The Late Quaternary vegetational and climatic history of Easter Island

Abstract

Easter Island occupies an exceptionally isolated position in the south Pacific Ocean. It is entirely volcanic, and is famous for its giant statues. Late Quaternary sediments have been investigated in three craters: Ran0 Raraku, Ran0 Aroi and Ran0 Kao, giving a continuous record over the past 30 Ka. Pollen records indicate that the island was formerly forested. Palynological and sedimentological evidence suggests a Late Pleistocene climate slightly cooler and drier than the present. Deforestation by people occurred mainly between 1200 and 800 yr BP. This may have led to an ecological disaster and to the decline of the megalithic civilization. The depauperation of the present native flora owes more to human activity than to isolation. Journalof Quaternary Science

Paleoecology of Easter Island: Evidence and uncertainties

“…Further pollen analyses of lake sediment cores from three volcanic craters showed a clear replacement of palm-dominated assemblages by grass-dominated ones, which has been interpreted in terms of deforestation by indigenous people Flenley et al, 1991). This generated a series of ecological and anthropological inferences that led to a still standing controversy about the role of humans (either natives or Europeans), the climate and even rats in the island's deforestation (HunterAnderson, 1998;Flenley and Bahn, 2007a, b;Hunt and Lipo, 2007;Flenley et al, 2007).…”

“…It has been suggested that during the late Pleistocene and most of the Holocene, prior to human establishment, the forests were dominated by palms Flenley et al 1991). Coupled stratigraphic variations in the pollen of these forest elements and of grasses allowed these authors to infer a cool and dry phase between 26 and 12 14 C kyr BP, followed by an increase in precipitation and an expansion of forests that persisted throughout the Holocene until the recent deforestation.…”

“…Pollen analyses are mostly based on the sediments inside the three volcanic craters ( Flenley et al, 1991;Butler and Flenley, 2001;Peteet et al, 2003;Gossen, 2007;Azizi and Flenley, 2008;Mann et al, 2008). Microscopic charcoal, a proxy for fire, was reported in Rano Aroi, Rano Raraku 9 and Rano Kao Mann et al, 2008).…”

“…This situation persisted during the last ~37 14 C kyr BP. The general interpretation was that the palm forests deduced from the Rano Raraku section grew on lowlands with their uppermost limit fluctuating around the Rano Aroi elevation (430 m) Flenley et al, 1991). This limit would have been characterized by shrub communities of one or several unknown Asteraceae (Tubuliflorae) and Coprosma (Azizi and Flenley, 2008).…”

Analytical pyrolysis and stable isotope analyses reveal past environmental changes in coralloid speleothems from Easter Island (Chile)

“…For the other speleothem layers, significantly more 13 Easter Island was an unaffected fire ecosystem prior to the first human arrivals that began ca. AD 1200 [80]. Therefore, the presence of a conspicuous light δ 13 C signature for LMWA in the Ca-rich layer could indicate that its formation and development may correspond to the period of the Polynesian settlement and the use of fire that ended with the complete deforestation of the island ca.…”