Comment on "Climate in the Western Cordillera of the Central Andes over the last 4300 years", by ... more Comment on "Climate in the Western Cordillera of the Central Andes over the last 4300 years", by Engel et al. (2014) Engel et al. (2014) present a new approach to understand Holocene climate changes in the Central Andes. They reconstruct the relative temperature changes in the Western Cordillera for
A multiproxy study of sediment cores from Zoñar Lake (37°29′00″N, 4°41′22″W, 300 m a.s.l.) suppor... more A multiproxy study of sediment cores from Zoñar Lake (37°29′00″N, 4°41′22″W, 300 m a.s.l.) supported by 11 14C AMS dates provides the first high-resolution centennial-scale reconstruction of past humidity changes in southern Spain during the last 4000 years. Arid periods occurred prior to 2.9 cal. kyr BP and during 1.3—0.6 cal. kyr BP (`Mediaeval Climate Anomaly'). The most humid period occurred during 2.6—1.6 cal. kyr BP encompassing the late Iron Age—Iberian and Roman epochs. Two humid periods of lower intensity occurred between 0.8 and 0.6 cal. kyr BP (AD 1200—1400) and about 400 cal. yr BP (around AD 1600) coinciding with the onset of the `Little Ice Age'. Humid conditions are synchronous with a decline in solar output and seem to correspond to atmospheric patterns similar to negative NAO phases. Arid conditions show better correlation with northern Africa climate evolution, suggesting a possible link to subtropical dynamics. The geographic location of Zoñar Lake and the...
A. 2002. The Prestige oil spill in Spain. Atlantic Seabirds 4(3): 131-140. The oiltanker Prestige... more A. 2002. The Prestige oil spill in Spain. Atlantic Seabirds 4(3): 131-140. The oiltanker Prestige, carrying a cargo of 77,000 tonnes of heavy bunker oil, sank off the coast of Galicia (NW Spain) on 19 November 2002. Most of the Galician coast was severely pollutedwith oil and hundreds of oiled seabirds were retrieved from beaches in the first weeks of the incident. The decision taken by Spanish authorities to tow the damaged vessel to deeper offshore waters has been described as a criminal act and was the reason why such a large area was affected. Seabird distribution in the offshore waters of Galicia has not been studied well and as a result, the impact of this spill on vulnerable populations is difficult to predict. Preliminary observations during dissections suggest that the most numerous victims (in decreasing order of abundance) have been: juvenile Razorbills (winter visitors), adult Atlantic Puffins (winter visitors), adult European Shags (residents), adult Northern Gannets (passage migrants), and juvenile Common Guillemots (winter visitors). By 23/24th November 2002 it was estimated that over 80% of Yellow-leggedGulls seen in coastal Galicia were oil-fouled, but relatively few of these were found dead or were received in rehabilitation centres. Proper impact assessments ofoil spills have often been neglected in the past and would have been neglected here again. It is concluded that we need to be better preparedfor dealingwith the seabird casualties of the next major oil spill in Europe and that there is an urgent need for a contingencyplanfor Europe to establish such procedures.
The black-necked grebe Podiceps nigricollis is a relatively scarce species but, likewise, a regul... more The black-necked grebe Podiceps nigricollis is a relatively scarce species but, likewise, a regular feature of the sheltered coastal waters of Galicia. In this paper a review is presented on its phenology, wintering population, distribution, habitat preferences and trends, based on bibliographic material, unpublished observations and the results of the Waterfowl January Census. The species was present mainly from November to March, with numerical peaks between January and February. In recent years (2002-06) its population in January was evaluated between 187 and 272 individuals and over 80% was supported by the coastal sites of Ribadeo, Ferrol and Arousa. With 80% of the records and 97% of the individuals recorded between 1993 and 2006, rias and estuaries were the most favoured habitats. Moreover, population proportions remained constant in both habitats between 1988-92 and 2002-06. However, record frequency in different habitats experienced a significant seasonal variation, with many more records than expected in rias during winter and more in wetlands (estuaries, lagoons and reservoirs) during autumn and spring. Grebes were located on extensive open waters, with depth ranges of 2-7 m and polihaline-euhaline salinity regimes in the major sites of the rias of Ferrol and Arousa. Its wintering population showed a strong upward trend between 1988 and 2006, with annual growth rates of 15.6% to 18.7% (according to different log-linear regression models). The increases were particularly pronounced in Ferrol and Arousa.
Lake Chungará (18º15'S, 69º09'W, 4520 m a... more Lake Chungará (18º15'S, 69º09'W, 4520 m asl 22.5 Km2 and 40 m of water depth) is a hydrologically closed lake located on the Andean Altiplano. The lake is polymictic, meso to eutrophic and currently primary productivity is mainly governed by diatoms and ...
