Ralph Fyfe

Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling

We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1° × 1° spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.

Pollen productivity estimates from the forest—tundra ecotone in west-central Sweden: implications for vegetation reconstruction at the limits of the boreal forest

Successful reconstruction of vegetation from fossil pollen data in the arctic and alpine tundra, and at the forest—tundra ecotone, is hampered by low pollen production of the major taxa in these environments and the likely dominance of the background pollen component. New approaches to the quantification of vegetation from pollen data (the REVEALS and LOVE models) rely on quantification of background and local pollen by applying models of pollen dispersal and deposition to modern pollen— vegetation survey work. To date, research within this emerging area has focused on lowland environments. This paper presents pollen productivity estimates (PPEs) from the forest—tundra ecotone derived from west central Sweden, discusses the relevant source area of pollen (RSAP) in this environment and estimates the background pollen contribution. The results suggest that the RSAP for moss polsters at the forest—tundra ecotone is c. 500 m, and that PPEs for the major forest tundra ecotone taxa show significant differences compared with previous studies from southern Sweden. Proximity to range limits (controlled by climatic factors) appears to be the main factor causing generally lower pollen production; however, individual taxa respond in different ways, depending on differences in growth behaviour, reproductive strategy and the species and subspecies that represent the pollen taxa. The background pollen component was dominated by arboreal taxa, and contributed c. 60% of the total pollen loading. Graminoids dominated the local component. The PPEs presented here are to date the most appropriate parameters to use for quantification of vegetation at the tundra treeline; however, the data demonstrate that caution needs to be exercised with regards to selection of appropriate PPEs for accurate quantification of taxa at their ecological range.

The European Modern Pollen Database (EMPD) project

Modern pollen samples provide an invaluable research tool for helping to interpret the quaternary fossil pollen record, allowing investigation of the relationship between pollen as the proxy and the environmental parameters such as vegetation, land-use, and climate that the pollen proxy represents. The European Modern Pollen Database (EMPD) is a new initiative within the European Pollen Database (EPD) to establish a publicly accessible repository of modern (surface sample) pollen data. This new database will complement the EPD, which at present holds only fossil sedimentary pollen data. The EMPD is freely available online to the scientific community and currently has information on almost 5,000 pollen samples from throughout the Euro-Siberian and Mediterranean regions, contributed by over 40 individuals and research groups. Here we describe how the EMPD was constructed, the various tables and their fields, problems and errors, quality controls, and continuing efforts to improve the available data.

Late Holocene climate: Natural or anthropogenic?

For more than a decade, scientists have argued about the warmth of the current interglaciation. Was the warmth of the preindustrial late Holocene natural in origin, the result of orbital changes that had not yet driven the system into a new glacial state? Or was it in considerable degree the result of humans intervening in the climate system through greenhouse gas emissions from early agriculture? Here we summarize new evidence that moves this debate forward by testing both hypotheses. By comparing late Holocene responses to those that occurred during previous interglaciations (in section 2), we assess whether the late Holocene responses look different (and thus anthropogenic) or similar (and thus natural). This comparison reveals anomalous (anthropogenic) signals. In section 3, we review paleoecological and archaeological syntheses that provide ground truth evidence on early anthropogenic releases of greenhouse gases. The available data document large early anthropogenic emissions consistent with the anthropogenic ice core anomalies, but more information is needed to constrain their size. A final section compares natural and anthropogenic interpretations of the C-13 trend in ice core CO2.

A pollen-based pseudobiomisation approach to anthropogenic land-cover change

The degree of anthropogenic modification of land cover through the mid to late Holocene is of significant interest for archaeologists, climate modellers and conservation ecologists, amongst others. Spatially extensive pollen data provide an appropriate resource for the reconstruction of land-cover change; however, traditional simple methods (e.g. the AP/NAP ratio) do not provide the degree of detail required for these user groups. A range of more sophisticated methods have been developed (e.g. mechanistic model-based methods), but they require a high degree of understanding of the pollen—vegetation relationship, which is resource- and time-consuming. This paper proposes a method of intermediate complexity by which major land-cover changes can be assessed for individual sites and regions. A pseudobiomisation approach is used, in which pollen taxa are assigned to different land-cover classes (LCC), and the sum of adjusted pollen proportions for each class used to determine an LCC affinity score for individual pollen samples within stratigraphic pollen sequences. In a pilot study, data from pollen core sites from northwest Scotland and southwest England for the last 8000 cal. BP have been classified into ten land-cover classes, including predominantly wooded, semi-open and open types. Results highlight how land-cover change was punctuated rather than gradual through the mid to late Holocene, and show how habitat diversity increased after ~6000 cal. BP with the arrival of agriculture, before reaching a minimum in early modern times. This pollen-based method is potentially applicable to the reconstruction of long-term land-cover change within Europe and other temperate-zone regions.

