Figure - available via license: CC BY
Content may be subject to copyright.
Source publication
Rising surface water temperatures in fluvial systems increasingly affect biodiversity negatively in riverine ecosystems, and a more frequent exceedance of thermal tolerance levels of species is expected to impoverish local species assemblages. Reliable prediction of the effect of increasing water temperature on habitat suitability requires detailed...
Contexts in source publication
Context 1
... reflection effect varies over time due to changes in solar angle and wind conditions. Previous studies have mapped water temperature of rivers and/or streams using airborne thermal imagery with an average error varying between 0.3 and 2.5 • C (Supporting information: Table S1). Aircrafts and helicopters have been used most often to carry the thermal sensors, but these are expensive to deploy, especially for small areas and repeated observations. ...Context 2
... ThermoMAP sensor mounted to a Sensefly Ebee UAV [36] was used to collect thermal imagery at four different moments during a day on 29 August 2017 ( Table 1). The ThermoMAP sensor performs an automatic temperature calibration in-flight based on the sensor's internal temperature and assumes an emissivity of 1 for the surveyed surface. ...Context 3
... ThermoMAP sensor mounted to a Sensefly Ebee UAV [36] was used to collect thermal imagery at four different moments during a day on 29 August 2017 ( Table 1). The ThermoMAP sensor performs an automatic temperature calibration in-flight based on the sensor's internal temperature and assumes an emissivity of 1 for the surveyed surface. ...Context 4
... temperature values as registered by the sensor were rescaled to temperatures in • C (T UAV ). In-situ water temperatures at 10 cm depth (T ref.10 ) and 50 cm depth (T ref.50 ) were calculated as the median of each logger's measurement over the 15-min duration of each flight (Table 1). T UAV values were extracted from the thermal imagery at the logger's locations and used to calculate the mean absolute error (MAE). ...Context 5
... UAV thermal images of our field study yielded water temperature measurements with a MAE of 0.81°C and at a high spatial (0.25 m) and temporal (four times per a single day) resolution. An extensive literature research of eight previous studies using thermal sensors in riverine environments (Table S1) reported an error ranging between −7 and 2.6 °C. Torgersen et al. [41] and Fullerton et al. [42] found lower errors, which can be explained by the more advanced sensors they used. ...Context 6
... these sensors are approximately ten times heavier than the ThermoMAP, and need to be deployed on a helicopter or aircraft, significantly decreasing their flexibility and increasing the costs for monitoring. Water temperature errors less than 1 °C were found in studies with 1) a sensor resolution smaller than the width of the rivers or lakes, to prevent a mixed signal with the non-aquatic temperatures of the banks, 2) reference water temperature measurements in the surface water layer (top 10 cm) and not near bottom of a water body, and 3) a relatively large sensor wave length range within the thermal infrared (8-12 µm) [41-43; Supporting information: Table S1). These aspects should be considered for future monitoring campaigns. ...Context 7
... UAV thermal images of our field study yielded water temperature measurements with a MAE of 0.81 • C and at a high spatial (0.25 m) and temporal (four times per a single day) resolution. An extensive literature research of eight previous studies using thermal sensors in riverine environments (Table S1) reported an error ranging between −7 and 2.6 • C. Torgersen et al. [41] and Fullerton et al. [42] found lower errors, which can be explained by the more advanced sensors they used. However, these sensors are approximately ten times heavier than the ThermoMAP, and need to be deployed on a helicopter or aircraft, significantly decreasing their flexibility and increasing the costs for monitoring. ...Context 8
... these sensors are approximately ten times heavier than the ThermoMAP, and need to be deployed on a helicopter or aircraft, significantly decreasing their flexibility and increasing the costs for monitoring. Water temperature errors less than 1 • C were found in studies with (1) a sensor resolution smaller than the width of the rivers or lakes, to prevent a mixed signal with the non-aquatic temperatures of the banks, (2) reference water temperature measurements in the surface water layer (top 10 cm) and not near bottom of a water body, and (3) a relatively large sensor wave length range within the thermal infrared (8-12 µm) ( [41][42][43]; Supporting information: Table S1). These aspects should be considered for future monitoring campaigns. ...Context 9
