The freshwater pearl mussel Margaritifera margaritifera is a benthic organism sensitive to hydrological regime alterations and habitat degradation driven by excessive fine bed material deposit ...(FBMD). Both issues are potentially exacerbated by climate change. Understanding how climate change affects future mussel habitats and the dispersal among them (dependent on the brown trout as fish host) can support the planning of effective conservation actions.
To project the impacts of climate change on the mussel, a semi‐mechanistic modelling cascade was implemented for the Aist catchment in Austria (630 km2), including a hydrological model, a hydraulic model, Random Forest Models for FBMD accumulation risk and Species Distribution Models. Two climate change models (RCPs 4.5 and 8.5) for two future horizons (2060 and 2090) were considered. A graph‐based assessment of the structural connectivity was used to measure the probability of successful dispersal.
Results show a reduction of peak discharge that cascades into a widespread reduction in shear stresses during high flow. The mussel's habitats, defined by hydraulics (i.e. patches with low shear stresses during high flow), are predicted to be stable over the simulated scenarios.
The pressure of FBMDs over the delineated habitat patches is predicted to increase in the future due to the reduced stream transport capacity, reducing up to 25% of the available patches in 2090 for RCP 8.5. Consequently, the mussel's dispersal probability decreases to 44.3%–75.6% of the maximum theoretical value, with the highest drops for short dispersal distances, impacting metapopulation dynamics.
Synthesis and applications. The widespread issue of fine sediment deposition in the streambed will be exacerbated for those catchments where climate change reduces the stream transport capacity. The impacts on the freshwater pearl mussel include habitat loss due to the formation of a new unsuitable substrate, and a decrease in the potential dispersal among the residual habitats. Thus, conservation plans that aim to protect the mussel in the future should focus on the mitigation of fine bed material deposits, prioritizing those subreaches that offer the highest potential for preserving connectivity among suitable habitats.
Zusammenfassung
Die Flussperlmuschel Margaritifera margaritifera bewohnt die Fließgewässersohle, und ist gegenüber Veränderungen des hydrologischen Regimes und der durch übermäßige Feinsedimentablagerung (FSA) verursachten Lebensraumzerstörung empfindlich. Beide Probleme werden durch den Klimawandel potenziell verschärft. Das Verständnis der Auswirkungen des Klimawandels auf zukünftig verfügbaren Lebensraum und das Verbreitungspotential (abhängig von der Bachforelle als Fischwirt) kann die Planung effektiver Schutzmaßnahmen unterstützen.
Um die Auswirkungen des Klimawandels auf diese Muschelart zu prognostizieren, wurde eine semi‐mechanistischer Modellierungsansatz für das Aist‐Einzugsgebiet in Österreich (630 km2) umgesetzt, welche ein hydrologisches Modell, ein hydraulisches Modell, ein Random Forest Klassifikationsverfahren zur Bestimmung des Risikos von Feinsedimentablagerungen und ein Artenverteilungsmodell beinhaltet. Dieser Ansatz wurde dann mit zwei Klimawandelmodelle (RCPs 4.5 und 8.5) für zwei Zukunftshorizonte (2060 und 2090) gekoppelt. Eine spezielle mathematische Analyse der Konnektivität (basierend auf der Graphentheorie) wurde verwendet, um die Wahrscheinlichkeit einer erfolgreichen Ausbreitung zu ermitteln.
Die Ergebnisse der Klimawandelszenarien zeigen eine Reduzierung des Spitzenabflusses, die zu einer Reduktion der Sohlschubspannungen bei hohem Durchfluss führt. Die durch die Hydraulik definierten verfügbaren Lebensräume der Muschel (d. h. Bereiche mit geringen Sohlschubspannungen bei hohem Durchfluss) werden in den simulierten Szenarien als stabil vorhergesagt.
Es wird prognostiziert, dass der Druck von Feinsedimentablagerungen auf die abgegrenzten Lebensraumbereiche in Zukunft aufgrund der reduzierten Transportkapazität zunehmen wird und bis zu 25% der verfügbaren Lebensraumbereiche im Jahr 2090 beim Szenario RCP 8.5 zusätzlich reduziert werden. Folglich sinkt die Ausbreitungswahrscheinlichkeit der Muschel auf 44,3–75,6% des maximalen theoretischen Wertes, mit den stärksten Abnahmen bei kurzen Ausbreitungsdistanzen.
