plants Review Human Settlement and Landscape Anthropization of Remote Oceanic Islands: A Comparison between Rapa Nui (Pacific Ocean) and the Azores (Atlantic Ocean) Valentí Rull 1,2 1 Botanic Institute of Barcelona, Spanish National Research Council (CSIC), Pg. Migdia s/n, 08038 Barcelona, Spain; vrull@csic.es or valenti.rull@icp.cat 2 Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, Bld. ICTA-ICP, C. Columnes s/n, Cerdanyola del Vallès, 08193 Barcelona, Spain 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 dif- ferences 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 re- placement (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. Citation: Rull, V. Human Settlement and Landscape Anthropization of Keywords: Rapa Nui; Easter Island; Azores Islands; human settlement; anthropization; flora; Remote Oceanic Islands: A Comparison between Rapa Nui vegetation; landscape; paleoecology; palynology (Pacific Ocean) and the Azores (Atlantic Ocean). Plants 2023, 12, 2089. https://doi.org/10.3390/ plants12112089 1. Introduction Academic Editor: Giuseppe Fenu Human settlement and landscape anthropization of oceanic islands is a topical issue that is able to provide small-scale models for understanding the effects of anthropogenic Received: 28 April 2023 pressure on ecological dynamics, thus informing biodiversity and ecosystem conserva- Revised: 22 May 2023 tion [1–3]. Anthropogenic extinctions accelerated five centuries ago by the development Accepted: 23 May 2023 of new navigation technologies, which made overseas travel significantly safer and more Published: 24 May 2023 efficient. This allowed European explorers to travel and colonize almost any corner of the planet, which caused irreversible ecological modifications involving deep landscape changes and the extinction of native species [4]. According to the IUCN (International Union for Conservation of Nature) Red List of Threatened Species (www.iucnredlist.org, Copyright: © 2023 by the author. Licensee MDPI, Basel, Switzerland. accessed on 22 May 2023), which is the most reliable source to assess the magnitude and This article is an open access article patterns of recent anthropogenic extinctions, approximately 900 species have gone extinct distributed under the terms and worldwide during the last 500 years as a consequence of human activities, such as over- conditions of the Creative Commons hunting, deforestation, habitat destruction, increased land use, replacement by introduced Attribution (CC BY) license (https:// species or the introduction of alien pathogens. Most of these extinctions occurred in the creativecommons.org/licenses/by/ Americas (30%), Africa (20%) and the Pacific islands (30%), followed by Eurasia, Australia 4.0/). and the Indo-Malayan region (<10% each) [4]. These numbers may be even larger if we Plants 2023, 12, 2089. https://doi.org/10.3390/plants12112089 https://www.mdpi.com/journal/plants Plants 2023, 12, x FOR PEER REVIEW 2 of 33 Plants 2023, 12, 2089 2 of 32 Australia and the Indo-Malayan region (<10% each) [4]. These numbers may be even larger if we consider extinctions predating European contact, mainly on oceanic islands [5], which are especially sensitive to human pressure due to size and connectivity constraints. consider In additionextinctions to direct predating European effects of human contact, actions, mainly islands on oceanic are very islands sensitive to the[5], which are introduction especially sensitive to human pressure due to size and connectivity constraints. of alien invasive species, which may constitute a major and persistent threat for autoch- In addition to direct effects of human thonous biodiversity. actions, islands are very sensitive to the introduction of alien invasive species, Notwhich onlymay constitute extinctions buta major and persistent also profound threatand ecosystem for autochthonous biodiversity. landscape disruptions have Not only extinctions but also profound ecosystem and landscape disruptions have been caused by the prehistoric and historical discovery and colonization of oceanic is- been caused by the prehistoric and historical discovery and colonization of oceanic islands. lands. Terrestrial insular ecosystems have been particularly affected by vegetation disturb- Terrestrial insular ecosystems have been particularly affected by vegetation disturbance ance and the introduction of plants and vertebrates from elsewhere [6–13]. Human im- and the introduction of plants and vertebrates from elsewhere [6–13]. Human impacts pacts on insular vegetation vary depending on the particular features of the target islands on insular vegetation vary depending on the particular features of the target islands and and archipelagos, and the cultural particularities of the colonizer people. In general, orig- archipelagos, and the cultural particularities of the colonizer people. In general, original inal plant communities have been changed to support human life at variable intensities, plant communities have been changed to support human life at variable intensities, ranging ranging from full ecosystem degradation to the total or partial replacement of autochtho- from full ecosystem degradation to the total or partial replacement of autochthonous vege- nous vegetation with species of varied geographical and ecological origins, which can be tation with species of varied geographical and ecological origins, which can be considered considered true (intentional or nonintentional) experiments of ecosystem engineering true (intentional or nonintentional) experiments of ecosystem engineering [14]. The less [14]. Thesituation frequent less frequent situation has been has been the the persistence of persistence preanthropic ofvegetation preanthropic duevegetation to little ordue no to littleimpact. human or no human impact. This review This review compares compares two two cases casesthat thatare arenow nowactively activelydiscussed discussed in in thethe scientific lit- scientific erature and represent contrasting scenarios from geographical, environmental, literature and represent contrasting scenarios from geographical, environmental, biological, biological, historical and historical and cultural cultural perspectives. perspectives. One One case case isis the the subtropical subtropical RapaRapa Nui Nui island island (also (also known as Easter Island) lying in the southeastern Pacific (Figure 1), known as Easter Island) lying in the southeastern Pacific (Figure 1), which was permanently which was perma- nently by settled settled ancientby Polynesians, ancient Polynesians, arrivingarriving from thefromwestthe west between between 800 CE and 8001200 CE andCE. 1200 The CE. The other case is the North Atlantic temperate Azores archipelago, other case is the North Atlantic temperate Azores archipelago, which was permanently which was perma- nently by settled settled by the Portuguese, the Portuguese, navigating navigating westward, westward, in the century. in the mid-15th mid-15thBoth century. Rapa Both Nui Rapa Nui and the Azores were heavily anthropized after settlement and the Azores were heavily anthropized after settlement but in very different ways but in very different due ways to due to thetiming the different different andtiming and the the cultural cultural contrast contrast between thebetween the settlers. respective respective settlers. Emphasis isEmphasis placed on is placed floristiconturnover floristic turnover and vegetation and vegetation change change as major as elements major elements of land- of landscape scape dynamics. dynamics. The similarities The similarities and differences and differences among the among the spatiotemporal spatiotemporal patterns ofpatterns discovery, of discovery, colonization colonization and landscape and landscape transformation transformation of Rapa Nui of Rapa andNuithe and the Azores Azores are dis- are discussed cussed and and compared. compared. The main The main aim is toaim is to provide provide a conceptual a conceptual framework framework that couldthatbecould usefulbe useful for comparing human settlement and anthropization for comparing human settlement and anthropization patterns across ocean-wide and patterns across ocean-wide and global global scales. scales. Figure1.1.Locations Figure LocationsofofRapa RapaNui Nuiand andthe theAzores AzoresIslands Islands(red (reddots) dots)in inthe thePacific Pacificand andAtlantic Atlantic oceans, oceans, respectively. AF, Africa; AS, Asia; AU, Australia; EU, Europe; NA, North America; SA, South Amer- respectively. AF, Africa; AS, Asia; AU, Australia; EU, Europe; NA, North America; SA, South America. ica. The review begins with a brief account of the main current features of the target islands (Section 2), followed by thematic sections subdivided into discovery and settlement (Section 3), deforestation and landscape transformation (Section 4) and the potential influ- ence of climatic changes (Section 5). Finally, a comparison is made between Rapa Nui and Plants 2023, 12, 2089 3 of 32 the Azores on the basis of the information provided in these sections (Section 6), followed by some general conclusions (Section 7) and the most relevant prospects identified for future research (Section 8). 2. Rapa Nui and the Azores The highly isolated and heavily anthropized Rapa Nui island and Azores archipelago have the same geological origin but differ in many environmental and biological features. Both island complexes were originated from hotspot volcanism, the first in the Pleistocene (0.8 million years ago or Ma) [15] and the second between the Late Miocene (8.2 Ma) and the Pleistocene (0.3 Ma), although the exact dates for each individual island are still debated [16–18]. This section concentrates on the main geographical, climatic, floristic and vegetational features that differentiate Rapa Nui from the Azores. The prehistoric and historical ecological variations will be discussed in the following sections within the context of human settlement, further spatiotemporal land-use patterns and environmental change. Emphasis will be placed on palynological reconstructions using lake and swamp sediments situated inside volcanic craters, which are described in this section, in combination with the available historical and archaeological information. Rapa Nui is an excellent example of full island degradation, while the Azores archipelago is a representative case of replacement, that is, the substitution of the original vegetation by newly assembled plant communities composed of species introduced from elsewhere [3]. 2.1. Rapa Nui Rapa Nui is a small (164 km2 ) subtropical southeastern Pacific island (27◦ 060 5200 Lat S; 109◦ 250 3100 Long W) (Figure 2) that has been considered among the most remote inhabited places on Earth. The island has a triangular shape and the maximum elevation is 511 m. The nearest continental coasts are from Chile (South America), situated ~3700 km east and—if the small (0.15 km2 ) islet Mottu Motiro Hiva (Salas y Gómez), situated 400 km E-NE is not considered—the nearest island is Pitcairn (Polynesia), which is located ~2100 km west. Geographically, Rapa Nui is part of eastern Polynesia, but politically it belongs to Chile. Approximately 45% of the Rapa Nui inhabitants consider themselves as Rapanui, that is, descendants of the Polynesian colonizers (the ancient Rapanui), whereas the others are of Chilean origin, although genetic mixing between these groups is common [19]. Plants 2023, 12, 2089 4 of 32 Plants 2023, 12, x FOR PEER REVIEW 4 of 33 Figure2.2. Sketch-map Figure Sketch-map of of the theAzores Azoresarchipelago archipelago(above) (above)and andRapa RapaNui (below) Nui at different (below) scales at different to to scales facilitate representation of the localities mentioned in the text. Rapa Nui (164 km 2), of 2 intermediate facilitate representation of the localities mentioned in the text. Rapa Nui (164 km ), of intermediate size between Flores (141 km2) and Faial (173 km2), is also represented in the upper panel (white box) size between Flores (141 km 2 ) 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 atcontain the same morescale ofone than thecoring Azoressite islands for comparison. (Al, Alagoinha Red mire; Az, dots Lake are Ca, Azul; the Lake coring areas, some Caldeirão; Cv, of Lakewhich Caveiro;more contain Fd, Lake than Funda; one coringGj, Lake Ginjal; site (Al, Pc, Picomire; Alagoinha bog; Px, Az,Lake LakePeixinho; Azul; Ca,Rs, Lake Lake Rasa). Details Caldeirão; Cv, Lake are available Caveiro; in Ref. Fd, Lake [20] for Funda; Gj,Rapa LakeNui and Pc, Ginjal; Refs. [14,21–23] Pico bog; Px,for the Peixinho; Lake Azores. Rs, Lake Rasa). Details are available in Ref. [20] for Rapa Nui and Refs. [14,21–23] for the Azores. The climate is subtropical, with small seasonal temperature variations due to the oce- anicThe influence. The climate is annual average subtropical, temperature with is 21 °Ctemperature small seasonal with a gentlevariations seasonal range due toof the 5–6 °C on average, between 18 °C in the Austral winter (July–September) ◦ and 23–24 oceanic influence. The annual average temperature is 21 C with a gentle seasonal range °C in of the Austral summer (January–March). The total annual rainfall ranges between 5–6 C on average, between 18 C in the Austral winter (July–September) and 23–24 ◦ C in ◦ ◦ 1100 and 1300 the mm. The Austral average summer seasonal variability (January–March). Theranges between total annual minima rainfall of 70–80 ranges mm/month between 1100 and 1300 mm. The average seasonal variability ranges between minima of 70–80 mm/month Plants 2023, 12, 2089 5 of 32 Plants 2023, 12, x FOR PEER REVIEW 5 of 33 (November–December) and maxima of 100–130 mm/month (April–June). Potential evap- (November–December) and maxima of 100–130 mm/month (April–June). Potential evap- otranspiration is approximately 850–950 mm/year; therefore, the climatic hydrological otranspiration is approximately 850–950 mm/year; therefore, the climatic hydrological balance (precipitation-evapotranspiration ratio) is above 1, which means that there is no balance (precipitation-evapotranspiration ratio) is above 1, which means that there is no water waterdeficit deficitduring during◦ a typical year a typical year[24]. [24].Some Somepreliminary preliminary studies studies suggested suggested a temperature a temperature decrease of − 0.85 C and 175 mm per 100 m elevation [25]. Precipitation decrease of −0.85 °C and 175 mm per 100 m elevation [25]. Precipitation seasonality seasonality is is controlled by the interplay between the Sotuh Pacific Anticyclone (SPA), controlled by the interplay between the Sotuh Pacific Anticyclone (SPA), the South Pacificthe South Pacific Convergence Convergence Zone (SPCZ)and Zone (SPCZ) andwesterly westerly storms storms tracts tracts [26]. [26]. The The interannual interannual variability variability is isrelatively relatively high, high, especially especially for for precipitation, precipitation, andinfluence and the the influence of the of El the NiñoElSouthern Niño Southern Os- Oscillation (ENSO) cillation (ENSO) on on these these trends trends is currently is currently debated debated [27–29].