The reigning paradigm holds that Easter Island suffered a socio-ecological collapse (ecocidal or ... more The reigning paradigm holds that Easter Island suffered a socio-ecological collapse (ecocidal or not) sometime in the last millennium, prior to European contact (AD 1720). We discuss some novel paleoecological and archaeological evidence that challenges this assumption. We use this case study to propose a closer collaboration between archaeology and paleoecology. This collaboration allows us to unravel historical trends in which both environmental changes and human activities might have acted, alone or coupled, as drivers of ecological and social transformations. We highlight a number of particular points in which scholars from disparate disciplines, working together, may enhance the scope and the soundness of historical inferences. These points are the following: (1) the timing of the initial Easter Island colonization and the origin of the settlers, (2) the pace of ecological and social transformations since that time until the present, and (3) the occurrence of potential climate-human synergies as drivers of socio-ecological shifts.
Climate change is nowadays a reality and one of the most important challenges that humanity has t... more Climate change is nowadays a reality and one of the most important challenges that humanity has to face this century, because of the threat that it represents, among others, for the economy, health, food and safety. There are increasingly more scientific evidences that we are at a critical moment, although we can still tackle the negative consequences of climate change if we take decisive actions at a global level.
This paper examines the interdependence among the different forcing factors in the evolution of t... more This paper examines the interdependence among the different forcing factors in the evolution of the Traba coastal wetland (Galicia, NW Spain) based on lithofacies and diatom analyses of three cores reaching the basement. According to radiocarbon data, the wetland originated 5700 cal yr BP, a time when similar systems on the Atlantic coast of the Iberian Peninsula were formed. Diatom assemblage data allow the estimation of the sea level position at 5700 cal yr BP at least 7 m below present-day mean sea level. Attenuation of the sea-level rise at that time was a major driving mechanism that permitted the establishment of an incipient beach-dune complex, causing water-logging in the Traba basin. However, the location of this incipient wetland on a basement high, which prevented an open connection to the sea, made topographic inheritance the main forcing factor in the subsequent evolution of the wetland. Thus, Traba was never a coastal lagoon system, as it has sometimes been defined. The maximum permeability of the beach-dune complex enclosing the wetland was recorded after its origin until 2900 cal yr BP, when increased stormy conditions affected the Galician shelf waters. Since then, the evolution of the wetland has been mainly controlled by more local factors, especially the continental sediment supply. Changes in land use in the basin have accelerated the infilling of the water body since the 19th century. This rapid infilling makes the whole system more prone to total encroachment in the short term, rather than to sea drowning. Palaeoenvironmental analyses showing the main trends in the long-term evolution of coastal wetlands can be of key importance in any management decisions aimed at preserving these kinds of sensitive coastal environments.
El zampullín cuellinegro Podiceps nigricollis es una especie relativamente escasa aunque caracter... more El zampullín cuellinegro Podiceps nigricollis es una especie relativamente escasa aunque característica de las aguas costeras resguardadas de Galicia. En el presente trabajo se presenta una revisión de su fenología, efectivos invernales, distribución, preferencias de hábitat y tendencias poblacionales, basada en material bibliográfico, observaciones inéditas y en los resultados de los censos de aves acuáticas de enero. La especie estuvo presente principalmente de noviembre a marzo, con máximos entre enero y febrero. En años recientes (2002-06) sus efectivos en el mes de enero se evaluaron entre 187 y 272 individuos y más del 80% se repartió entre las rías de Ribadeo, Ferrol y Arousa. Las rías y estuarios concentraron el 80% de los registros y el 97% de los individuos observados entre 1993 y 2006. Ambos hábitats mantuvieron constantes sus proporciones de individuos entre 1988-92 y 2002-06. Sin embargo, las frecuencias de registros en los distintos hábitats experimentaron una marcada variación estacional, con muchos más registros de los esperados en rías durante el invierno y en humedales (estuarios, lagunas y embalses) durante el otoño y la primavera. En los importantes reductos de Maniños (ría de Ferrol) y Rianxo (ría de Arousa), los zampullines se localizaron en áreas extensas de aguas rasas, con rangos batimétricos de 2-7 m y régimen de salinidad polihalinoeuhalino. Entre 1988 y 2006 sus efectivos totales experimentaron una fuerte tendencia al alza, que supuso tasas de incremento anual del 15,6% al 18,7% según diferentes modelos de regresión loglineal. Los incrementos fueron especialmente pronunciados en Ferrol y Arousa.
The status of the Great Northern Diver Gavia immer in Galicia, northwest Spain, is reviewed. Numb... more The status of the Great Northern Diver Gavia immer in Galicia, northwest Spain, is reviewed. Numbers peaked in late autumn and early winter, and again in spring. Post-breeding moult was recorded from November to mid December. Individuals in flight feather moult were recorded between February and March, the rest of the pre-breeding moult extending until the last birds departed around mid May. It is suggested that new birds arrive in the area in early spring to moult, replacing part of the wintering population. The species showed a strong preference for exposed sandy coasts in all seasons, but particularly in late winter and spring. The wintering population declined markedly following the Prestige oil spill in 2002/03 (c. 57% from 2002 to 2005). After 2005 the population returned to previous levels, possibly through immigration of birds from the nearby region of Asturias, where the wintering population collapsed in the same period. The average wintering population (uncorrected for detectability) was 123 birds (95% CI = 76–166), c. 2.5% of the estimated European wintering population.
