Article

A salt lake under stress: Relationships among birds, water levels, and invertebrates at a Great Basin saline lake

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  • Sustainable Northwest
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Abstract

Saline lakes are threatened globally and provide critical habitat for a diverse array of migratory and breeding waterbirds. The ability of large numbers of waterbirds to profitably use saline lakes is primarily dependent upon concentrations of invertebrate fauna that are only present within a narrow range of salinities. Additionally, waterbirds themselves can incur steep physiological costs as their salt loads increase, meaning that they are especially sensitive to changes in salinity. Nonetheless, relatively little is known about ecosystem function within natural saline lakes or how birds will respond to fluctuations in salinity across time, hindering efforts to maintain ecologically functional saline ecosystems. To help address this gap, we coupled data from waterbird surveys undertaken across 25 years at Lake Abert, Oregon, USA with data on lake area (a proxy for salinity) and invertebrate abundance to document how waterbird numbers changed in response to variation in lake area and the presence of their invertebrate prey. We found that as the area of Lake Abert decreased and salinity increased, both invertebrate and waterbird numbers declined, with especially high salinities associated with the presence of few waterbirds and invertebrates. However, we also found that at high lake levels and low salinities the abundance of most waterbirds and invertebrates either plateaued or declined as well. Our study reinforces physiological studies showing that both invertebrates and waterbirds can only tolerate a narrow range of salinities, and is among the first to document the effects of this tolerance range at the ecosystem level. As anthropogenic water usage increases and snowfall decreases in the coming century, Great Basin saline lakes are projected to increasingly face water shortages and high salinities. Conserving saline lake ecosystems thus requires mitigating these losses and maintaining water levels and salinities within the normal range of inter-annual variation. When conditions outside of this range occur too frequently or persist too long, they can result in dysfunctional ecosystems with deleterious consequences for the species that rely on them.

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... Extensive evidence already indicates regional declines in Great Basin waterbird abundance 9,10,22,23 . Great Basin shorebird populations have experienced a 70% decline since 1973, and more than half of the nine most important western saline lakes for birds have diminished by 50-95% over the past 150 years. ...
... Indeed, paleoclimatology shows Great Basin wetland systems are inherently vulnerable to even minor climatic shifts. Their hydrological inputs derive primarily from precipitation (rain, snowpack) and lose water through evapotranspiration 23,29,[32][33][34][35][36][37][38][39] . Recent changes in water availability, quality (defined as salinity) and quantity have altered the viability of these critical breeding sites and migratory pathways [40][41][42][43] . ...
... In this report, we consider multi-scale changes in hydro-climatology across the Great Basin and examine subsequent effects on waterbird needs, community composition and waterbird migratory connectivity using over 100 years of spatially explicit temperature and precipitation data, trends in streamflow 44 and recent trends in Breeding Bird Survey (BBS) data 45 . Previous studies have explored the association between climate-driven shifts in temperature and precipitation regimes 46,47 , yet few studies have made the direct link between climate change impacts on environmental water quantity and quality and subsequent biological responses 7,23,48 . We demonstrate that climate-induced increasing temperatures and shortened water seasons can have a negative effect on waterbird use and productivity among inland, arid land wetlands. ...
Article
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Wetlands in arid landscapes provide critical habitat for millions of migratory waterbirds across the world and throughout their annual cycle. the scope and scale of understanding avian use of these wetlands in conjunction with changes in climate are daunting yet critical to address lest we lose continent-wide migratory pathways. Here, we assess changes in waterbird use of North America's Pacific Flyway in the Great Basin by examining water availability and climate trends over the past 100 years. We found recent (1980-2015) climate warming has significantly reduced the amount and shifted seasonality of water flowing into wetlands. Further, we found remarkable changes in waterbird species composition over time. We propose that a reduced hydroperiod and lower water quality from reduction in water level and flow limits sites used by waterbirds. These factors reduce chick survivorship as they cannot metabolize saline water, which makes suitable freshwater conditions a limiting resource. Collectively, climate-induced changes in Great Basin wetlands suggest a major shift in freshwater ecosystems, resulting in degradation of a continental migratory route. This work illustrates the importance of examining multi-scale changes in critical regional resources to understand their impact across a hemispheric flyway and provides a model to examine other flyways.
... Habitat associations included semi-permanent, seasonal, and temporary wetlands. Seasonal and temporary wetlands are commonly correlated with shallow water that are important foraging requisites for shorebird species, while semi-permanent (i.e., littoral-lacustrine) wetland trends have been identified as a key indicator of lake salinity linked trophic function supporting shorebird energetic needs (Senner et al., 2018). Shorebirds in the Central Valley were associated with all wetland classes in addition to flooded agriculture to account for a greater diversity of hydrologic conditions and habitat use driven by humancontrolled flooding (Reiter et al., 2015). ...
... Habitat indicators for SONEC shorebirds were evaluated using wetland trends in closed basin lakes. While seasonal and temporary wetland abundance increased substantially in these sites (Supplementary Table 2 and Supplementary Figure 5), habitat impacts were characterized as moderate to acknowledge concerns about long-term ecosystem sustainability linked to accelerated patterns of lake drying shown by semi-permanent wetland loss (sensu Senner et al., 2018). In the Central Valley, semi-permanent, seasonal, and temporary wetland declines on duck clubs and wildlife refuges were indicators of significant shorebird migration and breeding (April-September) habitat impacts. ...
... Higher salinity can drastically reduce the diversity and biomass of benthic macroinvertebrates that serve as critical food resources for shorebirds and eared grebes. As water volumes continue to decrease, lakes can reach a point of infertility well before they dry entirely (Herbst, 2006;Moore, 2016;Senner et al., 2018). The transition of some declining freshwater lakes to saline states (sensu Thomas, 1995) may open habitat niches that offset losses in others. ...
Article
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Migratory waterbirds (i.e., shorebirds, wading birds, and waterfowl) rely on a diffuse continental network of wetland habitats to support annual life cycle needs. Emerging threats of climate and land-use change raise new concerns over the sustainability of these habitat networks as water scarcity triggers cascading ecological effects impacting wetland habitat availability. Here we use important waterbird regions in Oregon and California, United States, as a model system to examine patterns of landscape change impacting wetland habitat networks in western North America. Wetland hydrology and flooded agricultural habitats were monitored monthly from 1988 to 2020 using satellite imagery to quantify the timing and duration of inundation—a key delimiter of habitat niche values associated with waterbird use. Trends were binned by management practice and wetland hydroperiods (semi-permanent, seasonal, and temporary) to identify differences in their climate and land-use change sensitivity. Wetland results were assessed using 33 waterbird species to detect non-linear effects of network change across a diversity of life cycle and habitat needs. Pervasive loss of semi-permanent wetlands was an indicator of systemic functional decline. Shortened hydroperiods caused by excessive drying transitioned semi-permanent wetlands to seasonal and temporary hydrologies—a process that in part counterbalanced concurrent seasonal and temporary wetland losses. Expansion of seasonal and temporary wetlands associated with closed-basin lakes offset wetland declines on other public and private lands, including wildlife refuges. Diving ducks, black terns, and grebes exhibited the most significant risk of habitat decline due to semi-permanent wetland loss that overlapped important migration, breeding, molting, and wintering periods. Shorebirds and dabbling ducks were beneficiaries of stable agricultural practices and top-down processes of functional wetland declines that operated collectively to maintain habitat needs. Outcomes from this work provide a novel perspective of wetland ecosystem change affecting waterbirds and their migration networks. Understanding the complexity of these relationships will become increasingly important as water scarcity continues to restructure the timing and availability of wetland resources.
... As salinity increased > 9 g L −1 during drought conditions (2016) the number of aquatic invertebrate taxa in Lake Nyamithi reduced by approximately half compared to that of predrought conditions (2014). Similar results were obtained by Senner et al. [21] who reported decreased invertebrate numbers in North American saline lakes during periods of decreased water levels and subsequent increased salinity. Among the invertebrates that disappeared from Lake Nyamithi were most mollusks, water scorpions (Nepidae) and burrowing water beetles (Noteridae). ...
... By the end of the studied recovery period (November 2017) biodiversity had even surpassed that of the predrought period (2014), even though salinity was still higher in the recovery (7 g L −1 ) compared to the predrought (<4 g L −1 ) period. This may be related to a similar observation made in other, more saline, environments whereby biodiversity is highest at a level of intermediate salinity (for that particular ecosystem) and deviation from this "optimal" salinity (either above or below) results in a loss of biodiversity [20,21,105]. The increased biodiversity in the recovery (2017) may also be related to the reorganization phase that ecosystems undergo after a destabilizing event such as drought or flood. ...
... Thus, many of the invertebrate communities found in these ecosystems consist of taxa with adaptations to overcome these periods of disturbance and provide more resilience to changes in environmental conditions. These mechanisms of survival and recovery are essential to sustain ecosystem functions and services as aquatic invertebrates, especially zooplankton, are an important food source to other aquatic invertebrates and for fish and birds, particularly in saline lakes [3,10,21,109,110]. ...