[27–29]. In Rapa InNui, Rapa theNui, the com- combina- bination of a crater and a freshwater wetland is known as “rano”, and tion of a crater and a freshwater wetland is known as “rano”, and the most studied ranos the most studied ranos from a palynological point of view are the Aroi fen and the lakes from a palynological point of view are the Aroi fen and the lakes Kao and Raraku (Figures Kao and Raraku (Figures 2 and 3). 2 and 3). Figure3.3.Panoramic Figure Panoramic views views of of the the three three craters craters containing containing aquatic aquaticsediments sedimentsuseful usefulfor forpaleoecolog- paleoecological ical reconstruction in Rapa Nui. Rano is the indigenous name for a crater with a freshwater swamp reconstruction in Rapa Nui. Rano is the indigenous name for a crater with a freshwater swamp or a or a lake. Note the absence of primeval palm forests and the dominance of grasslands. In Rano Aroi, lake. Notetree the small the stands absence ofEucalyptus are primeval palm forestsplantations (Myrtaceae) and the dominance introducedoffrom grasslands. InIn Australia. Rano Rano Aroi, Ra- the small raku,tree the stands darker are Eucalyptus aquatic (Myrtaceae) vegetation plantations is dominated by the introduced fromsedge autochthonous Australia. ScirpusIncalifornicus. Rano Raraku, Photos: the darkerV. aquatic Rull. vegetation is dominated by the autochthonous sedge Scirpus californicus. Photos: V. Rull. According to the most recent update [30], the extant wild vascular flora of Rapa Nui is composed According of to 201the species most (21 ferns, recent 1 gimnosperm update and 179 [30], the extant angiosperms), wild of which vascular flora of Rapaonly Nui is 50 (25%) are composed of native and the 201 species (21remaining 151 (75%) areand ferns, 1 gimnosperm introduced. Half of the native 179 angiosperms), species of which only 50 (21 ferns (25%) are and 4 angiosperms) native are considered and the remaining 151 (75%)to be areendemic. Regarding introduced. vegetation Half of the nativetypes, species no ferns (21 tracesand of native palm forests 4 angiosperms) areremain on thetoisland, considered which isRegarding be endemic. mostly covered by grass vegetation types, meadows no traces of(74%), native with palma few patches forests of planted remain on the forests island,(6%) whichandis shrublands (2%) and mostly covered a by grass meadows (74%), with a few patches of planted forests (6%) and shrublands (2%) and a few Plants 2023, 12, 2089 6 of 32 Plants 2023, 12, x FOR PEER REVIEW 6 of 33 cultivated areas (4%). The remaining 14% of the surface corresponds to urban areas and uncovered/barren lands [31]. few cultivated areas (4%). The remaining 14% of the surface corresponds to urban areas 2.2. The Azores and uncovered/barren lands [31]. The North Atlantic temperate archipelago of the Azores Islands (37◦ –40◦ Lat N; 25◦ –31◦ Long 2.2. TheW)Azores is situated ~1400 km west of Portugal (Europe), with Madeira (~900 km SE) as the nearest island. The North Thetemperate Atlantic archipelago is composed archipelago of three of the Azores groups Islands –40° (37°of islands: 25°–Western Lat N; the Group 31° Long (Corvo W) is and Flores), situated ~1400thekmCentral west of Group Portugal (Faial, Graciosa, (Europe), São Jorge with Madeira and (~900 kmTerceira) SE) and the Eastern as the nearestGroup island.(Santa Marta and The archipelago is São Miguel) composed (Figure of three 2). The groups total surface of islands: is 2351 km2 the Western Group and the(Corvo and Flores), nine major islands the Central Group mentioned range(Faial, 17 km2 São fromGraciosa, Jorge to (Corvo) and745 km2 (São Terceira) and Miguel). the Eastern The maximum Group (Santa Marta elevations and São Miguel) are between (FigureMaria) 587 m (Santa 2). The and total2350 surface is 2351 km m (Pico). The2 Azores and the nine major islands mentioned range from 17 km 2 (Corvo) to 745 km2 (São Miguel). are part of the biogeographical region known as Macaronesia, together with the subtropical The maximum Madeira elevations and Canary are between Islands, and the587 m (Santa tropical Maria) Cape andIslands, Verde 2350 m (Pico). The Azores all of which are closer to are part of the biogeographical region known as Macaronesia, together with the subtrop- the African coasts. Politically, the Azores are an autonomous region of Portugal and the ical Madeira and Canary Islands, and the tropical Cape Verde Islands, all of which are society is typically Portuguese. closer to the African coasts. Politically, the Azores are an autonomous region of Portugal Thesociety and the Azorean climatePortuguese. is typically is temperate oceanic and is characterized by mild temperatures with The small annual variations, Azorean climate is temperate a strong seasonal oceanic precipitationbyregime and is characterized and significant in- mild temperatures terannual variability. At lower elevations, the average annual temperatures with small annual variations, a strong seasonal precipitation regime and significant inter- range from 16.7 ◦ C (Terceira) to 17.5 ◦ C (Corvo and Santa Maria) and the total annual precipitation annual variability. At lower elevations, the average annual temperatures range from 16.7 is°Cbetween (Terceira)775to mm 17.5 (Santa °C (Corvo Maria) and and Santa1716 Maria)mm and(Flores). the totalHowever, at higher elevations, annual precipitation is between 775 mm (Santa Maria) and 1716 mm ◦ (Flores). However, average annual temperatures may decrease to 10.8 C (900 m) and 6.2 C (2000 m), and total at ◦ higher elevations, averageprecipitation annual annual temperatures may bemay overdecrease 4000 mm to 10.8 [32].°C (900 m) and Maximum 6.2 °C (2000 occurs precipitation m), andbetween total annual precipitation may be over 4000 mm November and January and minimum values are recorded between June and[32]. Maximum precipitation occurs August, a between November and January and minimum values are recorded seasonality that is controlled by the displacement of the Azores anticylone [33,34]. between June and The August, a seasonality that is controlled by the displacement of the Azores anticylone interannual temperature and precipitation regimes are influenced mainly by the North [33,34]. The interannual temperature and precipitation regimes are influenced mainly by Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) [34,35]. The the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO) palynological records of therecords [34,35]. The palynological Azoresofarchipelago the Azoresare from Corvo archipelago are(Lake fromCaldeirão) Corvo (Lake and Flores (lakes Funda Caldeirão) andand Rasa, Flores andFunda (lakes Alagoinha mire) and Rasa, andinAlagoinha the Western Group, mire) in thePico Western(lakes Caveiro and Group, Peixinho, Pico (lakesand Picoand Caveiro bog) and Terceira Peixinho, and Pico(Lake bog)Ginjal), in the(Lake and Terceira central Group, Ginjal), in theand São Miguel central (Lake Group, Azul) in the and São Eastern Miguel (LakeGroup Azul) in(Figures 2 and the Eastern 4). (Figures 2 and 4). Group 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]. Plants 2023, 12, 2089 7 of 32 Regarding floristic composition, 1110 species of vascular plants have been reported outside cultivation, of which 811 (73%) are considered part of the true Azorean flora, which includes all permanent and self-sustaining populations, whereas the remaining 299 (27%) are considered non established [36]. Among the true floristic elements, only 24% (197 species) are indigenous and 76% (562 species) are introduced (69% naturalized and 6% established). Among the 197 indigenous taxa, 66 (30%) are endemic. Regarding vegetation, the most extensive type are pastures (42% of the total surface), followed by forests (35%) and crops (14%); the remaining surface corresponds to urban (5%) and barren areas (4%) [37]. Native vegetation represents 13% of the total and only 2.5% corresponds to primeval forests [32]. 3. Discovery and Settlement In this paper, a differentiation is made among terms and concepts such as discovery, settlement and contact, along with their different types, as shown in Table 1. Historical records report the arrival of the first Portuguese colonizers to Azores (Santa Maria and São Miguel islands) in 1432 CE and consider 1449 CE as the official settlement date [38]. However, the archipelago had already been discovered, as some of its islands already appear in maps from 1339 CE under the names of Corvinaris (Corvo) and Caprara (São Miguel) [39]. No indisputable archaeological evidence exists of former settlements. The situation is different in Rapa Nui, where abundant and well-dated archaeological and anthropological evidence exists for permanent settlement of the Polynesian Rapanui culture since at least 1200-1300 CE [40,41]. In this case, the first historical records date from 1722, when the island was visited by Dutch explorers, which is known as the European contact, and was the beginning of the end of the prehistoric Rapanui culture [42,43]. The possibility of human settlement before the dates documented by historical and archaeological evidence has been suggested for both Azores and Rapa Nui. This possibility is called here the early settlement hypothesis. Table 1. Terminology used in this paper. Adapted and expanded from Ref. [20]. Term Meaning Types Meaning Evidence (Examples) Finding the island for Sighting See the island in the distance Discovery Historical (maps, logbooks) the first time Landing Physically arrive on the island Ephemeral Temporary occupancy Historical (written documents); Recurrent occupancy archaeological (housing, Intermittent and abandonment monuments, art); paleoecological Physical occupancy of Settlement and archaeobotanical the island Permanent Long-lasting occupancy (biomarkers, cultivated plants, Local Restricted to one or a few sites fire); anthropological (DNA) Full Extensive to the whole island Stopover with or without Historical (written documents); Visit Arrival of a new cultural incidence archaeological (housing, Contact culture to an already Admixture Cultural/biological merging monuments, art); settled island anthropological (fossil skeletons, Violent occupation or slavery Invasion DNA, ethnography) practices 3.1. Rapa Nui The first paleoecological (palynological) studies on Rapa Nui sediments reported major island deforestation from ~800 CE, which was linked to the arrival of Polynesian colonizers [44,45]. Several dating problems related to the occurrence of stratigraphic gaps and sediment mixing cast doubts on the reliability of this chronology [46]. Mann et al. [47] suggested that Rapa Nui could have been settled, perhaps transiently or intermittently, by Polynesian hunter-gatherers several centuries before the 1200 CE Rapanui establishment, The first paleoecological (palynological) studies on Rapa Nui sediments reported ma- jor island deforestation from ~800 CE, which was linked to the arrival of Polynesian colo- nizers [44,45]. Several dating problems related to the occurrence of stratigraphic gaps and sediment mixing cast doubts on the reliability of this chronology [46]. Mann et al. [47] suggested that Rapa Nui could have been settled, perhaps transiently or intermittently, Plants 2023, 12, 2089 8 of 32 by Polynesian hunter-gatherers several centuries before the 1200 CE Rapanui establish- ment, when forests were cleared, but these authors did not provide evidence for this as- sumption. Later, Mieth & Bork [48], using edaphic evidence of landscape modification, when forests were cleared, but these authors did not provide evidence for this assumption. proposed an earlier phase of low-impact human occupation, beginning at 800 CE, before Later, Mieth & Bork [48], using edaphic evidence of landscape modification, proposed an the 1200 CE deforestation. This low-impact early settlement phase, ranging between ap- earlier phase of low-impact human occupation, beginning at 800 CE, before the 1200 CE de- proximately forestation. 