... Materials: The following are available online at http://www.mdpi.com/2072-4292/11/20/2367/s1, Figure S1: Measured water temperatures in the river Rhine at gauging station Lobith during 2017, Figure S2: The potentially occurring fraction (POF) of alien species in the river Waal near Gameren derived from remotely sensed water temperatures at 50 cm depth during a hot summer day, Figure S3: The potentially occurring fraction (POF) of native species in the river Waal near Gameren derived from remotely sensed water temperatures at 50 cm depth during a hot summer day, Table S1: Literature overview of thermal remote sensing of surface water temperature. Funding: This research is part of the research programme RiverCare, supported by the Dutch Technology Foundation TTW (formerly STW), which is part of the Netherlands Organization for Scientific Research (NWO), and which is partly funded by the Ministry of Economic Affairs under grant number P12-14 (Perspective Programme). ...Citations
... The natural thermal regime of rivers can be significantly altered by human activities 24 , including the operation of storage hydropower (i.e., induced thermopeaking) 22,25 , the use of water for cooling in thermal power plants 26 , flow regulation at artificial barriers 27,28 , urbanization 29 and climate change 30,31 . If the local water temperature changes too rapidly, this might trigger an avoidance response, driving fish to abandon habitats 21 . ...
Most fish species are ectothermic and rely on behavioral strategies to control their body temperature in heterothermal environments. Both thermotaxis and thermokinesis have been suggested as important underlying mechanisms. However, to what extent these behaviors allow fish to respond to rapid (timescales of minutes) and strong thermal disturbances, like those caused by anthropogenic water releases into natural freshwater systems, is poorly understood. Here, we quantify this response for a salmonid species with a novel laboratory approach coupled with image-based tracking. We exposed brown trout parr ( Salmo trutta ), acclimated to 12 °C, to rapidly forming cold- and warm-water interfaces with temperatures ranging from 4 to 20 °C. We found that fish actively avoided colder water (≤8 °C) through a rapid response that combined thermotaxis and thermokinesis. In contrast, fish did not avoid warmer water and frequently crossed interfaces having temperature contrasts of up to 8 °C. This study shows that brown trout parr swiftly deploy multiple behavioral strategies to minimize exposure to cold water and take advantage of warm water, illustrating their capability to cope with rapidly occurring thermal alterations.
... Based on the SSDs, the effective survivability between native and alien host fish species begins to diverge at around 25-30 • C; a water temperature rarely seen in the Netherlands. These higher temperatures can however be found in the shallower littoral zones of rivers and lakes such as shore channels or side channels, especially in the summer months (Collas et al., 2019). Additionally, water temperatures keep rising due to the extended drought periods resulting from climate change (Lennox et al., 2019). ...
Unionid populations are declining worldwide as they are threatened by anthropogenic habitat alterations, the introduction of invasive alien species and the effects of climate change. Several studies have focused on the habitat preferences of adult mussels but none to date have reported on the importance of the habitat preferences of host fish species. The aim of this study was to determine the habitat preferences of unionid host fish species in the Netherlands, to examine potential differences between native and alien host fish species, and to evaluate the effect of alien host fish species on unionid dispersal. Species sensitivity distributions (SSDs) were constructed for the range of occurrences and laboratory tolerance of host fish species in the Netherlands for water temperature, substrate type, flow velocity, and water depth. A case study was selected to assess the suitability to substrate type, flow velocity and water depth of a novel river habitat along longitudinal training dams in the river Waal. Unionid host fish species in the Netherlands preferred shallow littoral zones (0.1 m) with low flow velocity (0.05 m/s), an average water temperature of the Rhine delta (15°C), and most substrate types (ranging from silt to cobbles). Boulder substrate was the most limiting factor of the abiotic factors assessed for both native and alien host fish species. Management options for unionid populations should include host fish species in their assessments while focusing on creating and maintaining areas with limited boulders and implementing alien host fish species removal measures.