Article
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Climate induced drought is a prominent threat to natural saline aquatic ecosystems by modifying their hydrology and salinity, which impacts the biodiversity of these ecosystems. Lake Nyamithi is a naturally saline lake in South Africa that experienced the effects of a two-year supra-seasonal drought (2015–2016). This study aimed to determine potential effects of the drought and accompanying increased salinity (between 9.8 and 11.5 g L−1) on aquatic invertebrate communities of Lake Nyamithi, and assess their potential recovery following the drought. Aquatic invertebrates and water were collected for biodiversity and chemical assessments during predrought conditions (2014), the peak of the drought (2016) and after the site had received water (2017). Taxon richness was considerably reduced during the peak of the drought as many biota could not tolerate the increased salinity. Ecological resilience and recovery was evident in the lake since numerous biota (re)colonized the lake promptly after the site received water and salinity decreased (<8 g L−1). By the end of 2017, invertebrate biodiversity exceeded that of predrought conditions. Although some biota may be able to temporarily cope with extreme weather conditions, frequent or prolonged periods of drought and increased salinity pose a threat to naturally saline lakes such as Nyamithi and dilution with fresh water is vital for the persistence of species diversity and ecological integrity.
... Saline wetlands have distinct features, including highly saline soils, salt flats, and salt-tolerant plant species (LaGrange et al., 2003). The saline water environment is home to many water-related species, such as water birds, which are now threatened globally since the world's saline lake area is declining (Senner et al., 2018;Wurtsbaugh et al., 2017). Nebraska's eastern saline wetlands provide a critical habitat for many native species that are highly dependent on a saline environment. ...
... The change in salinity of the water ecosystem affects the species relying on this environment. For example, studies show that waterbirds can inhabit only a narrow range of salinities (Senner et al., 2018). A decrease in the water level and an increase in salinity result in a decline in waterbirds (Senner et al., 2018). ...
... For example, studies show that waterbirds can inhabit only a narrow range of salinities (Senner et al., 2018). A decrease in the water level and an increase in salinity result in a decline in waterbirds (Senner et al., 2018). The fragility of saline wetland ecosystems demands a better understanding of the relationships between salinity conditions and groundwater/surface connectivity. ...
Article
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Nebraska’s eastern saline wetlands are globally unique and highly vulnerable inland salt marsh ecosystems. This research aims to evaluate the status of the saline wetlands in eastern Nebraska to discover the conditions of saline wetland hydrology, hydrophytes, and hydraulic soil. The research adopts machine learning and Google Earth Engine to classify Sentinel-2 imagery for water and vegetation classification and the National Agriculture Imagery Program imagery for salinity conditions. Six machine learning models are applied in water, soil, and vegetation detection in the study area. The optimal model (linear kernel SVM) generates an overall accuracy of 99.95% for water classification. For saline vegetation classification, the optimal model is the gradient tree boost with an overall accuracy of 94.07%. The overall accuracy values of saline soil classification using the optimal model (linear kernel SVM) varied among different years. The results of this study show the possibility of an observation approach for continuously monitoring Nebraska’s eastern saline wetlands. The water classification results show that the saline wetlands in this area all have a similar temporal water cover pattern within each year. For saline vegetation, the peak season in this area is between June and July. The years 2019 (19.00%) and 2018 (17.69%) had higher saline vegetation cover rates than 2017 (10.54%). The saline soil classification shows that the saline soil area is highly variable in response to changes in the water and vegetation conditions. The research findings provide solid scientific evidence for conservation decision-making in these saline wetland areas.
... The high salt loads of saline lakes impose physiological stresses on many organisms, however, increasing their energetic requirements [11]. When saline lake water levels decline and their salinities rise [12], most vertebrates, macroinvertebrates, and other organisms are, therefore, unable to respond, leaving ecosystems comprised only a few archaea and harmful cyanobacteria [13,14]. As a result, as saline lake water levels have declined [15], so too have the population sizes of most species relying on them [16,17]. ...
... Such fluctuations are not uncommon in regions with saline lakes, but the combination of long-term declines and short-term instability can lead to frequent drying events, when a salar temporarily loses all surface water or reaches critically high salinities. In other saline lakes, such events have led to regime shifts in the benthos with stark reductions in biodiversity [13,14], including mass flamingo die-offs [36]. Flamingo abundance varied greatly from year-to-year. ...
Article
The development of technologies to slow climate change has been identified as a global imperative. Nonetheless, such 'green' technologies can potentially have negative impacts on biodiversity. We explored how climate change and the mining of lithium for green technologies influence surface water availability, primary productivity and the abundance of three threatened and economically important flamingo species in the 'Lithium Triangle' of the Chilean Andes. We combined climate and primary productivity data with remotely sensed measures of surface water levels and a 30-year dataset on flamingo abundance using structural equation modelling. We found that, regionally, flamingo abundance fluctuated dramatically from year-to-year in response to variation in surface water levels and primary productivity but did not exhibit any temporal trends. Locally, in the Salar de Atacama-where lithium mining is focused-we found that mining was negatively correlated with the abundance of two of the three flamingo species. These results suggest continued increases in lithium mining and declines in surface water could soon have dramatic effects on flamingo abundance across their range. Efforts to slow the expansion of mining and the impacts of climate change are, therefore, urgently needed to benefit local biodiversity and the local human economy that depends on it.
... Changes in salinity contribute to sea level rise which causes high tidal waves. Sea level rise causes floods that penetrate through the land and freshwater systems through estuaries, resulting in massive damage to the entire environment (Senner et al., 2018;Velez et al., 2016;Yang and Chui, 2017). This affects the country's economy as it costs government millions of rands to rehabilitate the affected areas. ...
... This affects the country's economy as it costs government millions of rands to rehabilitate the affected areas. It has been reported that salt intrusion by strong tidal waves into river systems could lead to mortality of different fresh water species as most of them are not used to high saline waters and the degradation of the estuary (Kijewska et al., 2016;Santos et al., 2017;Senner et al., 2018;Souid et al., 2018). Forbes and Demetriades have shown that the degraded estuaries had no balance in their ecosystem which resulted in the decline of ecotourism (Forbes and Demetriades, 2008). ...
Article
In this study, a simple and practical gold nanoparticle enabled colorimetric sensor technique was developed for the detection of sodium chloride. The synthesis of gold nanoparticles was based on the chemical reduction of gold (III) chloride trihydrate using tri-sodium citrate that also served as a capping agent thus, protecting the particles against aggregation. UV–vis spectra and transmission electron microscopy were used to characterise the synthesized citrate capped gold nanoparticles. The colorimetric response of sodium chloride was performed by the gold nanoparticle sensor, based on the property of localized surface plasmon resonance. The interaction between sodium ions, chloride and tri-sodium citrate causes rapid aggregation of the gold nanoparticles conjugates, resulting in color conversion from wine red to blue which is clearly visible by the naked eye. Thereby, we propose the use of gold nanoparticles as colorimetric sensors, as they cause a color change when interacting with sodium chloride which is recognized easily by naked eye with high selectivity. The detection limit of the sensor calculated by the linear relationship of localised surface plasmon resonance for sodium chloride was found to be 1.18 parts per thousand and the lowest quantified amount was 3.57 parts per thousand, making the developed sensor to be highly sensitive. The practical applicability of the gold nanoparticles was also verified by the detection of sodium chloride in estuary and seawater samples.
... The factors that determine habitat value are affected indirectly or directly by saline lakes' water levels, which depend on the balance among water inflows, precipitation, and evaporative water loss. For example, brine shrimp (Artemia spp.), an important invertebrate food re-source at some lakes, are sensitive to salinity changes caused by receding or rising lake levels (Dana and Lenz 1986;Senner et al. 2018). Water diversions and extractions for anthropogenic uses, such as irrigated agriculture, have historically reduced water inflows to saline lakes and associated wetlands (Wurtsbaugh et al. 2017;Donnelly et al. 2020) and, in combination with climate change (e.g., potential for reduced streamflow), will continue to affect water levels, timing, and salinity in the future (Ficklin et al. 2013;Jeppesen et al. 2015;Meixner et al. 2016). ...
... Given that the birds examined are migratory, ecological and demographic factors contributing to Great Salt Lake counts and trends might originate in other areas and seasons (Newton 2004). While many factors can affect trends at Great Salt Lake and other saline lakes, one receiving considerable regional and local attention is a reduction of water inflows affecting habitat amount, timing, and quality (e.g., by changing salinity) (Ivey and Herziger 2006; Wilsey et al. 2017;Senner et al. 2018;Haig et al. 2019). Securing adequate water supplies at key times of year is paramount to provide and sustain local and regional habitats for shorebirds, waterfowl, and other waterbirds (Ivey and Herziger 2006; Wilsey et al. 2017). ...
Preprint
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Millions of wetland-dependent birds annually depend on saline lakes and associated wetlands in the western United States. Understanding the population status and trends of birds with different life histories and habitats can guide efforts to secure water resources needed to sustain bird habitats. We used a 21-year dataset to examine population trends for 24 survey units presumed to be high-quality habitat for migratory shorebirds, waterfowl, and other waterbirds at Great Salt Lake and associated wetlands. As expected for high-quality habitats, we found stable or positive trends for 36 of 37 species or groups in fall, spring, or both seasons when considering survey units in aggregate. Despite stable or positive aggregate trends, negative trends did occur in some individual survey units. Foraging, migration distance, and taxonomic groupings were unrelated to trend direction. Research is needed to test whether survey units represent high-quality habitat. With declining regional water resources, stable and positive aggregate trends reinforce the importance of surveyed units at Great Salt Lake and associated wetlands to wetland-dependent birds. Ensuring continuation of stable and positive trends will require identifying environmental factors - including water quantity and quality - driving trends, and require coordinated regional management and monitoring of wetland-dependent birds.