800 This CE and 1200 low-impact earlyCE, is present settlement in many phase, ranging Rapa Nui chronologies between approximatelyusing 800 CE a vari- ety of archaeological and paleoenvironmental evidence [20,49,50]. and 1200 CE, is present in many Rapa Nui chronologies using a variety of archaeological The recent findingevidence and paleoenvironmental of paleoecological [20,49,50]. evidence compatible with human presence in sediments older than 800 CE has The recent finding of paleoecological suggested that the evidence first settlement compatible with human couldpresence have occurred in earlier. Especially sediments older thansignificant 800 CE hasissuggested the finding of the that pollen first from Verbena settlement litoralis could have(Verbenaceae), occurred a plantEspecially earlier. of tropicalsignificant Americanisorigin that isofpresently the finding pollen from widespread all over Verbena litoralis the island, ina Lake (Verbenaceae), plant Rarakuof tropical American sediments. origin that is presently This anthropochorous widespread (dispersed all overplant, by humans) the island, locally in Lake known as Raraku sediments. This anthropochorous (dispersed by humans) plant, “puringa” and characteristic of agricultural and ruderal disturbed sites, was previously locally known as “puringa” and characteristic of agricultural and ruderal disturbed sites, considered to have been introduced on the island in post-Columbian times (1492 CE), but was previously considered is actuallytopresent have been introduced in the on the island Raraku sediments, inina post-Columbian continuous and times (1492fashion, abundant CE), but from is450 actually BCE to present in the Raraku the present [51]. Thesediments, appearance in a of continuous V. litoralisand abundant pollen fashion, coincided with from the first 450 BCE to the present [51]. The appearance of V. litoralis pollen coincided with the first fires fires and a forest decline coeval with a grassland expansion (Figure 5), which was inter- and a forest decline coeval with a grassland expansion (Figure 5), which was interpreted in preted in terms of anthropogenic disturbance, probably by small human groups of un- terms of anthropogenic disturbance, probably by small human groups of unknown origin, asknown formerlyorigin, as formerly suggested by Mann suggested et al. [47]. by Mann Also et al. [47]. significant is theAlso significant presence of pollenis from the presence the of pollen from the Iridaceae Sisyringium (probably S. michrantum) Iridaceae Sisyringium (probably S. michrantum) between 410 CE and 630 CE in the sediments between 410 CE and 630 ofCEtheinAroi the bog. sediments of the This plant Aroiofbog. is also This plant American originisandalsois of American now naturalizedorigin and is now elsewhere. naturalized Other potentialelsewhere. indications Other potential of human indications disturbance are theof forest human disturbance declines are thebyforest documented declines 50–100 CEdocumented in Lake Kao [52] by 50 and–100 CE in Lake by 1730-910 CE Kao [52]Raraku in Lake and by[53]. 1730-910 However,CE intheLake lack Raraku of [53]. However, specific the lack anthropogenic of specific markers anthropogenic prevents markers prevents sound assessment. sound assessment. 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]. The sweet potato (Ipomoea batatas; Convolvulaceae), locally called “kumara”, is known to have been a fundamental food for ancient Polynesian societies, especially for Rapa Nui, where it has been suggested that the flourishment of the ancient Rapanui society would have not been possible without this plant [54]. The sweet potato was domesticated in tropical America >6000 years ago [55], and the oldest Polynesian records date to 1000 CE (almost 500 years before the Columbian arrival to America, in 1492 CE), as documented by carbonized fragments found in the Cook Islands [56]. On Rapa Nui, carbonized frag- The sweet potato (Ipomoea batatas; Convolvulaceae), locally called “kumara”, is known to have been a fundamental food for ancient Polynesian societies, especially for Rapa Nui, where it has been suggested that the flourishment of the ancient Rapanui soci- ety would have not been possible without this plant [54]. The sweet potato was domesti- Plants 2023, 12, 2089 cated in tropical America >6000 years ago [55], and the oldest Polynesian records date to 9 of 32 1000 CE (almost 500 years before the Columbian arrival to America, in 1492 CE), as docu- mented by carbonized fragments found in the Cook Islands [56]. On Rapa Nui, carbonized fragments ments or starch or starch grainsgrains of kumara of kumara have found have been been found on sediments on sediments and archaeological and archaeological sites since 1300 – since 1300–1400 CE, approximately 3–4 centuries before European contactcontact sites 1400 CE, approximately 3–4 centuries before European [53,57].[53,57]. Four Four hypotheses hypotheses havesuggested have been been suggested to explain to explain thislong-distance this fact: fact: long-distance seed dispersal, seed dispersal, back- back-and-forth and-forth traveling traveling to America, to America, the American the American originorigin of theoffirst theRapa first Rapa Nui settlers, Nui settlers, and andarrival the the arrival of American of American people people between between Polynesian Polynesian colonization colonization and and European European con- contact tact (Figure (Figure 6). After 6). After analyzing analyzing the multidisciplinary the multidisciplinary evidence evidence supporting supporting eacheach of these of these hy- hypotheses, Rull [58] concluded that all options remain open, which has potheses, Rull [58] concluded that all options remain open, which has been supported by been supported by more more recent recent investigations investigations [59–63]. [59–63]. Figure6.6.Four Figure Fourexisting existinghypotheses hypothesesfor forthe thearrival arrivalof ofthe thesweet sweetpotato potato(Ipomoea (Ipomoeabatatas) batatas)in inRapa RapaNui.Nui. According to the Long-Distance Dispersal hypothesis (LDD), sweet potato seeds could have arrived 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 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 humans to Rapa Polynesians Nui. America, to South The back-and-forth from where(BAF) hypothesis they could implies the the have transported pre-Columbian sweet potato arrival of to Polyne- Polynesians to South America, from where they could have transported the sweet sia and, from there, to Rapa Nui. The Heyerdahl (HYD) and the Newcomers (NCM) hypotheses potato to Polynesia and, from the propose there, to Rapa direct human Nui. The Heyerdahl transportation of (HYD) and the sweet potato Newcomers from (NCM) The South America. hypotheses propose difference is that thedirect the HYD hypothesis contends that human transportation ofthe plants sweet werefrom potato carried by Amerindians South America. The before Polynesian difference is thatsettle- the ment (400 CE), whereas the NCM hypothesis postulates that this occurred after Polynesian HYD hypothesis contends that the plants were carried by Amerindians before Polynesian settlement coloni- zation (400 CE),and does not whereas the clarify whether thepostulates NCM hypothesis Amerindians arrived that this in Rapa occurred Nui after by themselves Polynesian or were colonization carried by Polynesians in their back-and-forth voyages. Modified from Ref. [20]. 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]. Interestingly, pollen and macrofossil evidence from cultivated plants support a po- tential early colonization Interestingly, of Rapa pollen and Nui pointing macrofossil toward evidence from a pre-Columbian cultivated plants American supportorigin, a po- whichearly tential strongly suggestsofpre-European colonization contacttoward Rapa Nui pointing between the island andAmerican a pre-Columbian America, origin, as pro- posedstrongly which for the Polynesian region in general suggests pre-European [64]. contact This seems between to revive the island andthe former as America, Heyer- pro- dahl’sfor posed hypothesis [65] of the Polynesian an initial region settlement in general by Amerindian [64]. This seems to revive (or the Native American) former peo- Heyerdahl’s ples followed hypothesis [65]by a Polynesian of an invasion. initial settlement by Although Amerindian this(orhypothesis was declared Native American) dead peoples fol-a lowed by a Polynesian invasion. Although this hypothesis was declared dead a couple of decades ago after a thorough analysis of the available multidisciplinary evidence [66], the latest molecular analyses of human genomes suggest the presence of Amerindian people on Rapa Nui prior to Polynesian settlement [67,68]. Unfortunately, no archaeological evi- dence is available for these early settlers, which could have been removed by natural or anthropogenic agents (evidence clearing [20]) or hidden by recent sea-level rise [69,70]. It is possible that early settlements were local and ephemeral/intermittent, and the archaeo- logical evidence left was scattered and easy to remove. Thus, the only signs of early human settlement would remain fossilized in the unaltered sediments of lakes and bogs. Further research on molecular biomarkers would be of much help to resolve this conundrum. Plants 2023, 12, 2089 10 of 32 3.2. Azores In the Azores Islands, any eventual settlement before Portuguese colonization in the mid-15th century may be considered an early settlement. As stated above, there is no archaeological evidence of this fact but paleoecological records are, once more, the most informative in this sense. The first palynological records documented significant vegetation changes, notably deforestation, just after Portuguese settlement, in the Corvo, Flores (Western group; WG) and Pico (Central Group; CG) islands [21,22]. But this will be discussed in detail in the next section, here the focus is on the possibility of earlier settlements. The first Azorean record of pre-Portuguese human impact was from São Miguel Island (Eastern group; EG) and consisted on palynological evidence for the decline of Juniperus, one of the main elements of the pristine forests, coeval with the first fires and the appearance of cereal pollen, notably from rye (Secale), along with spores from coprophilous fungi (notably Sporormiella) growing in the dung of herbivores [14] (Figure 7). These animals were absent from the archipelago, as the only mammals inhabiting the Azores before human settlement were bats [39]. This was considered to be sound evidence for local-scale deforestation around the coring site (Lake Azul), cereal cultivation and animal husbandry, and occurred by 1290 CE, approximately one century and a half prior to the official Portuguese settlement of the islands and half a century before their historical Plants 2023, 12, x FOR PEER REVIEW 11 of 33 discovery, as documented in navigation charts. The geographical and cultural origins of potential early settlers remain unknown. Figure7.7.Summary Figure Summarypalynological palynologicalrecord recordfrom fromLake LakeAzul Azul(São (SãoMiguel MiguelIsland) Island)showing showingthe themajor major elements in relation to early settlement and further anthropization trends. CA, Columbian arrival elements in relation to early settlement and further anthropization trends. CA, Columbian arrival to to America. Simplified from Ref. [14]. America. Simplified from Ref. [14]. Morerecently, More recently,itithas hasbeen beenproposed proposedthatthatthe thearchipelago archipelagowould wouldhavehavebeen beensettled settled much earlier, by the early Middle Ages (700 – 850 CE), at least 6 – 7.5 centuries much earlier, by the early Middle Ages (700–850 CE), at least 6–7.5 centuries before the before the Portuguese, and suggested that the first settlers would have been the Norse, with Portuguese, and suggested that the first settlers would have been the Norse, with the aid of the aid of anomalous northeasterly winds and warmer temperatures [23]. These conclusions were based on new multiproxy analyses of lake sediments from five islands, two of the WG (Corvo, Flores), two of the CG (Pico, Terceira) and one from the EG (São Miguel), includ- ing the abovementioned Lake Azul record, which suggested the authors widespread and permanent transformations of terrestrial and aquatic ecosystems, including deforestation Plants 2023, 12, 2089 11 of 32 anomalous northeasterly winds and warmer temperatures [23]. These conclusions were based on new multiproxy analyses of lake sediments from five islands, two of the WG (Corvo, Flores), two of the CG (Pico, Terceira) and one from the EG (São Miguel), including the abovementioned Lake Azul record, which suggested the authors widespread and permanent transformations of terrestrial and aquatic ecosystems, including deforestation by logging and fire, and livestock grazing. As a consequence, the landscape would have already been deeply and extensively modified before Portuguese settlement [23]. This idea has been considered unlikely by other authors, who believed that the evidence is insufficient and the conclusions premature [71]. These critics emphasize that if the landscape would had been significantly anthropized in the Middle Ages, this should have been noted by the Portuguese colonizers, whose descriptions of natural systems, especially the flora and vegetation, were very detailed and accurate. In addition, a number of methodological and interpretation points were raised, including dating issues and alternative explanations for the occurrence of pollen from cultivated plants, charcoal and fecal lipids [71]. It is not the