... Acquiring precise and accurate data on the thermal experience of individual organisms remains a challenge. In mobile organisms such as fish, the temperature experienced by an individual may differ markedly from temperature estimates derived from fixed location data loggers or remotely sensed data (Collas et al., 2019). Consequently, individual and time-resolved records of thermal exposure histories are needed to accurately assess the responses of organisms to thermal variations in their environment, to understand life-stage thermal habitat partitioning and to predict their vulnerability in future climate change scenarios. ...
Water temperature is key to the study of aquatic ectotherm ecology, but precise measurements of individual‐based thermal experience remain difficult to validate. The stable isotope composition of oxygen in biominerals acts as a natural thermometer due to the temperature dependence of isotopic fractionation between water and mineral phases. Coefficients of published temperature‐dependent fractionation equations, however, vary among taxa (the so‐called ‘vital effect’) without apparent consistent predictors, implying that species‐specific experimental validation may be needed before inferring temperature from biomineral oxygen isotope thermometry.
Here, we describe a meta‐analysis conducted to assess the influence of biological and experimental sources of variation on the coefficients of published isotope thermometry equations.
We observed that the thermal sensitivity (equation slope) was resistant to any biological or experimental factors, while the isotopic spacing between water and biomineral (equation intercept) showed consistent variation. Experimental conditions and phylogeny were the two main sources of variation in equation coefficients, where experiment approaches influenced both equation intercepts and the fit of the linear regression.
Our results suggest that the use of common equation slopes and generalized taxa‐specific equation intercepts may be appropriate under some circumstances. We additionally suggest that processes related to oxygen balance and osmoregulation may influence equation intercepts, and suggest further experimental work in this area. Finally, our observations provide ground for improvement for future design and reporting of biomineral thermometry experiments.
... Among several environmental changes, increased air temperature affects the water cycle by increasing or altering water temperature, which causes changes in local weather, water quality and river bodies (Hassan et al., 2017;Gossiaux et al., 2019). This is because the water temperature is one of the most important factors for physicochemical properties of water quality (Szumiriska et al., 2020), aquatic habitats (Duggals et al., 2018), spawning rates (Besson et al., 2016) and fish growth (Collas et al., 2019). ...
Climate change refers to long-term local, regional and global alternations in average temperature and weather patterns. It has been a global concern in recent decades and is related to human activity. Fish can be stenothermal or eurythermal as well as warm-water or cold water depending on their tolerance limits of temperature. The decline of global fish production because of climate change in many parts of the world is widely documented as fishing down the food web or overfishing may lead to further decline of fisheries production and food insecurity. Changes in physicochemical parameters of water are one of the most important consequences of climate change that will have a significant impact on the fisheries. Water temperature is directly proportional to most of the physicochemical parameters such as turbidity, salinity, conductivity, FCO2, total hardness, TDS, nitrate, and ammonia. pH and DO have an inverse relationship, whereas BOD showed a direct relationship up to 50 0 C but total alkalinity and chloride provide no definite relationships. In this study, a relationship between these physicochemical parameters with raising or lowering temperature as well as the perspective consequences on fisheries is reviewed.
... For instance, both species diversity and abundances of YOY fishes in natural Amazon river-floodplains benefit from habitat heterogeneity, shallow water depth, and macrophyte coverage (Petry et al., 2003). When nursery areas are permanently connected to the river, and both fish species richness and spatial-temporal habitat heterogeneity are high, fish communities are more resilient to adverse conditions such as flood pulses (Van Looy et al., 2019), and extreme temperatures (Collas et al., 2019). Riparian ecotones are particularly important nursery areas for YOY fishes in river ecosystems as they provide a variety of relatively shallow, slow-flowing habitats with a wide range of substratum sizes, are generally high in food, and warm up fast (Grift et al., 2001;Schiemer et al., 2001a;Schiemer et al., 2001b;Nunn et al., 2012;Eick and Thiel, 2013;Pander and Geist, 2018;Stoffers et al., 2022). ...
