Human Settlement and Landscape Anthropization of Remote Oceanic Islands: A Comparison between Rapa Nui (Pacific Ocean) and the Azores (Atlantic Ocean)

Abstract

The flora and vegetation of oceanic islands have been deeply affected by human settlement and further landscape modifications during prehistoric and historical times. The study of these transformations is of interest not only for understanding how current island biotas and ecological communities have been shaped but also for informing biodiversity and ecosystem conservation. This paper compares two oceanic insular entities of disparate geographical, environmental, biological, historical and cultural characteristics-Rapa Nui (Pacific Ocean) and the Azores Islands (Atlantic Ocean)-in terms of human settlement and further landscape anthropization. The similarities and differences between these islands/archipelagos are discussed considering their permanent colonization, the possibility of earlier settlements, the removal of the original forests and the further landscape transformations leading to either full floristic/vegetational degradation (Rapa Nui) or major replacement (Azores). This comparison uses evidence from varied disciplines, notably paleoecology, archaeology, anthropology and history, to obtain a holistic view of the development of the respective socioecological systems from a human ecodynamic perspective. The most relevant issues still to be resolved are identified and some prospects for future research are suggested. The cases of Rapa Nui and Azores Islands may help set a conceptual basis for ocean-wide global comparisons among oceanic islands/archipelagos.

Keywords: Azores Islands; Easter Island; Rapa Nui; anthropization; flora; human settlement; landscape; paleoecology; palynology; vegetation.

Figure 1

Locations of Rapa Nui and the Azores Islands (red dots) in the Pacific and Atlantic oceans, respectively. AF, Africa; AS, Asia; AU, Australia; EU, Europe; NA, North America; SA, South America.

Figure 2

Sketch-map of the Azores archipelago (above) and Rapa Nui (below) at different scales to facilitate representation of the localities mentioned in the text. Rapa Nui (164 km²), of intermediate size between Flores (141 km²) and Faial (173 km²), is also represented in the upper panel (white box) at the same scale of the Azores islands for comparison. Red dots are the coring areas, some of which contain more than one coring site (Al, Alagoinha mire; Az, Lake Azul; Ca, Lake Caldeirão; Cv, Lake Caveiro; Fd, Lake Funda; Gj, Lake Ginjal; Pc, Pico bog; Px, Lake Peixinho; Rs, Lake Rasa). Details are available in Ref. [20] for Rapa Nui and Refs. [14,21,22,23] for the Azores.

Figure 3

Panoramic views of the three craters containing aquatic sediments useful for paleoecological reconstruction in Rapa Nui. Rano is the indigenous name for a crater with a freshwater swamp or a lake. Note the absence of primeval palm forests and the dominance of grasslands. In Rano Aroi, the small tree stands are Eucalyptus (Myrtaceae) plantations introduced from Australia. In Rano Raraku, the darker aquatic vegetation is dominated by the autochthonous sedge Scirpus californicus. Photos: V. Rull.

Figure 4

Google Earth image of the crater Sete Cidades, on Azorean São Miguel Island, and its three lakes (S, Santiago). The red dot in Lake Azul is the coring locality. The darker green patches are planted Cryptomeria (Cupressaceae) forests, introduced from Japan. Modified from Ref. [14].

Figure 5

Simplified pollen diagram from Lake Raraku for roughly the last 2.5 millennia showing the early appearance of Verbena (450 BCE) coinciding with a moderate palm forest decline and grassland expansion. Raw data from Ref. [51].

Figure 6

Four existing hypotheses for the arrival of the sweet potato (Ipomoea batatas) in Rapa Nui. According to the Long-Distance Dispersal hypothesis (LDD), sweet potato seeds could have arrived in Polynesian islands (or directly to Rapa Nui) by birds, winds or rafting, and then transported by humans to Rapa Nui. The back-and-forth (BAF) hypothesis implies the pre-Columbian arrival of Polynesians to South America, from where they could have transported the sweet potato to Polynesia and, from there, to Rapa Nui. The Heyerdahl (HYD) and the Newcomers (NCM) hypotheses propose the direct human transportation of sweet potato from South America. The difference is that the HYD hypothesis contends that the plants were carried by Amerindians before Polynesian settlement (400 CE), whereas the NCM hypothesis postulates that this occurred after Polynesian colonization and does not clarify whether the Amerindians arrived in Rapa Nui by themselves or were carried by Polynesians in their back-and-forth voyages. Modified from Ref. [20].

