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Islands are among the last regions on Earth settled and transformed by human activities, and they provide replicated model systems for analysis of how people affect ecological functions. By analyzing 27 representative fossil pollen sequences encompassing the past 5000 years from islands globally, we quantified the rates of vegetation compositional change before and after human arrival. After human arrival, rates of turnover accelerate by a median factor of 11, with faster rates on islands colonized in the past 1500 years than for those colonized earlier. This global anthropogenic acceleration in turnover suggests that islands are on trajectories of continuing change. Strategies for biodiversity conservation and ecosystem restoration must acknowledge the long duration of human impacts and the degree to which ecological changes today differ from prehuman dynamics., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Human‐mediated changes in island vegetation are, among others, largely caused by the introduction and establishment of non‐native species. However, data on past changes in non‐native plant species abundance that predate historical documentation and censuses are scarce. Islands are among the few places where we can track human arrival in natural systems allowing us to reveal changes in vegetation dynamics with the arrival of non‐native species. We matched fossil pollen data with botanical status information (native, non‐native), and quantified the timing, trajectories and magnitude of non‐native plant vegetational change on 29 islands over the past 5000 years. We recorded a proportional increase in pollen of non‐native plant taxa within the last 1000 years. Individual island trajectories are context‐dependent and linked to island settlement histories. Our data show that non‐native plant introductions have a longer and more dynamic history than is generally recognized, with critical implications for biodiversity baselines and invasion biology. [ABSTRACT FROM AUTHOR]

Aim: The accumulation of functional diversity in communities is poorly understood. Conveniently, the general dynamic model of island biogeography (GDM) makes predictions for how such diversity might accumulate over time. In this multiscale study of land snail communities on 10 oceanic archipelagos located in various regions of the globe, we test hypotheses of community assembly in systems where islands serve as chronosequences along island ontogeny. Location: Ten volcanic archipelagos. Time period: From 23 Ma to the present. Major taxa studied: Endemic land snails. Methods: Initially, we assembled geological island characteristics of area, isolation and ontogeny for all studied islands. We then characterized island‐scale biotic variables, including the species diversity and functional diversity of snail communities. From these data, we assessed relationships between island and snail community variables as predicted by the GDM, focusing initially on the islands of the Galápagos archipelago and thereafter with a broader analysis of 10 archipelagoes. Results: As in other studies of island assemblages, in Galápagos we find a hump‐shaped curve of species richness, with depauperate snail faunas on early‐ontogeny islands, increasing species richness on mid‐ontogeny islands and low species richness on islands in late ontogeny. We find exceptionally low functional diversity on early‐ontogeny islands that increases through mid‐ontogeny, whereas late‐ontogeny islands exhibit a range of functional diversity. The analysis including all 10 archipelagos indicates a major role of archipelago‐specific factors. In both sets of analyses, functional diversity is exceptionally low on early‐ontogeny islands, and island ontogeny is a significant predictor of morphology. Main conclusions: Consistent patterns of functional diversity across island ontogeny on all examined archipelagos indicate a common role for habitat filtering, ecological opportunity and competition in a diversity of systems, leading to predictable changes in functional diversity and average morphology through island ontogeny, whereas patterns of species richness appear subject to archipelago‐specific factors. [ABSTRACT FROM AUTHOR]

The extinction of iconic species such as the dodo and the deforestation of Easter Island are emblematic of the transformative impact of human colonization of many oceanic islands, especially those in the tropics and subtropics. Yet, the interaction of prehistoric and colonial-era colonists with the forests and forest resources they encountered can be complex, varies between islands, and remains poorly understood. Long-term ecological records (e.g., fossil pollen) provide the means to understand these human impacts in relation to natural change and variability pre- and postcolonization. Here we analyze paleoecological archives in forested landscapes of the Canary Islands and Cabo Verde, first colonized approximately 2,400 to 2,000 and 490 y ago, respectively. We demonstrate sensitivity to regional climate change prior to human colonization, followed by divergent but gradual impacts of early human settlement. These contrast with more rapid transformation in the colonial era, associated with significant increases in anthropogenic pressures. In the Canary Islands, at least two native tree taxa became extinct and lowland thermophilous woodlands were largely converted to agricultural land, yet relictual subtropical laurel forests persisted with limited incursion of nonnative species. In Cabo Verde, in contrast, thermophilous woodlands were depleted and substituted by open landscapes and introduced woodlands. Differences between these two archipelagos reflect the changing cultural practices and societal interactions with forests and illustrate the importance of long-term data series in understanding the human footprint on island ecosystems, information that will be critically important for current and future forest restoration and conservation management practices in these two biodiversity hotspots. [ABSTRACT FROM AUTHOR]

