716 research outputs found

    Observed and Projected Hydroclimate Changes in the Andes

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    The Andes is the most biodiverse region across the globe. In addition, some of the largest urban areas in South America are located within this region. Therefore, ecosystems and human population are affected by hydroclimate changes reported at global, regional and local scales. This paper summarizes progress of knowledge about long-term trends observed during the last two millennia over the entire Andes, with more detail for the period since the second half of the 20th century, and presents a synthesis of climate change projections by the end of the 21st century. In particular, this paper focuses on temperature, precipitation and surface runoff in the Andes. Changes in the Andean cryosphere are not included here since this particular topic is discussed in other paper in this Frontiers special issue, and elsewhere (e.g. IPCC,2019b). While previous works have reviewed the hydroclimate of South America and particular sectors (i.e., Amazon and La Plata basins, the Altiplano, Northern South America, etc.) this review includes for the first time the entire Andes region, considering all latitudinal ranges: tropical (North of 27°S), subtropical (27°S−37°S) and extratropical (South of 37°S). This paper provides a comprehensive view of past and recent changes, as well as available climate change projections, over the entire Andean range. From this review, the main knowledge gaps are highlighted and urgent research necessities in order to provide more mechanistic understanding of hydroclimate changes in the Andes and more confident projections of its possible changes in association with global climate change.Fil: Pabón Caicedo, José Daniel. Universidad Nacional de Colombia; ColombiaFil: Arias, Paola A.. Universidad de Antioquia; ColombiaFil: Carril, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Espinoza, Jhan Carlo. Universite Grenoble Alpes; FranciaFil: Fita Borrell, Lluís. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Goubanova, Katerina. Centro de Estudios Avanzados en Zonas Áridas; ChileFil: Lavado Casimiro, Waldo. No especifíca;Fil: Masiokas, Mariano Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Solman, Silvina Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

    The relative importance of native forest and shade-grown coffee plantations for habitat use, individual fitness and migration strategies of overwintering Neotropical migrant songbirds in Colombia

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    Winter habitat quality is one of the primary ecological factors limiting self-maintenance and survival of Nearctic-Neotropical migratory birds during the non-breeding season. I assessed the relative importance of shade-grown coffee plantations vs. forest in the Colombian Andes as winter habitat for Swainson’s Thrush (Catharus ustulatus), Gray-cheeked Thrush (Catharus minimus), and Canada Warbler (Cardellina canadensis). For Swainson’s Thrush, I used daily and seasonal mass change, age ratios, density and corticosterone levels as measurements of habitat quality; and for Canada Warbler I used daily and seasonal mass change and sex ratios. Automated radio-telemetry on a continental scale was used to determine the effect of overwintering habitat occupancy on spring departure date and migration pace of Swainson’s Thrush. Using light-level geolocators I assessed the link between winter habitat occupancy and migratory connectivity of Gray-cheeked Thrush, and measured population spread and its relationship with the species winter distribution. I determined migratory connectivity of Canada Warblers overwintering across the three Andean cordilleras in Colombia by analysing stable hydrogen- isotope values (δ2H) in feathers. Taken together, my results suggested that native forests are more suitable winter habitats than shade-grown coffee plantations for Swainson’s Thrush. Native forest maintained a higher number of individuals than coffee, and in general, individuals maintained or increased their daily and seasonal body condition. On the other hand, the results for Canada Warbler are not conclusive, the quality of coffee can improve in certain circumstances such as high precipitation. My research provides the first evidence that by overwintering in native forest, birds can adjust their departure date, migration speed, and fuel up sufficiently to cover about 25% of the total length of spring migration. Migratory connectivity revealed that the effect of land-use changes on the wintering grounds is likely to be amplified on the breeding grounds through strong migratory connectivity. While market-based conservation strategies primarily promote shade-grown coffee plantations for the conservation of Neotropical migrants, my research suggest that strategies to conserve and restore native forest are also urgently needed

    Hydroclimate of the Andes Part II: Hydroclimate Variability and Sub-Continental Patterns