... It was also found that earlier studies reported that hypersaline conditions are favourable for flamingo foraging grounds (Berruti 1983, Childress et al., 2008, Vargas et al., 2008. Shovelers are reported to prefer high water levels when their preferred prey is abundant (Senner et al., 2018). Hence, it is essential that the Pulicat Management ensures that optimum water depths are well-maintained especially during summer and the migratory season to attract a large diversity of wetland birds. ...
... The declining water levels and increasing salinities recorded in Pulicat in recent decades correspond strongly with similar conditions occurring at many other saline lakes/lagoon, globally, stressing the entire network of waterbird habitats (Senner et al., 2018), making it difficult for long-distance migratory birds to find alternative stop-over feeding sites. In Charadriiforms, in particular, the size of the salt gland may vary considerably with environmental conditions as there is a high likelihood of salt glands in Charadriiformes to become hypertrophic if they don't ingest freshwater (Mahoney & Jehl 142 1985). ...
Technical Report
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Impact of dredging and opening of the sea mouth into the Pulicat lake at Rayadoruvu village of Vakadu Mandal, on the habitat of Pulicat Bird Sanctuary, Andhra Pradesh.
... These organisms include specialized invertebrates (Williams, 1998) that can provide critical food resources for waterbirds (e.g. flamingos Phoenicopterus spp., Fig. 4) and Wilson's Phalaropes Phalaropus tricolor) (Senner et al., 2018). ...
Chapter
Of the Earth's three major biomes or realms, freshwater is the smallest, dwarfed in size and extent by terrestrial and marine realms. It has also been the most exposed to human exploitation, resulting in higher declines of biodiversity compared to other realms, primarily because of human reliance on fresh water and invasive species. Major sub-biomes in the freshwater realm can be grouped into seven categories: rivers and streams, lakes (salt, freshwater, oases and springs), palustrine wetlands (swamps, marshes, and floodplains), transitional waters (including estuarine and coastal lagoons), brackish tidal systems (deltas, intertidal forests, saltmarshes), subterranean water bodies and artificial wetlands (dams, rice paddies, aquaculture, canals and channels). A range of key freshwater characteristics, including the hydrological regime, water quality, and influences from terrestrial and marine drivers, form unique ecosystems around the world, providing for diverse species but ones which share many functional traits, reflected in convergent evolution. Direct or indirect appropriation of water resources (consumption, agriculture, and hydro-electricity) and disposal of waste water has devastated many of the world's freshwater ecosystems. Their protection demands identification of sustainable and cost-effective management of hydrological regimes and inflows, including protection and restoration of flows for the environment as well as management of invasive species, stopping habitat destruction and pollution.
... El cambio climático contemporáneo ha reducido significativamente la cantidad y distribución de los humedales en todo el mundo, así como la estacionalidad del agua que fluye hacia los humedales (Box et al. 2008, Barnett et al. 2016, Bradley & Yanega 2018. Esto ha tenido como consecuencia, cambios notables en la composición de las especies de aves acuáticas, peces e invertebrados en un período relativamente corto (Sada et al. 2005, Moore 2016, Senner et al. 2018, además de reducir la disponibilidad de sitios de agua dulce para las aves acuáticas y otras especies dependientes de los humedales. El cambio climático antropogénico aumenta los riesgos de desajustes entre la fenología de las especies y las condiciones ambientales, lo que resulta en el deterioro de las principales rutas migratorias (Koening 2002, Iknayan & Beissinger 2018. ...
Technical Report
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El estudio Determinación del riesgo de los impactos del Cambio Climático en las costas de Chile busca generar información de proyecciones de la amenaza, exposición, vulnerabilidad y riesgo de los sistemas humanos y naturales de la zona costera ubicados en 104 comunas de Chile continental, además de Rapa Nui y el Archipiélago Juan Fernández. El objetivo de este estudio es sentar las bases para el diseño de políticas e implementación de medidas de adaptación. El estudio se desarrolló entre octubre de 2019 y octubre de 2019 y se presenta mediante un resumen ejecutivo, 8 volúmenes temáticos y un Sistema de Información Geográfica (SIG). El equipo desarrollador consiste en 21 investigadores de 5 universidades (PUC, UV, UPLA, PUCV y UCM) y 3 centros de investigación (CCG-UC, CIGIDEN y COSTAR-UV). El estudio de amenaza se basa en el análisis histórico del oleaje y del nivel medio del mar (NMM), además de una proyección para el período 2026-2045 de estas variables y de la cota de inundación. En primer lugar, se analiza el comportamiento histórico del oleaje obtenido a partir un modelo numérico (WWIII) cada 2° de latitud (1980-2015). El análisis de clima medio del oleaje concluye que ha habido un incremento leve en la altura y el período, además de un giro al sur del oleaje, probablemente asociados a la migración al sur del Anticiclón Permanente del Pacífico Sur. El análisis de clima extremo demuestra en todo Chile se ha registrado un aumento en la cantidad de marejadas de 0.1 a 0.3 eventos más por año, dependiendo de la latitud. El estudio de NMM, basado en el análisis de 11 mareógrafos con más de 30 años de data, muestra que no existe una tendencia clara de aumento en Chile, lo que puede atribuirse a las deformaciones de la corteza producto del ciclo sísmico. En particular, en el norte existe un descenso del NMM probablemente asociado al acoplamiento de las placas tectónicas luego del terremoto de 1877. En segundo lugar, el estudio busca evaluar los cambios del oleaje (marejadas), NMM y cota de inundación entre el período histórico (1985-2004) y la proyección (2026-2045) correspondiente al escenario de emisiones RCP 8.5 del IPCC. El estudio de oleaje basa en el forzamiento del modelo WWIII mediante 6 modelos de viento en toda la cuenca del Pacífico. El modelo es calibrado y validado con registros de boyas direccionales y altimetría satelital entre 1980 y 2015. El estudio de clima medio concluye que la altura de ola y el período seguirán incrementándose levemente y el oleaje girará más al sur, también en forma moderada. Los eventos extremos, no obstante, serán más frecuentes e intensos, sobretodo en la zona central de Chile, lo que seguramente aumentará los daños en la infraestructura costera. El estudio de NMM, por su parte, se basa en 21 modelos disponibles en el CMIP5 los cuales se analizan cada 5 [km] en forma latitudinal. El estudio concluye que en todo Chile, incluidas Rapa Nui y Juan Fernández, se espera un ascenso de 0.15 a 0.18 [m], con un rango de incertidumbre del orden de ±0.1 [m] para la proyección. A fines de siglo, no obstante, el incremento sería del orden de 0.65 ±0.3 [m]. La cota de inundación, calculada a partir del oleaje, el NMM, la marea astronómica y la marea meteorológica, presenta valores de 2.5 [m] NRS en el extremo norte a 3.5 [m] NRS en el Canal Chacao para el escenario histórico y de entre 2.8 a 3.8 [m] NRS para ambos extremos. El aumento de la cota de inundación abarca desde +0.23 a +0.29 [m] en los extremos sur y norte, respectivamente. El estudio de exposición consiste en elaborar un modelo de elevación digital (DEM) en 106 comunas a partir de tres fuentes satelitales (ASTER GDEM-2, ALOS WORLD 3D y ALOS PALSAR). A partir del DEM se elabora un inventario de exposición de los sistemas humanos y naturales ubicados bajo los 10 metros sobre el nivel del mar (msnm). El inventario es generado a partir de información disponible en los servicios públicos, levantamientos en terreno y talleres efectuados en Antofagasta, Valparaíso y Concepción. Luego de un proceso de limpieza de 174.746 registros identificados inicialmente, se llega a un inventario con 18.376 entradas, separadas en 6 categorías (población, infraestructura, equipamiento, economía, sistemas naturales y otros), subdivididas a su vez en 76 tipos de entidades. La información más relevante del inventario es presentada a nivel nacional, regional y comunal. En síntesis, el inventario identifica un total de 972.623 personas habitando en los primeros 10 msnm y que en dicha área se ubican 546 caletas de pescadores, 1692 humedales, 256 campos dunares, 1172 playas, 156 lugares de interés para la biodiversidad, 1198 equipamientos (colegios, jardines infantiles, carabineros, entre otros), 171 terminales marítimos, 475 elementos de infraestructura costera y 477 asentamientos, entre otros elementos (Tabla 22, Volumen 1). A partir inventario y mediante el juicio experto, se definen 12 comunas críticas en las que se utilizan planos de borde costero del SHOA para refinar el cálculo de la vulnerabilidad. Las comunas críticas son Antofagasta, Coquimbo, Viña del Mar, Valparaíso, Pichilemu, Talcahuano, Coronel, Arauco, Puerto Saavedra, Valdivia, Rapa Nui y el Archipiélago Juan Fernández; ambas últimas que se detallan en el volumen de vulnerabilidad y riesgo en islas oceánicas. El estudio de vulnerabilidad se orienta a los sistemas humanos y naturales identificados en el estudio de exposición. Dada la gran cantidad y complejidad de categorías (6) y entidades