The Landscape Ecology of Rivers: from Patch-Based to Spatial Network Analyses

Habitat loss and discontinuity as drivers of habitat fragmentation: The role of contamination and connectivity of habitats

Habitat discontinuity of aquatic environments is a serious problem that might hamper the different activities performed by organisms. When combined with contamination, the consequences for the population's dynamics might be exacerbated, particularly regarding foraging activity. Therefore, the aim of this study was to evaluate the combined effects of habitat discontinuity and contamination on the foraging behavior by zebrafish (Danio rerio) and on their ability to explore heterogeneous landscapes. The organisms were exposed to three different scenarios of contamination (0, 0.5 and 25 μg L-1 of Cu) and habitat discontinuity (zero, low and high), using the Heterogeneous Multi-Habitat Assay System (HeMHAS). Generalized Bayesian linear models were used to analyze the data and evidence ratios (ER) were used to test the hypotheses. As results, both high levels of contamination and habitat discontinuity had significant effects on the probability of organisms to reach food (ER = 111.8 and > 1,000, respectively), the time taken to reach food (ER = 532.22 and > 1000, respectively) and the time spent in each compartment (ER = 614.4 and > 1000 for contamination and the number of connections available, respectively). As conclusion, the habitat fragmentation as a consequence of contamination and discontinuity affected the probability of fish to reach food and the time spent to reach it. This could lead to additional energy budget with serious consequences for population dynamics. Also, the HeMHAS demonstrated its suitability to assess the role of the contamination and habitat connectivity stressors in the spatial distribution and habitat selection response.

The Source-to-Sea Landscape: A hybrid integrative territory management approach

Whether fresh or salty, water is a unique resource, a continuum interlinked by the hydrological cycle. It forms a complex system connected to the landscape. When the landscape is altered, water flows and their benefits are impacted. Degraded land compromises water resources. The governance and management of landscape and water resources are handled in a fragmented manner and in separate contexts. The Source-to-Sea approach offers an integrative vision based on systems thinking that focuses its concerns on the interaction among parts, flows, and processes. It proposes a framework for the governance and management of freshwater and marine water but does not bring the landscape into the context of the approach. This research used an analytical-deductive method to explore the interactions and connections between the Source-to-sea approach, landscape concepts and approaches, and the guidelines of the European Landscape Convention. The main objective was to identify and assess the feasibility of integrating these elements. The integration resulted in a governance and management approach termed the S2S Landscape approach. It is grounded in systems thinking, practical learning, active participation, and adaptive governance and management, providing an integrated vision between landscape and water. The approach includes four essential steps (Comprehension, Involvement, Planning, and Execution and Monitoring) that address the complex connections that freshwater and marine water maintain in the landscape, considering physical, biological, socio-environmental, and economic aspects across all segments, from the land to the open sea. This S2S Landscape approach may be the path to address the challenges of governance and sustainable management of resources in an interconnected and constantly changing world.

The effects of longitudinal fragmentation on riverine beta diversity are modulated by fragmentation intensity

The loss of longitudinal connectivity affects river systems globally, being one of the leading causes of the freshwater biodiversity crisis. Barriers alter the dispersal of aquatic organisms and limit the exchange of species between local communities, disrupting metacommunity dynamics. However, the interplay between connectivity losses due to dams and other drivers of metacommunity structure, such as the configuration of the river network, needs to be explored. In this paper, we analyzed the response of fish communities to the network position and the fragmentation induced by dams while controlling for human pressures and environmental gradients. We studied three large European catchments covering a fragmentation gradient: Upper Danube (Austrian section), Ebro (Spain), and Odra/Oder (Poland). We quantified fragmentation through reach-scaled connectivity indices that account for the position of barriers along the dendritic network and the dispersal capacity of the organisms. We used generalized linear models to explain species richness and Local Contributions to Beta Diversity (LCBD) and multilinear regressions on the distance matrix to describe Beta Diversity and its Replacement and Richness Difference components. Results show that species richness was not affected by fragmentation. Network centrality metrics were relevant drivers of beta diversity for catchments with lower fragmentation (Ebro, Odra), and fragmentation indices were strong beta diversity predictors for the catchment with higher fragmentation (Danube). We conclude that in highly fragmented catchments, the effects of network centrality/isolation on biodiversity could be masked by the effects of dam fragmentation. In such catchments, metapopulation and metacommunity dynamics can be strongly altered by barriers, and the restoration of longitudinal connectivity (i.e. the natural centrality/isolation gradient) is urgent to prevent local extinctions.