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    This paper provides an updated review of the most relevant scientific literature related to the hydroclimate of the Andes. The Andes, the longest cordillera in the world, faces major challenges regarding climate variability and climate change, which impose several threats to sustainable development, including water supply and the sustainability of ecosystem services. This review focuses on hydroclimate variability of the Andes at a sub-continental scale. The annual water cycle and long-term water balance along the Andes are addressed first, followed by the examination of the effects of orography on convective and frontal precipitation through the study of precipitation gradients in the tropical, subtropical and extratropical Andes. In addition, a review is presented of the current scientific literature on the climate variability in the Andes at different timescales. Finally, open research questions are presented in the last section of this article.Fil: Arias, Paola A.. Universidad de Antioquia; ColombiaFil: Garreaud, René. Universidad de Chile; ChileFil: Poveda, Germán. Universidad Nacional de Colombia; ColombiaFil: Espinoza, Jhan Carlo. Universite Grenoble Alpes; FranciaFil: Molina Carpio, Jorge. Universidad Mayor de San Andrés; BoliviaFil: Masiokas, Mariano Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Viale, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Scaff, Lucia. University of Saskatchewan; CanadáFil: van Oevelen, Peter J.. George Mason University; Estados Unido

    Lake regionalization and diatom metacommunity structuring in tropical South America

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    Lakes and their topological distribution across Earth’s surface impose ecological and evolutionary constraints on aquatic metacommunities. In this study, we group similar lake ecosystems as metacommunity units influencing diatom community structure. We assembled a database of 195 lakes from the tropical Andes and adjacent lowlands (8°N–30°S and 58–79°W) with associated environmental predictors to examine diatom metacommunity patterns at two different levels: taxon and functional (deconstructed species matrix by ecological guilds). We also derived spatial variables that inherently assessed the relative role of dispersal. Using complementary multivariate statistical techniques (principal component analysis, cluster analysis, nonmetric multidimensional scaling, Procrustes, variance partitioning), we examined diatom–environment relationships among different lake habitats (sediment surface, periphyton, and plankton) and partitioned community variation to evaluate the influence of niche-and dispersal-based assembly processes in diatom metacommunity structure across lake clusters. The results showed a significant association between geographic clusters of lakes based on gradients of climate and landscape configuration and diatom assemblages. Six lake clusters distributed along a latitudinal gradient were identified as functional metacommunity units for diatom communities. Variance partitioning revealed that dispersal mechanisms were a major contributor to diatom metacommunity structure, but in a highly context-dependent fashion across lake clusters. In the Andean Altiplano and adjacent lowlands of Bolivia, diatom metacommunities are niche assembled but constrained by either dispersal limitation or mass effects, resulting from area, environmental heterogeneity, and ecological guild relationships. Topographic heterogeneity played an important role in structuring planktic diatom metacommunities. We emphasize the value of a guild-based metacommunity model linked to dispersal for elucidating mechanisms underlying latitudinal gradients in distribution. Our findings reveal the importance of shifts in ecological drivers across climatic and physiographically distinct lake clusters, providing a basis for comparison of broad-scale community gradients in lake-rich regions elsewhere. This may help guide future research to explore evolutionary constraints on the rich Neotropical benthic diatom species pool

    Lake Regionalization and Diatom Metacommunity Structuring in Tropical South America

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    Lakes and their topological distribution across Earth\u27s surface impose ecological and evolutionary constraints on aquatic metacommunities. In this study, we group similar lake ecosystems as metacommunity units influencing diatom community structure. We assembled a database of 195 lakes from the tropical Andes and adjacent lowlands (8°N–30°S and 58–79°W) with associated environmental predictors to examine diatom metacommunity patterns at two different levels: taxon and functional (deconstructed species matrix by ecological guilds). We also derived spatial variables that inherently assessed the relative role of dispersal. Using complementary multivariate statistical techniques (principal component analysis, cluster analysis, nonmetric multidimensional scaling, Procrustes, variance partitioning), we examined diatom–environment relationships among different lake habitats (sediment surface, periphyton, and plankton) and partitioned community variation to evaluate the influence of niche‐ and dispersal‐based assembly processes in diatom metacommunity structure across lake clusters. The results showed a significant association between geographic clusters of lakes based on gradients of climate and landscape configuration and diatom assemblages. Six lake clusters distributed along a latitudinal gradient were identified as functional metacommunity units for diatom communities. Variance partitioning revealed that dispersal mechanisms were a major contributor to diatom metacommunity structure, but in a highly context‐dependent fashion across lake clusters. In the Andean Altiplano and adjacent lowlands of Bolivia, diatom metacommunities are niche assembled but constrained by either dispersal limitation or mass effects, resulting from area, environmental heterogeneity, and ecological guild relationships. Topographic heterogeneity played an important role in structuring planktic diatom metacommunities. We emphasize the value of a guild‐based metacommunity model linked to dispersal for elucidating mechanisms underlying latitudinal gradients in distribution. Our findings reveal the importance of shifts in ecological drivers across climatic and physiographically distinct lake clusters, providing a basis for comparison of broad‐scale community gradients in lake‐rich regions elsewhere. This may help guide future research to explore evolutionary constraints on the rich Neotropical benthic diatom species pool

