Hydrographic shifts in coastal waters reflect climate-driven changes in hydrological regimes across Northwestern Patagonia.

Climate-driven changes in freshwater inputs have been shown to affect the structure and function of coastal ecosystems. We evaluated changes in the influence of river runoff on coastal systems of Northwestern Patagonia (NWP) over recent decades (1993-2021) by combined analysis of long-term streamflow time series, hydrological simulation, satellite-derived and reanalysis data on sea surface conditions (temperature, turbidity, and salinity). Significant decreases in minimum streamflow across a zone spanning six major river basins were evident at weekly, monthly, and seasonal scales. These changes have been most pronounced in mixed-regime northern basins (e.g., Puelo River) but appear to be progressing southward to rivers characterised by a nival regime. In the adjacent two-layer inner sea, reduced freshwater input corresponds with a shallower halocline and increased surface temperatures across northern Patagonia. Our results underscore the rapidly evolving influence of rivers on adjacent estuarine and coastal waters in NWP. We highlight the need for cross-ecosystem observation, forecasting, mitigation and adaptation strategies in a changing climate, together with corresponding adaptive basin management of systems that supply runoff to the coastal marine waters.

Adaptation strategies of giant viruses to low-temperature marine ecosystems.

Microbes in marine ecosystems have evolved their gene content to thrive successfully in the cold. Although this process has been reasonably well studied in bacteria and selected eukaryotes, less is known about the impact of cold environments on the genomes of viruses that infect eukaryotes. Here, we analyzed cold adaptations in giant viruses (Nucleocytoviricota and Mirusviricota) from austral marine environments and compared them with their Arctic and temperate counterparts. We recovered giant virus metagenome-assembled genomes (98 Nucleocytoviricota and 12 Mirusviricota MAGs) from 61 newly sequenced metagenomes and metaviromes from sub-Antarctic Patagonian fjords and Antarctic seawater samples. When analyzing our data set alongside Antarctic and Arctic giant viruses MAGs already deposited in the Global Ocean Eukaryotic Viral (GOEV) database, we found that Antarctic and Arctic giant viruses predominantly inhabit sub-10°C environments, featuring a high proportion of unique phylotypes in each ecosystem. In contrast, giant viruses in Patagonian fjords were subject to broader temperature ranges and showed a lower degree of endemicity. However, despite differences in their distribution, giant viruses inhabiting low-temperature marine ecosystems evolved genomic cold-adaptation strategies that led to changes in genetic functions and amino acid frequencies that ultimately affect both gene content and protein structure. Such changes seem to be absent in their mesophilic counterparts. The uniqueness of these cold-adapted marine giant viruses may now be threatened by climate change, leading to a potential reduction in their biodiversity.

More than 10,000 pre-Columbian earthworks are still hidden throughout Amazonia.

Indigenous societies are known to have occupied the Amazon basin for more than 12,000 years, but the scale of their influence on Amazonian forests remains uncertain. We report the discovery, using LIDAR (light detection and ranging) information from across the basin, of 24 previously undetected pre-Columbian earthworks beneath the forest canopy. Modeled distribution and abundance of large-scale archaeological sites across Amazonia suggest that between 10,272 and 23,648 sites remain to be discovered and that most will be found in the southwest. We also identified 53 domesticated tree species significantly associated with earthwork occurrence probability, likely suggesting past management practices. Closed-canopy forests across Amazonia are likely to contain thousands of undiscovered archaeological sites around which pre-Columbian societies actively modified forests, a discovery that opens opportunities for better understanding the magnitude of ancient human influence on Amazonia and its current state.

Corrigendum: Biogeography of southern ocean active prokaryotic communities over a large spatial scale.

[This corrects the article DOI: 10.3389/fmicb.2022.862812.].

Biogeography of Southern Ocean Active Prokaryotic Communities Over a Large Spatial Scale.