possibility of earlier human presence that is questioned but the fact that the Azores were already significantly and extensively anthropized prior to Portuguese arrival. These critiques were replied by the authors of the Norse hypothesis [72], although the new explanations provided did not satisfactorily address all points raised by the critics (Elias, pers. comm.) and left the debate open. The Norse hypothesis has also been questioned by Rull [73], who emphasized the unavailability of detailed raw data and the inaccuracy of some representations, as well as the lack of sufficient early Medieval records. Indeed, the authors of the Norse hypothesis presented their results in a synthetic fashion with no access to detailed analyses. In the case of landscape anthropization, a major point of the debate, pollen records are critical evidence, but only summary diagrams are provided, which hinders detailed reconstructions of vegetation change and comparison with other similar records. Particularly significant is the lack of differentiation within forest categories, especially between native and introduced forests. In Lake Azul, this separation is possible because the detailed pollen diagram was published some years ago [14], but in others, this cannot be evaluated with the information provided. Another issue is the inaccuracy of some representations, including cereal pollen, one of the most important proxies for anthropogenic impact. Indeed, in the same Lake Azul record, Secale pollen is represented only in the 13th century in the form of scattered occurrences [23], but it truly occurred between the 13th and 19th centuries [14] (Figure 7). Additionally, other cereal pollen, including maize (Zea) and wheat (Triticum), were omitted [23], but were actually present in a continuous and consistent fashion from the 13th century to the present [14]. Due to the lack of raw data, it is not possible to know whether the same occurs in other records and proxies. Finally, of the five records utilized by the proponents of the Norse hypothesis [23], only two from Corvo (WG) and Pico (CG) extended back to 600 CE, whereas one (Flores; WG) began in 900–1000 CE and the other two, from São Miguel (EG) and Terceira (CG), started in 1300–1400 CE (Figure 8). Whatever the evidence for human settlement, these records are in- sufficient to demonstrate that the whole archipelago was settled before 900 CE, as only two records from central and western islands are available before that date. Additionally, the only significant forest decline recorded before 900 CE corresponds to one of these records (Pico; CG), but its attribution to human activities is doubtful, since fire would have been linked with volcanic activity, as documented by a tephra layer, and both coprophilous fungi and fecal lipids present in humans and other omnivores were absent until the 11th–12th centuries. Therefore, the only potential evidence of human impact before those dates re- mains debatable, and the only widespread evidence for human presence did not occur until the 13–14th centuries, as previously proposed by Rull et al. [14]. Publishing the detailed data for all proxies, improving representation and retrieving new records encompassing the whole Middle Ages is strongly suggested to evaluate the possibility of early settlements before those dates. What seems truly difficult to prove is that these potential earlier settlers significantly anthropized the landscape across the whole archipelago, as this should have Plants 2023, 12, 2089 12 of 32 Plants 2023, 12, x FOR PEER REVIEW 13 of 33 been noticed by Portuguese settlers and is not recorded in the available palynological studies, which are extensive to the whole archipelago. Figure8.8.Arboreal Figure Arborealpollen pollenfluctuations fluctuationsininthe thefive fivesequences sequencesanalyzed analyzedby byRaposeiro Raposeiroetetal. al.[23], [23],sorted sorted chronologically. The arrows mark the main forest declines, according to the legend within the box. 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. 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. Redrawn and simplified from the original. ES, early settlement; Port, Portuguese settlement. 4.4.Deforestation Deforestationand andLandscape LandscapeTransformation Transformation Inthis In this case, case, several several types types ofof forest forestclearing clearingwill willbebeconsidered considered according according to to their ex- their tent, intensity and mode. The term deforestation will be reserved for full extent, intensity and mode. The term deforestation will be reserved for full forest removal, forest removal, whereaspartial whereas partialforest forestclearing clearingwill willbe bereferred referredtotoasasforest forestdecline. decline.Forest Forestdeclines declineswill willbe be considered major if the pollen from forest trees decreases above 50% considered major if the pollen from forest trees decreases above 50% with respect to the with respect to the initialabundance, initial abundance,moderate moderatewhenwhenthe thedecrease decreaseisisbetween between20% 20%and and50% 50%andandminor minorififthe the declineisis20% decline 20%ororless. less.In Inaddition, addition,deforestation deforestationmaymaybe bethe theresult resultof ofaasingle singleforest forestclearing clearing event(catastrophic event (catastrophicdeforestation) deforestation)or orthe theaccumulation accumulationof ofminor minorto tomajor majorforest forestdeclines declines (progressive deforestation), in which case, stepwise forest declines are called (progressive deforestation), in which case, stepwise forest declines are called forest decline forest decline pulsesor pulses orevents. events.All Allthe theabove aboveforest forestclearing clearingpatterns patternsmaymayoccur occuratatlocal local(single-site) (single-site)or or general(island-wide) general (island-wide)ambits. ambits. 4.1. 4.1.Rapa RapaNui Nui According Accordingtotothe available the palynological available palynological studies—historical studies—historical documents did not documents did appear not ap- until pearEuropean contact until European (1722 (1722 contact CE), when the island CE), when had already the island been deforested — been deforested—the had already pris- the pristine Rapa Nui forests were largely dominated by an unknown, likely extinct, palm species that is only known by its fruits very similar to the Chilean wine palm (Jubaea chilen- sis) (Figure 9) and has tentatively named as Paschalococcos disperta [74,75]. Other minor Plants 2023, 12, 2089 13 of 32 Plants 2023, 12, x FOR PEER REVIEW 14 of 33 tine Rapa Nui forests were largely dominated by an unknown, likely extinct, palm species that is only known by its fruits very similar to the Chilean wine palm (Jubaea chilensis) (Figure 9) and has tentatively named as Paschalococcos disperta [74,75]. Other minor for- forest est components components werewere Sophora Sophora (Fabaceae), (Fabaceae), Triumfetta Triumfetta (Tiliaceae), (Tiliaceae), Macaranga Macaranga andAcalypha and Acalypha (Euphorbiaceae),Coprosma (Euphorbiaceae), Coprosma(Rubiaceae), (Rubiaceae),along alongwithwithseveral severalunidentified unidentifiedAstraceae, Astraceae,Myr- Myr- taceaeand taceae andMoraceae/Urticaceae Moraceae/Urticaceae[45]. [45].These Theseprimeval primevaldense densepalm palmforests forests(approximately (approximately 16–20million 16–20 millionpalm palmtrees treesininbarely barely160 160km km2 , 2or , or100–120 100–120palms palmsperperkm km2 )2)would wouldhave havecovered covered 70 – 80% of the island [76,77]. 70–80% of the island [76,77]. Figure9.9.(A) Figure (A)The The Chilean Chilean wine wine palm palm Jubaea Jubaea chilensis chilensisgrowing growingininLa LaCampana CampanaNational Park, National onon Park, the Pacific Chilean coasts (photo courtesy by A. Mieth). (B) Flowers and fruits of sweet potato (Ipomoea the Pacific Chilean coasts (photo courtesy by A. Mieth). (B) Flowers and fruits of sweet potato batatas) (https://commons.wikimedia.org/wiki/File:Ipomoea_batatas_002.jpg, accessed on 22 (Ipomoea batatas) (https://commons.wikimedia.org/wiki/File:Ipomoea_batatas_002.jpg, accessed on May 2023). (C) A modern reproduction of a “manavai” in the Botanical Garden of Hanga Roa, the 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, ac- capital of Rapa Nui (https://commons.wikimedia.org/wiki/File:ToromiroRapanui.jpg, accessed on cessed on 22 May 2023). 22 May 2023). The classical literature on Rapa Nui usually considers a single type of forest removal, The classical literature on Rapa Nui usually considers a single type of forest removal, island-wide deforestation. However, the most recent studies have demonstrated that this island-wide deforestation. However, the most recent studies have demonstrated that this process was heterogeneous in both space and time and that island-wide deforestation was process was heterogeneous in both space and time and that island-wide deforestation was actuallythe actually theresult result ofof thethe accumulation accumulation of local of local minor minor to major to major forest forest declines declines and and defor- deforesta- estation events [78]. As mentioned above, the first forest declines documented tion events [78]. As mentioned above, the first forest declines documented occurred long occurred long before before the Polynesian the Polynesian settlement, settlement, but onlybuttwoonly could twobecould linkedbetolinked to the of the presence presence humansof humansofbecause because of the occurrence the occurrence of pollen fromof pollen from anthropogenic anthropogenic plants of plants of American American origin. The origin. The first of these minor forest declines occurred in Raraku by 450 first of these minor forest declines occurred in Raraku by 450 BCE [51], and the second BCE [51], and the second took placetook place in Aroi byin410–630 Aroi byCE 410–630 [79]. AllCE [79].forest other All other forest clearing clearing events events occurred occurred during the development of the Rapanui culture, initiated with Polynesian settlement, and occurredand during the development of the Rapanui culture, initiated with Polynesian settlement, in occurred in(Kao, progressive progressive Raraku)(Kao, Raraku) orfashion or catastrophic catastrophic (Aroi).fashion (Aroi). The first and last forest clearing events were recorded at Kao (Figure 10). The first of the events was a major local decline (1000–1050 CE), followed by a recovery and a moder- ate forest decline (1350 CE) that almost totally removed the Kao forests, a further modest recovery and a final minor but full deforestation event (1600 CE) [80]. The deforestation Plants 2023, 12, 2089 14 of 32 Plants 2023, 12, x FOR PEER REVIEW 15 of 3 The first and last forest clearing events were recorded at Kao (Figure 10). The first of the events was a major local decline (1000–1050 CE), followed by a recovery and a moderate forest decline (1350 CE) that almost totally removed the Kao forests, a further modest of Raraku took place in two steps, a major forest decline in 1200 CE and a minor but de recovery and a final minor but full deforestation event (1600 CE) [80]. The deforestation offinitive Rarakuforest took decline place in at two1450 CE a[51]. steps, majorTheforest onlydecline catastrophic in 1200deforestation CE and a minor wasbutrecorded a Aroi, where definitive forestforests declineexperienced at 1450 CE [51].a sustained The only increase catastrophicbetween approximately deforestation 1300 CE an was recorded 1520 CE, when an abrupt deforestation event began that fully removed at Aroi, where forests experienced a sustained increase between approximately 1300 CE these forests. In a cases, and 1520except for the CE, when first Raraku an abrupt event (1200 deforestation CE), forest event began declines that fully removedcoincided with charcoa these forests. Inpeaks all cases, except that indicating for the firefirst was Raraku a usualevent (1200for method CE), forestclearing. forest declines Spores coincided with of coprophilou charcoal fungi were only recorded in association with the last Kao event (1600 CE) andof peaks indicating that fire was a usual method for forest clearing. Spores after, sug coprophilous fungi were only recorded in association with the last Kao event (1600 CE) gesting that significant grazing practices occurred only since those dates, which marke and after, suggesting that significant grazing practices occurred only since those dates, the full island-wide deforestation [78]. No coincidences were observed in the chronolog which marked the full island-wide deforestation [78]. No coincidences were observed in or chronology the in the intensity of forest or in the declines intensity across of forest the across declines island,thewhich highlights island, the significant which highlights the spa tiotemporal significant heterogeneity spatiotemporal of Rapa Nui heterogeneity deforestation. of Rapa Nui deforestation. Figure Figure 10.10. Trends Trends of palm of palm pollen pollen in theinthree the three coherent coherent and continuous and continuous sequences sequences retrieved retrieved in Rapa in Rap Nui for the last millennium. The arrows mark thee main forest declines, according Nui for the last millennium. The arrows mark thee main forest declines, according to the legend to the legen within the box. Redrawn and simplified from Ref. [78], using raw data from Refs. within the box. Redrawn and simplified from Ref. [78], using raw data from Refs. [51,80,81]. [51,80,81]. Regarding Regarding cultivation, cultivation, the the firstfirst records records correspond