existentes (76), el análisis se reduce a evaluar si cada objeto del inventario de exposición será o no inundado durante la proyección (2026-2045) bajo el escenario RCP 8.5. Las líneas de inundación para el período histórico y la proyección se presentan en el SIG. El estudio concluye que 589 manzanas censales, 46357 personas y 18338 viviendas pasarían a ubicarse en zonas de inundación. Lo mismo ocurriría 17 puentes, 4245 puntos de la red vial, 8 centros de distribución de energía por hidrocarburos, 1 central termoeléctrica, 2 subestaciones y 53 elementos de infraestructura sanitaria. Con respecto al equipamiento comunal, 10 edificaciones de bomberos, 7 establecimientos de salud, 49 de educación y 5 de policía se ubicarían en zonas inundables. Por último, se identifican 358 elementos asociados al turismo en dichas zonas. Adicionalmente, y en volúmenes separados, se caracteriza la vulnerabilidad (y cuando es posible el riesgo) de playas, caletas, puertos y humedales, proponiendo también medidas de adaptación específicas para estos sistemas. En el estudio de vulnerabilidad en playas se determinan los cambios en la posición de la línea litoral para 35 playas en las regiones de Antofagasta, Coquimbo, Valparaíso, O’Higgins y Biobío. Para ello se usa el software DSAS, fotografías aéreas, imágenes satelitales y levantamientos topográficos. El análisis cubre desde 39 años (La Serena) a sólo 3 años (Lebu-Tirúa), pero en 33 playas exceden los 20 años. Los resultados integrados en el SIG indican que el 9% de estas playas presenta erosión alta (mayor a 1.5 m anuales), el 71% erosión, el 11% un estado estable y solo un 9% acreción. Los casos de mayor erosión corresponden a extensos litorales arenosos, asociados a campos dunares y humedales. El estudio histórico no establece las causas que explican la erosión generalizadas, que pueden ser de origen oceanográfico, geofísico, antrópico o hidrológico. En el estudio de riesgo en playas se estima, en forma general, que aquellas playas ubicadas entre Arica y el Canal Chacao experimentarán retrocesos medios de entre 3 y 23 [m] por efecto de cambios en oleaje y nivel del mar en el escenario RCP 8.5 en el período 20262045. La tendencia es que playas largas experimenten erosión en sus extremos sur y acreción en sus extremos norte debido a un leve cambio en la dirección del oleaje. La estimación del daño económico calculado en forma específica para 6 playas en la Región de Valparaíso permite estimar una pérdida cercana a los 500 mil dólares anuales producto del riesgo de erosión causada por cambio climático. En el estudio de vulnerabilidad en puertos se analiza el impacto histórico asociado a la pérdida de disponibilidad de sitios de atraque debido a oleaje (downtime). A partir de los certificados de cierre de puerto (2015 a 2017) y una base de datos de SERVIMET (2007 a 2014) se concluye que, entre 2008 y 2017, se registraron 9097 cierres de puerto en 19 capitanías expuestas al Océano Pacífico de las cuales se contó con información. Los puertos con mayor cantidad de cierres son Arica (850), Tocopilla (802) y Quintero (761). El estudio de riesgo en puertos se evalúa el downtime operacional en 9 puertos en Chile (Arica, Iquique, Mejillones, Antofagasta, Coquimbo, Quintero, Valparaíso, San Antonio y San Vicente). El oleaje en aguas profundas se transfiere a cada puerto utilizando un modelo numérico (SWAN). Luego, el downtime, expresado en horas de cierre por año, se calcula comparando el clima del oleaje local con límites operacionales definidos en la ROM 3.1-99 (PPEE, 2000) para el período histórico (1985-2004) y la proyección (2026-2045). Se concluye que algunos puertos mejorarán y otros empeorarán su operatividad y que el clima extremo será más severo a mediados de siglo. La mejora operativa puede explicarse por el giro al sur del oleaje que mejoraría las condiciones de abrigo de puertos ubicados en el extremo sur de las bahías. En términos económicos, el análisis a nivel agregado para los 9 puertos se traduce en pérdidas de US$ 4,12 millones anuales y ganancias por US$ 6,34 millones anuales, dando como resultado unas ganancias netas de US$ 2,22 millones anuales como efecto del cambio climático. El aumento del NMM, sumado al incremento en la frecuencia e intensidad de las marejadas, no obstante, significará un aumento significativo del sobrepaso y del daño estructural de obras portuarias. Se proponen medidas de adaptación para mejorar las condiciones operacionales y para la gestión de la infraestructura en un contexto de clima futuro más severo que el actual. Dada su similitud operacional, el estudio de vulnerabilidad en caletas equivale al de puertos y busca mostrar que estas han experimentado numerosos cierres debido a marejadas en la última década. En el estudio de riesgo en caletas de pescadores se evalúa el downtime operacional de las 546 caletas agrupadas cada 2° de latitud para el período histórico (1985-2004) y la proyección (2026-2045), considerando los límites operacionales definidos en base a focus groups y encuestas para diferentes actividades (buzos, recolectores, embarcaciones de eslora inferior y superior a 12 m). El oleaje en aguas profundas se transfiere a la costa utilizando una metodología simplificada que rescata la física fundamental de la zona de aproximación a la costa, pero no las condiciones locales de cada caleta. El análisis concluye que un 23% de los registros pesqueros artesanales se encuentran en zonas con predicciones de aumento en downtime de pesca (19°S a 34S). Hacia el sur, las condiciones operacionales asociadas al oleaje mejorarían en la proyección. Considerando los valores de desembarque y de precios en playa del año 2017, se estima una pérdida a nivel agregado que podría fluctuar entre los US$ 1,3 y 7,6 millones anuales para las caletas ubicadas entre los 19°S y 34°S, dependiendo del escenario. Las pérdidas en desembarque representan alrededor de un 2-5% de capturas actuales. El estudio de vulnerabilidad de humedales presenta la distribución comunal de 1692 humedales costeros. A nivel específico y dependiendo de la disponibilidad de información y levantamientos en terreno, se identifica una tendencia general a la reducción del área de los espejos de agua (18 de 21 casos analizados) que podría explicarse por la reducción de los caudales (100% de 30 ríos analizados). Debido al incremento histórico de la frecuencia e intensidad de las marejadas extremas, los episodios de sobrepaso que aportan agua salada a los humedales podrían generar cambios en el patrón de dominancia de las especies vegetales levantadas en los humedales costeros. No obstante, los cambios identificados en los humedales podrían deberse a otros factores no estudiados como la influencia de perturbaciones naturales provenientes de la cuenca (aluviones), al efecto del pastoreo ejercido por vacas y caballos, al pisoteo de turistas y al efecto combinado de dichos factores, tsunamis y tormentas marinas.
... Even though it is naturally saline, the diversity and abundance of aquatic invertebrates found in this ecosystem (108 taxa from 47 families) is comparable to that found in the river and floodplain and temporary pans. Overall, the diversity of aquatic invertebrates in the PRF is greater than that of comparable lowland river (see [23,24]), pan (see [25]) and saline lake (see [26]) ecosystems. These findings further demonstrate that the PRF is a biodiversity hotspot for aquatic invertebrates and of great ecological importance. ...
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Freshwater biodiversity is under constant threat from a range of anthropogenic stressors. Using South Africa’s Phongolo River and floodplain (PRF) as a study case, the aim of this chapter is to provide an overview of the conservation and management of freshwater biodiversity in a highly diverse subtropical ecosystem. The PRF is the largest floodplain system in South Africa which is severely threatened by irregularly controlled flood releases from a large upstream dam, prolonged drought, deteriorating water quality, organic pollutants and the increasing dependence of the local communities. Based on a decade of survey of the PRF conducted from 2010 to 2020, this chapter highlights the current diversity of aquatic organisms (invertebrates, fishes, frogs and their parasitic fauna), followed by an overview of their biological and physical stressors. The current challenges in the management of the aquatic biodiversity of this region and a way forward to conservation strategies are also addressed in this chapter.
... However, the construction of a reservoir on the river and diversion of water for agriculture have led to a reduction in the size of Lake Abert and a corresponding increase in its salinity. Numbers of phalaropes, avocets, and gulls declined up to 83% as lake levels dropped (Senner et al. 2018). Baskin (2005) Salton Sea, CA California's Salton Sea was an important wintering ground and migration stopover site where grebes were able to replenish their body condition by foraging on the abundant population of a polychaete, the pileworm (Neanthes succinea). ...
... The selection of the crane habitats was previously found to be influenced by several factors, such as wetland area, water level, food distribution, vegetation height, and distance from human interference sources [71][72][73], among which the water level had the largest impact [74][75][76][77]. This study focused on the spatiotemporal variation of the Siberian crane habitats and the response to changing water levels in the Poyang Lake wetland. ...