Synthese und anwendungen. Das weit verbreitete Problem der erhöhten Feinsedimentablagerung wird für Einzugsgebiete verschärft, in denen der Klimawandel den Abfluss und damit die Transportkapazität von Flüssen verringert, was sich auf geeignete Lebensräume von Süßwasserarten wie der Flussperlmuschel auswirkt. In diesen Einzugsgebieten sollte sich ein Managementplan zum Schutz der Art und vitaler Metapopulationen auf die Minderung von Feinsedimentablagerungen konzentrieren und den Teilgebieten Priorität einräumen, die das höchste Potenzial für die Erhaltung der Konnektivität zwischen geeigneten Lebensraumbereichen bieten. Die Entwicklung integrierter Modelle ist zwar datenintensiv und erfordert eine interdisziplinäre Integration, ermöglicht jedoch die Verknüpfung von hydrologischen Belastungen und ökologischen Reaktionen und unterstützt die Identifizierung angepasster Managementpraktiken.
The widespread issue of fine sediment deposition in the streambed will be exacerbated for those catchments where climate change reduces the stream transport capacity. The impacts on the freshwater pearl mussel include habitat loss due to the formation of a new unsuitable substrate, and a decrease in the potential dispersal among the residual habitats. Thus, conservation plans that aim to protect the mussel in the future should focus on the mitigation of fine bed material deposits, prioritizing those subreaches that offer the highest potential for preserving connectivity among suitable habitats.
1. Over the past centuries, European streams have been heavily influenced by humans through pollution and regulation. As a result, the quality and diversity of freshwater riparian habitats have ...declined strongly, and the diversity of riparian flora and fauna has decreased. Recent restoration measures have resulted in stream habitat improvements, but biodiversity improvements have failed to follow in fragmented streams. It has been suggested that dispersal limitation could play an important role in the lack of biodiversity improvement in restored streams, but to date, there is no conclusive evidence for this assumption. 2. In this study, we investigated whether colonization of restored streams by plants and macroinvertebrates is limited by dispersal. We hypothesized that colonization success increases with increasing availability of (nearby) source populations and with increasing ability of species to disperse over long distances. We related species composition in seven restored stream sections to species' abundances in the surroundings and to species' dispersal abilities. 3. For both plants and macroinvertebrates, colonization success is strongly related to the abundance of species in the local and regional species pools. 4. For plants, dispersal strategy has an additional influence on colonization success: short-lived plants with high production of small, well-dispersed seeds colonized best within the 3-to 5-year period after restoration. 5. The existence of dispersal strategy constraints could not be confirmed in macroinvertebrates, possibly because these are limited by a lack of connectivity on larger spatial scales. On the landscape scale, beneficial effects of increased plant diversity might further improve habitat suitability for macroinvertebrates. 6. Synthesis and applications. Dispersal appears to be a limiting factor for successful (re) colonization of restored streams in fragmented landscapes. In plants, this is attributed to limitations in seed dispersal abilities and likely to a lack of nearby source populations as well. In macroinvertebrates, lack of nearby source populations may also be a limiting factor. Hence, we suggest restoring landscape connectivity at larger spatial scales and optimizing the availability of near-natural 'source' areas in the vicinity of restoration projects, at least for plants, to improve the success of biodiversity restoration in fragmented habitats.
•Evaluating climate change data uncertainty in three SWAT models.•Reducing uncertainties through multi-criteria selection procedure.•Significant changes of 32 indicators of hydrologic alterations are ...projected.•Changes occur across regions and indicators, including alteration of extreme flows.•Important basis for impact research, especially for ecological freshwater studies.
Freshwater species are adapted to and depend on various discharge conditions, such as 32 indicators of hydrologic alteration (IHA). Knowing how these indicators will be altered under climate change is essential for predicting species response and to develop mitigation concepts. The simulation of IHA under climate change is subject to considerable uncertainties which should be considered to obtain credible and robust predictions. Therefore, we investigated the major uncertainties inherent in climate change data and processing: general circulation model (GCM) and regional climate model (RCM) choice, representative concentration pathway (RCP) scenario, bias correction (BC) method, all within three mesoscale catchments in the European ecoregions: Central Plains, Central Highlands, and Alpine. Highest uncertainties were caused by the GCM and RCM choice, followed by the type of BC and the RCP. For the prediction, we reduced these uncertainties tailored to the ideal depiction of the IHA in each ecoregion. Together with a significance test, this enabled a robust depiction of the change in IHA for two future time periods. We found diverging changes within the ecoregions, caused by the complex interaction between precipitation, temperature and the governing catchment hydrological processes. The results provide an important basis for further impact research, especially for ecological freshwater studies.
