A Continuous Palynological Record of Forest Clearing at Rano Kao (Easter Island, SE Pacific) During the last Millennium: Preliminary Report

Easter Island (Rapa Nui) deforestation has traditionally been viewed as a single event, synchronous in time and space across the island and caused by Polynesian settlers. However, recent studies have challenged this idea introducing the concept of spatio-temporal heterogeneity and suggesting a role for climate change. This paper presents a continuous paleovegetation record of the last millennium (~960 to ~1710 CE), based on palynological analysis of a peat core from Lake Kao. During this time interval, deforestation was gradual, with three main pulses at ~1070 CE, ~1410 CE and ~1600 CE, likely driven by drought, anthropogenic practices (mostly fire) or the coupling of both. Some forest regeneration trends have been documented after the first and the second deforestation pulses. Forests were totally removed by 1600 CE, coinciding with the full permanent human settlement of the Kao area. Comparison with other continuous palynological records available for the last millennium (Aroi marsh and Lake Raraku), confirms that forest clearing was heterogeneous in time and space, rather than synchronous island-wide.

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A Continuous Palynological Record of Forest Clearing at Rano Kao (Easter Island, SE Pacific) During the Last Millennium: Preliminary Report

Quaternary ◽

10.3390/quat2020022 ◽

2019 ◽

Vol 2 (2) ◽

pp. 22 ◽

Cited By ~ 9

Author(s):

Irantzu Seco ◽

Valentí Rull ◽

Encarni Montoya ◽

Núria Cañellas-Boltà ◽

Santiago Giralt ◽

...

Keyword(s):

Forest Regeneration ◽

Easter Island ◽

Time Interval ◽

Last Millennium ◽

Single Event ◽

Rapa Nui ◽

Time And Space ◽

Palynological Analysis ◽

Forest Clearing ◽

Palynological Records

Easter Island (Rapa Nui) deforestation has traditionally been viewed as a single event, synchronous in time and space across the island and caused by Polynesian settlers. However, recent studies have challenged this idea, introducing the concept of spatiotemporal heterogeneity and suggesting a role for climate change. This paper presents a continuous paleovegetation record of the last millennium (~960 to ~1710 CE), based on palynological analysis of a core from Lake Kao. During this time interval, deforestation was gradual, with three main pulses at ~1070 CE, ~1410 CE, and ~1600 CE, likely driven by drought, anthropogenic practices (mostly fire), or the coupling of both. Some forest regeneration trends have been documented after the first and the second deforestation pulses. Forests were totally removed by 1600 CE, coinciding with the full permanent human settlement of the Kao area. Comparison with other continuous palynological records available for the last millennium (Aroi marsh and Lake Raraku) confirms that forest clearing was heterogeneous in time and space, rather than synchronous island-wide.

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First Records and Descriptions of Early Life Stages of Cephalopods from Rapa Nui (Easter Island) and the Nearby Apolo Seamount

Pacific Science ◽

10.2984/73.1.8 ◽

2019 ◽

Vol 73 (1) ◽

pp. 163 ◽

Cited By ~ 1

Author(s):

Sergio A. Carrasco ◽

Erika Meerhoff ◽

Beatriz Yannicelly ◽

Christian M. Ibáñez

Keyword(s):

Early Life ◽

Easter Island ◽

Life Stages ◽

Early Life Stages ◽

Rapa Nui

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FIRST CHARACTERIZATION OF DRILLING PREDATION ON EASTER ISLAND - RAPA NUI

10.1130/abs/2017am-303900 ◽

2017 ◽

Author(s):

Julieta Martinelli ◽

◽

Sandra Gordillo ◽

Maria Carla De Aranzamendi ◽

...

