Climate change and cultural resilience in late pre-Columbian Amazonia

The long term response of ancient societies to climate change has been a matter of global debate. Until recently, the lack of integrative studies between archaeological, palaeoecological, and palaeoclimatological data had prevented an evaluation of the relationship between climate change, distinct subsistence strategies, and cultural transformations across the largest rainforest of the world, Amazonia. Here, we review the most relevant cultural changes seen in the archaeological record of six different regions within Greater Amazonia during late pre-Columbian times. We compare the chronology of those cultural transitions with high-resolution regional palaeoclimate proxies, showing that, while some societies faced major reorganisation during periods of climate change, others were unaffected and even flourished. We propose that societies with intensive, specialised land-use systems were vulnerable to transient climate change. In contrast, land-use systems that relied primarily on polyculture agroforestry, resulting in the formation of enriched forests and fertile Amazonian Dark Earths in the long term, were more resilient to climate change

4. HYBAM: un observatorio para medir el impacto del Cambio Climático sobre la erosión y los flujos de sedimentos en la zona Andino-Amazónica

La cuenca Amazónica es la más grande del mundo. La instalación del observatorio HYBAM con una amplia red de estaciones hidrológicas ubicadas desde el piedemonte andino hasta el océano Atlántico permite, desde el 2003, la generación de registros periódicos y confiables (nivel del agua, caudal, concentración de sedimentos y otros parámetros físico-químicos de la calidad del agua) a lo largo de toda la cuenca. Hoy en día, el desarrollo de técnicas satelitales, como la altimetría, permite completar eficientemente los datos obtenidos por las redes de medición en los ríos. El recrudecimiento de eventos extremos en la Amazonia (Inundaciones, sequias,) por efecto del cambio climático actual asociado a un cambio acelerado de ocupación de los suelos (deforestación, prácticas agrícolas), tiene una incidencia directa sobre la producción sedimentarla. Conocer los flujos de materiales transportados por los ríos es esencial tanto para la navegación fluvial como para guiar la explotación de los recursos naturales (agua, petróleo, minerales), para conocer el transporte de partículas contaminantes o para diseñar infraestructuras.Le bassin de l’Amazone est le plus grand du monde. La mise en œuvre de l’observatoire HYBAM avec un vaste réseau de stations hydrologiques situées sur les contreforts des Andes jusqu’á l’océan Atlantique permet de générer, depuis 2003, des données régulières et fiables tout le long du bassin (hauteur d’eau, débit, concentration de sédiments et d’autres paramètres physico-chimiques de qualité de l’eau). De nos jours, la mise au point des techniques par satellite, tels que l’altimétrie, permet de compléter efficacement les données obtenues par les réseaux de mesure dans les rivières. L’intensification des événements extrêmes dans la région amazonienne (inondations, sécheresses), liés au changement climatique actuel associé á un changement rapide de l’utilisation des terres (déforestation, pratiques agricoles), ont un impact direct sur la production de sédiments. Connaître les flux de matières transportés par les rivières est essentiel pour la navigation fluviale ainsi que pour guider l’exploitation des ressources naturelles (eau, pétrole, minéraux), connaître le trajet de particules polluantes ou concevoir des infrastructures.The Amazon basin is the largest basin in the world. The implementation of the HYBAM observatory, which has installed a large network of hydrological stations located from the Andean foothills down to the Atlantic Ocean, allows since 2003, generate periodical and reliable records (such as water level, flow, sediment concentration and other physicochemical parameters of water quality) along the entire basin. Nowadays, the development of satellite techniques, (such as altimetry), makes it possible to efficiently complete the data obtained by the measurement networks in rivers. The intensification of extreme events in the Amazon region (floods, droughts) occurred as a result of the current Climate Change associated with a more rapid change of land use (deforestation, agricultural practices) have a direct impact on sediment production. It is essential to know the flows of the materials transported by rivers, both for river navigation as well as to guide the exploitation of natural resources (water, oil, minerals), to know the transport of particulate pollutants, or to design infrastructures