1. Freshwater megafauna species (i.e., animals that can reach a body mass ≥30 kg, including fish, reptiles, mammals, and amphibians) play important roles in freshwater systems (e.g., by influencing ...habitat structure, trophic dynamics, or the dispersal of smaller species). As they tend to be large and charismatic, they may also function as flagship umbrella species in future freshwater conservation initiatives. Despite this, as a group they are highly threatened, and our knowledge of the nature of these threats is limited. In this study, we aim to improve our understanding of the impacts of alien species on native freshwater megafauna.
2. We undertook the first global assessment of the impacts of alien species on native freshwater megafauna using the Environmental Impact Classification for Alien Taxa (EICAT) framework. We conducted a literature review to identify published and grey literature on impacts, which we quantified and categorised by their severity and type, following the EICAT guidelines.
3. Negative impacts on native freshwater megafauna were caused by 61 alien species from a diverse range of taxonomic groups, including both freshwater and terrestrial alien species, and both vertebrates and invertebrates. They adversely affected 44 of 216 native freshwater megafauna species, including amphibians, fish, mammals, and reptiles. The Great Lakes Basin had the highest number of affected megafauna species (six of the 14 freshwater megafauna species it supports, mainly fish). Impacts occurred through a broad range of mechanisms (10 of the 12 identified mechanisms under EICAT); predation and competition were the most frequently reported mechanisms. Some impacts were relatively minor, adversely affecting the performance of individuals of native freshwater megafauna species. However, some reported impacts did cause declining populations of native freshwater megafauna species, and one impact contributed to the local extinction of the ship sturgeon (Acipenser nudiventris) in the Aral Sea. The vulnerability of native freshwater megafauna species to different types of impact varies during different life‐cycle stages (egg, juvenile, and adult).
4. Our understanding of impacts posed by alien species on native freshwater megafauna is limited because data are unavailable for many regions, particularly the Global South, including hotspots for freshwater megafauna diversity such as the Amazon, Congo, Mekong, and Ganges‐Brahmaputra basins. Freshwater megafauna species are often subject to multiple threats, which makes it difficult to determine the significance of alien species impacts relative to other threats such as habitat degradation and overexploitation. In addition, short‐term studies are likely to be masking the severity of the impacts identified. We call for more long‐term studies that attempt to identify population‐level impacts, and for studies that identify impacts in data‐deficient regions.
5. The EICAT assessments undertaken for this study will be reviewed by the EICAT Authority and subsequently incorporated into the IUCN EICAT database. They may be used to guide future research and conservation actions.
Charismatic megafauna species may act as both flagship and umbrella species. They influence local environments and biotas, determine related ecosystem processes and functions, and are associated with ...high levels of biodiversity. However, the intrinsic characteristics of megafauna species including long lifespan, large body size, sparseness and/or rarity, late maturity, and low fecundity, as well as high market value, make them very prone to extinction. Up to now, scientific interest and conservation efforts have mainly focused on terrestrial and marine megafauna, while freshwater species have received comparatively little attention, despite evidence suggesting that freshwaters are losing species faster than marine or terrestrial realms. The high susceptibility of freshwater megafauna to multiple threats, coupled with immense human pressure on freshwater ecosystems, places freshwater megafauna amongst the most threatened species globally. The main threats include overexploitation, dam construction, habitat degradation, pollution, and species invasion. These threats increase mortality, decrease productivity, and reduce fitness, causing the decline of populations and the extinction of freshwater megafauna species. Given the essential ecological and biological roles of freshwater megafauna, further research should focus on their distribution patterns, extinction risks, and population dynamics, thereby improving the knowledge base for conservation planning. Finally, freshwater megafauna‐based conservation strategies may raise public awareness for freshwater conservation and therefore benefit a broader range of freshwater species and functions. WIREs Water 2017, 4:e1208. doi: 10.1002/wat2.1208
This article is categorized under:
Water and Life > Conservation, Management, and Awareness
Water and Life > Nature of Freshwater Ecosystems
Water and Life > Stresses and Pressures on Ecosystems
Freshwater megafauna are facing a wide range of threats that could lead to the decline of populations, reduction of genetic variability, and species extinction.
Summary
Context dependency is an emerging topic that is challenging our understanding of the factors shaping biodiversity in metacommunities. River networks and other dendritic systems provide unique ...systems for examining variation in the processes shaping biodiversity between different metacommunities.
We examined biodiversity patterns in five benthic invertebrate data sets, from two catchments in central Germany, with the aim of exploring context dependency in these systems. We used variance partitioning to disentangle the variation explained in three biodiversity metrics: taxonomic richness, Simpson's diversity and local contribution to beta diversity (LCBD; a measure of the uniqueness of a site). As explanatory variables, we used proxies of network position (i.e. catchment size and altitude) and habitat conditions.
