Three Millennia of Climatic, Ecological, and Cultural Change on Easter Island: An Integrative Overview

Eastern Island (Rapa Nui) is famous for the legacy of an extinct civilization symbolized by the megalithic statues called moai. Several enigmas regarding the colonization of the island its deforestation and a presumed cultural collapse of the ancient civilization still remain elusive. According to the prevailing view, the first settlers arrived between AD 800 and AD 1200 from east Polynesia and overexploited the island's natural resources causing an ecological catastrophe leading to a cultural collapse (Flenley and Bahn, 2003 ). The main evidence for this theory was the abrupt replacement of palm pollen by grass pollen in the sediments of the island's lakes and mires (Raraku, Kao, and Aroi), which was interpreted in terms of a thorough deforestation between approximately AD 1200 and AD 1400/1600 (Flenley and King, 1984; Flenley et al., 1991; Mann et al., 2008). This ecocidal view is widely accepted not only by the scientific community but also by society, thanks to its popularization by the mass media

Late Holocene vegetation dynamics and deforestation in Rano Aroi: implications for Easter Island's ecological and cultural history

Easter Island (Rapa Nui) has been considered an example of how societies can cause their own destruction through the overexploitation of natural resources. The flagship of this ecocidal paradigm is the supposed abrupt, island-wide deforestation that occurred about one millennium ago, a few centuries after the arrival of Polynesian settlers to the island. Other hypotheses attribute the forest demise to different causes such as fruit consumption by rats or aridity but the occurrence of an abrupt, island-wide deforestation during the last millennium has become paradigmatic in Rapa Nui. We argue that such a view can be questioned, as it is based on the palynological study of incomplete records, owing to the existence of major sedimentary gaps. Here, we present a multiproxy (pollen, charcoal and geochemistry) study of the Aroi core, the first gap-free sedimentary sequence of the last millennia obtained to date in the island. Our results show changing vegetation patterns under the action of either climatic or anthropogenic drivers, or both, depending on the time interval considered. Palm forests were present in Aroi until the 16th century, when deforestation started, coinciding with fire exacerbation elikely of human origine and a dry climate. This is the latest deforestation event recorded so far in the island and took place roughly a century before European contact. In comparison to other Easter Island records, this record shows that deforestation was neither simultaneous nor proceeded at the same pace over the whole island. These findings suggest that Easter Island's deforestation was a heterogeneous process in space and time, and highlights the relevance of local catchment traits in the island's environmental and land management history

Seasonal patterns of pollen sedimentation in Lake Montcortès (Central Pyrenees) and potential applications to high-resolution paleoecology: a 2-year pilot study

14 páginas, 2 tablas, 10 figuras.Lakes with varved sediments are especially well suited for paleoecological study, from annual to even seasonal resolution. The interpretative power of such high-resolution paleoenvironmental reconstructions relies on the availability of modern analogs with the same temporal resolution. We studied seasonal pollen sedimentation in varved Lake Montcorte`s, Central Pyrenees (Spain), as a modern analog for highresolution reconstruction of Late Holocene vegetation and landscape dynamics. Seasonal samples were obtained from sediment traps that were submerged near the maximum water depth for a 2-year period (fall 2013 to fall 2015). Seasonal pollen sedimentation was compared with meteorological variables from a nearby weather station. Bulk pollen sedimentation, dominated by Pinus (pine) and Quercus (oak), followed a clear seasonal pattern that peaked during the spring/summer, coinciding with maximum temperature and precipitation, minimum relative humidity and moderate winds from the SSE. Pollen sedimentation lags (PSL) were observed formost pollen types, as substantial amounts of pollen were found in the traps outside of their respective flowering seasons. Two pollen assemblages were clearly differentiated by their taxonomic composition, corresponding to spring/summer and fall/winter. This pattern is consistent with existing interpretation of the sediment varves, specifically, that varves are formed by two-layer couplets that represent the same seasonality as pollen. We concluded that pollen sedimentation in Lake Montcorte`s exhibits a strong seasonal signal in the quantity of pollen, the taxonomic composition of the pollen assembalges, and relationships between the pollen and meteorological variables. Thus, varved sediments provide a potentially powerful tool for paleoecological reconstruction at seasonal resolution. This method could be used not only to identify paleoenvironmental trends, but also to identify annual layers and therefore date sediments, even in the absence of evident sediment laminations. A satisfactory explanation of PSL will require further studies that examine internal lake dynamics and pollen production/dispersal patterns.This work was funded by the Ministry of Economy and Competitivity (project MONT-500; reference CGL2012-33665; PI: Teresa Vegas-Vilarru´bia).Peer reviewe

Climate changes and cultural shifts on Easter Island during the last three millennia

Easter Island's cultural shifts have been explained mostly by anthropogenic forcing and climate changes have been dismissed as relevant drivers of societal change. Recent findings demand a more complex scenario in which climatic, ecological and cultural factors interact