    High Impact Weather Events in the Andes

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    Owing to the extraordinary latitudinal extent, a strong orographic variability with very high mountain tops, and the presence of deep valleys and steep slopes, the Andes and the population of the region are highly prone and vulnerable to the impacts of a large suite of extreme weather events. Here we provide a review of the most salient events in terms of losses of human and animal lives, economic and monetary losses in costs and damages, and social disruption, namely: (1) extreme precipitation events and related processes (Mesoscale Convective Systems, lightning), (2) cold spells, frosts, and high winds, (3) the impacts of ENSO on extreme hydro-meteorological events, (4) floods, (5) landslides, mudslides, avalanches, and (6) droughts, heat waves and fires. For our purposes, we focus this review on three distinctive regions along the Andes: Northern tropical (north of 8°S), Southern tropical (8°S-27°S) and Extratropical Andes (south of 27°S). Research gaps are also identified and discussed at the end of this review. It is very likely that climate change will increase the vulnerability of the millions of inhabitants of the Andes, impacting their livelihoods and the sustainable development of the region into the twenty first century amidst urbanization, deforestation, air, soil and water pollution, and land use changes.Fil: Poveda, Germán. Universidad Nacional de Colombia; ColombiaFil: Espinoza, Jhan Carlo. Universite Grenoble Alpes; FranciaFil: Zuluaga, Manuel D.. Universidad Nacional de Colombia; ColombiaFil: Solman, Silvina Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Garreaud, René. Universidad de Chile; ChileFil: van Oevelen, Peter J.. International GEWEX Project Office; Estados Unido

    Ecohydrology of paramos in Colombia: vulnerability to climate change and land use

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    High mountain ecosystems provide many environmental goods and services, particularly hydrological services. Besides the anthropic hazards to these ecosystems, climate change is expected to generate a decrease in runoff in Andean region, including paramos. However, there are not enough information about the hydrological functioning of paramo ecosystems and their vulnerability, to make decisions. This work aims to assess the vulnerability and ecohydrological resilience of Colombian paramo ecosystems to climate change, considering the land uses they have. To do this, we study three paramos: Belmira and Romerales in central and Chingaza in eastern Andes cordillera, we measured several hydro-climatic, vegetation and soil variables during at least two years, and we calibrate the WaSim hydrological model for specific basins in these ecosystems. We used the hydrological model to project the hydrological responses of studied basins with the expected climate changes in Colombian high mountain, in the medium term. Results show that eco-hydrological vulnerability to climate change of paramo of Chingaza is very low and Belmira has a low vulnerability; while the projected changes in Romerales are critical, indicating a very high vulnerability to climate change. The most altered paramos by anthropic activities evidence the loss of some of their hydrological characteristics, which make them more vulnerable to climate change, however, after these ecosystems have been impacted by changes in land use, it is possible to recover most of the properties and hydrological functioning of a natural ecosystem through a conservation or restoration program.Doctorad