Modelling vegetation land fragmentation in urban areas of Western Province, Sri Lanka using an Artificial Intelligence-based simulation technique

Vegetation land fragmentation has had numerous negative repercussions on sustainable development around the world. Urban planners are currently avidly investigating vegetation land fragmentation due to its effects on sustainable development. The literature has identified a research gap in the development of Artificial Intelligence [AI]-based models to simulate vegetation land fragmentation in urban contexts with multiple affecting elements. As a result, the primary aim of this research is to create an AI-based simulation framework to simulate vegetation land fragmentation in metropolitan settings. The main objective is to use non-linear analysis to identify the factors that contribute to vegetation land fragmentation. The proposed methodology is applied for Western Province, Sri Lanka. Accessibility growth, initial vegetation large patch size, initial vegetation land fragmentation, initial built-up land fragmentation, initial vegetation shape irregularity, initial vegetation circularity, initial building density, and initial vegetation patch association are the main variables used to frame the model among the 20 variables related to patches, corridors, matrix and other. This study created a feed-forward Artificial Neural Network [ANN] using R statistical software to analyze non-linear interactions and their magnitudes. The study likewise utilized WEKA software to create a Decision Tree [DT] modeling framework to explain the effect of variables. According to the ANN olden algorithm, accessibility growth has the maximum importance level [44] between -50 and 50, while DT reveals accessibility growth as the root of the Level of Vegetation Land Fragmentation [LVLF]. Small, irregular, and dispersed vegetation patches are especially vulnerable to fragmentation. As a result, study contributes detech and managing vegetation land fragmentation patterns in urban environments, while opening up vegetation land fragmentation research topics to AI applications.

Fish biomarker responses reflect landscape anthropic disturbance in savanna streams

Disturbance in the landscape surrounding streams can interfere with water quality and cause harm to aquatic organisms. In this study, we evaluate the influence of land use on the genetic and biochemical biomarkers of fish in streams of Brazilian savanna (Cerrado). We also evaluated whether biomarker responses are seasonally consistent. For this purpose, individuals of the Neotropical tetra fish Astyanax lacustris were exposed in cages for 96 h, in 13 streams draining agroecosystems with different degrees of disturbance during the dry and wet seasons. After exposure, blood, liver, and gills were collected for multibiomarker analyses (micronuclei, erythrocytic nuclear abnormalities, lipid peroxidation, antioxidant enzymes, and biotransformation enzyme). The results showed that the gradient of anthropic disturbance was positively associated with genotoxic damage (erythrocytic nuclear abnormalities) and negatively associated with antioxidant and biotransformation enzymes of the liver in both seasons. No association of the gradient of anthropic disturbance with the frequency of micronuclei and for most gill enzymes was found for both seasons. Landscape disturbance was also negatively associated with water quality in the wet season. These results indicate that changes in land use interfere with the genetic and biochemical processes of organisms. Thus, the multibiomarker approach may represent an effective strategy for assessing and monitoring terrestrial landscape disturbance.

Perturbation responses in co-evolved model meta-communities

A spatially explicit eco-evolutionary model assembles simulated meta-communities which are subjected to species and community perturbation experiments to determine factors affecting the stability of the global ecosystem. Spatial structure and resource variety increase the persistence of the ensembles against the removal of an individual species, yet they remain vulnerable to re-invasion by an existing member of the meta-community if it is introduced to all patches with minimal population. Optimal reserve placement strategies are identified for maximally preserving global biodiversity from the effects of sequences of patch disruption, and targeted reserve placement that shields the most or the rarest biodiversity is usually effective. However, if disturbed populations are permitted to re-settle in neighboring patches, then reserves should also be situated remotely to isolate their residents from invasion.

Freshwater fish biodiversity restoration in floodplain rivers requires connectivity and habitat heterogeneity at multiple spatial scales

With a sixth mass extinction looming and freshwater biodiversity declining at unprecedented rates, evaluating ecological efficacy of river restoration efforts is critical in combatting global biodiversity loss. Here, we present a comprehensive study of the functioning for fishes of 46 river restoration projects in the river Rhine, one of the world's most heavily engineered lowland rivers. Floodplains with permanent, either one- or two-sided lateral connectivity to the main channel, favour total fish abundance, and are essential as nursery areas for riverine fishes. Habitat heterogeneity had a strong positive effect on species richness but was negatively related with fish abundances. However, the effects of environmental variables varied between ecological groups and spatial scales. Surprisingly, richness of critical rheophilic fishes declined with large-scale habitat heterogeneity (~1000 m), while it increased at small scales (~100 m), possibly because of the presence of unfavourable habitats for this ecological group at larger scales. Clearly, there is no one-size-fits-all design for river restoration projects. Whether a river section is free-flowing or impounded dictates the scope and efficacy of restoration projects and, within a river section, multiple complementary restoration projects might be key to mitigate freshwater fish biodiversity loss. An essential element for success is that these projects should retain permanent lateral connection to the main channel.

