from the water column. Furthermore, impairment of vertical movements may reduce nutrient release from sediments.
7. The present study has key implications for water management and for the conservation of mussel populations. For instance, a responsible approach for maintaining ecosystem integrity should include the water needs of freshwater mussels in environmental flow recommendations and the conservation of riparian vegetation corridors to mitigate the effects of increased water temperature in rivers.

     

Insect dispersal does not limit the biological recovery of streams from acidification

• 1. The ecological recovery of streams from large‐scale perturbations, such as acidification, requires aquatic insects to disperse between catchments. While adults can usually fly, dispersal is seldom observed directly. Catches of insects in transects of traps perpendicular from streams suggest that lateral adult dispersal is limited. This paper evaluates whether this could explain limited biological recovery in streams recovering chemically from acidification.
• 2. At the replicate Llyn Brianne experimental catchments (Wales), Malaise traps (2000) and benthic sampling (1985–2005) were used to appraise inter‐catchment dispersal in acid‐sensitive Ephemeroptera, Plecoptera and Trichoptera. The results provide direct evidence for inter‐catchment dispersal: eight species from three Orders were caught as adults alongside acid streams where larvae never occurred in 21 years' benthic sampling.
• 3. These data refute the hypothesis that limited dispersal per se explains delayed biological recovery from acidification in Welsh streams. Other factors affecting colonization (e.g. ‘propagule pressure’, mating or oviposition behaviour) and persistence (e.g. continued acid episodes) must be involved, with the first of these possibilities still poorly understood. These data add to a growing body of literature illustrating insect dispersal between catchments, and they have wider relevance to the recovery and restoration of river ecosystems following basin‐scale impacts.

Copyright © 2006 John Wiley & Sons, Ltd.