Aim: Long‐term ecological data provide a stepped frame of island ecosystem transformation after successive waves of human colonization, essential to determine conservation and management baselines. However, the timing and ecological impact of initial human settlement on many islands is still poorly known. Here, we report analyses from a 4800‐year sedimentary sequence from Gran Canaria (Canary Islands), with the goal of disentangling forest responses to natural fire from early human pressure on the island. Location: La Calderilla, a volcanic maar caldera at 1,770 m a.s.l. on Gran Canaria. Taxon: Plants and fungi. Methods: A core from the caldera infill was analysed for sediment properties, pollen, micro‐ and macrocharcoal, with radiocarbon and biochronology dating. Fossil data were statistically zoned and interpreted with the help of cross‐correlation and ordination analyses. Surface samples and a pollen–vegetation training set were used as modern analogues for vegetation reconstruction. Results: Before human settlement (4,800–2,000 cal. yr bp), pine (Pinus canariensis) pollen dominated. Extensive dry pine forests characterized the highlands, although with temporary declining phases, followed by prompt (sub‐centennial scale) recovery. Towards 2,280 cal. yr bp there was a shift to open vegetation, marked by an increase in coprophilous spores. Coincidental with independent evidence of human settlement in the pine belt (2,000–470 cal. yr bp) there was a decline of pine and a peak in charcoal. Following historic settlement (470–0 cal. yr bp), pollen producers from anthropogenic habitats, secondary vegetation and coprophilous fungi increased in abundance, reflecting higher pressure of animal husbandry and farming. Modern moss polsters reflect extensive reforestation since 1950 ce (Common Era). Main conclusions: From 4,800 cal. yr bp, the pristine vegetation covering the Gran Canaria highlands was a mosaic of dry pine forests and open vegetation. The pine forests sustained intense fires, which may well have promoted habitat diversity. Human interference was initiated around 2,280 cal. yr bp probably by recurrent cultural firing and animal husbandry, triggering a steady trend of forest withdrawal and expansion of grasses and scrubs, until the final disappearance of the pine forest locally in the 20th century. Grasslands were found to be of ancient cultural origin in the summit areas of Gran Canaria, although they underwent an expansion after the Castilian Conquest. [ABSTRACT FROM AUTHOR]

Oceanic islands remained free of humans until relatively recent times. On contact, humans encountered pristine environments with unique ecosystems and species highly vulnerable to novel impacts. In the course of rendering an island habitable, the new settlers transformed it through fire, deforestation, hunting and introduction of pests and weeds. The result, as described for many oceanic islands globally, has been a catastrophe for biodiversity. Here we present the case of the Canary Islands, an Atlantic archipelago renowned for its exceptional biodiversity, and show that these islands have been no exception to the general rule. We review the archaeological, palaeoecological, palaeontological and ecological literature for the archipelago and discuss the ecological consequences – in particular habitat transformation and biodiversity loss – of human settlement. In contrast to previous views that prehistoric humans had only limited impacts on these islands, we show that vegetation change, increased fire, soil erosion, species introductions and extinctions follow the familiar oceanic pattern. Timing of human settlement of the Canary Islands has been controversial, with revised archaeological dates suggesting a relatively late arrival at the beginning of the Common Era, while palaeoecological and palaeontological evidence favours a presence several centuries earlier. While the matter is still not settled, we suggest that settlement sometime between 2400 and 2000 cal years BP is a possibility. • Prehistoric impact on the Canary Islands is reviewed with palaeoecological, palaeontological and archaeological evidence. • First Canarian settlers had substantial impact on the environment like other societies that colonized oceanic islands. • Palaeoenvironmental data suggests a possible earlier settlement than the recently revised archaeological dates. [ABSTRACT FROM AUTHOR]

São Tomé (Gulf of Guinea, Central Africa) is a 854 km2 tropical island that had a pivotal role in early European colonial expansion through the Atlantic between the 15th and 16th centuries. Historical sources suggest that native vegetation has been heavily impacted since human arrival (1470 CE) due to monoculture economies and the introduction of mammals and plants, some of which now have established wild populations. The Afromontane forest of São Tomé, located above 800 m.a.sl., is particularly rich in endemic plant species and has remained relatively unaffected by direct human impacts. Here, we explore how environmental change influenced this forest through the study of a sedimentary sequence from the volcanic crater of Lagoa Amélia (1340 m a.s.l.), a palustrine system located at the boundary between submontane (800–1400 m a.s.l.) and mist forest (above 1400 m a.s.l.). We used fossil pollen, non-pollen palynomorphs, sedimentology and charcoal to determine forest dynamics from the Late Pleistocene to the present. From 14,000 to 12,500 cal yr BP the forest was dominated by taxa from higher altitudes, adapted to cooler and drier climates (e.g. Afrocarpus mannii trees and Psychotria nubicola). After 12,500 cal yr BP, a potential uphill migration was identified by an increase in taxa like the trees Symphonia globulifera and Craterispermum cerinanthum. From 11,200 cal yr BP through the rest of the Holocene taxa from lower altitudes became dominant (e.g. Prunus africana , Polyscia s, and Sabicea) , except at c. 8500 cal yr BP when rapid cooling led to forest opening. Charcoal showed that fires were frequent during the Late Pleistocene (14,000 to 11,200 cal yr BP), becoming rare during the Holocene until anthropogenic fires started at c. 220 cal yr BP. Other recent anthropogenic impacts detected in Lagoa Amélia included the appearance of pollen of introduced plant species (e.g., Cestrum), and the increase in pollen of economically important species (Elaeis guineensis , Zea mays) and in fungal spores related to introduced herbivores. Our results reveal that climate changed the altitudinal distribution of the Afromontane forest in São Tomé during the Late Pleistocene, as observed on the African continent, and that this ecosystem was also strongly impacted by human arrival, through fire, farming, and introduced species. • We assess how climatic changes and humans influenced Afromontane forest around the Lagoa Amélia volcanic crater. • We document Late Pleistocene uphill migration of forest taxa and the occurrence of natural forest fires • During the Holocene taxa from lower altitudes became dominant and fires became rare. • We detect recent human impacts (200 cal yr BP-present) through fire and the introduction of plant and animals. • Comparison with mainland records suggests that island Afromontane forest long-term shifts were analogue to continental ones. [ABSTRACT FROM AUTHOR]