    Dissecting the assembly process of benthic communities from neotropical streams

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    § La conservación y rehabilitación de la estructura y funcionamiento de los ecosistemas requiere de un conocimiento profundo de las causas y consecuencias de su biodiversidad. Sin embargo, este conocimiento es aún escaso en regiones Neotropicales. § En esta tesis, utilizo el marco conceptual de las metacomunidades para caracterizar los posibles efectos que tienen los procesos de dispersión (en tiempos ecológicos y evolutivos), selección (impulsada por factores abióticos) y deriva ecológica en la diversidad y distribución de las comunidades bentónicas fluviales. 2 § La zona de estudio, de un área de aproximadamente 40,000 km , abarcó entre 26 y 32 segmentos de ríos prístinos del Orinoco colombiano. Los puntos de muestreo abarcaron un gradiente de elevación de 300 a 3400 m.s.n.m. que incluyó un conjunto heterogéneo de ecorregiones y paisajes. § Mediante una aproximación de ligar patrones y posibles mecanismos, esta tesis proporciona evidencias de que la dispersión, la selección y la deriva están directamente involucradas en el proceso de ensamblaje de las comunidades bentónicas fluviales. § Mis hallazgos indican que uno o más eventos de limitación de la dispersión en un marco de tiempo evolutivo (eventos de aislamiento alopátrico) formaron diferentes pools de especies dentro de la cuenca del Orinoco. La extensión de estos pools coincide parcialmente con la distribución de las ecorregiones, lo que sugiere que los eventos que moldearon los paisajes fluviales y la estructura de la vegetación afectaron de manera similar la diversidad y distribución de las especies bentónicas en ecosistemas fluviales. § Adicionalmente, dentro de cada ecorregión, la dispersión, la selección y la deriva están interactuando para restringir la estructura y la dinámica de las comunidades y metacomunidades entre y dentro de los ríos. Dependiendo de la comunidad (p.e. diatomeas o insectos), el papel de cada uno de estos procesos puede prevalecer sobre el de los demás. § Estos hallazgos tienen implicaciones tanto para la investigación básica como para la aplicada (p.e. biomonitoreo) en las disciplinas de la ecología de metacomunidades y de agua dulce, así como en la conservación y la biogeografía.§ The conservation and rehabilitation of ecosystem structure and functioning requires of a deep knowledge on the causes and consequences of its biodiversity. The assembly of Neotropical communities, particularly in riverine ecosystems, remains to be dissected. § I used the metacommunity framework to dissect the relative influences of dispersal (in ecological and evolutionary timeframes), selection (driven by abiotic factors) and ecological drift on the assembly process of freshwater benthic communities. § The study was carried out at 26-32 different stream segments within an area of 2 about 40,000km , in the Colombian Orinoco. The area encompasses an elevation gradient from 3400 to 300m a.s.l. and includes a heterogeneous assembly of ecoregions and landscapes. § By using a pattern-matching approach, I provide evidences supporting that dispersal, selection and drift are directly involved in the assembly of freshwater benthic communities. § My findings indicate that one or more events of dispersal limitation (i.e. allopatric isolation) in an evolutionary timeframe shaped distinct pools of taxa in the Orinoco basin. The extent of these pools partially matches the distribution of the ecoregions, suggesting that those events molding the riverscapes and the vegetation structure similarly affect the diversity and distribution of benthic species. § Within each ecoregion, dispersal, selection and drift interact to constrain the structure and dynamics of communities and metacommunities among and within streams. Depending on the taxa belonging to each pool of species, the role of one of these processes may prevail over the others. § These findings have implications for both basic and applied research in the disciplines of metacommunity and freshwater ecology as well as of conservation and biogeography.Linking functional diversity patterns of algae and invertebrates to scale-dependent constrains of rivers from the Orinoco basinTesis con fines de doble titulación bajo el Convenio de cotutela entre la Universidad de Girona y la Universidad Nacional de Colombia.Doctorad

    Evaluating the Controls of Neogene Exhumation in the Tropical Northern Andes (colombia)