A sedimentary and micropaleontological study of the Quillagua Formation provides a detailed paleo... more A sedimentary and micropaleontological study of the Quillagua Formation provides a detailed paleohydrological reconstruction of the lacustrine system which occupied the present-day hyperarid Quillagua-Llamara fore-arc Basin (Northern Chile) from lattermost Miocene (5:8 š 0:4 Ma) to Early Pliocene times. Diatom and lithofacies analyses were carried out in two correlated stratigraphic sections of the lacustrine system. The Quebrada Temblor section is located at the southern margin of the ancient lake and is directly influenced by the freshwater inputs of a northward flowing fluvial system draining the Precordillera and Calama regions. The Cerro Mogote section occupies a western marginal location in the northern zone sheltered from direct fluvial inputs from the south but subjected to the activity of the alluvial fan systems of the Coastal Range. A mostly shallow oligosaline waterbody occupied the basin during the interval studied, though with fluctuations in salinity and the extent of the inner, open waters. The southern margin sector -represented by Quebrada Temblor -had, in general terms, a palustrine oligosaline character with almost freshwater conditions during certain periods, which favoured the establishment of semi-permanent to permanent freshwater plumes overlying a saline waterbody. Development of shoreline facies subjected to desiccation events was also characteristic at the top of this section. The innermost shallow lacustrine areas -represented by Cerro Mogote -maintained more homogeneous oligosaline characteristics and more persistent open waters. They were also subjected to freshwater pulses mediated in this case by the activity of the terminal alluvial fan zones. Paleohydrological evolution of the basin was strongly conditioned not only by shifts in the climatic-tectonic system but by variations in the local hydrological parameters. Four hierarchical orders of variability in the lake level of the basin were distinguished both by stratigraphic analysis of lithofacies and from changes undergone by the diatom record. Strong intrasample mixing of diatoms of incompatible salinity spectra and the presence of fine laminated lacustrine facies in some terms define the highest order short-term intra-or inter-annual pulses experienced by the lacustrine system (higher than 6th order). Diatom-based punctuated interruptions of the minor order bathymetrical trends highlight the high frequency variability in the basin (probably 6th order, 0.001-0.01 Ma), while the deepening=shallowing facies defined by the arrangement of the decimetre thick lithological sequences revealed a lower order of variability (5th order, 0.01-0.1 Ma). Combined lithofacies and diatom analyses delineate the lowest order of variability (4th order, 0.1-1 Ma) allowing the reconstruction of two well-established highstand and lowstand situations which implied the existence of a regressive trend between two transgressive trends. This order of variability is related to : S 0 0 3 1 -0 1 8 2 ( 9 9 ) 0 0 0 6 6 -8 310 R. Bao et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 153 (1999) the interplay of tectonic events in the Calama Basin, and the regional climatic evolution during late Neogene to Pliocene times.
High-resolution geochemical analyses obtained using an X-ray fluorescence (XRF) Core Scanner, as ... more High-resolution geochemical analyses obtained using an X-ray fluorescence (XRF) Core Scanner, as well as mineralogical data from the Lago Chungara´sedimentary sequence in the northern Andean Chilean Altiplano (181S), provided a detailed reconstruction of the lacustrine sedimentary evolution during the last 14,000 cal. yr BP. The high-resolution analyses attained in this study allowed to distinguish abrupt periods, identify the complex structures of the early and mid-Holocene arid intervals and to compare their timing with Titicaca lake and Sajama ice records. Three main components in the lake sediments have been identified: (a) biogenic component, mainly from diatoms (b) volcanics (ash layers) from the nearby Parinacota Volcano and (c) endogenic carbonates. The correlation between volcanic input in Lago Chungara´and the total particles deposited in the Nevado Sajama ice core suggests the Parinacota Volcano as the common source. The geochemical record of Lago Chungara´indicates an increase in siliceous productivity during the early Holocene, lagging behind the rise in temperatures inferred from the Nevado Sajama ice core. The regional mid-Holocene aridity crisis can be characterized as a number of short events with calcite and aragonite precipitation in the offshore lake zones. r
The rocky and indented coast of NW Iberia is characterized by the presence of highly valuable and... more The rocky and indented coast of NW Iberia is characterized by the presence of highly valuable and vulnerable, small and shallow barrier–lagoon systems structurally controlled. The case study was selected to analyse barrier–lagoon evolution based on detailed sedimentary architecture, chronology, geochemical and biological proxies. The main objective is to test the hypothesis of structural control and the significance at regional scale of any high-energy event recorded. This work is also aimed at identifying general patterns and conceptualizing the formation and evolution of this type of coastal systems. The results allowed us to establish a conceptual model of Holocene evolution that applies to rock-bounded barrier–lagoon systems. The initial stage (early Holocene) is characterized by freshwater peat sedimentation and ended by marine flooding. The timing of the marine flooding depends on the relation between the elevation of the basin and the relative mean sea-level position; the lower the topography, the earlier the marine inundation. Thus, the age of basin inundation ranged from 8 to 4 ka BP supporting significant structural differences. Once marine inundation occurred, all systems followed similar evolutionary patterns characterized by a phase of landward barrier migration and aeolian sedimentation towards the back-barrier (i.e. retrogradation) that extended circa 3.5 ka BP. The later phases of evolution are characterized by a general trend to the stabilization of the barriers and the infilling of the lagoons. This stabilization may be temporally interrupted by episodes of enhanced storminess or sediment scarcity. In this regard, washover deposits identified within the sedimentary architecture of the case study explored here suggest pervasive high-energy events coeval with some of the cooling events identified in the North Atlantic during the mid- to late Holocene.