Riparian Buffers as a Critical Landscape Feature: Insights for Riverscape Conservation and Policy Renovations

Riparian zones are critical for functional integrity of riverscapes and conservation of riverscape biodiversity. The synergism of intermediate flood-induced disturbances, moist microclimates, constant nutrient influx, high productivity, and resource heterogeneity make riparian zones disproportionately rich in biodiversity. Riparian vegetation intercepts surface-runoff, filters pollutants, and supplies woody debris as well as coarse particulate organic matter (e.g., leaf litter) to the stream channel. Riparian zones provide critical habitat and climatic refugia for wildlife. Numerous conservation applications have been implemented for riparian-buffer conservation. Although fixed-width buffers have been widely applied as a conservation measure, the effectiveness of these fixed buffer widths is debatable. As an alternative to fixed-width buffers, we suggest adoption of variable buffer widths, which include multiple tiers that vary in habitat structure and ecological function, with each tier subjected to variable management interventions and land-use restrictions. The riparian-buffer design we proposed can be delineated throughout the watershed, harmonizes with the riverscape concept, thus, a prudent approach to preserve biodiversity and ecosystem functions at variable spatial extents. We posit remodeling existing conservation policies to include riparian buffers into a broader conservation framework as a keystone structure of the riverscape. Watershed-scale riparian conservation is compatible with landscape-scale conservation of fluvial systems, freshwater protected-area networks, and aligns with enhancing environmental resilience to global change. Sustainable multiple-use strategies can be retrofitted into watershed-scale buffer reservations and may harmonize socio-economic goals with those of biodiversity conservation.

Freshwater systems and ecosystem services: Challenges and chances for cross-fertilization of disciplines

Freshwater ecosystems are among the most threatened in the world, while providing numerous essential ecosystem services (ES) to humans. Despite their importance, research on freshwater ecosystem services is limited. Here, we examine how freshwater studies could help to advance ES research and vice versa. We summarize major knowledge gaps and suggest solutions focusing on science and policy in Europe. We found several features that are unique to freshwater ecosystems, but often disregarded in ES assessments. Insufficient transfer of knowledge towards stakeholders is also problematic. Knowledge transfer and implementation seems to be less effective towards South-east Europe. Focusing on the strengths of freshwater research regarding connectivity, across borders, involving multiple actors can help to improve ES research towards a more dynamic, landscape-level approach, which we believe can boost the implementation of the ES concept in freshwater policies. Bridging these gaps can contribute to achieve the ambitious targets of the EU's Green Deal.

Introducing a flat ontology into landscape research: a case study of water governance experiments in South Africa

CONTEXT

Contemporary resource management paradigms within the developed world build on an understanding of human agency as ontologically distinct from the mode of existence of plants and animals. Because of this perspective, which gives priority to human agency, policies typically take their point of departure with human societies and associated ecosystems deemed of particular value.

OBJECTIVES

As an alternative to this worldview, social theorists have introduced what is known as "flat ontology", where all beings are bestowed equal rights to negotiate their existence. To explore the implications of introducing such an understanding into landscape management, a participatory planning process for water allocation was developed and tested in a case study in the Eerste River Catchment in South Africa.

METHODS

The planning process was mediated using the approach "politics of nature" (PoN), which aims to operationalize flat ontology to renegotiate water allocation based on the needs of all beings instead of the desire of a subset of humans. PoN allowed participants to playfully co-develop a common ontology and value-set. Data documenting these processes were collected digitally and analysed.

RESULTS

Results indicate that the approach engendered a rethinking of key relationships between human agency and ecosystem functionality, illustrating a potential for PoN-approaches to be deployed for governance of complex landscapes.

CONCLUSIONS

On the basis of experiments using PoN-methodology in the context of watershed management, it is discussed how the introduction of a flat ontology in landscape research, could inspire new ways of designing and intervening with collaborative resource management processes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10980-021-01374-9.

