Radiocarbon dating, pollen and non-pollen palynomorph analyses from a lake core were used to establish the timing and effects of farming activities around Lake Igaliku, Eastern Settlement, Greenland. The absence of agro-pastoral impact before the medieval colonization by Europeans provides an opportunity to understand the development of farming activity in a pristine landscape. The results show that the first phase of clearance and grazing pressure, without the expansion of the Norse apophyte (native plant, in habitats created by humans) Rumex acetosa type, could have occurred in the 9-10th century A.D. The presence of Norse settlers and livestock is clearly recorded from the 11-12th century A.D. with increasing frequencies of the Norse apophytes Rumex acetosa type and Ranunculus acris type, and coprophilous fungi. This colonization phase is followed by a period of decreasing human impact at the beginning of the 14th century, with a decrease in weeds, apophytes and coprophilous fungi suggesting a reduced grazing pressure. The regrowth of Salix and Betula and the disappearance of anthropogenic indicators except Rumex acetosa type between the 15th and 18th century demonstrate the abandonment of the settlement, until the development of contemporary agriculture in the 20th century.

Assessing the extent to which changes in lacustrine biodiversity are affected by anthropogenic or climatic forces requires extensive palaeolimnological data. We used high-throughput sequencing to generate time-series data encompassing over 2200 years of microbial eukaryotes (protists and Fungi) diversity changes from the sedimentary DNA record of two lakes (Lake Bourget in French Alps and Lake Igaliku in Greenland). From 176 samples, we sequenced a large diversity of microbial eukaryotes, with a total 16 386 operational taxonomic units distributed within 50 phylogenetic groups. Thus, microbial groups, such as Chlorophyta, Dinophyceae, Haptophyceae and Ciliophora, that were not previously considered in lacustrine sediment record analyses appeared to be potential biological markers of trophic status changes. Our data suggest that shifts in relative abundance of extant species, including shifts between rare and abundant taxa, drive ecosystem responses to local and global environmental changes. Community structure shift events were concomitant with major climate variations (more particularly in Lake Igaliku). However, this study shows that the impacts of climatic fluctuations may be overpassed by the high-magnitude eutrophication impacts, as observed in the eutrophicated Lake Bourget. Overall, our data show that DNA preserved in sediment constitutes a precious archive of information on past biodiversity changes.

Vegetation and lake-level data from the archaeological site of Tresserve, on the eastern shore of Lake Le Bourget (Savoie, France), are used to provide quantitative estimates of climatic variables over the period 4000-2300 cal BP in the northern French Pre-Alps, and to examine the possible impact of climatic changes on societies of the Bronze and early Iron Ages. The results obtained indicate that phases of higher lake level at 3500-3100 and 2750-2350 cal BP coincided with major climate reversals in the North Atlantic area. In west-central Europe, they were marked by cooler and wetter conditions. These two successive events may have affected ancient agricultural communities in west-central Europe by provoking harvest failures, more particularly due to increasing precipitation during the growing season. However, archaeological data in the region of Franche-Comté (Jura Mountains, eastern France) show a general expansion of population density from the middle Bronze Age to the early Iron Age. This suggests a relative emancipation of proto-historic societies from climatic conditions, probably in relation to the spread of new modes of social and economic organisation.

This is the first integrated multiproxy study to investigate climate, catchment evolution and lake ecology in South Greenland. A 4-m-long sedimentary sequence from Lake Igaliku (618 00 0 N, 458 26 0 W, 15 m asl) documents major environmental and climatic changes in south Greenland during the last 10 ka. The chronology is based on a 210 Pb and 137 Cs profile and 28 radiocarbon dates. The paleoenvironmental history is interpreted on the basis of magnetic susceptibility, grain size, total organic carbon, total nitrogen and sulphur, sedimentation rates, pollen, and diatom assemblages. The basal radiocarbon date at ca. 10 cal ka BP provides a minimum age for the deglaciation of the basin, which is followed by *500 years of high sedimentation rates in a glaciomarine environment. After the glacio-isostatic emergence of the basin ca. 9.5 cal ka BP, limnological and terrestrial proxies suggests early warmth, which may have been interrupted by a cold, dry and windy period between 8.6 and 8.1 cal ka BP. A dry and windy event *5.3-4.8 cal ka BP preceded the Neoglacial transition at Lake Igaliku, which is characterized by a shift toward moister and perhaps cooler conditions *4.8 cal ka BP, causing major changes in terrestrial and aquatic ecological conditions. Significant cooling is documented after *3 cal ka BP. Since *1 cal ka BP the climatic-driven changes were overprinted by the human influence of Norse and recent agriculture.