Is Neolithic land use correlated with demography? An evaluation of pollen-derived land cover and radiocarbon-inferred demographic change from Central Europe

The transformation of natural landscapes in Middle Europe began in the Neolithic as a result of the introduction of food-producing economies. This paper examines the relation between land-cover and demographic change in a regionally restricted case study. The study area is the Western Lake Constance area which has very detailed palynological as well as archaeological records. We compare land-cover change derived from nine pollen records using a pseudo-biomisation approach with 14C date probability density functions from archaeological sites which serve as a demographic proxy. We chose the Lake Constance area as a regional example where the pollen signal integrates a larger spatial pattern. The land-cover reconstructions for this region show first notable impacts at the Middle to Young Neolithic transition. The beginning of the Bronze Age is characterised by increases of arable land and pasture/meadow, whereas the deciduous woodland decreases dramatically. Changes in the land-cover classes show a correlation with the 14C density curve: the correlation is best with secondary woodland in the Young Neolithic which reflects the lake shore settlement dynamics. In the Early Bronze Age, the radiocarbon density correlates with open land-cover classes, such as pasture, meadow and arable land, reflecting a change in the land-use strategy. The close overall correspondence between the two archives implies that population dynamics and land-cover change were intrinsically linked. We therefore see human impact as a key driver for vegetation change in the Neolithic. Climate might have an influence on vegetation development, but the changes caused by human land use are clearly detectable from Neolithic times, at least in these densely settled, mid-altitude landscapes.

Mesolithic to Bronze Age Vegetation Change and Human Activity in the Exe Valley, Devon, UK.

This paper presents the results of the first investigation of vegetation change and human activity from a river valley west of the Somerset Levels. The record is contrasted with the pollen and archaeological record from south-west uplands (Dartmoor and Exmoor) and the Somerset Levels. Vegetation change and archaeological evidence are shown to be generally consistent, with evidence from the middle valley of Mesolithic vegetation disturbance (with nearby lithics), Neolithic clearance of terraces and slopes in the lower valley and Neolithic–Bronze Age ceremonial and domestic activity, but in the upper reach the maintenance of wooded valley floor conditions probably with management until historic times. The valley floor and surrounding slope vegetation history is found to be significantly different to that of the uplands with lime and elm being significant components of the prehistoric woodland record. The data suggest that lime is restricted to terraces and lowlands below 200 m OD throughout the prehistoric period. The pollen data from the valley suggest the lowlands had a rich and mixed ecology providing a wide range of resources and that, despite less visible archaeological remains, human activity is manifest through palynological evidence from the Mesolithic to the Bronze Age. The largest expanse of valley-floor terrace, the Nether Exe Basin, which was at least partially deforested in the early Neolithic contains a rich assemblage of Neolithic–Bronze Age ceremonial, funerary and domestic archaeology associated with an early and clear palynological record of woodland clearance, arable and pastoral activity.

Late-glacial and Holocene European pollen data

ABSTRACT The European Pollen Database (EPD) is a community effort to archive and make available pollen sequences from across the European continent. Pollen sequences provide records that may be used to infer past vegetation and vegetation change. We present here maps based on 828 sites from the EPD giving an overview of changes in postglacial pollen assemblages in Europe over the past 15,000 years. The maps show the distribution and abundance of 54 different pollen taxa at 500 year intervals, supported by new age-depth models and associated chronological uncertainty analysis. Results show the individualistic patterns of spread of different pollen taxa, and provide a standardized dataset for further analysis, defining a spatial context for the study of past plant and vegetation changes and other aspects of environmental history in Europe.

The first 100 years of pollen analysis

In 1916, Swedish geologist Ernst Jakob Lennart von Post delivered a provocative lecture in Oslo, Norway, advocating the use of pollen grains in bog sediments as indicators of past vegetation and climate. The lecture spawned many applications and represents a landmark in multidisciplinary science.

Holocene fluctuations in human population demonstrate repeated links to food production and climate

Significance The relationship between human population, food production, and climate change is a pressing concern in need of high-resolution, long-term perspectives. Archaeological radiocarbon dates have increasingly been used to reconstruct past population dynamics, and Britain and Ireland provide both radiocarbon sampling densities and species-level sample identifications that are globally unrivalled. We use this evidence to demonstrate multiple instances of human population downturn over the Holocene that coincide with periodic episodes of reduced solar activity and climate reorganization as well as societal responses in terms of altered food-procurement strategies. We consider the long-term relationship between human demography, food production, and Holocene climate via an archaeological radiocarbon date series of unprecedented sampling density and detail. There is striking consistency in the inferred human population dynamics across different regions of Britain and Ireland during the middle and later Holocene. Major cross-regional population downturns in population coincide with episodes of more abrupt change in North Atlantic climate and witness societal responses in food procurement as visible in directly dated plants and animals, often with moves toward hardier cereals, increased pastoralism, and/or gathered resources. For the Neolithic, this evidence questions existing models of wholly endogenous demographic boom–bust. For the wider Holocene, it demonstrates that climate-related disruptions have been quasi-periodic drivers of societal and subsistence change.