Contrary to our expectation, we found no evidence of a decline in LCBD downstream in our study. Local habitat conditions and catchment land use played a much stronger role than catchment size and altitude in explaining variation in the three biodiversity metrics. Observed patterns were highly variable between different data sets in our study. These findings suggest that factors shaping biodiversity patterns in these systems are highly context dependent and less related to their position along the river network than local habitat conditions.
Given the clear context dependency between data sets, we urge researchers to focus on disentangling the factors driving the high levels of variability between individual systems through the study of a number of replicate, rather than single, metacommunities.
Aim: Freshwater megafauna remain underrepresented in research and conservation, despite a disproportionately high risk of extinction due to multiple human threats. Therefore, our aims are threefold; ...(i) identify global patterns of freshwater megafauna richness and endemism, (ii) assess the conservation status of freshwater megafauna and (iii) demonstrate spatial and temporal patterns of human pressure throughout their distribution ranges. Location: Global. Methods: We identified 207 extant freshwater megafauna species, based on a 30 kg weight threshold, and mapped their distributions using HydroBASINS subcatchments (level 8). Information on conservation status and population trends for each species was extracted from the IUCN Red List website. We investigated human impacts on freshwater megafauna in space and time by examining spatial congruence between their distributions and human pressures, described by the Incident Biodiversity Threat Index and Temporal Human Pressure Index. Results: Freshwater megafauna occur in 76% of the world's main river basins (level 3 HydroBASINS), with species richness peaking in the Amazon, Congo, Orinoco, Mekong and Ganges-Brahmaputra basins. Freshwater megafauna are more threatened than their smaller counterparts within the specific taxonomic groups (i.e., fishes, mammals, reptiles and amphibians). Out of the 93 freshwater megafauna species with known population trends, 71% are in decline. Meanwhile, IUCN Red List assessments reported insufficient or outdated data for 43% of all freshwater megafauna species. Since the early 1990s, human pressure has increased throughout 63% of their distribution ranges, with particularly intense impacts occurring in the Mekong and Ganges-Brahmaputra basins. Main conclusions: Freshwater megafauna species are threatened globally, with intense and increasing human pressures occurring in many of their biodiversity hotspots. We call for research and conservation actions for freshwater megafauna, as they are highly sensitive to present and future pressures including a massive boom in hydropower dam construction in their biodiversity hotspots.
Regional‐scale ecological processes, such as the spatial flows of material, energy, and organisms, are fundamental for maintaining biodiversity and ecosystem functioning in river networks. Yet these ...processes remain largely overlooked in most river management practices and underlying policies. Here, we propose adoption of a meta‐system approach, where regional processes acting at different levels of ecological organization – populations, communities, and ecosystems – are integrated into conventional river conservation, restoration, and biomonitoring. We also describe a series of measurements and indicators that could be assimilated into the implementation of relevant biodiversity and environmental policies. Finally, we highlight the need for alternative management strategies that can guide practitioners toward applying recent advances in ecology to preserve and restore river ecosystems and the ecosystem services they provide, in the context of increasing alteration of river network connectivity worldwide.
Freshwater ecosystems have a higher percentage of threatened and extinct species than terrestrial or marine realms, but remain under‐represented in conservation research and actions arguably as a ...consequence of less popularity and promotion.
Cover images of conservation journals were used as a proxy of exposure and potential promotion opportunities provided for different ecosystems and species. To examine whether articles related to cover images received more attention, citations and Altmetric scores of cover‐featured articles were compared with non‐featured ones within the same host journal issue.
Freshwater ecosystems (10.4%) were featured less often than marine (15.2%) or terrestrial (74.4%) ecosystems on covers of 18 conservation journals from 1997 to 2016. All 15 most featured species are from terrestrial or marine ecosystems.
In addition, cover‐featured studies showed higher citations and Altmetric scores than non‐featured ones within the same host journal issue, indicating that cover‐featured articles received more attention. Further investigations are needed to examine the relationship (i.e. whether there is a true causality) between being featured on the cover, and citations and Altmetric scores received by articles, as well as potentially resulting in greater conservation efforts. Nevertheless, we believe that providing exposure opportunities is likely to better inform the public about the continuing degradation of freshwater ecosystems and its impacts on human well‐being, including economic loss and danger to public health. Journal editors can contribute by balancing their selection of featured ecosystems and species when opportunities arise.
Increasing exposure opportunities for freshwater ecosystems through various channels seems a promising approach to raise public awareness and appreciation of freshwater biodiversity. Scientists can play an active role and form an alliance with journal editors, conservation organizations, and media, to increase momentum in society for fresh waters to be experienced as essential ecosystems and prevent further degradation of freshwater habitats and biodiversity loss.
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