The activity of marine microorganisms depends on community composition, yet, in some oceans, less is known about the environmental and ecological processes that structure their distribution. The objective of this study was to test the effect of geographical distance and environmental parameters on prokaryotic community structure in the Southern Ocean (SO). We described the total (16S rRNA gene) and the active fraction (16S rRNA-based) of surface microbial communities over a ~6,500 km longitudinal transect in the SO. We found that the community composition of the total fraction was different from the active fraction across the zones investigated. In addition, higher α-diversity and stronger species turnover were displayed in the active community compared to the total community. Oceanospirillales, Alteromonadales, Rhodobacterales, and Flavobacteriales dominated the composition of the bacterioplankton communities; however, there were marked differences at the order level. Temperature, salinity, silicic acid, particulate organic nitrogen, and particulate organic carbon correlated with the composition of bacterioplankton communities. A strong distance-decay pattern between closer and distant communities was observed. We hypothesize that it was related to the different oceanic fronts present in the Antarctic Circumpolar Current. Our findings contribute to a better understanding of the complex arrangement that shapes the structure of bacterioplankton communities in the SO.

Lidar reveals pre-Hispanic low-density urbanism in the Bolivian Amazon.

Archaeological remains of agrarian-based, low-density urbananism1-3 have been reported to exist beneath the tropical forests of Southeast Asia, Sri Lanka and Central America4-6. However, beyond some large interconnected settlements in southern Amazonia7-9, there has been no such evidence for pre-Hispanic Amazonia. Here we present lidar data of sites belonging to the Casarabe culture (around AD 500 to AD 1400)10-13 in the Llanos de Mojos savannah-forest mosaic, southwest Amazonia, revealing the presence of two remarkably large sites (147 ha and 315 ha) in a dense four-tiered settlement system. The Casarabe culture area, as far as known today, spans approximately 4,500 km2, with one of the large settlement sites controlling an area of approximately 500 km2. The civic-ceremonial architecture of these large settlement sites includes stepped platforms, on top of which lie U-shaped structures, rectangular platform mounds and conical pyramids (which are up to 22 m tall). The large settlement sites are surrounded by ranked concentric polygonal banks and represent central nodes that are connected to lower-ranked sites by straight, raised causeways that stretch over several kilometres. Massive water-management infrastructure, composed of canals and reservoirs, complete the settlement system in an anthropogenically modified landscape. Our results indicate that the Casarabe-culture settlement pattern represents a type of tropical low-density urbanism that has not previously been described in Amazonia.

Legacies of Indigenous land use and cultural burning in the Bolivian Amazon rainforest ecotone.

The southwestern Amazon Rainforest Ecotone (ARE) is the transitional landscape between the tropical forest and seasonally flooded savannahs of the Bolivian Llanos de Moxos. These heterogeneous landscapes harbour high levels of biodiversity and some of the earliest records of human occupation and plant domestication in Amazonia. While persistent Indigenous legacies have been demonstrated elsewhere in the Amazon, it is unclear how past human-environment interactions may have shaped vegetation composition and structure in the ARE. Here, we examine 6000 years of archaeological and palaeoecological data from Laguna Versalles (LV), Bolivia. LV was dominated by stable rainforest vegetation throughout the Holocene. Maize cultivation and cultural burning are present after ca 5700 cal yr BP. Polyculture cultivation of maize, manioc and leren after ca 3400 cal yr BP predates the formation of Amazonian Dark/Brown Earth (ADE/ABE) soils (approx. 2400 cal yr BP). ADE/ABE formation is associated with agroforestry indicated by increased edible palms, including Mauritia flexuosa and Attalea sp., and record levels of burning, suggesting that fire played an important role in agroforestry practices. The frequent use of fire altered ADE/ABD forest composition and structure by controlling ignitions, decreasing fuel loads and increasing the abundance of plants preferred by humans. Cultural burning and polyculture agroforestry provided a stable subsistence strategy that persisted despite pronounced climate change and cultural transformations and has an enduring legacy in ADE/ABE forests in the ARE. This article is part of the theme issue 'Tropical forests in the deep human past'.

Ice Age megafauna rock art in the Colombian Amazon?

Megafauna paintings have accompanied the earliest archaeological contexts across the continents, revealing a fundamental inter-relationship between early humans and megafauna during the global human expansion as unfamiliar landscapes were humanized and identities built into new territories. However, the identification of extinct megafauna from rock art is controversial. Here, we examine potential megafauna depictions in the rock art of Serranía de la Lindosa, Colombian Amazon, that includes a giant sloth, a gomphothere, a camelid, horses and three-toed ungulates with trunks. We argue that they are Ice Age rock art based on the (i) naturalistic appearance and diagnostic morphological features of the animal images, (ii) late Pleistocene archaeological dates from La Lindosa confirming the contemporaneity of humans and megafauna, (iii) recovery of ochre pigments in late Pleistocene archaeological strata, (iv) the presence of most megafauna identified in the region during the late Pleistocene as attested by archaeological and palaeontological records, and (v) widespread depiction of extinct megafauna in rock art across the Americas. Our findings contribute to the emerging picture of considerable geographical and stylistic variation of geometric and figurative rock art from early human occupations across South America. Lastly, we discuss the implications of our findings for understanding the early human history of tropical South America. This article is part of the theme issue 'Tropical forests in the deep human past'.