correspond to the already to the already mentionedmentioned micro- micro and macrofossil remains of sweet potato, dated to 1300–1400 CE [53,57]. and macrofossil remains of sweet potato, dated to 1300–1400 CE [53,57]. Small-scale Small-scale cul- cult tivation practices seem to have coexisted with forests since the beginning vation practices seem to have coexisted with forests since the beginning of Polynesian seof Polynesian settlement [82]. However, as deforestation progressed, newly opened terrains were increas- tlement [82]. However, as deforestation progressed, newly opened terrains were increas ingly used for agriculture. The ancient Rapanui did not practice extensive cultivation or ingly used for agriculture. The ancient Rapanui did not practice extensive cultivation o widespread irrigation, and crops were restricted to meter-scale gardens called “manavai” widespread (Figure 9), whoseirrigation, and crops water supply were restricted was heavily dependent to onmeter-scale rainfall [25]. gardens called To minimize “manavai evap- (Figure 9), whose water supply was heavily dependent on rainfall oration and erosion, the manavai were protected from wind and surficial runoff by rock [25]. To minimize evap oration walls, andand erosion, the soils the inside manavai were coveredwere protected by rocks fromheat, to preserve wind and surficial moisture runoff by roc and nutrients, awalls, and practice the soils called lithicinside mulchingwere covered [83,84]. by rocks Based to preserve on extensive field heat, moisture surveys, the firstand esti-nutrient mations yielded a surface of nearly 80 km 2 of mulching area, approximately half of the a practice called lithic mulching [83,84]. Based on extensive field surveys, the first estima island tions surface, yieldedduring a surfacea period between of nearly 80 kmabout 2 of1460 and 1860 mulching CEapproximately area, [85]. The proliferation half ofofthe islan gardening cultivation on newly deforested terrains during the development of the ancient surface, during a period between about 1460 and 1860 CE [85]. The proliferation of gar dening cultivation on newly deforested terrains during the development of the ancien Rapanui culture was modeled by Steiglechner & Merico [86] using multiproxy evidenc (Figure 11). In addition to sweet potato, the main plants cultivated by the ancient Rapanu were “yam” (Dioscorea alata; Dioscoreaceae), “ipu kaha” or bottle gourd (Lagenaria sicerari Plants 2023, 12, 2089 15 of 32 Rapanui culture was modeled by Steiglechner & Merico [86] using multiproxy evidence (Figure 11). In addition to sweet potato, the main plants cultivated by the ancient Rapanui Plants 2023, 12, x FOR PEER REVIEW 16 of 33 were “yam” (Dioscorea alata; Dioscoreaceae), “ipu kaha” or bottle gourd (Lagenaria siceraria; Cucurbitaceae), “taro” (Colocasia esculenta; Araceae), “ti” (Cordyline fruticosa; Asparagaceae), “mahute” or paper mulberry (Broussonetia papirifera; Moraceae) and “maika” or banana banana (Musa sp.;(Musa sp.; Musaceae), Musaceae), as documented as documented byreports by historical historical andreports pollen,and pollen,and phytoliths phytoliths starch and starch grains from dryland soils and lake/swamp sediments grains from dryland soils and lake/swamp sediments [53,75,87–90]. [53,75,87–90]. Figure 11. Forest (green areas) retreat and garden (blue and pink dots) proliferation in Rapa Nui 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. 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) thou- The green sand intensity trees per cell.represents The colorthe of density of palms, dots is the ranging resource from 0 (white) preference, to 7 (dark in percentage green)vs. of trees thousand gardens, trees per cell. The color of dots is the resource preference, in ranging from 20% (pink) to 80% (blue). Modified from Ref. [86]. percentage of trees vs. gardens, ranging from 20% (pink) to 80% (blue). Modified from Ref. [86]. Landscape anthropization did not stop with Rapanui deforestation and gardening but Landscape anthropization was exacerbated did not stopcontact, after European with Rapanui deforestation as documented in and gardening historical but records was exacerbated after European contact, as documented in historical records [42,43,54]. [42,43,54]. A major deterioration occurred in 1875 CE when the whole island was trans- A major deterioration occurred in 1875 CE when the whole island was transformed into a formed into a ranch, mostly for sheep. If the former forest removal had eliminated the ranch, mostly for sheep. If the former forest removal had eliminated the palm-dominated palm-dominated forests, intensive and extensive grazing removed most of the autochtho- forests, intensive and extensive grazing removed most of the autochthonous plant species nous plant species that remained. After a pause in which alien plant species were intro- that remained. After a pause in which alien plant species were introduced, notably coconut duced, notably coconut trees (Cocos nucifera), a second and even more intense landscape trees (Cocos nucifera), a second and even more intense landscape degradation phase took degradation phase took place as a result of the reactivation of extensive livestock practices. place as a result of the reactivation of extensive livestock practices. In 1903 CE, the island In 1903 CE, the island experienced the worst vegetation deterioration of its entire history. experienced the worst vegetation deterioration of its entire history. The introduction The introduction of exotic species continued with the planting of Eucalyptus forest stands, of exotic species continued with the planting of Eucalyptus forest stands, which are still which are still standing on the island (Figure 3), along with other species for reforestation standing on the island (Figure 3), along with other species for reforestation and ornamental and ornamental purposes, or to protect soils from erosion. A thorough account of the na- purposes, or to protect soils from erosion. A thorough account of the native and introduced tive and introduced species are provided in Refs. [30,75]. species are provided in Refs. [30,75]. 4.2.Azores 4.2. Azores Thehistorical The historicalaccounts accountsofofPortuguese Portuguesesettlers settlersand andthe theavailable availablepalynological palynologicalrecords records coincideininthat coincide that thethe pre-settlement pre-settlement forests forests were were of laurisilva of the the laurisilva type,type, that that is, is, temperate temperate ever- evergreen forests with a predominance of species with laurus-like coriaceous green forests with a predominance of species with laurus-like coriaceous shiny leaves thatshiny leaves that favor mist condensation on their surface thus creating a humid microhabitat (Figure 12). These laurisilvas were dominated by Laurus azorica (Lauraceae), Juniperus brevifolia (Cupressaceae), Prunus azorica (Rosaceae) and Morelle faya (Myricaceae), with other trees and shrubs, such as Frangula azorica (Rhamnaceae), Taxus baccata (Taxaceae), Picconia azorica (Oleaceae), Myrsine africana (Myrsinaceae), Viburnum tinus (Adoxaceae), and the Plants 2023, 12, 2089 16 of 32 favor mist condensation on their surface thus creating a humid microhabitat (Figure 12). These Plants 2023, 12, x FOR PEER REVIEW laurisilvas were dominated by Laurus azorica (Lauraceae), Juniperus brevifolia (Cu- 17 of 33 pressaceae), Prunus azorica (Rosaceae) and Morelle faya (Myricaceae), with other trees and shrubs, such as Frangula azorica (Rhamnaceae), Taxus baccata (Taxaceae), Picconia azorica (Oleaceae), Myrsine africana (Myrsinaceae), Viburnum tinus (Adoxaceae), and the Ericaceae Ericaceae Erica azorica,Erica azorica,cylindraceum Vaccinium Vaccinium cylindraceum and Callunaand Calluna vulgaris vulgaris [39,91]. [39,91]. Today, Today, theisveg- the vegetation etationanthropogenic largely is largely anthropogenic as a consequence as aofconsequence of centuriesand centuries of deforestation of deforestation and the introduction of the introduction of exotic species, leading to the replacement of most original forests, exotic species, leading to the replacement of most original forests, which are restricted to a which aresmall few restricted to a are sites that fewunder smallprotection sites that are under [92,93]. Theprotection landscape[92,93]. The has been landscape almost has been completely almostincompletely rebuilt rebuilt a process that hasinbeen a process that has subdivided been into subdivided three into three main phases: main phases: a a pre-settlement pre-settlement phase, phase, an extractive an and phase extractive phase andphase a transformative a transformative [21,91]. phase [21,91]. Figure12.12.Native Figure Native and and introduced introduced plants plants on on SãoSão Miguel Miguel Island. Island. (A)(A) Leaves Leaves of Laurus of Laurus azorica azorica fromfrom a a laurisilva remnant in Ruta do Tronqueiro. (B) Conifer forests of Cryptomeria japonica around laurisilva remnant in Ruta do Tronqueiro. (B) Conifer forests of Cryptomeria japonica around Furnas, Furnas, with a typical understory dominated by Hedychium gardnerianum. (C) Typical landscape from São 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 Miguel Island, with extensive crops and pastures intermingled with Cryptomeria forests (dark green patches) and Hydrangea macrophylla in the foreground. Photos: V. Rull. patches) and Hydrangea macrophylla in the foreground. Photos: V. Rull. Duringthe During thepre-settlement pre-settlementphase, phase,between betweenPortuguese Portugueselanding landing(1432 (1432CE)CE)and and the the of- ficial settlement official (1449 CE), settlement (1449 CE),several severaltypes typesofofdomestic domestic animals animals (sheep, (sheep, goats, goats, pigs, pigs, horses) horses) were released on the uninhabited islands in the hope that their populations increasednat- were released on the uninhabited islands in the hope that their populations increased urally and naturally and facilitated facilitated the establishment the establishmentofofeventual eventualfuture futurecolonizers colonizersininthe theabsence absenceofofwild herbivores. wild herbivores.It has been It has documented been documented that these that introductions these introductionswere werehighly highlysuccessful successful but thethe but impact impact ononprimeval primevalforests forests was minimaland was minimal andofoflocal localnature. nature. The The proliferation proliferation of the of the introduced introduced livestock livestock suggests suggests thatthat natural natural open open vegetation vegetation typesthan types other other than laurisilvas laurisilvas were were available available for theseforanimals these animals to These to graze. graze.open Thesecommunities open communities would would have have been been up- upland grasslands [91] and[91] land grasslands are and represented in the pollen are represented diagrams in the pollen by small percentages diagrams of Poaceae of by small percentages Poaceae and other herbs and ferns [21]. During the extractive phase, initiated with Portu- guese settlement, native forests were intensively exploited for construction (houses and ships), firewood and charcoal production, which is clearly reflected in paleoecological rec- ords by the decline of pollen from laurisilva elements, especially Juniperus, Ilex and Morella Plants 2023, 12, 2089 17 of 32 and other herbs and ferns [21]. During the extractive phase, initiated with Portuguese settlement, native forests were intensively exploited for construction (houses and ships), firewood and charcoal production, which is clearly reflected in paleoecological records by the decline of pollen from laurisilva elements, especially Juniperus, Ilex and Morella [14,21]. In these palynological records, Laurus pollen is poorly represented, but the local presence of this tree is documented by the occurrence of its characteristic stomata. Historical records document the overexploitation until exhaustion of many autochthonous plant species and communities—especially those useful for medical purposes, wood/charcoal extrac- tion, fruit harvesting and the production of oils, dyes or materials for leather tanning, in which most of the abovementioned elements of native forests were involved—due to the colonialist mindset of the first settlers [91]. The unsustainable exploitation of natural resources and their ensuing exhaustion led to the introduction of new production systems imported from the continent, such as wheat, sweet potato or corn cultivation, along with the expansion of upland pastures for animal husbandry. This inaugurated the transformative phase, which was especially active during the last two centuries. Other important monocultures developed during this phase were sugar cane (Saccharum officinarum), grape (Vitis vinifera; Vitaceae), pepper (Capsicum; Solanaceae), pineapple (Ananas comosus; Bromeliaceae) and especially orange (Citrus sinensis; Rutaceae). A detailed account of the transformative phase on São Miguel Island is provided by Moreira [39] that could serve as a reference for the archipelago. The first great agricultural success was the extensive cultivation of orange trees im- ported from China, whose maximum development was attained at the beginning of the 18th century and largely transformed the landscape and the economy of the island. Most forests were cut down to obtain the timber needed to make the boxes in which the oranges were exported. At that time, the Australian tree Pittosporum undulatum (Pittosporaceae) was introduced as a hedgerow species to protect orange crops from