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The Poyang Lake wetland in China is the largest wintering destination for Siberian cranes worldwide. Understanding the spatiotemporal characteristics of crane habitats is of great importance for ecological environment governance and biodiversity protection. The shallow water, grassland, and soft mudflat regions of the Poyang Lake wetland are ideal habitats for wintering Siberian cranes. Based on Landsat Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Operational Land Imager (OLI) remote sensing images, habitat areas were extracted and associated with various water levels taken on multiple dates. Landscape metrics were applied to describe the spatial structural characteristics of the crane habitats, and spatial statistics are used to explore the cold and hot spots of their distribution. Moreover, three indicators including sustainability, stability, and variety were applied to evaluate the vulnerability of the crane habitats under different hydrological conditions. Our findings indicate: (a) The main crane habitats exhibit a gradual decreasing degree of fragmentation in time, an obvious uncertainty of shape complexity and a relatively stable connectivity. (b) The crane habitats have a consistent spatial pattern of highly aggregated distributions associated with various water levels. (c) The hot spots of the habitats formed multiple “sheet” belts centered on the “Lake Enclosed in Autumn” regions, while the cold spots indicate a spatial pattern of axial distributions. (d) The majority of the hot spots of the habitats were distributed in sub-lakes found in the southeast part of the Poyang Lake watershed and the Nanjishan and Wucheng nature reserves, while the cold spots were mainly distributed in the main channels of the basins of Poyang Lake. (e) The sustainable habitats were mainly distributed in the “Lake Enclosed in Autumn” regions and intensively aggregated in two national nature reserves. (f) Under conditions of extremely low to average water levels (5.3–11.46 m), an increase of water level causes a decrease of the stability and variety of the crane habitats and weakens the aggregation structure.
... One stark example is that in 2014, water diversions coupled with drought caused Lake Abert to shrink to 5% of its maximum size, and the salinity more than tripled (Moore 2016, Larson et al. 2016). This caused a loss of the phalarope prey base, and a subsequent decline in shorebird use (Larson et al. 2016, Moore 2016, Senner et al. 2018. ...
Technical Report
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Given saline lake habitat is threatened worldwide by water diversion and climate change, there is an urgent need to better understand phalarope population and trends. We conducted coordinated monitoring of western North American staging areas of historical importance to phalaropes: Great Salt Lake (Utah), Mono Lake (California), Lake Abert (Oregon), Owens Lake (California), south San Francisco Bay (California), and Chaplin Lake (Saskatchewan). We conducted surveys at each site during week-long “survey windows,” from mid-July to mid-September, 2019 and 2020, with the goal of at least one survey per site per window. Methods were standardized within sites but varied across sites, including plane-based, boat-based, and land-based surveys. We report results from Great Salt Lake, Mono Lake, and Lake Abert in 2019 and for all surveyed sites in 2020.
... Bai et al. (2012) [22] attributed the reduced area of terminal lakes in Central Asia to a large irrigation quota and dry climate. Therefore, multiple studies show that the ecological service function of lakes and wetlands is seriously weakened by the drying of terminal lakes under the influence of human activities [23]. As an important ecological barrier in arid areas, terminal lakes suffer almost irreversible damage. ...
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Obtaining the water volume of small-and medium-sized lakes in enclosed watersheds with scarce data is a global focus of research. River flow into a lake is an important factor affecting the water volume. However, most river flow measurement methods involve long cycles, low efficiency , and transdisciplinary expertise, making rapid assessments in ungauged basins impossible. This paper proposes a remote sensing flow estimation method based on multi-source remote sensing data, which quickly assesses river flow and provides important input data for lake water volume simulation. The cross-section flow was estimated by extracting the river width. The calculated results were consistent with the measured data, with accuracy greater than 90%. The results compared with daily data measured at hydrological stations, and the Nash coefficient was greater than 0.9. Additionally, the simulation method for lake area, water volume, and water level was constructed using river inflow input data, greatly reducing the parameters required by the conventional lake water volume simulation method. Based on the remote sensing discharge estimation method, we quickly and conveniently obtained changes in river flow into the lake, simulated lake water volume, and provided the basis for water resource management in terminal lake basins with scarce data.
... El cambio climático contemporáneo ha reducido significativamente la cantidad y distribución de los humedales en todo el mundo, así como la estacionalidad del agua que fluye hacia los humedales (Box et al. 2008, Barnett et al. 2016, Bradley & Yanega 2018. Esto ha tenido como consecuencia, cambios notables en la composición de las especies de aves acuáticas, peces e invertebrados en un período relativamente corto (Sada et al. 2005, Moore 2016, Senner et al. 2018, además de reducir la disponibilidad de sitios de agua dulce para las aves acuáticas y otras especies dependientes de los humedales. El cambio climático antropogénico aumenta los riesgos de desajustes entre la fenología de las especies y las condiciones ambientales, lo que resulta en el deterioro de las principales rutas migratorias (Koening 2002, Iknayan & Beissinger 2018. ...
... While agricultural and managed wetlands are heavily used by migratory birds across the country and they are an important contributor to conservation of wetland wildlife they do not fully replace all the system functions or habitat values of historic wetlands and an over representation of agricultural wetlands reduces system variability and the availability of resources. For example, saline lakes throughout the west provide critical stopover and molting habitat for a diverse assemblage of waterbirds (Jehl 1994;Senner et al. 2018), but the structure and function of these habitats differ dramatically from agricultural wetlands and agricultural water use threatens their future viability. Similarly, large-scale agriculture and urban development drove the loss of vernal pools in California (AECOM 2009) and moist-soil management and flooded agricultural fields fail to replace the values of these pools (King 1998). ...
Article
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Water is essential for wetland function and sustaining migratory networks for wetland wildlife across broad landscapes. Groundwater declines and surface flow reductions that impact aquatic and wetland organisms are common in the western U.S. and increasingly in the eastern U.S. Agriculture is the largest consumptive water use in the U.S. and understanding economic incentives of water-use practices and the legal context of water rights is foundational to identifying meaningful water solutions that benefit all sectors of society. In this paper, we provide a brief overview of water rights in the U.S. and synthesize the literature to provide a broad overview of how federal farm policy influences water-use decisions. We conclude that the ultimate cause of many water-use conflicts is an inefficient farm economy that is driven by several proximate factors, of which outdated water laws and subsidies that encourage increased water use are among the most important. Development of multi-scale water budgets to assess project impacts and by working more intensively at local watershed and aquifer scales may improve conservation efforts. Finally, detailed analyses to understand the impacts of specific federal policies on agricultural water use may enhance water conservation efforts, facilitate long-term food and water security, and provide greater protection for wetland and aquatic resources.
... Waterbirds are sensitive to changes in salinity. The ability of large numbers of waterbirds to profitably use saline lakes basically depends on concentrations of invertebrate fauna (Senner et al., 2018). Waterbird use of these arid-land wetlands throughout the annual cycle depends on physiological adaptations that take advantage of abundant saline wetland-derived prey. ...
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Influeix la salinitat en la diversitat i l’estructura dels ocells aquàtics hivernants als aiguamolls del Sàhara, a Algèria? Durant el període 2017-2019 es van registrar 42 espècies d’ocells aquàtics hivernants al complex d’aiguamolls de la vall d’Oued Righ, al Sàhara algerià. Les diferències de salinitat expliquen les variacions en la riquesa d’espècies i en la distribució dels ocells aquàtics als diversos aiguamolls estudiats. Els ambients oligohalins (0,5-5 ‰) i mesohalins (5-18 ‰), representats pel llac Aiata, el llac Sidi Khelil i l’Oued Kherouf, són els més favorables per als anàtids, excepte el gènere Tadorna, que és present als punts d’estudi euhalins (30-40 ‰) i hiperhalins (> 40 ‰). El flamenc rosat Phoenicopterus roseus i la gavina de bec prim Chroicocephalus genei es distingeixen per ser presents a les zones més holomorfes del complex com ara Chott Merouane. Dades publicades a GBIF (Doi: 10.15470/6fqd0h)
... Some waterbirds are known to prey on the invertebrates (Weston 2007;Pedler et al. 2018), although comprehensive data on the relationships between these predators and prey are lacking. It is possible that declines in the abundance and availability of the invertebrates (e.g. if salt lakes are dry for longer periods of time and are more saline) will affect the population dynamics of these birds (Senner et al. 2018). Fish predation may also be important at certain times in some waterbodies (Chessman and Williams 1987;Becker and Laurenson 2007), although fish are absent from most of the Australian salt lakes, which are typically either ephemeral or highly saline (De Deckker 1983b). ...
Article
This study synthesises information on the biology of the unique and diverse halophilic macroinvertebrates of Australian salt lakes, focusing on gastropods and crustaceans. This information is needed to evaluate and manage the threats posed to these invertebrates by increased periods of drought and secondary salinisation. Most of these species are endemic to Australian salt lakes, and some have adapted to extreme conditions (e.g. salinities >100 g L-1 and pH <5). This study identifies key general findings regarding the taxonomy, ecology and life histories of these invertebrates, such as that many 'new' species have been uncovered in the past 20 years, with more likely to come. The study also identifies critical knowledge gaps, such as the need to elucidate the abiotic and biological drivers of the field distributions of species, including why some species are widespread and common whereas other congeneric species are rare or have narrow distributions. Those species that are either restricted to low salinity environments or survive dry periods as aestivating adults (as opposed to desiccation-resistant eggs) are probably the most vulnerable to increasing salinisation and drought. Future work should prioritise the development of a sound taxonomy for all groups, because this is needed to underpin all other biological research.