Non-uniform tropical forest responses to the 'Columbian Exchange' in the Neotropics and Asia-Pacific.

It has been suggested that Iberian arrival in the Americas in 1492 and subsequent dramatic depopulation led to forest regrowth that had global impacts on atmospheric CO2 concentrations and surface temperatures. Despite tropical forests representing the most important terrestrial carbon stock globally, systematic examination of historical afforestation in these habitats in the Neotropics is lacking. Additionally, there has been no assessment of similar depopulation-afforestation dynamics in other parts of the global tropics that were incorporated into the Spanish Empire. Here, we compile and semi-quantitatively analyse pollen records from the regions claimed by the Spanish in the Atlantic and Pacific to provide pan-tropical insights into European colonial impacts on forest dynamics. Our results suggest that periods of afforestation over the past millennium varied across space and time and depended on social, economic and biogeographic contexts. We argue that this reveals the unequal and divergent origins of the Anthropocene as a socio-political and biophysical process, highlighting the need for higher-resolution, targeted analyses to fully elucidate pre-colonial and colonial era human-tropical landscape interactions.

[Mental health and environmental health. A prospective view. SESPAS Report 2020]. / Salud mental y salud ambiental. Una visión prospectiva. Informe SESPAS 2020.

Since the dawn of psychiatry, the environment has been an essential factor in the study and understanding of mental illness. Traditionally, the interrelationship between genome and environment has been a central theme in research on the etiopathogenesis of mental health problems and in the very conception of mental health. In its application to psychopathology and mental health, psychiatric enviromics was defined as «the study of environmental conditions and processes that promote mental health or increase the risk of developing mental disorders¼. However, environmental health -at least in Spain and in connection with its powers within the Spanish General Health System- has paid attention to aspects pertaining to risks associated with the physical, chemical and biological pollution of the air, the water and the ground, as well as to its correlation with food pollution. Although environmental risks such as air quality, extreme temperatures, noise, climate change and various environmental toxicants can play a particularly important role, they can hardly be identified as single etiopathogenic elements. This work reviews the recent literature on environmental research and problems of psychiatric morbidity and mortality. Although the results are inconclusive, future lines of research should consider a more agile interdisciplinary collaboration, allowing, on the one hand, a better understanding of mental illness and, on the other hand, to be able to shift from "traditional" environmental health to an environmental health that takes social environmental factors into account and seriously addresses the still little studied concept of "social pollution".

Early Holocene crop cultivation and landscape modification in Amazonia.

The onset of plant cultivation is one of the most important cultural transitions in human history1-4. Southwestern Amazonia has previously been proposed as an early centre of plant domestication, on the basis of molecular markers that show genetic similarities between domesticated plants and wild relatives4-6. However, the nature of the early human occupation of southwestern Amazonia, and the history of plant cultivation in this region, are poorly understood. Here we document the cultivation of squash (Cucurbita sp.) at about 10,250 calibrated years before present (cal. yr BP), manioc (Manihot sp.) at about 10,350 cal. yr BP and maize (Zea mays) at about 6,850 cal. yr BP, in the Llanos de Moxos (Bolivia). We show that, starting at around 10,850 cal. yr BP, inhabitants of this region began to create a landscape that ultimately comprised approximately 4,700 artificial forest islands within a treeless, seasonally flooded savannah. Our results confirm that the Llanos de Moxos is a hotspot for early plant cultivation and demonstrate that-ever since their arrival in Amazonia-humans have markedly altered the landscape, with lasting repercussions for habitat heterogeneity and species conservation.