Vegetation and landscape around Lake Montcortès (Catalan pre-Pyrenees) as a tool for palaeoecological studies of lake sediments

Vegetation and landscape around Lake Montcortès (Catalan pre-Pyrenees) as a tool for palynological studies of lake sediments. Lake Montcortès (42º 19′ N, 0º 59′ E; 1,027 m elevation) is an excellent target for high-resolution palaeoecological studies because its annually-laminated sediments extending back to the early-middle Holocene. The detailed knowledge of present vegetation patterns around the lake and the pollen they release to lake sediments is essential for a reliable interpretation of past vegetation dynamics. This study aims to identify and map the vegetation types currently growing around the lake. For this purpose, a quadrangular area of ca. 48 ha was defined. The floristic study resulted in a catalogue of 534 species. Vegetation analysis was based on 42 phytosociological inventories used to synthesise and map the relevant plant landscape units. As a result, we obtained 52 vegetation units as expressions of the CORINE habitats previously defined for Catalonia. Each of these habitats was described in floristic, physiognomic, phytogeographic, environmental and human-use terms. The next step will be the palynological study of the more representative species of the described vegetation types, as a means to optimise future palynological interpretations

Seasonal patterns of pollen sedimentation in Lake Montcortès (Central Pyrenees) and potential applications to high-resolution paleoecology: a two-year pilot study.

Lakes with varved sediments are especially well suited for paleoecological study, from annual to even seasonal resolution. The interpretative power of such high-resolution paleoenvironmental reconstructions relies on the availability of modern analogs with the same temporal resolution. We studied seasonal pollen sedimentation in varved Lake Montcorte`s, Central Pyrenees (Spain), as a modern analog for highresolution reconstruction of Late Holocene vegetation and landscape dynamics. Seasonal samples were obtained from sediment traps that were submerged near the maximum water depth for a 2-year period (fall 2013 to fall 2015). Seasonal pollen sedimentation was compared with meteorological variables from a nearby weather station. Bulk pollen sedimentation, dominated by Pinus (pine) and Quercus (oak), followed a clear seasonal pattern that peaked during the spring/summer, coinciding with maximum temperature and precipitation, minimum relative humidity and moderate winds from the SSE. Pollen sedimentation lags (PSL) were observed for most pollen types, as substantial amounts of pollen were found in the traps outside of their respective flowering seasons. Two pollen assemblages were clearly differentiated by their taxonomic composition, corresponding to spring/summer and fall/winter. This pattern is consistent with existing interpretation of the sediment varves, specifically, that varves are formed by two-layer couplets that represent the same seasonality as pollen. We concluded that pollen sedimentation in Lake Montcorte`s exhibits a strong seasonal signal in the quantity of pollen, the taxonomic composition of the pollen assembalges, and relationships between the pollen and meteorological variables. Thus, varved sediments provide a potentially powerful tool for paleoecological reconstruction at seasonal resolution. This method could be used not only to identify paleoenvironmental trends, but also to identify annual layers and therefore date sediments, even in the absence of evident sediment laminations. A satisfactory explanation of PSL will require further studies that examine internal lake dynamics and pollen production/dispersal patterns

Macrofossils in Raraku Lake (Easter Island) integrated with sedimentary and geochemical records: Towards a palaeoecological synthesis for the last 34,000 years

Macrofossil analysis of a composite 19m long sediment core from Rano Raraku Lake (Easter Island) wasrelated to litho-sedimentary and geochemical features of the sediment. Strong stratigraphical patterns are shown by indirect gradient analyses of the data. The good correspondence between the stratigraphical patterns derived from macrofossil (Correspondence Analysis) and sedimentary and geochemical data (Principal Component Analysis) shows that macrofossil associations provide sound palaeolimnological information in conjunction with sedimentary data. The main taphonomic factors influencing the macrofossil assemblages are run-off from the catchment, the littoral plant belt, and the depositional environment within the basin. Five main stages during the last 34,000 calibrated years BP (calyrBP) are characterised from the lithological, geochemical, and macrofossil data. From 34 to 14.6calkyrBP (last glacial period) the sediments were largely derived from the catchment, indicating a high energy lake environment with much erosion and run-off bringing abundant plant trichomes, lichens, and mosses into the centre of Raraku Lake. During the early Holocene the infilling of the lake basin and warmer conditions favoured the growth of a littoral plant belt that obstructed terrigenous input. Cladoceran remains and Solanaceae seeds are indicative of reduced run-off and higher values of N and organic C indicate increased aquatic and catchment productivity. From 8.7 to 4.5calkyrBP a swamp occupied the entire basin. The increase of Cyperaceae seeds reflects this swamp development and, with oribatid mites and coleopteran remains, indicates a peaty environment and more anoxic conditions in Raraku. At around 4.5calkyrBP dry conditions prevented peat growth and there is a sedimentary hiatus. About 800calyrBP, peat deposition resumed. Finally, in the last few centuries, a small lake formed within the surrounding swamp. Evidence of human activity is recorded in these uppermost sediments. © 2011 Elsevier Ltd.This research was funded by the Spanish Ministry of Science and Education through the projects LAVOLTER (CGL2004-00683/BTE), GEOBILA (CGL2007-60932/BTE) and CONSOLIDER GRACCIE (CSD2007-00067) and an undergraduate grant (BES-2008-002938 to N. Cañellas-Boltà).Peer Reviewe