High-resolution laminated lacustrine sediments are excellent archives of the past hydrological ch... more High-resolution laminated lacustrine sediments are excellent archives of the past hydrological changes and they provide valuable insights about the climatic processes that trigger these changes. The paleoclimatic records located in the Southern Hemisphere are fundamental for understanding the evolution of the El Niño - Southern Oscillation (ENSO) since this climatic phenomena is the main cause of droughts and floods in many areas of South America and other regions of the world, like Spain and Egypt. Available regional paleoclimate reconstructions show that modern climatic patterns in South America were established during the Late Holocene. The laminated sediments of Lago Chungará (18° 15' S - 69° 10' W, 4520 m a.s.l., Chilean altiplano) have allowed us to characterize the evolution of this climatic phenomena for the transition Late Glacial - Early Holocene (12,300 - 9,500 calendar years BP) as well as its relationship with other climate forcings, namely the solar activity. T...
Azores archipelago lies in the southern area of the dipole that defines the North Atlantic Oscill... more Azores archipelago lies in the southern area of the dipole that defines the North Atlantic Oscillation (NAO). During the negative phase of the NAO, the Azores high pressure is displaced southwards allowing the storms to cross the islands increasing the precipitation in this area and also in southern Europe. This fact makes them excellent key places to perform accurate high-resolution climate reconstructions. Lake Azul (37o 52' 21"N - 37o52'21"W) is a monomictic lake infilling the volcanic complex of Sete Cidades which is located in São Miguel island. This monomictic and eutrophic lake was formed around 22000 cal. years B.P. by consecutive collapses of the underneath volcanic caldera. The last eruption of the Sete Cidades crater complex was radiocarbon-dated at 500-650 cal years B.P. At present, macrophytes are restricted to the lake shore and consist mainly of Potamogeton spp., Myriophyllum alterniflorum, Ceratophyllum demersum, Nymphaea alba, and, Chara fragilis. ...
Earlier palynological studies of lake sediments from Easter Island suggest that the island underw... more Earlier palynological studies of lake sediments from Easter Island suggest that the island underwent a recent and abrupt replacement of palm-dominated forests by grasslands, interpreted as a deforestation by indigenous people. However, the available evidence is inconclusive due to the existence of extended hiatuses and ambiguous chronological frameworks in most of the sedimentary sequences studied. This has given rise to an ongoing debate about the timing and causes of the assumed ecological degradation and cultural breakdown. Our multiproxy study of a core recovered from Lake Raraku highlights the vegetation dynamics and environmental shifts in the catchment and its surroundings during the late Holocene. The sequence contains shorter hiatuses than in previously recovered cores and provides a more continuous history of environmental changes. The results show a long, gradual and stepped landscape shift from palm-dominated forests to grasslands. This change started c. 450 BC and lasted about two thousand years. The presence of Verbena litoralis, a common weed, which is associated with human activities in the pollen record, the significant correlation between shifts in charcoal influx, and the dominant pollen types suggest human disturbance of the vegetation. Therefore, human settlement on the island occurred c. 450 BC, some 1500 years earlier than is assumed. Climate variability also exerted a major influence on environmental changes. Two sedimentary gaps in the record are interpreted as periods of droughts that could have prevented peat growth and favoured its erosion during the Medieval Climate Anomaly and the Little Ice Age, respectively. At c. AD 1200, the water table rose and the former Raraku mire turned into a shallow lake, suggesting higher precipitation/evaporation rates coeval with a cooler and wetter Pan-Pacific AD 1300 event. Pollen and diatom records show large vegetation changes due to human activities c. AD 1200. Other recent vegetation changes also due to human activities entail the introduction of taxa (e.g. Psidium guajava, Eucalyptus sp.) and the disappearance of indigenous plants such as Sophora toromiro during the two last centuries. Although the evidence is not conclusive, the American origin of V. litoralis re-opens the debate about the possible role of Amerindians in the human colonisation of Easter Island.
occurred at ca AD 800 it coincided with the warmer conditions of the Medieval Climate Anomaly, wh... more occurred at ca AD 800 it coincided with the warmer conditions of the Medieval Climate Anomaly, whereas if it took place at ca AD 1300 it was favored by enhanced westerlies at the onset of the Little Ice Age. Changes in land uses (farming, intensive cattle) during the last century had a large impact in the hydrology and limnology (eutrophication) of the lake.