La farmacia comunitaria como fuente de información de la calidad del aire de las ciudades. A propósito de un estudio de opinión / Community pharmacy as an information source about the air quality of cities. About an opinion study

INTRODUCCIÓN: la Comunidad de Madrid soporta episodios de alta contaminación que le han obligado a elaborar protocolos de actuación que incluyen informar a los ciudadanos. La farmacia comunitaria podría informar al paciente, no sólo de los riesgos de la exposición a los contaminantes, sino también de pautas de prevención ante ellos. El objetivo de este estudio ha sido conocer si la población sabe si la contaminación afecta a su salud y si la farmacia puede ser un buen canal para difundir dicha información. MATERIALES Y MÉTODOS: estudio epidemiológico observacional de tipo transversal (n = 284). La recogida de la información se hizo mediante entrevista personal, realizada por un farmacéutico en las farmacias colaboradoras, desde enero a junio de 2018.RESULTADOS: el 94,2 % de los encuestados cree que la contaminación atmosférica tiene implicaciones en la salud y conoce su riesgo. Un 45,4 % refiere no saber cuándo se superan los niveles de contaminación en el municipio donde vive. Solo un 14,1 % recibía información por los canales de la Administración. El 86,9 % cree no recibir suficiente información en materia de contaminación y salud. Al 74,6 % le gustaría recibir dicha información y un 68,8 % [IC (95 %): 63,0-74,5], la querría de forma individual a través de la farmacia comunitaria. DISCUSIÓN: si bien la población sabe que la contaminación atmosférica afecta a su salud, no recibe suficiente información. Los sistemas empleados por la Administración no son efectivos y se identifica a la farmacia comunitaria como un lugar idóneo para recibir la información requerida

INTRODUCTION: Madrid region suffers high pollution level episodes, leading it the elab-oration of action protocols that include informing citizens. From the community pharma-cy, we could seek to inform the patient, not only of the risks of exposure to this scenario, but also about prevention guidelines against it. The objective of this study was to know if there is a need of information about how contamination affects health and if the phar-macy can be a good channel to disseminate this information.MATERIALS AND METHODS: Observational epidemiological transversal study (n = 284). The information was collected through a personal interview conducted by a pharmacist in the collaborating pharmacies from January to June 2018.RESULTS: 94.2% of respondents believe that air pollution has health implications and knows its risks. 45.4% report not knowing when pollution levels are exceeded in the town where they live. Only 14,1% received information through the administration channels. 86.9% believe that they do not receive enough information regarding pollution and health. 74.6% wants to receive this information and 68.8% [CI (95%): 63,0-74,5], want it individually and using the community pharmacy as a channel.DISCUSSION: Citizens know that air pollution affects their health, although they do not receive enough information. The systems used by the administration are not effective and that postulates the community pharmacy as an agent of interest for the distribution of the required information

Salud mental y salud ambiental. Una visión prospectiva. Informe SESPAS 2020 / Mental health and environmental health. A prospective view. SESPAS Report 2020

El ambiente ha sido, desde los albores de la psiquiatría, un factor fundamental en el estudio y la comprensión de las enfermedades mentales. La relación entre genoma y ambiente ha constituido tradicionalmente un tema central en la investigación de la etiopatogenia de los problemas de salud mental y en la concepción misma de esta. En su aplicación a la psicopatología y a la salud mental, la ambiómica psiquiátrica se ha definido como «el estudio de las condiciones y procesos ambientales que promueven la salud mental o incrementan los riesgos de trastornos mentales». Sin embargo, la salud ambiental, al menos en España y en relación con sus competencias dentro del sistema de salud general, ha centrado su atención en los aspectos relativos a los riesgos ligados a la contaminación física, química o biológica del aire, el agua o la tierra, así como a su correlato alimenticio. Aunque los riesgos ambientales, como la calidad del aire, las temperaturas extremas, el ruido, el cambio climático y distintos tóxicos ambientales, pueden desempeñar un papel muy importante, difícilmente pueden ser identificados como elementos etiopatogénicos únicos. Este trabajo revisa la literatura reciente sobre la investigación ambiental y los problemas de morbimortalidad psiquiátrica. Si bien los resultados son poco concluyentes, las futuras líneas de investigación deberían considerar una colaboración interdisciplinaria más ágil, que permita, por un lado, entender mejor la enfermedad mental, y por otro, avanzar desde la salud ambiental «tradicional» a una que contemple los factores ambientales de tipo social abordando el concepto aún poco estudiado de «contaminación social»