Figure 7

Summary palynological record from Lake Azul (São Miguel Island) showing the major elements in relation to early settlement and further anthropization trends. CA, Columbian arrival to America. Simplified from Ref. [14].

Figure 8

Arboreal pollen fluctuations in the five sequences analyzed by Raposeiro et al. [23], sorted chronologically. The arrows mark the main forest declines, according to the legend within the box. The gray band is the time interval proposed by the authors for the purported Norse settlement. Redrawn and simplified from the original. ES, early settlement; Port, Portuguese settlement.

Figure 9

(A) The Chilean wine palm Jubaea chilensis growing in La Campana National Park, on the Pacific Chilean coasts (photo courtesy by A. Mieth). (B) Flowers and fruits of sweet potato (Ipomoea batatas) (https://commons.wikimedia.org/wiki/File:Ipomoea_batatas_002.jpg, accessed on 22 May 2023). (C) A modern reproduction of a “manavai” in the Botanical Garden of Hanga Roa, the capital of Rapa Nui (https://commons.wikimedia.org/wiki/File:ToromiroRapanui.jpg, accessed on 22 May 2023).

Figure 10

Trends of palm pollen in the three coherent and continuous sequences retrieved in Rapa Nui for the last millennium. The arrows mark thee main forest declines, according to the legend within the box. Redrawn and simplified from Ref. [78], using raw data from Refs. [51,80,81].

Figure 11

Forest (green areas) retreat and garden (blue and pink dots) proliferation in Rapa Nui during the last millennium, simulated with an agent-based model of human-resource interactions. The green intensity represents the density of palms, ranging from 0 (white) to 7 (dark green) thousand trees per cell. The color of dots is the resource preference, in percentage of trees vs. gardens, ranging from 20% (pink) to 80% (blue). Modified from Ref. [86].

Figure 12

Native and introduced plants on São Miguel Island. (A) Leaves of Laurus azorica from a laurisilva remnant in Ruta do Tronqueiro. (B) Conifer forests of Cryptomeria japonica around Furnas, with a typical understory dominated by Hedychium gardnerianum. (C) Typical landscape from São Miguel Island, with extensive crops and pastures intermingled with Cryptomeria forests (dark green patches) and Hydrangea macrophylla in the foreground. Photos: V. Rull.

Figure 13

The EHLFS (environment-human-landscape feedbacks and synergies) framework as applied to Rapa Nui. E, environment; H, humans; L, landscape. After Ref. [103].

Figure 14

The different states of the EHLFS socioecosystem identified for the prehistory of Rapa Nui. Modified from Ref. [104].

Figure 15

Hydroclimatic fluctuations as reconstructed in three lake sediment records from São Miguel [106], Pico [105] and Flores [107] islands using different proxies. Redrawn and composed from the original sources.

Figure 16

Comparison between the flora and vegetation of Rapa Nui and the Azores in terms of anthropization (data from Table 2). Vegetation types: C, crops; IF, introduced forests; MP, meadows/pastures; N, native; O, others. Anthropization indices: FAI, Floristic Anthropization Index; VAI, Vegetation Anthropization Index.

Figure 17

Chronological synthesis of the events and processes described in former sections for Rapa Nui and the Azores, considering the last 1.5 millennia. The gray bands highlight the phases of coincidence between Rapa Nui and the Azores trends explained in the text. Climatic phases according to Ref. [110]; TA, temperature anomaly with respect to preindustrial values. Climatic phases: L, Little Ice Age; MCA, Medieval Climate Anomaly; MW, Modern Warming. Rapa Nui localities: A, Aroi; K, Kao; R, Raraku. Azores islands: C, Corvo; F, Flores; M, São Miguel; P, Pico; T, Terceira. NA, Native Americans; R/EG, reforestation with alien trees and extensive grazing.

Figure 18

Peopling of the Pacific from East Asian archipelagos. M, Mangareva Island. Modified from Ref. [20] using raw data from Ref. [111].