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    Understanding how tectonic and climatic forces influence erosion and shape mountains is important to understand the evolution of the landscapes through earth\u27s history. This dissertation aims to determine how do tectonic processes and climate variability interact to shape Earth\u27s tropical mountains. In chapter 1, I studied the Eastern Cordillera of the Northern Andes, a mountain range located in Colombia in the tropics of South America. To obtain exhumation rates, I used thermochronology, which is a method that records—over timescales of millions of years—the rate at which rocks located at great depths within the Earth cool as they are transported to the surface through the erosion of overlying rock from the surface. The results show that the rates and timing of exhumation are spatially variable along the Eastern Cordillera and the highest erosion rates occur near the places that have the most tectonically active faults. These zones of highest exhumation are associated with inherited structures. This finding shows that higher precipitation rates are not always associated with higher erosion rates and, by extension, that precipitation rates along the Eastern Cordillera are not a major factor controlling erosion rates. This study underscores the importance of a thorough characterization of the location and recent activity of faults in a region to understand erosion patterns and natural hazards in tropical mountains. In chapter 2, I explore how the timing of incision of kilometer-scale canyons into high topography can inform us about the surface uplift history of mountain ranges by tectonic and geodynamic processes or via changes in paleoclimate. The main goal of the project was to decipher the timing and, ultimately, the role of tectonic versus climatic mechanisms that led to incision of the Cauca River Canyon in the northern Central Cordillera of the Northern Andes. To do so, I used thermochronology, because the cooling history of rocks on the walls of canyons, as a response to locally focused exhumation, can be used to constrain the rate and timing of canyon incision. Previously published U-Th/He data from other canyons in the Central Cordillera revealed old cooling ages ranging from 26-45 Ma. The absence of younger ages in these canyons could be explained if these canyons were incised recently (\u3c 10 Ma) but the magnitude of incision was insufficient to reveal the younger cooling ages below a Partial Retention Zone. By studying the much deeper Cauca River Canyon, where incision has exposed lower structural levels, I was able to reveal younger U-Th/He ages at the valley bottom which helped to constrain the timing of incision at 6-7 Ma. The Cauca Canyon was carved because of major rock uplift in the northern Central Cordillera and propagation of an erosion wave into the mountain range starting in the latest Miocene. In chapter 3, I explored how the topography of the Northern Andes has responded to Neogene variations in slab geometry, climate, and drainage reorganization. I also discuss how the Neogene topographic changes may be one of the drivers that make the tropical Northern Andes of Colombia one the world\u27s most biodiverse places on earth. I used a geomorphic analysis to characterize the topography of the Western and Central Cordilleras of the Northern Andes. The topographic analysis was supplemented with erosion rate estimates based on gauged suspended sediment loads and river incision rates from volcanic sequences. There are several geomorphic differences from south to north in the Central Cordillera, which coincide with the proposed location of a slab tear and flat slab subduction under the northern Central Cordillera, as well as with a major transition in the channel slope of the Cauca River. Slab flattening appears to be the most likely cause of strong and recent uplift in the Northern Andes leading to ~2 km of surface uplift since 8–4 Ma. Large scale drainage reorganization of major rivers is probably mainly driven by changes in upper plate deformation in relation to development of the flat slab subduction geometry. Instead, to the south of the slab tear, other factors such as the emplacement of volcanic rocks likely play important roles in driving drainage reorganization. Several isolated biologic observations above the area of slab flattening suggest that surface uplift of the Central Cordillera isolated former lowland species on the high elevation plateaus, and drainage reorganization may have driven diversification of aquatic species

    Multi-Temporal Analysis of the Glacier Retreat Using Landsat Satellite Images in the Nevado of the Ampay National Sanctuary, Peru

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    Glaciers are humanity\u27s most extraordinary water reservoirs, covering approximately 10% of the total Earth surface. The investigation of the retreat of the glacier surface in the Ampay National Sanctuary is carried out using the historical series of Landsat images and applying the normalized snow differential index between the years 1991 to 2017. The meteorological data from the Tamburco and Abancay stations have been considered to determine the deglaciation and quantify the retreat of the Ampay glacier. The supervised classification spatial visualization method for the Landsat 2 Multispectral Scanner image and the normalized snow differential index have been used to determine the glacier cover area with Landsat 5, Landsat 7, and Landsat 8 Operational Land Imager/Thermal Infrared Sensor images. The results show a significant decrease in the surface of the Ampay glacier due to the increase in temperature. The surface of the Ampay glacier in 1991 was 2.13 km2 and in 2017 – 1.09 km2, showing a loss of 1.04 km2 (48.92%) as a consequence of significant climate variability (temperature and precipitation). In 2015, an apparent accumulation of snow was recorded on the Ampay glacier, reaching 2.595 km2, but in the following years, the glacier surface has been decreasing until it reached 1.086 km2 in 2017. It is concluded that the glacial retreat of the Ampay National Sanctuary in the last 25 years with a tendency to continuous deglaciation puts the water resource at risk
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