... However, the construction of a reservoir on the river and diversion of water for agriculture have led to a reduction in the size of Lake Abert and a corresponding increase in its salinity. Numbers of phalaropes, avocets, and gulls declined up to 83% as lake levels dropped (Senner et al. 2018). Baskin (2005) Salton Sea, CA California's Salton Sea was an important wintering ground and migration stopover site where grebes were able to replenish their body condition by foraging on the abundant population of a polychaete, the pileworm (Neanthes succinea). ...
Article
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Great Salt Lake (GSL) is the largest hypersaline lake in North America and is the fall staging area for a high proportion of North America’s Wilson’s Phalaropes (Phalaropus tricolor) and Red-necked Phalaropes (Phalaropus lobatus). Unfortunately, diversion of freshwater for agriculture and development has decreased the size of GSL by 48%. To assess the potential impact of a smaller GSL on phalaropes, we collected data from 2013 to 2015 from sites where large, dense flocks of phalaropes congregated and sites where there were no phalaropes. At each site, we measured the densities of invertebrates that were preyed upon by phalaropes, including larval and adult brine flies (Ephydridae), adult brine shrimp (Artemia franciscana), chironomid larvae (Chironomidae), and corixid adults (Corixidae). Abiotic characteristics measured included water depth, water salinity, water temperature, wind speed, and benthic substrate. We analyzed high-salinity sites separately from low-salinity sites because they contained different invertebrates. High-salinity sites were in Carrington and Gilbert bays and were relatively deep (mostly <2 m). At the high-salinity sites, phalaropes exhibited a preference for sites with an abundance of adult brine flies and for microbialite substrates. The low-salinity sites were in Ogden and Farmington bays and were shallow (<1 m). At low-salinity sites, large phalarope flocks were more likely to occur at sites that were shallower, less saline, and had a high biomass of benthic macroinvertebrates. Our results indicate that physical features and prey availability are both important in determining phalarope habitat use at GSL. Phalaropes prefer to use shallower parts of GSL and brackish waters. These areas will be especially impacted by decreased freshwater inflow into GSL.
... However, there is little information about the ecosystem function of these water bodies. It is an important issue to examine the changes in these ecosystems for such reasons (Oren 2016;Senner et al. 2018). ...
... As water volumes continue to decrease, lakes can reach a point of infertility well before they dry completely (Herbst, 2006;Senner et al., 2018). Transition of some declining freshwater lakes to saline states (sensu Thomas, 1995-Walker Lake) may open habitat niches in snowmelt watersheds that offset losses in others. ...
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Migrating waterbirds moving between upper and lower latitudinal breeding and wintering grounds rely on a limited network of endorheic lakes and wetlands when crossing arid continental interiors. Recent drying of global endorheic water stores raises concerns over deteriorating migratory pathways, yet few studies have considered these effects at the scale of continental flyways. Here, we investigate the resiliency of waterbird migration networks across western North America by reconstructing long‐term patterns (1984‐2018) of terminal lake and wetland surface water area in 26 endorheic watersheds. Findings were partitioned regionally by snowmelt‐ and monsoon‐driven hydrologies and combined with climate and human water‐use data to determine their importance in predicting surface water trends. Nonlinear patterns of lake and wetland drying were apparent along latitudinal flyway gradients. Pervasive surface water declines were prevalent in northern snowmelt watersheds (lakes ‐27%, wetlands ‐47%) while largely stable in monsoonal watersheds to the south (lakes ‐13%, wetlands +8%). Monsoonal watersheds represented a smaller proportion of total lake and wetland area, but their distribution and frequency of change within highly arid regions of the continental flyway increased their value to migratory waterbirds. Irrigated agriculture and increasing evaporative demands were the most important drivers of surface water declines. Underlying agricultural and wetland relationships however were more complex. Approximately seven percent of irrigated lands linked to flood irrigation and water storage practices supported 61% of all wetland inundation in snowmelt watersheds. In monsoonal watersheds, small earthen dams meant to capture surface runoff for livestock watering, were a major component of wetland resources (67%) that supported networks of isolated wetlands surrounding endorheic lakes. Ecological trends and human impacts identified herein underscore the importance of assessing flyway scale change as our model depictions likely reflect new and emerging bottlenecks to continental migration.
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Fisheries in Cuitzeo, the second largest Mexican lake, used to take place on the permanent freshwater East and Central Basins as opposed to the temporal, saline, and initially thought barren West Basin. The 1980 fisheries collapse forced fishers to look for non-conventional fishing products elsewhere in the lake. The West Basin’s temporal, saline-alkaline, and shallow water provides exceptional habitat for ephydrids to flourish. Locally known as “pupa”, ephydrids are collected in large numbers. Although consumed since pre-Hispanic times, no other commercial fisheries of ephydrids are known worldwide. This study records the species composition and abundance of the “pupa” throughout an annual cycle in the West Basin, where fisheries occur. Two species were found: Ephydra hians and Lamproscatella muria. Ephydrids co-occurred in June and July at the end of the dry season when salinity was highest. L. muria was more abundant (954 ± 2385 ind m−2) than E. hians (94 ± 38 ind m−2). The relatively low salinity of the West Basin favoured L. muria over E. hians, which prefers higher salinities. This “pupa” fishery is still unpredictable due to the astatic nature of the lake, and hence limited economic importance to the local fishers.
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Utah’s Great Salt Lake (GSL) is so saline that the only invertebrates that survive in the open water are brine fly larvae and brine shrimp. In the absence of competition from other invertebrates, they are incredibly abundant. Only a few avian species can take advantage of their abundance because a bird cannot eat them without also ingesting salt. Moreover, brine shrimp and brine flies are so tiny that only a few avian species can consume the massive number of brine shrimp and brine flies required to meet a bird’s nutritional needs. For example, eared grebes need to consume 28,000 adult brine shrimp each day to survive. To achieve this, an eared grebe has to spend 7 h daily foraging and needs to harvest one shrimp per second during foraging.
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Understanding relationships between habitat and ecological processes often depends on the spatial scale at which the landscape is measured. A common objective in studies of avian nesting ecology is to link habitat characteristics with nest predation for generating potential conservation and management strategies aimed at increasing avian reproductive success. Yet scale dependence likely plays a considerable role in these assessments, particularly when multiple species of nest predators are present. We identified nest predators of snowy plovers, a ground-nesting shorebird, and modeled predator-specific hazard rates of nest mortality in relation to the landscape at multiple spatial scales (200 m, 500 m, 1 km, 2.5 km, and 5 km) and at the nest site. We used a Bayesian latent indicator approach for weighting the influence of habitat across spatial scales and to gain insight into the hierarchical nature of how specific predators responded to the landscape when preying upon plover nests. We did not identify a common spatial scale that best predicted nest predation by all predators, though our results indicated that unfragmented playa and marsh habitats at large spatial scales reduced nest predation by all nest predators. Land cover features including grass, shrubs, human development, and open water elicited variable responses depending on the predator group, and predator groups responded at different spatial scales. Further, the spatial configuration of nests (nest dispersion) influenced nest predation by common ravens Corvus corax and foxes (kit fox Vulpes macrotis and red fox Vulpes vulpes), suggesting that certain predators develop a search image for nests. Our results illustrate that clarifying complex relationships between nest predation and habitat characteristics requires the incorporation of predator identity and scale dependence. Thus, management and conservation plans aiming to increase avian productivity by altering or restoring habitats will likely benefit from consideration of predator-specific patterns at multiple spatial scales.
Chapter
This article aims to characterize saline lakes, especially to differentiate them from freshwater lakes. They range in various modes of origin, shoreline level stability, salt load and ionic dominances. Species diversity is generally inversely proportional to salinity. While many common higher taxonomic groups of animals occur in saline lakes, those of hypersaline waters are distinctive and include brine shrimps, ostracods and rotifers. These halophilic groups employ osmotic regulation often at cost to their life cycles. Faunas vary a little between continents, but with the old landscape of Australia is most unique. Saline lakes host a much greater and scientifically interesting variety of microbial life than freshwaters; some unique lake structures include microbial mats, stromatolites and thrombolites. Saline lakes are poorly managed throughout the world. Many are being denied water inflow, directly or indirectly while changing land use inflicts secondary salinization on others. For almost all the future is bleak.
Article
The formation of carbonate spherulites, recognized as part of the South-Atlantic Pre-Salt reservoir rocks, remains enigmatic. Well-chosen analogues provide insights into depositional and diagenetic conditions and the biotic versus abiotic processes that might influence or even control spherulite growth. Radial fibrous calcite spherulites of the Batateira beds in the Barbalha Formation (Aptian, Araripe, NE Brazil) formed mainly in organic and clay-rich laminite layers as nodules that grew around different nuclei, now represented by, amongst others, micrite and apatite ostracods. They vertically alternate with clays, but also carbonate laminites, which locally also contain spherulites. Characterization of the organic matter content of spherulitites (petrography, total organic carbon, vitrinite reflectance, stable isotopes) reveals TOC’s of up to 30% related to the presence of mainly oil-prone alginite next to huminite, inertinite, sporinites and zooclasts. The complex mixture of clays, dominantly autogenic mixed layered illite-montmorrilonite, which alternate with lacustrine carbonates and evaporites, is diagnostic for lakes in a semi-arid environment. The occurrence of gypsum, calcitic alveolar honeycomb spherulite textures, preferential concentration of pyrite at the spherulite-matrix contact and inward spherulite perforations suggest bacterial activity under shallow and evaporitic syn-depositional conditions. Although the Barbalha spherulites formed chemically-driven in a viscous matrix, the microbial influence, mainly as lamalginite in the clayey matrix, is undeniable. The mixed organic-silicate gel catalyzed calcite spherulite formation. The Barbalha spherulites consequently illustrate the complementary influence of clays, organic matter and evaporitic syn-sedimentary conditions.