Comment on "Climate in the Western Cordillera of the Central Andes over the last 4300 years", by ... more Comment on "Climate in the Western Cordillera of the Central Andes over the last 4300 years", by Engel et al. (2014) Engel et al. (2014) present a new approach to understand Holocene climate changes in the Central Andes. They reconstruct the relative temperature changes in the Western Cordillera for
A multiproxy study of sediment cores from Zoñar Lake (37°29′00″N, 4°41′22″W, 300 m a.s.l.) suppor... more A multiproxy study of sediment cores from Zoñar Lake (37°29′00″N, 4°41′22″W, 300 m a.s.l.) supported by 11 14C AMS dates provides the first high-resolution centennial-scale reconstruction of past humidity changes in southern Spain during the last 4000 years. Arid periods occurred prior to 2.9 cal. kyr BP and during 1.3—0.6 cal. kyr BP (`Mediaeval Climate Anomaly'). The most humid period occurred during 2.6—1.6 cal. kyr BP encompassing the late Iron Age—Iberian and Roman epochs. Two humid periods of lower intensity occurred between 0.8 and 0.6 cal. kyr BP (AD 1200—1400) and about 400 cal. yr BP (around AD 1600) coinciding with the onset of the `Little Ice Age'. Humid conditions are synchronous with a decline in solar output and seem to correspond to atmospheric patterns similar to negative NAO phases. Arid conditions show better correlation with northern Africa climate evolution, suggesting a possible link to subtropical dynamics. The geographic location of Zoñar Lake and the...
A. 2002. The Prestige oil spill in Spain. Atlantic Seabirds 4(3): 131-140. The oiltanker Prestige... more A. 2002. The Prestige oil spill in Spain. Atlantic Seabirds 4(3): 131-140. The oiltanker Prestige, carrying a cargo of 77,000 tonnes of heavy bunker oil, sank off the coast of Galicia (NW Spain) on 19 November 2002. Most of the Galician coast was severely pollutedwith oil and hundreds of oiled seabirds were retrieved from beaches in the first weeks of the incident. The decision taken by Spanish authorities to tow the damaged vessel to deeper offshore waters has been described as a criminal act and was the reason why such a large area was affected. Seabird distribution in the offshore waters of Galicia has not been studied well and as a result, the impact of this spill on vulnerable populations is difficult to predict. Preliminary observations during dissections suggest that the most numerous victims (in decreasing order of abundance) have been: juvenile Razorbills (winter visitors), adult Atlantic Puffins (winter visitors), adult European Shags (residents), adult Northern Gannets (passage migrants), and juvenile Common Guillemots (winter visitors). By 23/24th November 2002 it was estimated that over 80% of Yellow-leggedGulls seen in coastal Galicia were oil-fouled, but relatively few of these were found dead or were received in rehabilitation centres. Proper impact assessments ofoil spills have often been neglected in the past and would have been neglected here again. It is concluded that we need to be better preparedfor dealingwith the seabird casualties of the next major oil spill in Europe and that there is an urgent need for a contingencyplanfor Europe to establish such procedures.
The black-necked grebe Podiceps nigricollis is a relatively scarce species but, likewise, a regul... more The black-necked grebe Podiceps nigricollis is a relatively scarce species but, likewise, a regular feature of the sheltered coastal waters of Galicia. In this paper a review is presented on its phenology, wintering population, distribution, habitat preferences and trends, based on bibliographic material, unpublished observations and the results of the Waterfowl January Census. The species was present mainly from November to March, with numerical peaks between January and February. In recent years (2002-06) its population in January was evaluated between 187 and 272 individuals and over 80% was supported by the coastal sites of Ribadeo, Ferrol and Arousa. With 80% of the records and 97% of the individuals recorded between 1993 and 2006, rias and estuaries were the most favoured habitats. Moreover, population proportions remained constant in both habitats between 1988-92 and 2002-06. However, record frequency in different habitats experienced a significant seasonal variation, with many more records than expected in rias during winter and more in wetlands (estuaries, lagoons and reservoirs) during autumn and spring. Grebes were located on extensive open waters, with depth ranges of 2-7 m and polihaline-euhaline salinity regimes in the major sites of the rias of Ferrol and Arousa. Its wintering population showed a strong upward trend between 1988 and 2006, with annual growth rates of 15.6% to 18.7% (according to different log-linear regression models). The increases were particularly pronounced in Ferrol and Arousa.
Lake Chungará (18º15'S, 69º09'W, 4520 m a... more Lake Chungará (18º15'S, 69º09'W, 4520 m asl 22.5 Km2 and 40 m of water depth) is a hydrologically closed lake located on the Andean Altiplano. The lake is polymictic, meso to eutrophic and currently primary productivity is mainly governed by diatoms and ...