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.
... Hydroacoustics, such as side-scan sonar (SSS), have been used for riverine habitat substrate mapping, including mussel beds, whereas acoustic Doppler current profilers (ADCPs) have been used to assess water depth-specific flow velocity in mussel habitats [26,[52][53][54][55][56][57][58]. By combining detailed spatial abiotic conditions measurements with available SSDs for native and alien freshwater mussels, a prediction of their POFs may be derived to evaluate the local suitability of habitat in river systems [38,44,45,59]. We hypothesize that shore channels along LTDs provided suitable habitats for native freshwater mussels due to favorable substrate type, water depth, and near-bottom flow velocity conditions. ...
... Species sensitivity distributions (SSDs) from the scientific literature [38,45,Collas,lished data] were used to calculate the POFs for the ambient substrate type, water depth, and near-bottom flow velocity ( Fig. 2). Then, the data were processed using SonarWiz 7.2 from Chesapeake Technology or Microsoft Excel, converted to POF predictions using R programming, and subsequently mapped using ArcGIS® software from ESRI [52,53,59,63]. ...
... For each LTD shore channel, the substrate type, water depth, and nearbottom flow velocity maps produced were used with the SSDs in order to calculate the POFs of native and alien freshwater mussels per pixel. SSDs provided predictions of habitat suitability (POFs) for each map pixel based on their unique abiotic parameter values [49,59]. This was completed by using the "calc" function from the raster package of R statistics to apply the SSDs on the abiotic condition maps based on the mean and standard deviation of the distributions [80]. ...
Longitudinal training dams (LTDs) in the river Waal are novel river training structures that protect the littoral zone from the adverse effects of navigation providing new habitats for riverine macroinvertebrates. In order to inform river management and to better understand their ecological value for native and alien mussel species, it is important to assess the habitat suitability of the protected LTD shore channels. We applied spatial hydroacoustics surveys consisting of side-scan sonar (SSS) and acoustic Doppler current profiler (ADCP) of the substrate type, water depth and flow velocity in three shore channels in combination with species sensitivity distributions (SSDs) to predict habitat suitability for native and alien mussel species. SSDs allowed for the prediction of habitat suitability as a potentially occurring fraction (POF) of a species pool. High substrate type, water depth, and near-bottom flow velocity POFs were found for ≥ 70%, 100%, and 4–51% of the total shore channel area, respectively, suggesting that shore channels provide suitable habitat for both native and alien mussel species. To enhance the shore channels as habitat for native mussel species, we recommend increasing shallow areas dominated by fine (silt/clay) and sand substrate types with low near-bottom flow velocities (near 0 m/s). In contrast, the total area of hard substrate (e.g., boulders) in the shore channels should be reduced as it strongly favored invasive alien mussel species in our study. Future research should include additional abiotic parameters to enhance the habitat suitability predictions and compare the results for different riverine habitats.
... For instance, both species diversity and abundances of YOY fishes in natural Amazon river-floodplains benefit from habitat heterogeneity, shallow water depth, and macrophyte coverage (Petry et al. 2003). When nursery areas are permanently connected to the river, and both fish species richness and spatial-temporal habitat heterogeneity are high, fish communities are more resilient to adverse conditions such as flood pulses (Van Looy et al. 2019), and extreme temperatures (Collas et al. 2019). Riparian ecotones are particularly important nursery areas for YOY fishes in river ecosystems as they provide a variety of relatively shallow, slow-flowing habitats with a wide range of substratum sizes, are generally high in food, and warm up fast Schiemer et al. 2001a;Schiemer et al. 2001b;Nunn et al. 2012;Eick & Thiel 2013;Stoffers et al. 2022b). ...
