Núria Cañellas-Boltà

Challenging Easter Island"s collapse: the need for interdisciplinary synergies

The reigning paradigm holds that Easter Island suffered a socio-ecological collapse (ecocidal or not) sometime in the last millennium, prior to European contact (AD 1720). We discuss some novel paleoecological and archaeological evidence that challenges this assumption. We use this case study to propose a closer collaboration between archaeology and paleoecology. This collaboration allows us to unravel historical trends in which both environmental changes and human activities might have acted, alone or coupled, as drivers of ecological and social transformations. We highlight a number of particular points in which scholars from disparate disciplines, working together, may enhance the scope and the soundness of historical inferences. These points are the following: (1) the timing of the initial Easter Island colonization and the origin of the settlers, (2) the pace of ecological and social transformations since that time until the present, and (3) the occurrence of potential climate-human synergies as drivers of socio-ecological shifts.

Modern non-pollen palynomorphs sedimentation along an elevational gradient in the south-central Pyrenees (southwestern Europe) as a tool for Holocene paleoecological reconstruction

Non-pollen palynomorphs (NPPs) are microfossils other than pollen and spores from plants found within samples prepared for pollen analyses. Their utility as paleoecological indicators is rapidly growing because of their potential to complement palynological reconstructions of past communities and environments. The study of modern NPP sedimentation patterns using surface samples from different substrates, vegetation types, and environmental conditions is needed to characterize the main environmental and anthropogenic factors involved in establishing ecological gradients. Here, we analyze modern NPP distribution along an elevational transect from the south-central Pyrenees. We use these data to test the potential influence of elevation, vegetation type, sampling sites, and human disturbance on modern NPP distribution and to obtain a NPP modern-analog model, which will enhance further paleoecological interpretations. Our study used the same surface samples obtained in a previous modern-analog palynological study, along an elevational transect from 870 to 2600 m a.s.l. We identified 55 NPPs, including 13 unidentified morphotypes that were described and depicted. Individual NPP analysis and multivariate statistical methods showed that altitude plays a significant role in the NPP distribution along the transect, but other factors such as soil moisture, landscape openness, and grazing intensity also influenced the composition of NPP assemblages. Our results also recognized some characteristic NPP assemblages linked to elevational vegetation belts and individual NPP morphotypes related with specific microhabitats, both with potential paleoecological indicator capacity. This work is a first step to improve the knowledge of the NPP’s indicator value in the study area.

Three Millennia of Climatic, Ecological, and Cultural Change on Easter Island: An Integrative Overview

Publications fees were covered by the Catalan Agency of Management of University and Research Grants (AGAUR), grant 2014SGR1207.

Vegetation shifts, human impact and peat bog development in Bassa Nera pond (Central Pyrenees) during the last millennium

High-mountain lakes are suitable ecosystems for studying local environmental shifts driven by large-scale climate changes, with potential applications to predict future scenarios. The precise features in the response of species assemblages are not fully understood, and human pressure may often hide climatic signals. To investigate the origin and impact of past environmental changes in high-mountain ecosystems and apply this palaeoecological knowledge to anticipate future changes, we performed a multi-proxy study of a sediment core from Bassa Nera, a pond located close to montane–subalpine ecotone in the southern central Pyrenees. Combining pollen and diatom analysis at multidecadal resolution, we inferred vegetation shifts and peat bog development during the past millennium. We introduced a montane pollen ratio as a new palaeoecological indicator of altitudinal shifts in vegetation. Our results emphasize the sensitivity of the montane ratio to detect upward migrations of deciduous forest and the presence of the montane belt close to Bassa Nera pond during the Medieval Climate Anomaly. Changes in aquatic taxa allowed to date the onset of the surrounding peat bog which appeared and infilled the coring site around AD 1565. Overall, our results suggest a low-intensity human pressure and changes in management of natural resources during the last millennium, where farming was the main activity from the Medieval Climate Anomaly until AD 1500. Afterwards, people turned to highland livestock raising coinciding with the ‘Little Ice Age’.