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Walker Lake is a monomictic, nitrogen-limited, terminal lake located in western Nevada. It is one of only eight large (Area>100 km^2, Z_{ mean}>15 m) saline lakes of moderate salinity (3–20 g l^−1) worldwide, and one of the few to support an endemic trout fishery (Oncorhynchus clarki henshawi). As a result of anthropogenic desiccation, between 1882 and 1996 the lake's volume has dropped from 11.1 to 2.7 km^3 and salinity has increased from 2.6 to 12–13 g l^−1. This study, conducted between 1992 and 1998, examined the effects of desiccation on the limnology of the lake. Increases in salinity over the past two decades caused the extinction of two zooplankton species, Ceriodaphnia quadrangula and Acanthocyclops vernalis. Recent increases in salinity have not negatively affected the lake's dominant phytoplankton species, the filamentous blue-green algae Nodularia spumigena. In 1994 high salinity levels (14–15 g l^−1) caused a decrease in tui chub minnow populations, the main source of food for Lahontan cutthroat trout, and a subsequent decrease in the health of stocked trout. Lake shrinkage has resulted in hypolimnetic anoxia and hypolimnetic accumulation of ammonia (800–2000 g-N l^−1) and sulfide (15 mg l^−1) to levels toxic to trout. Internal loading of ammonia via hypolimnetic entrainment during summer wind mixing (170 Mg-N during a single event), vertical diffusion (225–500 Mg-N year^−1), and fall destratification (540–740 Mg-N year^−1) exceeds external nitrogen loading (15–16 g l^−1) to support trout and chub fisheries in 20 years, and in 50–60 years the lake will reach hydrologic equilibrium at a volume of 1.0 km^3 and a salinity of 34 g l^−1.
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We re-assessed the population size and trend of 52 species and 75 taxa of shorebirds that occur in North America by reviewing published papers, soliciting unpublished data, and seeking the opinions of experts. New information resulted in changing population estimates for 35 of the 71 taxa that could be compared directly to the estimates published in 2006; from this comparison, 28 estimates increased and seven decreased. Almost all of the increases (88%) were the result of more comprehensive surveys being conducted or re-analyses of existing data rather than actual increases in numbers. Retaining the previous estimate was almost always due to a lack of new information. Recent trend analysis indicates that many shorebird populations have stabilized in recent years after large declines during the early 1980s and mid-1990s. Although many shorebird populations listed as threatened or endangered by the U.S. and Canadian governments have increasing population trends, none have reached recovery targets. Information on population trends remains virtually unknown for 25% of the shorebirds occurring in North America, and surveys are needed to determine the state of these populations.
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The Salton Sea is a highly saline lake that has long supported sportfishery and large populations of fish-eating birds. A study was initiated in 1999 to assess the status of orangemouth corvina (Cynoscion xanthulus), bairdiella (Bairdiella icistia) and tilapia (Oreochromis mossambicus × O. urolepis). Multimesh (50 × 2 m) gillnets were set at nine stations in 1999, ten stations in 2000 and six stations in 2002. These stations were sampled every two months in 1999, every three months in 2000 and once in 2002. O. mossambicus was the most abundant of the four species, with a maximum mean catch per unit effort (CPUE) 13.8 kg net−1 h−1 or 29.9 fish net−1 h−1 being observed at the river mouth stations in August 1999. From spring to summer, tilapia CPUE increased at nearshore and river mouth stations and decreased at pelagic stations, apparently reflecting migration away from midlake areas in response to anoxia or hypoxia caused by periodic springtime overturn events in deep waters. Tilapia catches in nearshore, river mouth and pelagic habitats were 83 and 60% males in 1999 and 2000, respectively. Tilapia catches in rivers in August 1999 averaged only 6% male. During 1999–2000, the tilapia population consisted essentially of only the 1995 and 2000 year classes. Harsh conditions at the Salton Sea have led to erratic reproduction and survival rates and unstable age structures for its resident fishes. Massive parasite infestations of fry and physiological stressors such as anoxia, high sulfide levels, high salinity and high and low temperatures are potential causes of the irregular recruitment and periodic dieoffs of tilapia. The abundance of all fish species declined over the years of study. Between 1999 and 2002, the late summer mean CPUEs for tilapia, bairdiella and orangemouth corvina at four nearshore stations dropped from 16 fish to 0.02 fish, from 4.7 fish net to 0.23 fish, and from 0.08 fish to 0.02 fish, respectively. During 2000–2003, parallel declines occurred in estimated numbers of adult fish involved in mass mortality events at the Sea. The boom-and-bust dynamics of tilapia and other fish populations in the Sea have major consequences for fish-eating bird populations, for other components of the ecosystem, and for the recreational value of the lake.
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We evaluated the conditions under which patch size effects are important determinants of local population density for animals living in patchy landscapes. This information was used to predict when patch size effects will be expected to occur following habitat loss and fragmentation. Using meta-analysis, we quantitatively reviewed the results of 25 published studies that tested for a relationship between patch size and population density. Patch size effects were strong for edge and interior species (negative and positive patch size effects, respectively), but negligible for generalist species that use both edge and interior habitat. We found significant differences in mean patch size effects between migratory and residential species, between herbivores and carnivores, and among taxonomic groups. We found no evidence that patch size effects were related to landscape characteristics such as the proportion of landscape covered by habitat, median patch size, or the scale at which a study was conducted. However, species in the Western Hemisphere tended to have larger absolute effect sizes, and eastern species tended to be more variable in their response. For landscapes undergoing habitat loss and fragmentation, our results predict the following: (1) among generalist species that use both the edge and the interior of a habitat patch, the decline in population size associated with habitat destruction should be accounted for by pure habitat loss alone; (2) for interior species, the decline in population size associated with habitat fragmentation per se will be greater than that predicted from pure habitat loss alone; (3) for edge species, the decline in population size will be less than that predicted by pure habitat loss alone; (4) these relative effects will not be influenced by the extent of habitat loss, but they will be affected by the pattern of habitat when large or small patches are preferentially removed; and (5) as loss and fragmentation increase within a landscape, migratory species will generally suffer less of a decline in population size than resident species.
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Three elements of wetland biodiversity (aquatic invertebrates, waterbirds and overstorey vegetation of the wetland edge) have been monitored since 1998 at Lake Eganu and Paperbark Swamp in the Western Australian Wheatbelt to provide information about the changes occurring in wetland biodiversity in a landscape that is severely affected by dryland salinization. Changes in extent of wetland vegetation since the 1960s were examined using historical aerial photographs and waterbird use of Lake Eganu during the early 1980s was compared with recent waterbird survey results. Lake Eganu, which is within a major drainage line, started to become salinized in the mid-1960s, about 70 years after land clearing began in the catchment, and its salinity has increased an order of magnitude. The extent of wetland overstorey vegetation and the richness of freshwater aquatic invertebrates have both declined about 80%. Waterbird richness has also declined over the past 20 years, with changes in species composition. Salinization has not occurred at Paperbark Swamp, which is in a small catchment off the main drainage line, and there has been no consistent change in the biodiversity elements monitored.
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Salt stress can suppress the immune function of fish and other aquatic animals, but such an effect has not yet been examined in air-breathing vertebrates that frequently cope with waters (and prey) of contrasting salinities. We investigated the effects of seawater salinity on the strength and cost of mounting an immune response in the dunlin Calidris alpina, a long-distance migratory shorebird that shifts seasonally from freshwater environments during the breeding season to marine environments during migration and the winter period. Phytohaemagglutinin (PHA)-induced skin swelling, basal metabolic rate (BMR), body mass, fat stores, and plasma ions were measured in dunlins acclimated to either freshwater or seawater (salinity: 0.3 and 35.0 ‰, respectively). Seawater-acclimated dunlins mounted a PHA-induced swelling response that was up to 56 % weaker than those held under freshwater conditions, despite ad libitum access to food. Freshwater-acclimated dunlins significantly increased their relative BMR 48 h after PHA injection, whereas seawater-acclimated dunlins did not. However, this differential immune and metabolic response between freshwater- and seawater-acclimated dunlins was not associated with significant changes in body mass, fat stores or plasma ions. Our results indicate that the strength of the immune response of this small-sized migratory shorebird was negatively influenced by the salinity of marine habitats. Further, these findings suggest that the reduced immune response observed under saline conditions might not be caused by an energy or nutrient limitation, and raise questions about the role of osmoregulatory hormones in the modulation of the immune system.