... Heterogeneous nursery areas are beneficial to fish biodiversity (Stoffers et al. 2022a) and prevent communities from becoming homogeneous (Schiemer et al. 2013;Brennan et al. 2019). Furthermore, restored floodplains with high levels of habitat heterogeneity are more resilient to a broad range of adverse conditions, including extreme temperatures (Collas et al. 2019), and flood pulses (Van Looy et al. 2019). Permanent twosided river-floodplain connectivity increases habitat heterogeneity in restored floodplains by creating nursery habitats with varying flow velocities, which are critical for successful recruitment of rheophilic fishes (Nunn et al. 2007b;Stoffers et al. 2021). ...
Rivers have played a significant role in human history. As a consequence, they have undergone extensive modification for flood protection, transportation, and irrigation of agricultural land. These large-scale river modifications have destroyed more than 30% of the world's floodplains in the last 50 years, and it is estimated that up to 90% of floodplains in Europe and North America are now ecologically degraded. This has had a negative impact on fish populations, as floodplains play an important role in their life cycle. As a result of the degradation, fragmentation, or complete loss of their flowing spawning and nursery habitats in the lower Rhine, several rheophilic fish species have become rare or extinct and overall fish diversity declined.
In recent decades, the importance of healthy fish populations in rivers has been increasingly recognised, and floodplain restoration has become a priority in freshwater conservation programs. After major river flooding events in the Netherlands in 1993 and 1995, the "Room for the River" programme was launched to reduce the risk of flooding and improve the ecological quality of floodplains. This has been supplemented since 2000 by the EU Water Framework Directive (WFD 2000/60/EC), which focuses on improving and protecting the ecological quality of European rivers. Many floodplain restoration projects in the Rhine have been executed as part of these programmes, with measures such as lowering groynes, reopening side channels, connecting floodplains, and relocating dikes. Although the proportion of floodplain nurseries has increased because of these restoration efforts, fish populations have not yet recovered as desired. Almost all the original fish species is still present in the Rhine, but eurytopic species (less habitat-critical species) strongly dominate the fish fauna, while rheophilic species (specialised river fishes that need flowing water) are still underrepresented. One possible explanation is that nursery conditions in restored floodplains are insufficient for these more sensitive rheophilic species. Therefore, to improve recruitment success and restoring riverine fish populations in the Rhine, a better understanding of how restored floodplains function as nurseries for such species is required. This was the aim of this thesis. The primary objective was to assess the temporal and spatial habitat use of young-of-the-year (YOY) fish in the shoreline zones of restored floodplains at multiple scales. This was pursued by investigating the underlying processes of fish recruitment dynamics (abundance and species richness) in relation to habitat connectivity, availability and heterogeneity. The foundation encompassed a large-scale field study that sampled habitat conditions and YOY fish communities in 46 restored floodplains for four years (2017-2020). The findings of this study are summarised into the following four key results.
Ecological efficacy of restoration projects
Fish densities and diversity were higher in each type of restoration project than in shoreline habitats of the main channel. The nursery potential of restored floodplains is primarily determined by habitat heterogeneity and connectivity to the main channel, as the highest fish diversities were found in two-sided connected floodplains (2SC), while the greatest abundances were found in one-sided connected floodplains (1SC). In 2SCs, due to flowing water habitats, rheophilic fish species were nearly four times more abundant than in 1SCs. In 1SCs, the eurytopic abundances and species richness were highest, most likely due to the overall high levels of shoreline vegetation and shelter habitats in this restoration type. The presence of flowing water was the most important physical habitat variable explaining species composition of the YOY fish community in restored floodplains. In general, an increasing occurrence of flowing water in local habitats reduced fish abundances, while increasing the number of rheophilic species. Other nursery local habitat characteristics that were preferred by rheophilic fishes were shallow depths (<0.5 m), gentle bank slopes (<20°), and a variety of coarse substratum types (sand to gravel). The highest eurytopic abundances and species richness were found in habitat patches with a high degree of shoreline vegetation and structural complexity.