wind. The orange industry declined by 1830 CE for economic reasons and because of the action of fungal and insect parasites. By 1860 CE, large-scale pineapple cultivation was introduced to replace orange crops. Again, large amounts of timber were needed for pineapple exportation, but the is- land was largely deforested and had to be reforested using several Pinus (Pinaceae) species imported from Europe, Cryptomeria japonica (Cupressaceae) from Japan, and Eucalyptus spp. (Myrtaceae) and Acacia melanoxylon (Fabaceae) from Australia. The decline of the remaining native forest elements such as Erica azorica and Myrsine africana, along with the introduction of Pinus pinaster and Cryotomeria japonica by 1750–850 CE, are manifest in the lake Azul pollen record. These introduced tree species, together with P. undulatum, still dominate the forests of São Miguel (Figure 4), which occupy 25% of the island’s surface, whereas the other 75% is dedicated to human activities [91]. During the 18th and 19th centuries, many exotic ornamental species were also intro- duced to decorate public and private parks and gardens. Some of these species have become naturalized and are successful invaders, such as Hedychium gardnerianum (Zingiberaceae), which is native to the Himalayas and is dominant in the understory of many planted forests, mainly those of Cryptomeria. Another naturalized species that is widespread across the island, especially in ruderal habitats, is Hydrangea macrophylla (Hydrangeaceae), which is native to China and Japan (Figure 12). Among the trees, P. undulatum and Clethra arborea (introduced from Madeira) are the most successful invaders. Human pressure has been variable on the different islands, with Corvo and Flores being the least affected and São Miguel being among the most disturbed ones [37]. São Miguel Island has been taken here as an example of anthropogenic vegetation replacement [3]. The historical landscape transfor- mation of São Miguel Island was described in detail by Moreira [39], and its paleoecological manifestation has been documented in the palynological study of Lake Azul [14]. In summary, the Azores Islands have not been fully deforested, and the extant forest formations are a mixture of native laurisilvas and newly assembled forest associations composed of alien tree species imported from elsewhere (Europe, Japan, Astralia), not occurring naturally in their places of origin. The main deforestation events documented Plants 2023, 12, 2089 18 of 32 palynologically occurred by 1290 CE (São Miguel) and shortly after Portuguese settlement (Pico, Flores) and involved the main native laurisilva elements [14,21]. In the other islands, although a number of minor to major forest declines have been documented (Figure 8), the lack of detailed pollen diagrams hinders more accurate interpretations. 5. Potential Influence of Climatic Changes The idea that environmental changes heavily influence human societies until the point that they may trigger cultural demises is known as environmental determinism and is opposed by those who consider that cultural developments are a consequence of exclusively human actions (human determinism). The debate is maintained by the difficulty of demonstrating that a given cultural change is actually a consequence of a particular environmental shift. In most cases, these inferences are based on chronological coincidences, but unequivocal mechanistic demonstrations remain elusive [94]. This is the case for Rapa Nui and the Azores, where these chronological coincidences have been used as preliminary evidence for possible causal relationships. In both cases, the issue has been analyzed considering two main contexts, namely, the role of climatic/oceanographic conditions on the settlement of islands and the influence of environmental shifts on sociecological changes in already colonized islands. 5.1. Rapa Nui The Polynesians arrived in Rapa Nui some time during the Medieval Climate Anomaly (MCA; 800–1300 CE), when warm/dry climates, higher sea levels and changes in wind patterns would have favored long-distance voyaging across the Pacific [95]. According to some paleoclimatic reconstructions, Polyensian settlement would have been facilitated by the occurrence of some climate windows for off-wind sailing between 800–820 CE and 1180–1250 CE, characterized by persistent westerly wind anomalies [96]. According to the same models, some windows also existed for off-wind sailing routes from South America and back in some periods between 910–930 CE and 1220–1260 CE. These figures are consistent with different hypotheses for Rapa Nui colonization but the authors favor Polynesian settlement between 1140 CE and 1250 CE, because its coincidence with current archaeological evidence [40,41]. This option is also supported by a recent biomarker study, accompanied by paleoclimatic reconstructions, pointing toward Polynesian settlement between 1150 CE and 1300 CE [97]. Other paleoclimatic/paleoceanographic models suggest that, in addition to winds and currents, climatic variability would have been a major driver in Pacific colonization ventures and propose precipitation as a key parameter in this regard [98]. The main drivers involved in Rapa Nui precipitation patterns are currently debated, with emphasis on the potential role of ENSO (El Niño Southern Oscillation) and the Pacific subtropical anticyclone [28,29]. A sustained drought documented on Rapa Nui between 500 CE and 1170 CE [51] partially overlapped the MCA and the 800–1200 CE settlement phase, which would be consistent with the occurrence of a significant climatic shift during the Polynesian settlement of Rapa Nui. Sear et al. [97] proposed that a similar drought between 800 CE and 1100 CE would have instigated initial eastward exploration from central Polynesia, culminating in Rapa Nui discovery and settlement roughly a century later. In addition to climate, regional volcanism and paleotsunamis that occurred during the last millennium have been suggested as potential modulators of transoceanic navigation, but this has not been studied in depth, and firm evidence is still unavailable [99]. In the classical literature, environmental shifts as drivers of ecological and cultural change on Rapa Nui have been systematically ignored by most archaeologists and explicitly dismissed by some paleoecologists. For example, Bahn & Flenley [100] argued that if palm forests survived the large temperature and moisture fluctuations experienced during the last 34,000 years, including the Last Glacial Maximum (LGM; occurred ~20,000 years ago), it would be unreasonable that they could have been annihilated by the comparatively lower climatic variability of the last millennia. Therefore, they concluded that the full island Plants 2023, Plants 2023,12, 12,x2089 FOR PEER REVIEW 19 of 32 20 deforestation other side and the ensuing of the debate,cultural collapse wasthat some proposed a consequence intense and of the overexploitation prolonged droughts th of natural resources by the ancient Rapanui society (possibly in combination with fruit- curred during the Little Ice Age cold reversal (LIA; 1300–1850 CE) could have been in eating Polynesian rats), who caused their own demise (ecocide). On the other side of mental the debate,for forest some clearing proposed [78]. that Recent intense andpaleoecological prolonged droughts research has identified that occurred during one of droughts the Little Ice(1520–1710 CE) coinciding Age cold reversal with full (LIA; 1300–1850 CE)island could deforestation [51,101].for have been instrumental This sugg that clearing forest forest removal could [78]. Recent have been due paleoecological to the research hascombined action identified one (amplification of these droughts feedb (1520–1710 of humans CE)andcoinciding climatewithandfullfurther island deforestation regeneration, [51,101]. which Thishadsuggested that forest been documented afte removal could have been due to the combined action (amplification feedbacks) vious clearing events, could have been hindered by the continued drought, along wi of humans and climate and further regeneration, which had been documented after previous clearing expansion of cultivation gardens [102]. events, could have been hindered by the continued drought, along with the expansion of Thisgardens cultivation type of[102]. feedbacks and synergies between climate and humans had not been viously considered This type in the of feedbacks andRapa Nui literature synergies and opened between climate a new opportunity and humans had not been for a ho approach in the analysis of socioecological systems, known as EHLFS (environmen previously considered in the Rapa Nui literature and opened a new opportunity for a holistic approach in the man-landscape analysis of feedbacks andsocioecological synergies) systems, known [103]. The EHLFSas EHLFS (environment- approach was used to d human-landscape feedbacks and synergies) [103]. The EHLFS approach was used to six states in the development of the Rapa Nui socioecosystem during the last millenn define six states in the development of the Rapa Nui socioecosystem during the last under a human ecodynamic perspective [104]. These stages were characterized by sp millennium, under a human ecodynamic perspective [104]. These stages were characterized bytemporal changes spatiotemporal in the changes interactions in the interactions between environmental between environmental (E), (E), human human (H) and (H) and scape (L)(L)subsystems landscape (Figures1313 subsystems (Figures and and 14).14). Figure Figure 13.13. The The EHLFS EHLFS (environment-human-landscape (environment-human-landscape feedbacks feedbacks and synergies) and synergies) frameworkframework as plied to Rapa Nui. E, environment; H, humans; L, landscape. After Ref. applied to Rapa Nui. E, environment; H, humans; L, landscape. After Ref. [103]. [103]. , x FOR PEER REVIEW 21 of 33 Plants 2023, 12, 2089 20 of 32 Figure 14. The different states of the EHLFS socioecosystem identified for the prehistory of Rapa Nui. Modified from Ref. [104]. Plants 2023, 12, Plants 2023, 12,2089 x FOR PEER REVIEW 22 of 33 21 of 32 5.2. Azores to infer the origin and the most likely routes of Norse colonizers. These authors concluded that,Inin their proposal early Medievalfor antimes, early settlement by Norsewas the temperature people and the associated anomalously high and widespread the predomi- landscape anthropization, Raposeiro et al. [23] utilized paleoclimatic simulations to infer nant winds reaching the Azores came from the NE, which would have facilitated the nav- the origin and the most likely routes of Norse colonizers. These authors concluded that, in igation from northern Europe, where the Norse lived, to the Azores. The problem is that early Medieval times, the temperature was anomalously high and the predominant winds these authors utilized paleoclimatic reconstructions from 850 CE onward, which do not reaching the Azores came from the NE, which would have facilitated the navigation from match the northern period Europe, that the where theyNorse considered lived, toasthe theAzores. time ofThe Norse settlement problem (700–850 is that these CE), and authors therefore, their inferences are unwarranted. The same methodology utilized paleoclimatic reconstructions from 850 CE onward, which do not match the period was used to infer the predominant that they consideredclimatic conditions as the during time of Norse the Portuguese settlement arrival, (700–850 CE), which would and therefore, their have infer- been ences are unwarranted. The same methodology was used to infer the predominant climatic (in- fostered by a shift in wind patterns favoring the navigation between southern Europe cluding Portugal) conditions during the and the Azores Portuguese [23]. which would have been fostered by a shift in arrival, The firstfavoring wind patterns paleoecological reconstructions the navigation from the between southern Pico(including Europe and Flores islands and Portugal) [21] em- the Azores [23]. phasized the lack of a clear relationship between the reconstructed forest trends and the The first available paleoecological paleoclimatic reconstructions records before andfrom afterthePortuguese Pico and Flores islands[105] settlement [21] em- and at- phasized tributed this fact to the highly maritime nature of the Azorean climate. Similarand the lack of a clear relationship between the reconstructed forest trends the were results available obtainedpaleoclimatic records record in the São Miguel before and [14],after Portuguese which suggested settlement [105] and that humans attributed would have been this fact to the highly maritime nature of the Azorean climate. Similar the main drivers of vegetation and landscape change. More recent paleoclimatic recon- results were obtained in the São Miguel record [14], which suggested that humans would have been the main structions identified the AMO and the NAO as the main mechanisms affecting the drivers of vegetation and landscape change. More recent paleoclimatic reconstructions Azorean climate and discussed some potential relationships among climate changes, cul- identified the AMO and the NAO as the main mechanisms affecting the Azorean climate tural and ecological shifts [106,107]. However, the available paleoclimatic records show and discussed some potential relationships among climate changes, cultural and ecological significant shifts departures, [106,107]. However, especially the available in paleoclimatic relation to hydrological records showbalance significant(Figure 15), and a departures, consistentinpaleoclimatic especially frameworkbalance relation to hydrological for the (Figure whole archipelago is still to paleoclimatic 15), and a consistent be attained. Addi- tionally, an integrated socioecological assessment similar framework for the whole archipelago is still to be attained. Additionally, an to the EHLFS approach integrated has not socioecological assessment similar to the EHLFS approach has not yet been attempted. be- yet been attempted. Therefore, in the present state of knowledge, the relationships tween environmental, Therefore, in the present anthropogenic state of knowledge, and landscape changes the relationships remainenvironmental, between unknown. Signifi- cant additional anthropogenic andefforts are still landscape needed changes to clarify remain the potential unknown. Significantrole of past climate additional changes efforts are still on needed to clarifysystems. socioecological the potential role of past climate changes on socioecological systems. Figure15. Figure 15.Hydroclimatic Hydroclimaticfluctuations fluctuationsasasreconstructed reconstructedininthree threelake lakesediment sedimentrecords records from from São Mi- São guel [106], Pico [105] and Flores [107] islands using different proxies. Redrawn and composed Miguel [106], Pico [105] and Flores [107] islands using different proxies. Redrawn and composed from the original sources. from the original sources. 