Keyword(s):

Easter Island ◽

Rapa Nui ◽

Drilling Predation

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Daily accumulation rates of marine litter on the shores of Rapa Nui (Easter Island) in the South Pacific Ocean

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2021.112535 ◽

2021 ◽

Vol 169 ◽

pp. 112535

Author(s):

Martin Thiel ◽

Bárbara Barrera Lorca ◽

Luis Bravo ◽

Iván A. Hinojosa ◽

Hugo Zeballos Meneses

Keyword(s):

Pacific Ocean ◽

South Pacific ◽

Easter Island ◽

Accumulation Rates ◽

The South ◽

Rapa Nui ◽

Marine Litter ◽

South Pacific Ocean

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Real-time spatio-temporal event detection on geotagged social media

Journal Of Big Data ◽

10.1186/s40537-021-00482-2 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Yasmeen George ◽

Shanika Karunasekera ◽

Aaron Harwood ◽

Kwan Hui Lim

Keyword(s):

New York ◽

Social Media ◽

Event Detection ◽

Detection System ◽

Time And Space ◽

Social Media Data ◽

Event Time ◽

Spatio Temporal ◽

Geographical Space ◽

Media Data

AbstractA key challenge in mining social media data streams is to identify events which are actively discussed by a group of people in a specific local or global area. Such events are useful for early warning for accident, protest, election or breaking news. However, neither the list of events nor the resolution of both event time and space is fixed or known beforehand. In this work, we propose an online spatio-temporal event detection system using social media that is able to detect events at different time and space resolutions. First, to address the challenge related to the unknown spatial resolution of events, a quad-tree method is exploited in order to split the geographical space into multiscale regions based on the density of social media data. Then, a statistical unsupervised approach is performed that involves Poisson distribution and a smoothing method for highlighting regions with unexpected density of social posts. Further, event duration is precisely estimated by merging events happening in the same region at consecutive time intervals. A post processing stage is introduced to filter out events that are spam, fake or wrong. Finally, we incorporate simple semantics by using social media entities to assess the integrity, and accuracy of detected events. The proposed method is evaluated using different social media datasets: Twitter and Flickr for different cities: Melbourne, London, Paris and New York. To verify the effectiveness of the proposed method, we compare our results with two baseline algorithms based on fixed split of geographical space and clustering method. For performance evaluation, we manually compute recall and precision. We also propose a new quality measure named strength index, which automatically measures how accurate the reported event is.

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Thermal Imaging Shows Submarine Groundwater Discharge Plumes Associated with Ancient Settlements on Rapa Nui (Easter Island, Chile)

Remote Sensing ◽

10.3390/rs13132531 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2531

Author(s):

Robert J. DiNapoli ◽

Carl P. Lipo ◽

Timothy S. de Smet ◽

Terry L. Hunt

Keyword(s):

Fresh Water ◽

Submarine Groundwater Discharge ◽

Groundwater Discharge ◽

Water Sources ◽

Easter Island ◽

Human Populations ◽

Rapa Nui ◽

Hydrologic Processes ◽

Submarine Groundwater ◽

Aerial Systems

Submarine groundwater discharge (SGD) is an important component of many coastal environments and hydrologic processes, providing sources of nutrients to marine ecosystems, and potentially, an important source of fresh water for human populations. Here, we use a combination of unpiloted aerial systems (UAS) thermal infrared (TIR) imaging and salinity measurements to characterize SGD on the remote East Polynesian island of Rapa Nui (Easter Island, Chile). Previous research has shown that coastal freshwater seeps are abundant on Rapa Nui and strongly associated with the locations of ancient settlement sites. We currently lack, however, information on the differential magnitude or quality of these sources of fresh water. Our UAS-based TIR results from four locations on Rapa Nui suggest that locations of variably-sized SGD plumes are associated with many ancient settlement sites on the island and that these water sources are resilient to drought events. These findings support previous work indicating that ancient Rapa Nui communities responded to the inherent and climate-induced hydrological challenges of the island by focusing on these abundant and resilient freshwater sources. Our results highlight the efficacy of using UAS-based TIR for detecting relatively small SGD locations and provide key insights on the potential uses of these water sources for past and current Rapa Nui communities.

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