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We describe a method for estimating the total number of shorebirds that use a migration stopover site during spring and fall migration. We combined weekly shorebird counts with parameter estimates for detection probability, sampled proportion, and length of stay on the Squaw Creek National Wildlife Refuge. Double sampling was used to determine detection probability and estimated values varied among wetland units from a low of 0.07 to a high of 0.82. The sampled proportion of most wetland units was 100% but was lower in some of the larger units. Length of stay (measured for Pectoral [Calidris melanotos] and Least Sandpipers [C. minutilla] combined) averaged 10.0 days in spring and 3.7 days in fall. Spring shorebird numbers were approximately five times greater than fall numbers on the Refuge. Annual shorebird numbers varied among years from an estimated low in 2003 of 15 734 to a high in 2002 of 69 570. Peak daily counts during study years averaged only 12% of estimated spring totals and 4% of fall totals. An estimate of shorebird numbers based on summing weekly counts, not corrected for detection probability or sampled proportion, would have been only 21% (spring) to 31% (fall) of the total number of birds. These results reveal that peak counts and nonadjusted counts can significantly underestimate the number of shorebirds that use migration stopover sites in the midcontinent of North America.
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Saline lakes occur throughout the world and have significant economic, ecological, biodiversity, and cultural value. In addition to the wide array of human-caused impacts they experience in common with their freshwater counterparts, they are particularly vulnerable to changing hydrologic regimes due to climate change or water diversions. We review experience briefs addressing management issues at five lakes: Aral Sea (Kazakhstan/Uzbekistan), Issyk-kul (Kyrgyz Republic), Lake Nakuru (Kenya), Lake Poopó (Bolivia), and Chilika Lake (India). The Aral Sea experience illustrates the rapidity with which desiccation may occur and highlights the worldwide threat to all salt lakes with defined surface inflows as the demand for irrigated agriculture increases. It also shows the need for trans-boundary institutional structures for the management of water resources. All five experience briefs illustrate the linkage between lakes and their watershed and the need for basin-wide management. The role of international NGOs (e. g. Ramsar Bureau, Wetlands International, Birdlife International) in fostering an appreciation of non-economic values and promoting sustainable management is of particular importance to saline lake conservation; all five lakes considered here include Ramsar sites, "Wetlands of International Importance." The importance of stakeholder involvement in management is becoming widely recognized at all levels of governance (local to international). Experiences at Chilika Lake and Lake Nakuru provide examples of the success of stakeholder involvement.
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The Eared Grebe (Podiceps nigricollis Brehm) is the North American bird species most closely associated with highly saline habitats, and in winter and early spring it is the most abundant waterbird at the Salton Sea. During the fall, the great majority of the North American population stages at hypersaline lakes in the Great Basin, departing in early winter for wintering areas in southern California and Mexico, principally in the central Gulf of California. On the northward return flight, nearly all the population passes through the Salton Sea, where concentrations of >1 million have been reported in February–March. After staging for several weeks, grebes leave in March–April and migrate toward breeding grounds in the northern United States and southern Canada. The Sea's development as the species' major spring staging area may be as recent as the 1960s, and presumably awaited the establishment of appropriate prey populations of marine worms. In the past decades, two major dieoffs at the Sea each resulted in the undiagnosed death of tens of thousands of birds. Whether the cause(s) are endemic to the Sea or involve the grebes' migration routes and stopover locations is unknown. Because of problems in estimating numbers, the significance of these mortality events is hard to evaluate. Population trends are better studied at fall staging areas, especially Mono Lake, where population turnover is inconsequential, grebes are virtually the only species present, and numbers can be ascertained by aerial photography.
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We used aerial surveys to study abundance and distribution of waterfowl (ducks, geese, swans, and coots) during spring in southern Oregon and northeastern California (SONEC). Total waterfowl-use days in SONEC during the 119-day, 5 January–3 May, spring period was similar during 2002 (127,977,700) and 2003 (128,076,200) and averaged 1,075,900 birds per day (bpd); these estimates should be adjusted upward 4%–10% to account for areas not surveyed. Waterfowl abundance peaked in mid-March in both years: 2,095,700 in 2002 and 1,681,700 in 2003. Northern Pintail (Anas acuta) was the most abundant species in both years, accounting for 25.6% of the 2002 and 24.5% of the 2003 waterfowl-use days. Pintail abundance peaked during the 13 March survey at 689,300 in 2002 and 532,100 in 2003. All other dabbling ducks accounted for 27.6% and 28.6%, diving ducks for 13.5% and 9.2%, geese for 24.6% and 29.3%, swans for 2.8% and 1.9%, and coots for 5.8% and 6.4% of the spring waterfowl-use days in SONEC during 2002 and 2003, respectively. Although use days changed little for total waterfowl (+0.08%) and dabbling ducks (−0.1%), diving duck use was lower (−32%), and goose use days were greater (+19%) in 2003 than in 2002. Distribution was similar in both years, with the most waterfowl use in the Lower (66%) and Upper (14%) Klamath subregions; 2%–6% occurred in each of the other subregions. Although the Lower Klamath subregion received the greatest overall waterfowl use, distribution among subregions varied among species and surveys, and all subregions were important during some part of the spring for 1 or more species. Peak spring abundance in SONEC during 2002 and 2003 averaged 50.3% of the midwinter abundance in California (all survey regions) and southern Oregon (69-3 survey region) for all waterfowl, 46.1% for dabbling ducks, 62.4% for diving ducks, 68.8% for geese, 109.4% for swans, and 43.8% for coots. Each spring, 75% of all waterfowl use in SONEC occurred on federal, state, or Nature Conservancy lands (i.e., protected areas). On protected areas there was a higher percentage of dabbling ducks (80.5%), geese (70.5%), and coots (81.5%) than diving ducks (60.4%) and swans (49%). Waterfowl use of Klamath Basin National Wildlife Refuge (NWR) averaged 42% greater during spring 2002–2003 (568,500 bpd) than during 1998–2001 (Gilmer et al. 2004). Numerous factors likely impacted magnitude and distribution of waterfowl use of SONEC during spring, including weather, waterfowl populations, SONEC habitat, and species ecology. SONEC is a critical spring staging area for waterfowl that winter in the Central Valley of California and other Pacific Flyway regions and should be a major focus area for waterfowl-habitat conservation efforts.
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ABSTRACT  Current methods for conducting ground-based surveys of breeding waterfowl pairs make the unlikely assumption that detection probabilities are constant and approach 100%. To test this assumption, we conducted independent double-observer pair surveys in North Dakota, USA, to evaluate sources of variation in detection probabilities for 8 common species of prairie-nesting ducks. An experienced observer had 0.911 detection probability averaged over all 8 species (range = 0.866-0.944) versus 0.790 (range = 0.537-0.890) for a novice observer. Detection probabilities also varied substantially among species, but patterns were not consistent between observers. Detection probabilities declined as number of ducks per wetland increased, presumably due to difficulty in identifying large numbers of flushing ducks. Other covariates affecting detection probabilities included size of social groups, precipitation, survey methodology (roadside vs. walk-up), cloud cover, time of day, and amount of wetland vegetation, but these covariates only affected detection probabilities by 2–5%. Our results demonstrated that the assumption of 100% detection probabilities for ground-based waterfowl counts was clearly false and surveys based on this erroneous assumption underestimated population size by 10–29%. We recommend that future investigators measure detection probabilities explicitly by using double-observer methodologies.
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Anderson, T.W., M.A. Tiffany and S.H. Hurlbert. 2007. Stratification, sulfide, worms, and decline of the Eared Grebe (Podiceps nigricollis) at the Salton Sea, California. Lake Reserv. Manage. 23:500–517. Over the last half century the Salton Sea has been an important migratory stopover site for the Eared Grebe (Podiceps nigricollis). However, in recent years there have been sporadic mass mortalities (i.e., 150,000 in 1992) and a great reduction in the number of grebes visiting during the winter. We propose that a worsening food supply is causing the decline and that starvation may be a major cause of the unexplained mortalities. While at the Sea, grebes forage almost exclusively on a benthic polychaete, the pileworm (Neanthes succinea). This resident pileworm population has increasingly been subject to periodic crashes driven by exposure to anoxic, sulfide rich, hypolimnetic water following lake mixing events. A set of interlocking mechanisms seem to be operating. These involve, in particular, increasing lake salinity, weather events favoring lake stratification, and booms and busts in tilapia (Oreochromis mossambicus × O. urolepis hornorum) and plankton populations, including those of toxic cyanobacteria. In spring, Eared Grebes arrive from the Gulf of California and many arrive in need of food to fuel the remainder of their migration. When pileworms are scarce, many grebes are able to continue on toward their northern breeding grounds, but those that lack sufficient energy stores are forced to stay and may eventually perish. This analysis is surely incomplete, and definitive explanations of the excessive drinking and waterlogged plumage often exhibited by Eared Grebes during mass dieoffs have yet to be found.
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Many inland waters are becoming more saline from human activities, particularly in semi-arid and arid regions. The causes and distribution of anthropogenic salinisation, the salinisation of freshwater lakes, rivers and streams, and increases in the salinity of large, permanent saline lakes are discussed. The impacts of anthropogenic salinisation are far-reaching, increasing, deleterious and largely irreparable. Environmental, social and environmental costs are high. Attention is drawn to the importance of anthropogenic salinisation and its impacts. The need for better recognition of the costs of salinisation and for more effective management is stressed.