6. Comparisons between Rapa Nui and the Azores 6.1. Present Conditions Although Rapa Nui is more distant than the Azores from both the mainland and the nearest island, the species/area relationship, a key parameter in island biogeography since Plants 2023, 12, 2089 22 of 32 6. Comparisons between Rapa Nui and the Azores 6.1. Present Conditions Although Rapa Nui is more distant than the Azores from both the mainland and the nearest island, the species/area relationship, a key parameter in island biogeography since the time of McArthur & Wilson [108], is >3.5 times higher (Table 2). This feature was already recognized by Carine & Schaeffer [109], who emphasized the low number and extent of radiations and the scarcity of single-island endemics in the Azorean flora. These authors attributed these anomalous numbers, compared to the remaining Macaronesian and other Atlantic archipelagos, to the long-term stability of the Azorean climate, which would have inhibited speciation, and/or the incomplete knowledge of the Azorean flora. Later, the same authors reaffirmed the second explanation by recognizing many undiscovered genetically distinct taxonomic entities that drastically increased the diversity patterns and made the Azores more similar to other Atlantic archipelagos [92]. Table 2. Main traits of the Rapa Nui and Azores flora and vegetation in relation to anthropization. The category “others” in vegetation types includes urban areas, unvegetated terrains and badlands. FAI (Floristic Anthropization Index) is the proportion of anthropogenic (introduced) vs. native species, ranging from 0 (pristine) to 1 (fully anhthropized). VAI (Vegetation Anthropization Index) uses the same calculation applied to the percentage of natural vs. anthropogenic vegetation cover. Raw data from the above sections. Rapa Nui Azores Extent Total surface (km2 ) 164 2351 Nearest continent (km) 3700 1400 Isolation Nearest island (km) 2100 900 Total species (n) 201 811 Species/area 1.22 0.34 Vascular flora Native (%) 25 24 Introduced (%) 75 76 Endemics (%) 12 30 Native types (%) 0 13 Introduced forests (%) 6 22 Vegetation cover Meadows/pastures (%) 74 42 Crops (%) 4 14 Others (%) 16 9 FAI 0.75 0.76 Anthropization VAI 1 0.87 Floristically, the degree of anthropization is very similar with approximately three quarters species introduced and the others are native, in both cases (Table 2, Figure 16). The main difference lies in vegetation cover, as in Rapa Nui all extant vegetation types are introduced, whereas in the Azores native plant communities are still preserved in 13% of their total surface. Additionally, although meadows and pastures are dominant in both cases, open communities are relatively more extensive in Rapa Nui (74%) than in the Azores (42%), whereas the introduced forests are significantly reduced in the first (6%) compared with the second (22%). Croplands are also much more important in the Azores (14%) than in Rapa Nui (6%). Therefore, it could be concluded that floristic anthropization is similar in both cases (FAI 0.75–0.76), but vegetation anthropization is significantly higher in Rapa Nui (VAI 1.00) than in the Azores (VAI 0.87). Plants 2023,12, Plants 2023, 12,2089 x FOR PEER REVIEW 23 of 2432of 33 Figure16. Figure 16.Comparison Comparisonbetween betweenthe theflora flora and and vegetation vegetation of of Rapa Rapa Nui Nui andand thethe Azores Azores in terms in terms of of anthropization (data from Table 2). Vegetation types: C, crops; IF, introduced forests; MP, mead- anthropization (data from Table 2). Vegetation types: C, crops; IF, introduced forests; MP, mead- ows/pastures; N, native; O, others. Anthropization indices: FAI, Floristic Anthropization Index; VAI, ows/pastures; N, native; O, others. Anthropization indices: FAI, Floristic Anthropization Index; VAI, Vegetation Anthropization Index. Vegetation Anthropization Index. 6.2.Early 6.2. EarlySettlement Settlement Fromthe From theabove abovediscussion discussiononon this this subject, subject, it can it can be be concluded concluded thatthat thethe evidence evidence for for earlysettlement early settlementisis consistent consistent in in both Rapa Nui and and the the Azores. Azores.However, However,there thereisisnonocon- conclusive evidence clusive evidence forfor intense intense andand widespread widespread anthropization anthropization in in anyany of them of them before before Poly- Polyensian ensian (Rapa (RapaNui)Nui)andandPortuguese Portuguese (Azores) (Azores) colonization. colonization.InInboth bothcases, cases,early settlers early settlers would wouldhavehave consisted consistedof local ephemeral of local and/orand/or ephemeral intermittent populations intermittent practicingpracticing populations small- scale cultivation and animal husbandry, who did not leave archaeological small-scale cultivation and animal husbandry, who did not leave archaeological remains remains or their traces were too faint that they were erased with time or by further or their traces were too faint that they were erased with time or by further permanent permanent settlers. In Rapa Nui, early settlers would have introduced tropical American settlers. In Rapa Nui, early settlers would have introduced tropical American anthropo- anthropochorous weeds, such as Verbena chorous weeds,and suchSisyringium, as Verbena and suggesting potential Sisyringium, pre-Polynesian suggesting potential connections pre-Polynesian withcon- South America, a possibility that has been supported by recent genetic analyses of other nections with South America, a possibility that has been supported by recent genetic anal- American domesticates, notably the sweet potato, and human populations. Interestingly, yses of other American domesticates, notably the sweet potato, and human populations. the most consistent and widespread paleoecological evidence for early Azorean colonizers Interestingly, the most consistent and widespread paleoecological evidence for early corresponds to dates (1200–1400 CE) similar to the Polyensian settlement of Rapa Nui. Azorean colonizers corresponds to dates (1200–1400 CE) similar to the Polyensian settle- This indicates that, despite the disparate geographical position in two different oceans, ment the of Rapa different Nui. and origin Thiscultural indicates that, despite features of the the disparate colonizers and geographical the differentposition navigation in two different oceans, technology the different and trajectories needed origin and at to arrive cultural Rapa Nui features and the of Azores, the colonizers they were and the differ- probably settled during the same time window, in the transition between the MCA and the Azores, ent navigation technology and trajectories needed to arrive at Rapa Nui and the LIA they were (Figure 17). probably settled The difference during is that, the same in Rapa timesettlement Nui, this window, was in the transitionwhereas permanent, between in the the Azores, stable settlement did not occur until the Portuguese occupation (1449 CE). Thewas MCA and the LIA (Figure 17). The difference is that, in Rapa Nui, this settlement permanent, origin whereas and identity in the of these Azores, early settlersstable settlement remains unknown. did The not existence occur until the Portuguese of 14th-century occupation European maps(1449 CE). The depicting some origin Azoreanand islands identitywould of these earlythat suggest settlers theseremains unknown. early colonizers The existence would have been ofof14th-century a similar origin European mapspermanent that further depictingsettlers, some Azorean but there islands would sug- is no empirical gest thatfor evidence these thisearly colonizers would have been of a similar origin that further permanent hypothesis. settlers, but there is no empirical evidence for this hypothesis. Plants 2023,12, Plants2023, 12,2089 x FOR PEER REVIEW 24 25 ofof3233 Figure17. Figure 17. Chronological Chronological synthesis synthesisof ofthe theevents eventsand andprocesses described processes describedin former sections in former for Rapa sections for Nui and the Azores, considering the last 1.5 millennia. The gray bands highlight the phases of coin- Rapa Nui and the Azores, considering the last 1.5 millennia. The gray bands highlight the phases of cidence between Rapa Nui and the Azores trends explained in the text. Climatic phases according 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 toIce Ref. [110]; Age; TA, Medieval MCA, temperature anomaly Climate with respect Anomaly; to preindustrial MW, Modern Warming.values. RapaClimatic phases:A,L,Aroi; Nui localities: LittleK, Ice Age; MCA, Medieval Climate Anomaly; MW, Modern Warming. Rapa Nui localities: A, Aroi; Kao; R, Raraku. Azores islands: C, Corvo; F, Flores; M, São Miguel; P, Pico; T, Terceira. NA, Native K, Kao; R, Raraku. Azores islands: C, Corvo; F, Flores; M, São Miguel; Americans; R/EG, reforestation with alien trees and extensive grazing. P, Pico; T, Terceira. NA, Native Americans; R/EG, reforestation with alien trees and extensive grazing. 6.3. Permanent Settlement 6.3. Permanent Settlement The combination of archaeological and paleoecological evidence, together with The combination of archaeological and paleoecological evidence, together with paleo- paleoclimatic/paleoceanographic reconstructions agree that Polynesian settlement would climatic/paleoceanographic reconstructions agree that Polynesian settlement would have have occurred approximately 1200 CE (1150–1300 CE), approximately two centuries and occurred approximately 1200 CE (1150–1300 CE), approximately two centuries and a half a half prior the Portuguese occupation of the Azores. Polynesians arrived in Easter Island prior the Portuguese occupation of the Azores. Polynesians arrived in Easter Island after a after a millennial transpacific journey starting 5000 years ago (3000 BCE), when Taiwanese millennial transpacific journey starting 5000 years ago (3000 BCE), when Taiwanese sailors sailors colonized the Philippines [111]. The next step was the colonization of the Bismarck colonized the Philippines [111]. The next step was the colonization of the Bismarck Islands, Islands, north of Papua New Guinea, by 1500 BCE. This was a fundamental stage because north of Papua New Guinea, by 1500 BCE. This was a fundamental stage because it im- it implied the disconnection from the original Taiwanese culture and the development of plied the disconnection from the original Taiwanese culture and the development of a new a new culture, culture, known as known aswhich Lapita, Lapita,was which the was seedthe seed of all of all Polynesian Polynesian cultures.cultures. Theculture The Lapita Lapita culture experienced experienced a rapid expansion a rapid expansion reaching reaching Tonga andTonga Samoa and SamoaPolynesia) (western (western Polynesia) by 950 BCE,by 950 BCE, followed by a long pause of approximately 2000 years before the followed by a long pause of approximately 2000 years before the expansion toward eastern expansion to- ward eastern Polynesia. ThePolynesia. Theof archipelagos archipelagos of Society, Society, Tuamotu and Tuamotu Marquesas, andasMarquesas, as well as well as Mangareva Island, were not colonized until 600–900 CE. The last expansion wave started fromstarted Mangareva Island, were not colonized until 600–900 CE. The last expansion wave these from these archipelagos archipelagos in three in three different different Hawaii directions: directions: (800Hawaii (800 CE), CE), Easter Easter Island Island (800– (800–1200 CE), 1200 and CE),Zealand, New and New theZealand, the last Island last Polynesian Polynesian to be Island to bebycolonized, colonized, 1200–1300byCE 1200–1300 CE (Figure 18). (Figure Some 18).studies recent Some recent point tostudies a muchpoint latertocolonization a much laterwave colonization (900–1200wave (900–1200 CE) from CE) western from western Polynesia (Samoa,Polynesia Tonga) (Samoa, [97,112],Tonga) and the[97,112], and under topic is now the topic is now under discussion [113]. discussion [113]. Plants 2023,12, Plants2023, 12,2089 x FOR PEER REVIEW 25 of 26 of 32 33 Figure18. Figure 18.Peopling Peoplingofofthe thePacific Pacificfrom fromEast EastAsian