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Palynological analysis of the last ca. 4300 cal year BP using a sediment core taken from high mountain (ca. 1900 m elevation) Lake Sant Maurici sediments (southern-central Pyrenees) showed remarkable vegetation constancy during the Bronze Age and the Middle Ages. Records of the Iron Age and the Roman period were missing due to a major sedimentary gap. During the studied periods, the vegetation around the lake was largely dominated by pine (Pinus) forests with birch (Betula), oak (Quercus) and hazel (Corylus) trees, as is the case today. The composition of these forests and the abundance of their components remained quite stable, despite the occurrence of temperature and moisture shifts. The degree of human disturbance, notably that of pastoralism and cereal cultivation by scattered and temporary settlements, was very low and had little or no effect on the dominant forests. This situation contrasts with most high-elevation (subalpine and alpine) environments of the central Pyrenees that were massively anthropized during the Middle Ages. Further research should be aimed at finding sediments corresponding to the Iron Age and the Roman period to verify whether the vegetation constancy can be extended throughout the Late-Holocene. Past records of this type may allow the estimation of natural and anthropogenic thresholds for irreversible forest changes, which would be useful for conservation purposes.

This paper presents three extreme examples of the potential consequences of human settlement on the vegetation of oceanic and continental islands. The Neotropical Pantepui continental archipelago of sky islands is an example of pristinity, due to the almost nonexistent human impact that results from the remoteness and inaccessibility of these islands as well as the lack of natural resources to exploit. Easter Island is used to illustrate total vegetation degradation by deforestation and the exhaustion of natural resources, which has transformed the island into badlands with no signs of recovery. The Azores Islands have been chosen to illustrate replacement as, after initial postsettlement deforestation and extractive practices, a further transformative phase consisting of creating an almost totally anthropogenic vegetation with mostly exotic species occurred. The paper describes in some detail the developments of each case and the historical context in which they took place using historical, archeological and paleoecological evidence. Many intermediate states are possible among these three extremes, which can be represented with a ternary diagram (the PDR diagram), which is useful for characterizing the state of each island or archipelago in terms of human impact on terrestrial ecosystems and informing conservation and restoration practices.

After decades of human-deterministic explanations for the collapse of the ancient Rapanui culture that inhabited Easter Island (Rapa Nui) before European contact (1722 CE), paleoecological studies developed over the last decade have provided sound evidence of climate changes and their potential socioecological impacts. Especially significant is the occurrence of a century-scale drought (1570–1720 CE) during the Little Ice Age (LIA). Freshwater is a critical resource on Easter Island that heavily depends on rain, which maintains the only three permanent surficial freshwater sources on the island: two lakes (Rano Kao and Rano Raraku) and a marsh (Rano Aroi). Under these conditions, the LIA drought could have significantly affected human life; however, the Rapanui society remained healthy, showing remarkable resilience. There are two main hypotheses on how the ancient Rapanui could have obtained freshwater to guarantee their continuity. One of these hypotheses proposes that Lake Kao was a permanent source of freshwater, even during the LIA drought, which led to some intraisland cultural and population reorganizations. The coastal groundwater hypothesis dismisses the use of lakes and other surficial freshwater sources to maintain the water-stressed Rapanui population and contends that the only routine freshwater sources during the LIA drought were the abundant and widespread coastal seeps fed by fresh/brackish groundwater. The pros and cons of these two hypotheses are discussed on the basis of the available archeological and paleoecological evidence, and it is concluded that given the present state of knowledge, neither can be rejected. Therefore, these two proposals could be complementary rather than mutually exclusive.