Species-specific nursery habitat use
Within the rheophilic guild, considerable species-specific differences in preferred nursery patch habitat conditions were found. Ide (Leuciscus idus), nase (Chondrostoma nasus), and dace (Leuciscus leuciscus) favoured shallow floodplain habitats with slowly flowing or stagnant water, whereas barbel (Barbus barbus) preferred fast-flowing dynamic nursery habitats in the main channel. Young fish do not stay in one habitat during their first growing season, but show ontogenetic shifts in habitat use, with substantial differences observed across and within ecological guilds. Both eurytopic and rheophilic fishes preferred shallow, slow-flowing, sheltered habitats early in their development. Following that, most eurytopic species move to deeper, more sheltered areas around a size of 5 cm. The rheophilic species either move to these deeper areas as well or to dynamic, fast-flowing waters at a larger size of 10 cm.
Spatial habitat heterogeneity
This study demonstrated that there is no "one-size-fits-all" design for floodplain restoration in the lower river Rhine, since each project (type) can provide nursery habitat for different ecological guilds, individual species, or community features (biodiversity or abundance).
Habitat heterogeneity had a beneficial effect on overall species richness, while it appeared to have a surprisingly negative effect on fish abundance. Its effects, however, varied across ecological groups and spatial scales: rheophilic species richness decreased with large-scale habitat heterogeneity, while increasing at small scales. This could be due to their highly specialised set of preferred local habitat conditions.
Temporal changes in ecological efficacy
The scope and ecological efficacy of restoration projects as fish nurseries are strongly affected by whether a river section is free-flowing (Waal and IJssel) or impounded (Nederrijn). Furthermore, floodplain restoration projects must develop and maintain suitable environmental conditions for decades to remain effective as fish nurseries. I observed that the ecological efficacy of river restoration projects as fish nurseries changes over time. The highest rheophilic abundances were found in 10 to 15-year-old 1SCs and 2SCs, while rheophilic species richness decreased steadily with floodplain age. There were no noticeable changes in project ecological efficacy for eurytopic species over time. Hydraulic conditions that caused sedimentation (sand deposition) near the river-floodplain inlet were the primary driving forces causing these shifts in the YOY fish community, by diminishing the flowing conditions in ageing restoration projects.
In conclusion, this thesis shows that restoring floodplains in the lower river Rhine is effective. Each project type provides nursery habitat for different ecological guilds, individual species, and community features (biodiversity or abundance). To increase rheophilic fish populations and overall fish diversity in modified large rivers, I propose that river restoration efforts concentrate on establishing spatially heterogeneous patterns and processes in floodplain restoration projects along the river (as in natural rivers), with a focus on 1SC and 2SC projects of appropriate dimensions that have year-round and long-lasting connectivity with the main channel.
... RGB sensors were the most commonly used sensors throughout the reviewed studies (Figure 2f), either alone or in combination with another sensor (n = 103). These sensors are preferable because they are inexpensive, typically provided as the native camera on a UAV, and RGB orthophotographs were used in numerous vegetation mapping cases (e.g., [40][41][42][43][44][45]). Multispectral sensors were also prevalent in wetland studies (n = 27), as they are useful in mapping shallow environments (down to about 1 meter underwater) [46] and for vegetation health assessments [27,47,48]. ...
... The mapping and modeling of abiotic environmental features such as land cover classes [4,58,65,124,129] and water [32,45,66,127,131] are important for understanding surface dynamics and how landscapes evolve, which complements the multitude of UAV wetland vegetation studies by providing information on the structure and habitat of these species. We reviewed fifteen papers pertaining to abiotic surveys, which was the second largest number of papers in one category, following the vegetation inventory group (Figure 3). ...