Emergent dual scaling of riverine biodiversity

A prevailing paradigm suggests that species richness increases with area in a decelerating way. This ubiquitous power law scaling, the species-area relationship, has formed the foundation of many conservation strategies. In spatially complex ecosystems, however, the area may not be the sole dimension to scale biodiversity patterns because the scale-invariant complexity of fractal ecosystem structure may drive ecological dynamics in space. Here, we use theory and analysis of extensive fish community data from two distinct geographic regions to show that riverine biodiversity follows a robust scaling law along the two orthogonal dimensions of ecosystem size and complexity (i.e., the dual scaling law). In river networks, the recurrent merging of various tributaries forms fractal branching systems, where the prevalence of branching (ecosystem complexity) represents a macroscale control of the ecosystem's habitat heterogeneity. In the meantime, ecosystem size dictates metacommunity size and total habitat diversity, two factors regulating biodiversity in nature. Our theory predicted that, regardless of simulated species' traits, larger and more branched "complex" networks support greater species richness due to increased space and environmental heterogeneity. The relationships were linear on logarithmic axes, indicating power law scaling by ecosystem size and complexity. In support of this theoretical prediction, the power laws have consistently emerged in riverine fish communities across the study regions (Hokkaido Island in Japan and the midwestern United States) despite hosting different fauna with distinct evolutionary histories. The emergence of dual scaling law may be a pervasive property of branching networks with important implications for biodiversity conservation.

Riverscape approaches in practice: perspectives and applications

Landscape perspectives in riverine ecology have been undertaken increasingly in the last 30 years, leading aquatic ecologists to develop a diverse set of approaches for conceptualizing, mapping and understanding 'riverscapes'. Spatiotemporally explicit perspectives of rivers and their biota nested within the socio-ecological landscape now provide guiding principles and approaches in inland fisheries and watershed management. During the last two decades, scientific literature on riverscapes has increased rapidly, indicating that the term and associated approaches are serving an important purpose in freshwater science and management. We trace the origins and theoretical foundations of riverscape perspectives and approaches and examine trends in the published literature to assess the state of the science and demonstrate how they are being applied to address recent challenges in the management of riverine ecosystems. We focus on approaches for studying and visualizing rivers and streams with remote sensing, modelling and sampling designs that enable pattern detection as seen from above (e.g. river channel, floodplain, and riparian areas) but also into the water itself (e.g. aquatic organisms and the aqueous environment). Key concepts from landscape ecology that are central to riverscape approaches are heterogeneity, scale (resolution, extent and scope) and connectivity (structural and functional), which underpin spatial and temporal aspects of study design, data collection and analysis. Mapping of physical and biological characteristics of rivers and floodplains with high-resolution, spatially intensive techniques improves understanding of the causes and ecological consequences of spatial patterns at multiple scales. This information is crucial for managing river ecosystems, especially for the successful implementation of conservation, restoration and monitoring programs. Recent advances in remote sensing, field-sampling approaches and geospatial technology are making it increasingly feasible to collect high-resolution data over larger scales in space and time. We highlight challenges and opportunities and discuss future avenues of research with emerging tools that can potentially help to overcome obstacles to collecting, analysing and displaying these data. This synthesis is intended to help researchers and resource managers understand and apply these concepts and approaches to address real-world problems in freshwater management.

Two classes of functional connectivity in dynamical processes in networks

The relationship between network structure and dynamics is one of the most extensively investigated problems in the theory of complex systems of recent years. Understanding this relationship is of relevance to a range of disciplines-from neuroscience to geomorphology. A major strategy of investigating this relationship is the quantitative comparison of a representation of network architecture (structural connectivity, SC) with a (network) representation of the dynamics (functional connectivity, FC). Here, we show that one can distinguish two classes of functional connectivity-one based on simultaneous activity (co-activity) of nodes, the other based on sequential activity of nodes. We delineate these two classes in different categories of dynamical processes-excitations, regular and chaotic oscillators-and provide examples for SC/FC correlations of both classes in each of these models. We expand the theoretical view of the SC/FC relationships, with conceptual instances of the SC and the two classes of FC for various application scenarios in geomorphology, ecology, systems biology, neuroscience and socio-ecological systems. Seeing the organisation of dynamical processes in a network either as governed by co-activity or by sequential activity allows us to bring some order in the myriad of observations relating structure and function of complex networks.