Mediterranean polyculture revisited: olive, grape and subsistence strategies at Palaikastro, East Crete, between the Late Neolithic and Late Bronze Age

This paper examines agriculture, farming and dietary resources in east Crete, and re-evaluates the role of grape and olive in its prehistoric economy, these being key in debates on the emergence of social complexity. To do so bioarchaeological, paleoenvironmental and landscape survey data from the Bronze Age town at Palaikastro and its territory are combined. The results indicate a highly compartmentalised landscape, including intensive crop cultivation and extensive animal herding with careful monitoring to maintain productivity. A heightened specialisation in ovicaprine management at Palaikastro and east Crete seems to be delineated. Marine resources were regularly exploited from easily accessible coastal areas. Other activities included viticulture since the Early Minoan period, with the possible involvement of several houses in wine-making. A final important activity in the area was large-scale olive tree management since the Final Neolithic period and through to the Late Bronze Age, that seems to be entangled with ovicaprine herding and grazing. Thus, the demand for olive oil production does not seem to have been the driving force behind the intensification of the tree management, at least initially, but a corollary of its use in other aspects of the local economy

Paleoecology of Easter Island: evidence and uncertainties

The existence of palm-dominated forests covering the island since the last glaciation and the recent deforestation by humans are paradigmatic in Easter Island's paleoecological reconstructions. The timing and mode of the deforestation are controversial, but there is general agreement that it actually occurred, and it is often given as an example of a human-induced environmental catastrophe with philosophical implications for the future of the whole planet. To evaluate whether this is the only well-supported hypothesis or if there might be other scenarios compatible with the paleoecological data, this paper reviews all the available evidence on past vegetation changes on Easter Island. The discussion is centered on three main points: 1) the alleged nature and extension of the former forests, 2) the taxonomic identity of the dominant palms, and 3) the nature of the recent ecological changes leading to a treeless island. The potential causes of the assumed deforestation are beyond the scope of this study. Concerning the first point, palynological and anthracological results obtained so far are not only compatible with a forested island, but also with other scenarios, for example a mosaic vegetation pattern with forests restricted to sites with a high freshwater table (gallery forests), which are mostly around the permanent lakes and along the coasts. With regard to palm identity, some extant species have been proposed as potential candidates, but the palms that dominated these forests seem to have become extinct and their identity remains unknown. The existence of a sedimentary hiatus around the dates of forest decline complicates the picture and reinforce the possibility of climatic changes. It is concluded that the hypothesis of a previously forested island has yet to be demonstrated. Therefore, the recent ecological disaster, human-induced or not, is still speculative. Several types of future studies are proposed for a better understanding of Easter Island's ecological history, including: modern analog studies from similar situations, pollen dispersal modeling, high-resolution multi-proxy studies along the cores obtained so far, more coring campaigns in the search for older sediments, and DNA and isotopic analyses of plant remains for taxonomic identification purposes

Vegetation dynamics at Raraku Lake catchment (Easter Island) during the past 34,000 years

Easter Island is a paradigmatic example of human impact on ecosystems. The role of climate changes in recent vegetation shifts has commonly been rejected without proper assessment. A palynological study of a long sediment core from Raraku Lake documents the vegetation dynamics for the last 34 ka and investigates their driving forces, particularly the effects of climate variability on vegetation changes. Significant relationships between pollen assemblage changes and sedimentary and geochemical proxies demonstrate the rapid response of vegetation to lake crater basin hydrology and climatic changes. The lake surroundings were occupied by an open mixed palm grove during the Last Glacial period. Poaceae and Sophora increased at the expense of palms and Triumfetta, and Coprosma practically disappeared, in response to slightly wetter and/or colder climate during the Last Glacial Maximum. Palms and Triumfetta thrived in awarmer and/or drier climate during the deglaciation. Minor vegetation changes (a slight increase in Sophora and a drop in Asteraceae and Poaceae) occurred between 13.2 and 11.8 cal ka BP and can be related to rapid changes in the Younger Dryas chronozone. The increase in herbaceous taxa indicates a gradual shallowing of the lake and development of a mire during the Holocene, caused by sediment infilling and warmer and drier climate. Relatively rapid vegetation changes in the Holocene were caused by climate and by plant succession on the expanding mire. The rates of vegetation change observed in the mirewere similar to those at the initial stages of human impact identified in a previous study. These results reveal significant vegetation changes prior to human presence, due to the interplay of climate variations (temperature and moisture), changes in lake basin form by infilling and intrinsic dynamics of plant succession. Hence, the potential contribution of these factors in vegetation shifts during the period of human presence should not be neglected