2. Cambios climáticos del Holoceno

Existe una variabilidad natural del clima. Se debe tanto a factores externos (como el cambio de la órbita de la Tierra) como internos (como erupciones volcánicas o movimientos tectónicos entre otros). Los paleo-climatólogos estudian los cambios del clima del pasado a través de complejos análisis de sedimentos de lagos, de testigos de hielo de los glaciares o también de estalagmitas de las cavernas. Estos registros son como libros donde está escrita la historia del clima de la Tierra. Usando estos marcadores ambientales y gracias a los modelos climáticos a diferentes escalas espaciales y de tiempo, los investigadores buscan discriminar cual es la parte natural del cambio climático actual de la parte debida a la actividad humana y disminuir las incertidumbres en las proyecciones futuras del clima.Il existe une variabilité climatique naturelle. Elle est due aussi bien à des facteurs externes (comme le changement d’orbite de la Terre) qu’internes (comme les éruptions volcaniques ou les mouvements tectoniques entre autres). Les paléo-climatologues étudient les changements du climat du passé en réalisant des analyses complexes de sédiments de lacs, de carottes glaciaires ou encore de stalagmites des grottes. Ces registres sont comme des livres où est écrite l’histoire du climat de la Terre. A partir de ces marqueurs environnementaux et des modelés climatiques à différentes échelles d’espace et de temps, les chercheurs cherchent à connaître quelle part du changement climatique actuel est naturelle et quelle part est liée à l’activité humaine et réduire les incertitudes dans les projections climatiques.There is natural climate variability. It ¡s due to both external factors (such as changes in Earth’s orbit) as well as internal factors (such as volcanic eruptions and tectonic movements among others). Paleoclimatologists study historic climate changes performance by complex analysis of lake sediments, ice cores or stalagmite caves. These records are like books in where the history of Earth’s climate has been written. Thanks to these environmental markers and the climate models at different scales of space and time, researchers seek to differentiate which part of the current climate change is natural and which part is due to human activity, in order to reduce uncertainties in future climate projections

Influence of climate changes on carbon accumulation in high Andean peatlands during the last 2 500 years

High-altitude cushion peatlands contain important records for high-resolution palaeoenvironmental studies, due to their high carbon accumulation rates and sensitivity to climatic changes. In this study, we present the paleoenvironmental history for the last 2 500 years based on the study of APA01 core, located in the headwaters of the Cachi river basin in Ayacucho. Radiocarbon dating by an accelerator mass spectroscopy (AMS) and by an elemental PDZ Europa ANCA-GSL analyzer to estimate particulated organic carbon were determined. Our results reveal changes in the peatlands during the Late Holocene. The palaeo climate varied significantly during the last 2 500 years. During the Medieval Climatic Anomaly (ACM) from around 1040 DC (Before Christ - BC, in spanish paper) to 1300 DC, the drier climate caused a slowdown in peat accumulation due to a reduced water table inducing a reduced organic matter production with a negative peak of carbon concentration. At the end of the Small Ice Age (PEH), between 1600 DC and 1890 DC, carbon accumulation showed high variability. Subsequently, the peat environment is mainly characterized by a considerable increase of carbon accumulation rates due to high sedimentation rates that is possibly related to the retreat of glaciers in the Central Andes. The recent drastic increase in the sedimentation rate and the reduction of carbon concentrations are a warning of a possible future decline of these ecosystems

Simulating the implications of glaciers' retreat for water management : a case study in the Rio Santa basin, Peru

This paper presents a model of Andean glacier hydrology which can be used to assess the water management implications of possible future glacier retreat. The approach taken uses the Water Evaluation and Planning (WEAP) system and integrates both hydrologic processes and representations of the operations of built infrastructure. The model is applied in the Rio Santa watershed in Peru to illustrate how alternative water management strategies can be simulated. The WEAP platform built for this study has been used to engage with local stakeholders for water management

Precipitation changes over the eastern Bolivian Andes inferred from speleothem (delta O-18) records for the last 1400 years