Since the dawn of psychiatry, the environment has been an essential factor in the study and understanding of mental illness. Traditionally, the interrelationship between genome and environment has been a central theme in research on the etiopathogenesis of mental health problems and in the very conception of mental health. In its application to psychopathology and mental health, psychiatric enviromics was defined as «the study of environmental conditions and processes that promote mental health or increase the risk of developing mental disorders». However, environmental health -at least in Spain and in connection with its powers within the Spanish General Health System- has paid attention to aspects pertaining to risks associated with the physical, chemical and biological pollution of the air, the water and the ground, as well as to its correlation with food pollution. Although environmental risks such as air quality, extreme temperatures, noise, climate change and various environmental toxicants can play a particularly important role, they can hardly be identified as single etiopathogenic elements. This work reviews the recent literature on environmental research and problems of psychiatric morbidity and mortality. Although the results are inconclusive, future lines of research should consider a more agile interdisciplinary collaboration, allowing, on the one hand, a better understanding of mental illness and, on the other hand, to be able to shift from "traditional" environmental health to an environmental health that takes social environmental factors into account and seriously addresses the still little studied concept of "social pollution"

Blood lead in children and associations with trace elements and sociodemographic factors.

BACKGROUND: No safe blood lead concentration in children has been identified. Lead can affect nearly every system in the body and is especially harmful to the developing central nervous system of children. The aim of this study is to analyze blood lead in a population of children and its association with sociodemographic variables, biochemical parameters, copper, iron, selenium and zinc. METHODS: We recruited 155 children (86 boys and 69 girls) with a mean age of 7.3 (SD:4.1). Blood lead and serum selenium concentrations were measured by electrothermal atomic absorption spectrometry. Serum copper and zinc concentrations were measured by flame atomic absorption spectrometry. Serum iron levels were determined by colorimetric assay. A risk exposure questionnaire for lead was administered to the participants. RESULTS: The median blood lead level was 1.1 (IQR 0.7-1.6) µg/dL. Regarding risk exposure factors, the youngest children (<2 years) who played outdoors presented a median blood lead concentration of 1.1 µg/dL IQR: 0.48-1.48, compared to the median of 0.3 µg/dL IQR:0.2-0.48 in the children who stated they played at home (p = 0.024). Significant differences were also found when taking into account those parents who smoked (median 1.3 IQR 0.8-1.9 µg/dL vs 0.9 IQR 0.5-1.4 µg/dL of non-smokers, p = 0.002). Children who drank tap water had higher blood lead levels (median 1.2 IQR 0.7-1.6 µg/dL) than those who drank bottled water (median 0.7 IQR 0.2-1.3 µg/dL p = 0.014). In addition, children whose mothers had not finished school had higher blood lead levels (median 1.7 IQR 1.2-2.3 µg/dL) than those whose mothers had finished school (median 1.2 IQR 0.7-1.7 µg/dL) and those whose mothers had gone to university (median 0.9 IQR 0.5-1.4 µg/dL) p = 0.034. In the multivariate lineal regression analysis we continue to observe the association between mother's higher level of education and lower blood levels (p = 0.04) and the interaction between age and outdoor play (p = 0.0145). CONCLUSIONS: In spite of the decline in blood lead concentrations, associated risk factors continue to exist in vulnerable populations such as children.

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 using archaeological, palaeoecological and palaeoclimatological data 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 reorganization during periods of climate change, others were unaffected and even flourished. We propose that societies with intensive, specialized 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 earth in the long term, were more resilient to climate change.

Interannual Variability of Dinophysis acuminata and Protoceratium reticulatum in a Chilean Fjord: Insights from the Realized Niche Analysis.

Here, we present the interannual distribution of Dinophysis acuminata and Protoceratium reticulatum over a 10-year period in the Reloncaví Fjord, a highly stratified fjord in southern Chile. A realized subniche approach based on the Within Outlying Mean Index (WitOMI) was used to decompose the species' realized niche into realized subniches (found within subsets of environmental conditions). The interannual distribution of both D. acuminata and P. reticulatum summer blooms was strongly influenced by climatological regional events, i.e., El Niño Southern Oscillation (ENSO) and the Southern Annual Mode (SAM). The two species showed distinct niche preferences, with blooms of D. acuminata occurring under La Niña conditions (cold years) and low river streamflow whereas P. reticulatum blooms were observed in years of El Niño conditions and positive SAM phase. The biological constraint exerted on the species was further estimated based on the difference between the existing fundamental subniche and the realized subniche. The observed patterns suggested that D. acuminata was subject to strong biological constraint during the studied period, probably as a result of low cell densities of its putative prey (the mixotrophic ciliate Mesodinium cf. rubrum) usually observed in the studied area.