The reigning paradigm holds that Easter Island suffered a socio-ecological collapse (ecocidal or ... more The reigning paradigm holds that Easter Island suffered a socio-ecological collapse (ecocidal or not) sometime in the last millennium, prior to European contact (AD 1720). We discuss some novel paleoecological and archaeological evidence that challenges this assumption. We use this case study to propose a closer collaboration between archaeology and paleoecology. This collaboration allows us to unravel historical trends in which both environmental changes and human activities might have acted, alone or coupled, as drivers of ecological and social transformations. We highlight a number of particular points in which scholars from disparate disciplines, working together, may enhance the scope and the soundness of historical inferences. These points are the following: (1) the timing of the initial Easter Island colonization and the origin of the settlers, (2) the pace of ecological and social transformations since that time until the present, and (3) the occurrence of potential climate-human synergies as drivers of socio-ecological shifts.
Climate change is nowadays a reality and one of the most important challenges that humanity has t... more Climate change is nowadays a reality and one of the most important challenges that humanity has to face this century, because of the threat that it represents, among others, for the economy, health, food and safety. There are increasingly more scientific evidences that we are at a critical moment, although we can still tackle the negative consequences of climate change if we take decisive actions at a global level.
This paper examines the interdependence among the different forcing factors in the evolution of t... more This paper examines the interdependence among the different forcing factors in the evolution of the Traba coastal wetland (Galicia, NW Spain) based on lithofacies and diatom analyses of three cores reaching the basement. According to radiocarbon data, the wetland originated 5700 cal yr BP, a time when similar systems on the Atlantic coast of the Iberian Peninsula were formed. Diatom assemblage data allow the estimation of the sea level position at 5700 cal yr BP at least 7 m below present-day mean sea level. Attenuation of the sea-level rise at that time was a major driving mechanism that permitted the establishment of an incipient beach-dune complex, causing water-logging in the Traba basin. However, the location of this incipient wetland on a basement high, which prevented an open connection to the sea, made topographic inheritance the main forcing factor in the subsequent evolution of the wetland. Thus, Traba was never a coastal lagoon system, as it has sometimes been defined. The maximum permeability of the beach-dune complex enclosing the wetland was recorded after its origin until 2900 cal yr BP, when increased stormy conditions affected the Galician shelf waters. Since then, the evolution of the wetland has been mainly controlled by more local factors, especially the continental sediment supply. Changes in land use in the basin have accelerated the infilling of the water body since the 19th century. This rapid infilling makes the whole system more prone to total encroachment in the short term, rather than to sea drowning. Palaeoenvironmental analyses showing the main trends in the long-term evolution of coastal wetlands can be of key importance in any management decisions aimed at preserving these kinds of sensitive coastal environments.
El zampullín cuellinegro Podiceps nigricollis es una especie relativamente escasa aunque caracter... more El zampullín cuellinegro Podiceps nigricollis es una especie relativamente escasa aunque característica de las aguas costeras resguardadas de Galicia. En el presente trabajo se presenta una revisión de su fenología, efectivos invernales, distribución, preferencias de hábitat y tendencias poblacionales, basada en material bibliográfico, observaciones inéditas y en los resultados de los censos de aves acuáticas de enero. La especie estuvo presente principalmente de noviembre a marzo, con máximos entre enero y febrero. En años recientes (2002-06) sus efectivos en el mes de enero se evaluaron entre 187 y 272 individuos y más del 80% se repartió entre las rías de Ribadeo, Ferrol y Arousa. Las rías y estuarios concentraron el 80% de los registros y el 97% de los individuos observados entre 1993 y 2006. Ambos hábitats mantuvieron constantes sus proporciones de individuos entre 1988-92 y 2002-06. Sin embargo, las frecuencias de registros en los distintos hábitats experimentaron una marcada variación estacional, con muchos más registros de los esperados en rías durante el invierno y en humedales (estuarios, lagunas y embalses) durante el otoño y la primavera. En los importantes reductos de Maniños (ría de Ferrol) y Rianxo (ría de Arousa), los zampullines se localizaron en áreas extensas de aguas rasas, con rangos batimétricos de 2-7 m y régimen de salinidad polihalinoeuhalino. Entre 1988 y 2006 sus efectivos totales experimentaron una fuerte tendencia al alza, que supuso tasas de incremento anual del 15,6% al 18,7% según diferentes modelos de regresión loglineal. Los incrementos fueron especialmente pronunciados en Ferrol y Arousa.
The status of the Great Northern Diver Gavia immer in Galicia, northwest Spain, is reviewed. Numb... more The status of the Great Northern Diver Gavia immer in Galicia, northwest Spain, is reviewed. Numbers peaked in late autumn and early winter, and again in spring. Post-breeding moult was recorded from November to mid December. Individuals in flight feather moult were recorded between February and March, the rest of the pre-breeding moult extending until the last birds departed around mid May. It is suggested that new birds arrive in the area in early spring to moult, replacing part of the wintering population. The species showed a strong preference for exposed sandy coasts in all seasons, but particularly in late winter and spring. The wintering population declined markedly following the Prestige oil spill in 2002/03 (c. 57% from 2002 to 2005). After 2005 the population returned to previous levels, possibly through immigration of birds from the nearby region of Asturias, where the wintering population collapsed in the same period. The average wintering population (uncorrected for detectability) was 123 birds (95% CI = 76–166), c. 2.5% of the estimated European wintering population.
