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Pollen, phytolith and starch analyses of dryland soils from Easter Island show widespread vegetation clearance and Polynesian-introduced crops

by Mark Horrocks last modified 2017-08-25 07:46 AM

Horrocks M, Baisden WT, Flenley J, Feek D, Love CM, Haoa-Cardinali S, González Nualart L, Edmunds Gorman T. 2017. Palynology 41, 339-350.


To investigate the extent of ancient agriculture on Easter Island, this study examines pollen, phytoliths and starch preserved in dryland soils from 15 profiles at 11 sites encompassing a large portion of the island. The identification of four Polynesian-introduced cultigens, at seven of the sites, provides botanical evidence for island-wide horticulture, showing the potential for using dryland soils for the study of ancient agriculture. The study also highlights the value of using combined microfossil analyses of pollen, phytoliths and starch, with different crop taxa variably represented by different types of microfossils.

Phytoliths show better preservation than pollen in Easter Island dryland soils, especially with increasing depth. The Arecaceae and Poaceae are over-represented in Easter Island phytolith spectra, with dicotyledonous trees and shrubs, Cyperaceae and ferns poorly represented. The cultigens identified, cf. Broussonetia papyrifera (paper mulberry), Colocasia esculenta (taro), cf. Ipomoea batatas (sweet potato) and Musa (banana) sp., appear to have differential representation in microfossil spectra in part because of variable production of microfossil types and amounts. This could give a false impression of past species’ importance, with B. papyrifer and C. esculenta in particular, relatively well-represented. The identification of phenolic inclusions represents a new microfossil type for C. esculenta. Large differences in some microfossil proportions at one of the two high-altitude sites compared with low-altitude sites provide evidence for impact of the higher altitude climatic conditions on the suite of crops grown across Easter Island. In addition, the discovery of C. esculenta pollen and cf. B. papyrifera phytoliths at the other high-altitude site, to our knowledge represents the first cultigen evidence at high altitude on the island from outside Rano Aroi crater.


Pollen, phytoliths, starch, dryland soils, deforestation, ancient agriculture, Easter Island.

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