Here we present high-resolution delta O-18 records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional- to large-scale atmospheric circulation over South America and allow interpreting changes in delta O-18 during the last 1400 yr as a function of changes in precipitation regimes over the southern tropical Andes. Two distinct phases with more negative delta O-18 values, interpreted as periods of increased convective activity over the eastern Andean Cordillera in Bolivia are observed concomitantly with periods of global climate anomalies during the last millennium, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) respectively. Changes in the Bolivian delta O-18 record during the LIA are apparently related to a southward displacement of the Intertropical Convergence Zone (ITCZ), which acts as a main moisture driver to intensify convection over the tropical continent. During the MCA, however, the increased convective activity observed in the Bolivian record is likely the result of a different mechanism, which implies moisture sourced mainly from the southern tropical Atlantic. This interpretation is consistent with paleoclimate records further to the north in the tropical Andes that show progressively drier conditions during this time period, indicating a more northerly position of the ITCZ. The transition period between the MCA and the LIA shows a slight tendency toward increased delta O-18 values, indicating weakened convective activity. Our results also reveal a non-stationary anti-phased behavior between the delta O-18 reconstructions from Bolivia and northeastern Brazil that confirms a continental-scale east-west teleconnection across South America during the LIA

Calibration of speleothem delta O-18 records against hydroclimate instrumental records in Central Brazil

delta O-18 in speleothems is a powerful proxy for reconstruction of precipitation patterns in tropical and sub-tropical regions. The aim of this study is to calibrate the delta O-18 record of speleothems against historical precipitation and river discharge data in central Brazil, a region directly influenced by the Southern Atlantic Convergence Zone (SACZ), a major feature of the South American Monsoon System (SAMS). The present work is based on a sub annual resolution speleothem record covering the last 141 years (the period between the years 1870 and 2011) from a cave in central Brazil. The comparison of this record with instrumental hydroclimate records since 1921 allows defining a strong relationship between precipitation variability and stable oxygen isotope ratios from speleothems. The results from a monitoring program of climatic parameters and isotopic composition of rainfall and cave seepage waters performed in the same cave, show that the rain delta O-18 variability is dominated by the amount effect in this region, while delta O-18 drip water remains almost constant over the monitored period (1.5 years). The delta O-18 of modern calcite, on the other hand, shows clear seasonal variations, with more negative values observed during the rainy season, which implies that other factors also influence the isotopic composition of carbonate. However, the relationship between delta O-18 of carbonate deposits and rainwater is supported by the results from the comparison between speleothem delta O-18 records and historical hydroclimate records. A significant correlation between speleothem delta O-18 and monsoon rainfall variability is observed on sub-decadal time scales, especially for the monsoon period (DJFM and NDJFM), once the rainfall record have been smoothed with a 7-9 years running mean. This study confirms that speleothem delta O-18 is directly associated with monsoon rainfall variability in central Brazil. The relationship between speleothem delta O-18 records and hydroclimatic historical records allows approximation of the absolute changes in mean annual rainfall during the last millennia in the SACZ/SAMS domain

Global karst springs hydrograph dataset for research and management of the world's fastest-flowing groundwater [Data paper]

Karst aquifers provide drinking water for 10% of the world's population, support agriculture, groundwater-dependent activities, and ecosystems. These aquifers are characterised by complex groundwater-flow systems, hence, they are extremely vulnerable and protecting them requires an in-depth understanding of the systems. Poor data accessibility has limited advances in karst research and realistic representation of karst processes in large-scale hydrological studies. In this study, we present World Karst Spring hydrograph (WoKaS) database, a community-wide effort to improve data accessibility. WoKaS is the first global karst springs discharge database with over 400 spring observations collected from articles, hydrological databases and researchers. The dataset's coverage compares to the global distribution of carbonate rocks with some bias towards the latitudes of more developed countries. WoKaS database will ensure easy access to a large-sample of good quality datasets suitable for a wide range of applications: comparative studies, trend analysis and model evaluation. This database will largely contribute to research advancement in karst hydrology, supports karst groundwater management, and promotes international and interdisciplinary collaborations