... This is a useful technique in abiotic UAV research that pertains to modeling shoreline losses and habitat destruction [4,130], floodplain connectivity [127], carbon storage estimates [129], and topobathymetry [58,128]. Real-time kinematic (RTK) GPS can greatly enhance the precision of such studies [4,5,45,58,65,124,131] and ground control points (GCPs) [4,45,58,65,66,124,129] can generate greater horizontal and vertical accuracy in landscape modeling and change detection studies. In particular, Correll and colleagues [28] rigorously employed RTK to measure elevation in a tidal marsh. ...
Recent developments in technology and data processing for Unoccupied Aerial Vehicles (UAVs) have revolutionized the scope of ecosystem monitoring, providing novel pathways to fill the critical gap between limited-scope field surveys and limited-customization satellite and piloted aerial platforms. These advances are especially ground-breaking for supporting management, restoration, and conservation of landscapes with limited field access and vulnerable ecological systems, particularly wetlands. This study presents a scoping review of the current status and emerging opportunities in wetland UAV applications, with particular emphasis on ecosystem management goals and remaining research, technology, and data needs to even better support these goals in the future. Using 122 case studies from 29 countries, we discuss which wetland monitoring and management objectives are most served by this rapidly developing technology, and what workflows were employed to analyze these data. This review showcases many ways in which UAVs may help reduce or replace logistically demanding field surveys and can help improve the efficiency of UAV-based workflows to support longer-term monitoring in the face of wetland environmental challenges and management constraints. We also highlight several emerging trends in applications, technology, and data and offer insights into future needs.
... ThermoMAP, [41] River/lake temperature mapping, SW-GWD identification, thermal plumes identification, river discharge. [44] be complex and requires expertise. ...
In less than two decades, UASs (unmanned aerial systems) have revolutionized the field of hydrology, bridging the gap between traditional satellite observations and ground-based measurements and allowing the limitations of manned aircraft to be overcome. With unparalleled spatial and temporal resolutions and product-tailoring possibilities, UAS are contributing to the acquisition of large volumes of data on water bodies, submerged parameters and their interactions in different hydrological contexts and in inaccessible or hazardous locations. This paper provides a comprehensive review of 122 works on the applications of UASs in surface water and groundwater research with a purpose-oriented approach. Concretely, the review addresses: (i) the current applications of UAS in surface and groundwater studies, (ii) the type of platforms and sensors mainly used in these tasks, (iii) types of products generated from UAS-borne data, (iv) the associated advantages and limitations, and (v) knowledge gaps and future prospects of UASs application in hydrology. The first aim of this review is to serve as a reference or introductory document for all researchers and water managers who are interested in embracing this novel technology. The second aim is to unify in a single document all the possibilities, potential approaches and results obtained by different authors through the implementation of UASs.
... If species' current distributions are confined by factors other than flow or water temperature (e.g., biogeographic dispersal barriers or anthropogenic pressures), species might be able to withstand larger temperature and flow extremes than inferred based on their current geographic range 27,28 . The same holds if species are able to adapt to new water temperature and flow conditions 16 or if fishes have the possibility to hide from extremes in micro-climatic refugia, for example due to water stratification or small-scale thermal heterogeneity 29 , which are not included in our hydrological model 21 . ...
Climate change poses a significant threat to global biodiversity, but freshwater fishes have been largely ignored in climate change assessments. Here, we assess threats of future flow and water temperature extremes to ~11,500 riverine fish species. In a 3.2 °C warmer world (no further emission cuts after current governments’ pledges for 2030), 36% of the species have over half of their present-day geographic range exposed to climatic extremes beyond current levels. Threats are largest in tropical and sub-arid regions and increases in maximum water temperature are more threatening than changes in flow extremes. In comparison, 9% of the species are projected to have more than half of their present-day geographic range threatened in a 2 °C warmer world, which further reduces to 4% of the species if warming is limited to 1.5 °C. Our results highlight the need to intensify (inter)national commitments to limit global warming if freshwater biodiversity is to be safeguarded.