The geography of metapopulation synchrony in dendritic river networks

Dendritic habitats, such as river ecosystems, promote the persistence of species by favouring spatial asynchronous dynamics among branches. Yet, our understanding of how network topology influences metapopulation synchrony in these ecosystems remains limited. Here, we introduce the concept of fluvial synchrogram to formulate and test expectations regarding the geography of metapopulation synchrony across watersheds. By combining theoretical simulations and an extensive fish population time‐series dataset across Europe, we provide evidence that fish metapopulations can be buffered against synchronous dynamics as a direct consequence of network connectivity and branching complexity. Synchrony was higher between populations connected by direct water flow and decayed faster with distance over the Euclidean than the watercourse dimension. Likewise, synchrony decayed faster with distance in headwater than mainstem populations of the same basin. As network topology and flow directionality generate fundamental spatial patterns of synchrony in fish metapopulations, empirical synchrograms can aid knowledge advancement and inform conservation strategies in complex habitats.

Taxonomic and functional turnover of Amazonian stream fish assemblages is determined by deforestation history and environmental variables at multiple scales

Abstract High rates of deforestation, either in the past or the present, affect many of the ecological processes in streams. Integrating deforestation history and the current landscape structure enhances the evaluation of ecological effects of land-use change. This is especially true when contemporary landscape conditions are similar but the temporal path to those conditions differs. One approach that has shown promise for evaluating biodiversity responses over time and space is the β-diversity partitioning, which combines taxonomic and functional trait-based approaches. We tested hypotheses related to stream fish assemblages’ turnover in watersheds with different environmental conditions and deforestation histories. We sampled fish from 75 watersheds in the Machado River basin, Brazil, and environmental factors were quantified at multiple scales. Taxonomic turnover was higher than expected by chance, whereas functional turnover was lower than expected by the observed taxonomic turnover, indicating that deterministic processes are structuring these assemblages. The turnover, and the environmental factors differed among watersheds with different deforestation histories. Besides being scale-dependent, turnover patterns are also likely dependent on land use dynamics and involve time-lags.

Channel and cut-bluff failure connectivity in a river system: Case study of the braided-wandering Belá River, Western Carpathians, Slovakia

Straightforward sediment transport is not common in nature and material is storage during transport and reworked by the same processed that lead to initial mass erosion. Despite the development of quantitative assessment by application high accuracy topography measurement, lack of conceptualisation and combination with precise elevation model changes is still missing. This paper presents a field-based channel-bluff connectivity study based on a sediment cascade approach. A TLS (terrestrial laser scanning) time-series database was generated by systematic monitoring of cut-bluff slope surface of the braided-wandering Belá River. The database was used to estimate volume changes and allowed to develop the conceptualisation model of coupling of cut-bluff slope based on spatial and temporal analyses of channel hydrology, gravity conditioned transformation of matter and a detailed of sediment budget calculations. Historical analyses have shown that a flow direction perpendicular to the slope is crucial to activate cut-bluff slope material movement and initiate a sediment cascade, as significant contributors of sediment into the river. Sediment supply to the channels correlates with the magnitude of flood events (maximum discharge, cumulative discharge, cumulative discharge higher than RI_1.5, and duration of discharges higher than RI_1.5) and lateral migration as a main factor controlling the behaviour of the cut-bluff slope-channel system. During the survey from March 2016 to November 2018, were transported 10,103 m³ (25,964 t) of fine-grained sediment into the river channel.

Sparing and sharing land for maintaining the multifunctionality of large floodplain rivers

Large floodplain rivers (LFRs) are among the most threatened ecosystems on Earth and their utilization is expected to grow. Therefore, the need to develop more effective spatial prioritization tools to maintain their multifunctionality becomes increasingly important. We present a novel approach to land use design and conservation planning of LFRs and demonstrate its applicability using a case study for the Danube River, Central-Europe. Specifically, we use indicators of habitat naturalness and complexity to define four main land use functions for LFRs: (1) relatively intact areas with high habitat complexity, which are of high priority for conservation (C), (2) degraded and simplified areas, which are not suited for conservation, but for human utilization (HU), (3) relatively natural areas with low habitat complexity, which are suited both for conservation and for sustainable use of goods and services (LS), (4) degraded areas with relatively high habitat complexity potential, which should be used for rehabilitation (R). While C and HU spare land primarily for conservation and for human utilization, respectively, categories LS and R share land both for biodiversity conservation and for human use and well-being. Results of the case study show that the different land use functions did not clearly separate spatially along the evaluated segment, but distributed relatively equally. Area weighted indices highlighted the importance of large floodplains, while non-weighted indices indicated the importance of many smaller segments with narrow floodplain riparian zone, which can still be important for conservation or rehabilitation purposes. Our multiscale analysis revealed how land use categorizations depend on index use, index weightings and spatial resolution of land use function maps, which should be considered by management. The suggested methodology provides a transparent framework to any stakeholder groups on how to plan out management actions in the context of land conservation and ecosystem services delivery of LFRs.