A sedimentary and micropaleontological study of the Quillagua Formation provides a detailed paleo... more A sedimentary and micropaleontological study of the Quillagua Formation provides a detailed paleohydrological reconstruction of the lacustrine system which occupied the present-day hyperarid Quillagua-Llamara fore-arc Basin (Northern Chile) from lattermost Miocene (5:8 š 0:4 Ma) to Early Pliocene times. Diatom and lithofacies analyses were carried out in two correlated stratigraphic sections of the lacustrine system. The Quebrada Temblor section is located at the southern margin of the ancient lake and is directly influenced by the freshwater inputs of a northward flowing fluvial system draining the Precordillera and Calama regions. The Cerro Mogote section occupies a western marginal location in the northern zone sheltered from direct fluvial inputs from the south but subjected to the activity of the alluvial fan systems of the Coastal Range. A mostly shallow oligosaline waterbody occupied the basin during the interval studied, though with fluctuations in salinity and the extent of the inner, open waters. The southern margin sector -represented by Quebrada Temblor -had, in general terms, a palustrine oligosaline character with almost freshwater conditions during certain periods, which favoured the establishment of semi-permanent to permanent freshwater plumes overlying a saline waterbody. Development of shoreline facies subjected to desiccation events was also characteristic at the top of this section. The innermost shallow lacustrine areas -represented by Cerro Mogote -maintained more homogeneous oligosaline characteristics and more persistent open waters. They were also subjected to freshwater pulses mediated in this case by the activity of the terminal alluvial fan zones. Paleohydrological evolution of the basin was strongly conditioned not only by shifts in the climatic-tectonic system but by variations in the local hydrological parameters. Four hierarchical orders of variability in the lake level of the basin were distinguished both by stratigraphic analysis of lithofacies and from changes undergone by the diatom record. Strong intrasample mixing of diatoms of incompatible salinity spectra and the presence of fine laminated lacustrine facies in some terms define the highest order short-term intra-or inter-annual pulses experienced by the lacustrine system (higher than 6th order). Diatom-based punctuated interruptions of the minor order bathymetrical trends highlight the high frequency variability in the basin (probably 6th order, 0.001-0.01 Ma), while the deepening=shallowing facies defined by the arrangement of the decimetre thick lithological sequences revealed a lower order of variability (5th order, 0.01-0.1 Ma). Combined lithofacies and diatom analyses delineate the lowest order of variability (4th order, 0.1-1 Ma) allowing the reconstruction of two well-established highstand and lowstand situations which implied the existence of a regressive trend between two transgressive trends. This order of variability is related to : S 0 0 3 1 -0 1 8 2 ( 9 9 ) 0 0 0 6 6 -8 310 R. Bao et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 153 (1999) the interplay of tectonic events in the Calama Basin, and the regional climatic evolution during late Neogene to Pliocene times.
High-resolution geochemical analyses obtained using an X-ray fluorescence (XRF) Core Scanner, as ... more High-resolution geochemical analyses obtained using an X-ray fluorescence (XRF) Core Scanner, as well as mineralogical data from the Lago Chungara´sedimentary sequence in the northern Andean Chilean Altiplano (181S), provided a detailed reconstruction of the lacustrine sedimentary evolution during the last 14,000 cal. yr BP. The high-resolution analyses attained in this study allowed to distinguish abrupt periods, identify the complex structures of the early and mid-Holocene arid intervals and to compare their timing with Titicaca lake and Sajama ice records. Three main components in the lake sediments have been identified: (a) biogenic component, mainly from diatoms (b) volcanics (ash layers) from the nearby Parinacota Volcano and (c) endogenic carbonates. The correlation between volcanic input in Lago Chungara´and the total particles deposited in the Nevado Sajama ice core suggests the Parinacota Volcano as the common source. The geochemical record of Lago Chungara´indicates an increase in siliceous productivity during the early Holocene, lagging behind the rise in temperatures inferred from the Nevado Sajama ice core. The regional mid-Holocene aridity crisis can be characterized as a number of short events with calcite and aragonite precipitation in the offshore lake zones. r
The rocky and indented coast of NW Iberia is characterized by the presence of highly valuable and... more The rocky and indented coast of NW Iberia is characterized by the presence of highly valuable and vulnerable, small and shallow barrier–lagoon systems structurally controlled. The case study was selected to analyse barrier–lagoon evolution based on detailed sedimentary architecture, chronology, geochemical and biological proxies. The main objective is to test the hypothesis of structural control and the significance at regional scale of any high-energy event recorded. This work is also aimed at identifying general patterns and conceptualizing the formation and evolution of this type of coastal systems. The results allowed us to establish a conceptual model of Holocene evolution that applies to rock-bounded barrier–lagoon systems. The initial stage (early Holocene) is characterized by freshwater peat sedimentation and ended by marine flooding. The timing of the marine flooding depends on the relation between the elevation of the basin and the relative mean sea-level position; the lower the topography, the earlier the marine inundation. Thus, the age of basin inundation ranged from 8 to 4 ka BP supporting significant structural differences. Once marine inundation occurred, all systems followed similar evolutionary patterns characterized by a phase of landward barrier migration and aeolian sedimentation towards the back-barrier (i.e. retrogradation) that extended circa 3.5 ka BP. The later phases of evolution are characterized by a general trend to the stabilization of the barriers and the infilling of the lagoons. This stabilization may be temporally interrupted by episodes of enhanced storminess or sediment scarcity. In this regard, washover deposits identified within the sedimentary architecture of the case study explored here suggest pervasive high-energy events coeval with some of the cooling events identified in the North Atlantic during the mid- to late Holocene.