Cabo Verde was the first tropical archipelago colonized by Europeans. Historians have suggested that the first colonizers initiated archipelago-wide ecosystem degradation, loss of vegetation cover, and erosion. However, the human–environment interactions that led to the archipelago's current environmental status remain poorly understood. Here, we report the first palaeoecological study of past vegetation change and disturbance regimes for Cabo Verde. We present a 2130-yr old sediment sequence from a volcanic caldera (Cova de Paúl) located at ~1200 m asl on Santo Antão Island, for which we analyzed fossil pollen, non-pollen palynomorphs (NPPs), charcoal, silica bodies, and grain size distribution. Our analyses do not show evidence of the presence of temperate, tropical or subtropical forests growing on the summits of Santo Antão in pre-human times. The pollen record shows that scrubland and grasslands dominated the highlands and underwent compositional changes ca. 1850 and 1300 cal yr BP. These shifts overlap with erosion phases and are linked to intensified seasonality. Steady rates of sedimentation marked the period 1230 to ca. 350 cal yr BP, but an increase in charcoal concentrations indicate a drying phase. Increases in regional and local fire, peaks of coprophilous fungi and the presence of New World crop pollen (Zea mays) are interpreted as the onset of Portuguese settlement of the highlands after 450 BP. Sustained erosion between ca. 350 and 100 cal yr BP indicate soil degradation, and the pollen record shows the increase in introduced herbaceous taxa (Rosaceae, Centaurea , Verbenaceae) and exotic tree taxa (e.g. Pinus), while shifting abundances of coprophilous fungi indicate changes in land-use. The record shows stabilization of soils in the last century due to recent afforestation of the highlands. Further palaeoecological studies have the potential to provide further detail of the long-term dynamics of Cabo Verde ecosystems and to inform conservation initiatives. • We present the first palaeoecological record from Cabo Verde: a 2130-yr sediment sequence from Santo Antão Island. • We found no signs of ancient woodlands in one of the highest and most humid islands of Cabo Verde. • Pre-human landscapes experienced erosion phases linked to intensified monsoonal activity and increased seasonality. • Human transformation of local landscapes led to compound perturbations in the ecosystems and erosion of local soils. [ABSTRACT FROM AUTHOR]

Tropical dry islands are currently facing major challenges derived from anthropogenic and climatic pressures. However, their trajectories of environmental change, which could provide relevant information applicable to biodiversity conservation, remain understudied. This is mainly due to poor micro-fossil preservation and irregular sediment deposition. Multi-proxy palaeoecological analyses spanning decades to 1000s of years can add perspective as to how vegetation, fungal communities, and the fauna responded to previous natural and anthropogenic disturbances. In São Nicolau, Cabo Verde, we used palaeoecological methods to analyse a highland soil profile (1000 m asl) dated to 5900 cal yr BP. We analysed how vegetation (abundances in pollen of native and introduced species, and leaf wax n -alkanes), ferns and fungal communities (abundance of non-pollen palynomorphs) varied over time in relation to fire (charcoal concentration) and erosion regimes (grain sizes and elemental composition). Between 5000 and 400 cal yr BP the highlands held native woody taxa such as Euphorbia tuckeyana , Dracaena draco subsp. caboverdeana , and Ficus , taxa that can be used for future reforestation programmes. From 400 cal yr BP to the present day, replacement of native taxa by introduced and cultivated taxa (Pinus , Eucalyptus , Asystasia , Opuntia) has occurred. Vegetation burning and grazing caused loss of vegetation and erosion, acting as conjoined drivers of scrubland degradation. This dataset helps to set historically contextualised restoration goals such as the re-introduction of native species, monitoring of recently introduced species and control of free grazing. This can serve as a model system for the conservation of tropical dry islands' biodiversity. Unlabelled Image • Palaeoecological analyses reveal 5900-yr of ecological change in São Nicolau. • Fern-rich endemic-dominated scrublands present (5000–410 cal yr BP) even after fire. • Introduced grazers and vegetation burning caused erosion and landscape opening. • Results are used to set historically-contextualised conservation/restoration goals. • Methods are applicable in other dry tropical islands in Cabo Verde and beyond. [ABSTRACT FROM AUTHOR]