Asianarchipelagos. archipelagos.M, M,Mangareva MangarevaIsland. Island.Modified Modified from Ref. [20] using raw data from Ref. [111]. from Ref. [20] using raw data from Ref. [111]. Thenavigation The navigationskills skills of of ancient ancient Pacific Pacific peoples peoples are well are well known,known, and developments and developments such such as the as the double-hulled double-hulled canoe canoe or the or the star-and-wind star-and-wind compass compass are outstanding are outstanding examplesexamples [114]. [114].these With Withand these and innovations, other other innovations, the Polynesians the Polynesians and their and their ancestors ancestors had had beenbeenableable to to discover the whole Pacific world from Asia to South America discover the whole Pacific world from Asia to South America long before the European long before the European arrivalto arrival toAmerica. America. In the words of of Kirch Kirch [115]: [115]: “…long “ . . . longbefore beforethetheSpanish Spanish andandlater the later French the French andandEnglish, English, other otherpeoples peopleshad hadexplored exploredthe the vastness vastness of the Pacific, Pacific, discovered discovered virtually every virtually every single single one oneof ofits itshabitable habitableislands, islands,and andfounded foundedsuccessful successful colonies colonies on on most”. The permanent settlement most”. settlementof ofthetheAzores Azoreswas waspart partofof thethe maritime maritime expansion expansion of the of Portuguese the Portuguese empire, which empire, began which began in the early in the 15th 15th early century withwith century the occupation the occupation of theofwest- the western African ern African coasts coasts and and Macaronesia Macaronesia and attained and attained its maximum its maximum extension extension in theinfirst thequar- first quarter of the ter of the 16th 16th century, century, with with thethefunding fundingofofnumerous numerouscolonies colonies around around the globe, globe, from from Brazil BraziltotoPapua PapuaNew NewGuinea, Guinea,where wherethey theyarrived arrivedapproximately approximately3000 3000years yearsafter afterthetheAsian Asian founders founders of of the ancient ancient Lapita Lapitaculture. culture.The The voyage voyage between between Portugal Portugal andand the Azores, the Azores, sep- separated arated by by ~1400 ~1400 km,km, is just is just under under half half of theofjourney the journeyfrom from Mangareva Mangareva to Rapa to Nui Rapa(~2600 Nui (~2600 km) (Figure km) (Figure 18), which 18), which was the was the stage latest latest ofstage the of the eastward eastward Polynesian Polynesian expansion expansion before before reaching the South American coasts [64,115]. The Polynesian reaching the South American coasts [64,115]. The Polynesian and Portuguese expansions and Portuguese expansions were similar were similar in magnitude, in magnitude, but they divergedbut theyindiverged that the in that first wastheexclusively first was exclusively Pacific and Pacific spanned andmillennia, spanned millennia, whereas the whereas secondthe second progressed progressed mainly across mainly across the the Atlantic andAtlantic Indian and Indian oceans andoceans and lasted lasted barely barelyIn a century. a century. In this this context, thecontext, permanent the settlement permanentofsettlement Rapa Nui of RapaCE) (~1200 Nuioccurred (~1200 CE) occurred approximately approximately two centuries and two acenturies half beforeandthata half before of the Azores that of (1449 the Azores (1449 CE), which preceded the Columbian arrival CE), which preceded the Columbian arrival to America (1492 CE) by almost half a centuryto America (1492 CE) by almost and thehalf a century Rapa and the Rapa Nui European contact Nui European (1722 CE) bycontact a couple (1722 CE) by a(Figure of centuries couple of centuries 17). (Figure 17). 6.4. Deforestation 6.4. Deforestation A fundamental difference between Rapa Nui and the Azores is that the former was A fundamental difference between Rapa Nui and the Azores is that the former was fully deforested by 1600 CE, whereas in the latter, the progressive decline of native forests fully deforested by 1600 CE, whereas in the latter, the progressive decline of native forests due to their overexploitation, was compensated by a widespread reforestation (18th cen- due to their overexploitation, was compensated by a widespread reforestation (18th century tury onward) with alien species from diverse origins. These introduced forests have accli- onward) with alien species from diverse origins. These introduced forests have acclimated mated very well to the archipelago and are so dense, healthy and exuberant that they very well to the archipelago and are so dense, healthy and exuberant that they could seem could seem pristine to an unaware visitor. Another difference is that, in Rapa Nui, forest pristine to an unaware visitor. Another difference is that, in Rapa Nui, forest clearing clearing pulses didpulses did not chronologically not coincide coincide chronologically on thelocalities, on the studied studied localities, whereas whereas in the in the Azores, Azores, two two of clusters clusters of clearing clearing eventsdocumented events were were documented by 1200–1450 by 1200–1450 CE (before CE (before and atand theat the beginning of Portuguese occupation) and by 1700 CE (two centuries and a beginning of Portuguese occupation) and by 1700 CE (two centuries and a half before half before permanent settlement), involving islands from the three geographical groups (Figure 17). Plants 2023, 12, 2089 26 of 32 permanent settlement), involving islands from the three geographical groups (Figure 17). The first cluster had two different phases, before and after Portuguese settlement. Before 1449 CE, at the time of early settlers, clearing pulses were usually less intense, with some exceptions, than just after permanent occupation, when native forests experienced a general, abrupt and significant decline. The 1700 CE cluster occurred when native forests were already decimated and was characterized by minor to moderate declines shortly after the general reforestation. The whole picture suggests that Azorean forests were cleared in a more homogeneous spatial fashion after Portuguese settlement. Before those dates, forest clearing pulses would have been more heterogeneous in both space and time, similar to what occurred on Rapa Nui, when different sites were deforested at different times after asynchronous local clearing events. However, early settlers never reduced native forests as intensively as Portuguese colonizers or the ancient Rapanui on their island. 6.5. Landscape Transformation The progressive replacement of Rapa Nui palm forests by gardened lands coincided chronologically with the extractive phase in the Azores (Figure 17). Therefore, forest overexploitation was dominant in both cases between the 15th and 18th centuries. The main difference was the final result, which on Rapa Nui was full island deforestation, whereas in the Azores, the declining native forests were replaced by others composed of alien species from diverse origins. This Azorean reforestation began in the early 19th century and coincided, in part, with maximum vegetation deterioration in Rapa Nui, which took place during the “island ranch” phase. In both cases, this was the phase of maximum landscape anthropization, but the respective manifestations were different and have been typified as a degradation on Rapa Nui and a replacement (or landscaping) on the Azores. The introduction of allochthonous trees in Rapa Nui during the ranch period was a local and restricted practice (they occupy barely 6% of the island surface), and cannot be considered a proper replacement. 7. Conclusions There is sound evidence for early ephemera/intermittent settlement in both Rapa Nui and the Azores, prior to Polynesian and Portuguese permanent settlement, respectively. In Rapa Nui, this evidence dates to a couple of millennia ago and points toward a potential Amerindian origin, as proposed by the long discredited Heyerdahl’s hypothesis. In the Azores, the evidence is much more recent (13th–14th centuries) and there is no indication of the origin of the early settlers. According to archaeological evidence, the permanent Polynesian settlement of Rapa Nui (1200–1300 CE) would have occurred a couple of centuries prior to that of the Azores by Portuguese (1449 CE), which is well documented historically. The permanent settlement of Rapa Nui was the culmination of a millennial-scale process of occupation of virtually all Pacific islands/archipelagos from eastern Asia, whereas the occupation of the Azores occurred at the beginning of the expansion of the Portuguese empire. In this expansion, the Portuguese arrived in Papua New Guinea approximately 3000 years after the ancient Asian colonizers. Rapa Nui was fully deforested by 1600 CE, whereas the primeval Azores forests were never totally removed and occupy a small percentage (<3%) of the total surface. The remaining total forest cover was planted during the last two centuries using allochthonous tree species from Europe, Japan and Australia, which have been successfully naturalized. The Rapa Nui deforestation was the sum of local and apparently random forest clearing pulses, whereas in the Azores, forest clearing events were of the same type at the beginning and became more widespread after permanent settlement. Major landscape transformations occurred at similar times (15th–18th centuries) in both Rapa Nui and the Azores, and the same was true for the time of maximum landscape anthropization (19th century), which was characterized by full land degradation in Rapa Nui and widespread vegetation replacement in the Azores. Plants 2023, 12, 2089 27 of 32 Presently, although Rapa Nui is much smaller and more isolated than the Azores, the species/area relationship is almost four times larger in the first. The percentage of endemic species is more than two times greater in the Azores. The anthropization index is almost the same if we consider the flora (three quarters of which is introduced in both cases), but is lower in the Azores if the vegetation is taken into account. Indeed, no traces of native vegetation remain on Rapa Nui, whereas in the Azores, it occupies approximately 13% of the total surface. A summary of the similarities and differences is provided in Table 3. In general, most similarities correspond to the time after permanent human settlement of both Rapa Nui and the Azores, whereas the differences are more widespread over the pre and post-settlement phases (see also Figure 17). Table 3. Similarities and differences between Rapa Nui and the Azores in terms of human settlement and landscape anthropization, as discussed in the text. RN, Rapa Nui; AZ, Azores. Process Similarities Differences Consistent evidence Timing and origin: Early (forest clearing, fire, cultivated RN—Amerindian component (450 BCE) settlement plants/weeds) AZ—Unknown origin (13th–14th centuries) Origin and expansion routes: RN—Ancient Polynesians (late eastward Permanent Timing (1200–1450 CE) expansion) settlement AZ—Modern Portuguese (early westward imperial expansion) Intensity: RN—Full deforestation (1600 CE) by Forest Overexploitation and time of random local pulses clearing initiation (15th century) AZ—Partial deforestation by generalized events Type of transformation: Timing of major RN—expansion of gardening cultivation Landscape transformations (15th–18th and extensive grazing transformation centuries) and maximum AZ—extractive practices and further anthropization (19th century) reforestation (18th century) Species/area relationships: RN—1.22; AZ—0.34 Present Endemic species (%): Floristic anthropization (75%) conditions RN—12%; AZ—30% Vegetation anthropization: RN—1.00; AZ—0.87 8. Prospects for Future Research Much work is still to be done for a thorough assessment on human settlement and landscape transformation in Rapa Nui and the Azores. Early settlement is a key point and, although it is consistently supported by the available evidence, its spatiotemporal patterns remain largely unknown and need further paleoecological, archaeological and anthropological research for a sound assessment. In Rapa Nui, the use of molecular biomarkers for human presence and activities is still lacking and could be instrumental in clarifying the origin and cultural features of potential early settlers. In the Azores, more records encompassing the last millennia across the whole archipelago are still needed for an archipelago-wide appraisal. Another important aspect that remains hypothetical is the influence of environmental (mainly climatic) changes on the studied island socioecosystems. The available paleoclimatic and paleoecological records are supportive of meaningful environment-human-landscape feedbacks and synergies, but the finding of new records and the use of novel proxies are needed for an unequivocal assessment and the establishment of causal relationships. Paleoclimatic trends of the last millennia remain largely unknown or Plants 2023, 12, 2089 28 of 32 are rather contradictory in both Rapa Nui and the Azores, and further research is needed to clarify this point. The development of new lake/swamp coring campaigns is encouraged to establish a coherent paleoenvironmental framework to be compared with the available archaeological, anthropological and historical information in the way toward a holistic view using human ecodynamic approaches such as the EHLFS or similar approaches [104]. 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