High-resolution laminated lacustrine sediments are excellent archives of the past hydrological ch... more High-resolution laminated lacustrine sediments are excellent archives of the past hydrological changes and they provide valuable insights about the climatic processes that trigger these changes. The paleoclimatic records located in the Southern Hemisphere are fundamental for understanding the evolution of the El Niño - Southern Oscillation (ENSO) since this climatic phenomena is the main cause of droughts and floods in many areas of South America and other regions of the world, like Spain and Egypt. Available regional paleoclimate reconstructions show that modern climatic patterns in South America were established during the Late Holocene. The laminated sediments of Lago Chungará (18° 15' S - 69° 10' W, 4520 m a.s.l., Chilean altiplano) have allowed us to characterize the evolution of this climatic phenomena for the transition Late Glacial - Early Holocene (12,300 - 9,500 calendar years BP) as well as its relationship with other climate forcings, namely the solar activity. T...
Azores archipelago lies in the southern area of the dipole that defines the North Atlantic Oscill... more Azores archipelago lies in the southern area of the dipole that defines the North Atlantic Oscillation (NAO). During the negative phase of the NAO, the Azores high pressure is displaced southwards allowing the storms to cross the islands increasing the precipitation in this area and also in southern Europe. This fact makes them excellent key places to perform accurate high-resolution climate reconstructions. Lake Azul (37o 52' 21"N - 37o52'21"W) is a monomictic lake infilling the volcanic complex of Sete Cidades which is located in São Miguel island. This monomictic and eutrophic lake was formed around 22000 cal. years B.P. by consecutive collapses of the underneath volcanic caldera. The last eruption of the Sete Cidades crater complex was radiocarbon-dated at 500-650 cal years B.P. At present, macrophytes are restricted to the lake shore and consist mainly of Potamogeton spp., Myriophyllum alterniflorum, Ceratophyllum demersum, Nymphaea alba, and, Chara fragilis. ...
Earlier palynological studies of lake sediments from Easter Island suggest that the island underw... more Earlier palynological studies of lake sediments from Easter Island suggest that the island underwent a recent and abrupt replacement of palm-dominated forests by grasslands, interpreted as a deforestation by indigenous people. However, the available evidence is inconclusive due to the existence of extended hiatuses and ambiguous chronological frameworks in most of the sedimentary sequences studied. This has given rise to an ongoing debate about the timing and causes of the assumed ecological degradation and cultural breakdown. Our multiproxy study of a core recovered from Lake Raraku highlights the vegetation dynamics and environmental shifts in the catchment and its surroundings during the late Holocene. The sequence contains shorter hiatuses than in previously recovered cores and provides a more continuous history of environmental changes. The results show a long, gradual and stepped landscape shift from palm-dominated forests to grasslands. This change started c. 450 BC and lasted about two thousand years. The presence of Verbena litoralis, a common weed, which is associated with human activities in the pollen record, the significant correlation between shifts in charcoal influx, and the dominant pollen types suggest human disturbance of the vegetation. Therefore, human settlement on the island occurred c. 450 BC, some 1500 years earlier than is assumed. Climate variability also exerted a major influence on environmental changes. Two sedimentary gaps in the record are interpreted as periods of droughts that could have prevented peat growth and favoured its erosion during the Medieval Climate Anomaly and the Little Ice Age, respectively. At c. AD 1200, the water table rose and the former Raraku mire turned into a shallow lake, suggesting higher precipitation/evaporation rates coeval with a cooler and wetter Pan-Pacific AD 1300 event. Pollen and diatom records show large vegetation changes due to human activities c. AD 1200. Other recent vegetation changes also due to human activities entail the introduction of taxa (e.g. Psidium guajava, Eucalyptus sp.) and the disappearance of indigenous plants such as Sophora toromiro during the two last centuries. Although the evidence is not conclusive, the American origin of V. litoralis re-opens the debate about the possible role of Amerindians in the human colonisation of Easter Island.
occurred at ca AD 800 it coincided with the warmer conditions of the Medieval Climate Anomaly, wh... more occurred at ca AD 800 it coincided with the warmer conditions of the Medieval Climate Anomaly, whereas if it took place at ca AD 1300 it was favored by enhanced westerlies at the onset of the Little Ice Age. Changes in land uses (farming, intensive cattle) during the last century had a large impact in the hydrology and limnology (eutrophication) of the lake.
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