Publisher Correction: Evidence for mid-Holocene rice domestication in the Americas.

In the HTML version of this Article originally published, Fig. 4 was a duplicate of Fig. 1. This has now been amended.

Medieval Climate Variability in the eastern Amazon-Cerrado regions and its archeological implications.

The South American Monsoon System is responsible for the majority of precipitation in the continent, especially over the Amazon and the tropical savannah, known as 'Cerrado'. Compared to the extensively studied subtropical and temperate regions the effect of the Medieval Climate Anomaly (MCA) on the precipitation over the tropics is still poorly understood. Here, we present a multiproxy paleoprecipitation reconstruction showing a consistent change in the hydrologic regime during the MCA in the eastern Amazon and 'Cerrado', characterized by a substantial transition from humid to drier conditions during the Early (925-1150 C.E.) to Late-MCA (1150-1350 C.E.). We compare the timing of major changes in the monsoon precipitation with the expansion and abandonment of settlements reported in the archeological record. Our results show that important cultural successions in the pre-Columbian Central Amazon, the transition from Paredão to Guarita phase, are in agreement with major changes in the hydrologic regime. Phases of expansion and, subsequent abandonment, of large settlements from Paredão during the Early to Late-MCA are coherent with a reduction in water supply. In this context we argue that the sustained drier conditions during the latter period may have triggered territorial disputes with Guarita leading to the Paredão demise.

The legacy of 4,500 years of polyculture agroforestry in the eastern Amazon.

The legacy of pre-Columbian land use in the Amazonian rainforest is one of the most controversial topics in the social1-10 and natural sciences11,12. Until now, the debate has been limited to discipline-specific studies, based purely on archaeological data8, modern vegetation13, modern ethnographic data3 or a limited integration of archaeological and palaeoecological data12. The lack of integrated studies to connect past land use with modern vegetation has left questions about the legacy of pre-Columbian land use on the modern vegetation composition in the Amazon, unanswered11. Here, we show that persistent anthropogenic landscapes for the past 4,500 years have had an enduring legacy on the hyperdominance of edible plants in modern forests in the eastern Amazon. We found an abrupt enrichment of edible plant species in fossil lake and terrestrial records associated with pre-Columbian occupation. Our results demonstrate that, through closed-canopy forest enrichment, limited clearing for crop cultivation and low-severity fire management, long-term food security was attained despite climate and social changes. Our results suggest that, in the eastern Amazon, the subsistence basis for the development of complex societies began ~4,500 years ago with the adoption of polyculture agroforestry, combining the cultivation of multiple annual crops with the progressive enrichment of edible forest species and the exploitation of aquatic resources. This subsistence strategy intensified with the later development of Amazonian dark earths, enabling the expansion of maize cultivation to the Belterra Plateau, providing a food production system that sustained growing human populations in the eastern Amazon. Furthermore, these millennial-scale polyculture agroforestry systems have an enduring legacy on the hyperdominance of edible plants in modern forests in the eastern Amazon. Together, our data provide a long-term example of past anthropogenic land use that can inform management and conservation efforts in modern Amazonian ecosystems.

Uncoupling human and climate drivers of late Holocene vegetation change in southern Brazil.

In the highlands of southern Brazil an anthropogenitcally driven expansion of forest occurred at the expense of grasslands between 1410 and 900 cal BP, coincident with a period of demographic and cultural change in the region. Previous studies have debated the relative contributions of increasing wetter and warmer climate conditions and human landscape modifications to forest expansion, but generally lacked high resoltiuon proxies to measure these effects, or have relied on single proxies to reconstruct both climate and vegetation. Here, we develop and test a model of natural ecosystem distribution against vegetation histories, paleoclimate proxies, and the archaeological record to distinguish human from temperature and precipitation impacts on the distribution and expansion of Araucaria forests during the late Holocene. Carbon isotopes from soil profiles confirm that in spite of climatic fluctuations, vegetation was stable and forests were spatially limited to south-facing slopes in the absence of human inputs. In contrast, forest management strategies for the past 1400 years expanded this economically important forest beyond its natural geographic boundaries in areas of dense pre-Columbian occupation, suggesting that landscape modifications were linked to demographic changes, the effects of which are still visible today.