On the basis of sediment and pollen analyses of a radiocarbon-dated sediment sequence from Lake Joux in the Swiss Jura Mountains (west-central Europe), this paper presents a high-resolution record of lake-level and vegetation changes for the last millennium. The lake-level record makes it possible to determine that low-stands of the water-table dominated at c. AD 1200—1400, and from 1720 onward, with interruptions by short-lived rise events at c. AD 1340 and 1840. Highstands prevailed at c. AD 1100, and around AD 1450, 1550 and 1700. The comparison of the Joux lake-level record with a solar irradiance record based on cosmogenic nucleides supports the hypothesis of a major solar forcing of climate variations in west-central Europe over the last millennium. In agreement with other palaeohydrological records established in Western Europe and in the central North Atlantic Ocean, the Joux lake-level record suggests that, on a multicentennial scale, the period of the `Little Ice Age' coincided in the European mid-latitudes with wetter climatic conditions, and probably with an increase in summer precipitation. Variations in the hydrological cycle appear to have been associated with changes in the general atmospheric circulation pattern, probably coupled with variations in oceanic circulation and solar activity. The Joux record also points to changes in water resources expected to result from ongoing global warming. Finally, despite the severe climatic conditions which prevail in the Joux Valley, the human impact history at Lake Joux over the last millennium seems to reflect political choices and economic context more than climatic changes.

The paper presents the results of a palaeoecological study of Neolithic archaeological layers from a wetland, multilayer site, Serteya II (Western Russia). It contains, domestic structures, rich organic artefacts, skeletons, and ecofacts preserved within lacustrine deposits that are extremely important on a European scale. We employed a set of specialised palaeoecological analyses and accelerator mass spectrometry radiocarbon dating to identify the principal environmental conditions which attracted Neolithic hunter‐fisher‐gatherer communities from 4300 to 1600 cal. BC. The distinct impact of communities using a nonproductive economy on the ecology of the palaeolake shore zone was recorded. Also, palaeolake water level changes influenced the palaeoeconomic activity of local Neolithic societies, such as gathering of plants (for the medicinal use or serving as dietary components), fishing activities, and possible funeral practices. In addition, the identified phases of high‐water level changes, which were responses to climatic oscillations, were correlated with supraregional climatic events, especially ca. 6.2, 5.9, and 4.2 ka cal. BP. Thus, our results allowed for the reconstruction of environment transformations and conditions of Neolithic communities' activity, as well as for a better understanding of the relationships between local Neolithic communities' way of life and neolithisation processes in Eastern Europe.

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International audienceThe environmental impact of the Norse landnám in Greenland has been studied extensively. But to date, no study has quantified the soil erosion that Norse agricultural practices are believed to have caused. To resolve this problem, a high resolution sedimentary record from Lake Igaliku in South Greenland is used to quantitatively reconstruct 2500 years of soil erosion driven by climate and historical land use. An accurate chronology allows for the estimation of detritic fluxes and their uncertainties. Land clearance and the introduction of grazing livestock by the Norse around 1010 AD caused an acceleration of soil erosion up to 8 mm/century in 1180 AD which is two-fold higher than the natural pre-landnám background. From 1335 AD to the end of the Norse Eastern Settlement (in the mid-fifteenth century), the vegetation began to recover from initial disturbance and soil erosion decreased. After an initial phase of modern sheep breeding similar to the medieval one, the mechanization of agriculture in the 1980s caused an unprecedented soil erosion rate of up to 21 mm /century, five times the pre anthropogenic levels. Independently, a suite of biological and geochemical proxies (including Ti and diatom concentrations, C:N ratio, 13C and 15N of organic matter) confirm that the medieval and modern anthropogenic erosion far exceeds any natural erosion over the last 2500 years. Our findings question the veracity of the catastrophic scenario of overgrazing and land degradation considered to have been the major factor responsible for Norse settlement demise. They also shed light on the sustainability of modern practices and their consequences for the future of agriculture in Greenland