Mediterranean fire histories since the Last Glacial Maximum from lake sedimentary micro- charcoals
AGUFM, Dec 1, 2006
Varve-based Reconstruction of Seasonal Hydroclimate from Nar Gölü, Turkey over the last 2.6 ka BP
Historical landscape change in Cappadocia (central Turkey): a palaeoecological investigation of annually laminated sediments from Nar lake
The Holocene, 2008
Coupled multiproxy indicators (pollen, stable isotopes and charcoal) reconstructed from annually ... more Coupled multiproxy indicators (pollen, stable isotopes and charcoal) reconstructed from annually laminated lake sediments from Nar Gölü in Cappadocia (central Turkey) complemented by documentary and archaeological evidence provide a detailed record of environmental changes and their causes from late Antiquity (AD 300) to the present day. Stable isotope data indicate marked shifts in the variability in summer drought intensity and winter—spring rainfall, but these did not coincide in time with changes in vegetation and land use shown by pollen data. Rather, human impacts appear to have been the main driver of landscape ecological changes in Cappadocia over the last two millennia. Pollen and charcoal data indicate four principal land-use phases: (i) an early Byzantine agrarian landscape characterized by cereals and tree crops, and marking the later part of the so-called Beyşehir Occupation phase; (ii) a period of landscape abandonment and the establishment of secondary woodland f...
Annual record of lake response to the last 900 years of climate change in central Turkey
ABSTRACT Lakes are a widespread palaeoresource and many are sensitive enough to record the compar... more ABSTRACT Lakes are a widespread palaeoresource and many are sensitive enough to record the comparatively subtle climate variations of the last millennium. Varved lake sediments provide the chronological framework from which changes in climate proxies can be observed on annual, decadal and century time scales and compared to other high resolution archives such as tree rings and ice cores. 900 consecutive varves from Nar Gölü, a crater lake in central Turkey, have been analysed individually for geochemical proxies of climate change, including oxygen and stable carbon isotope ratios. The resulting curves show significant variation over decadal and century time scales throughout the recorded time frame. Decadal scale cycles are observed (dominant periodicity of 62 years), as are large and rapid shifts in the isotope system, particularly c. 1400 AD. Modern lake waters at Nar are evaporatively enriched in heavy isotopes compared to rain waters. The co-variation of oxygen and carbon isotope records also suggests evaporation is the dominant driving force behind isotope change. Comparison of recent proxy data with instrumental records suggests relative humidity is the most significant climate variable driving this evaporation. However, the dominant controlling mechanisms change with time, even over sub-millennial time scales. These changes can be explained using other lake proxies and by comparison with other archives.
Two Centuries of Change in the Biology of a Fluctuating Tropical Soda Lake
Fossil and modern pollen data sets are used to infer Holocene vegetation change for 6 case study ... more Fossil and modern pollen data sets are used to infer Holocene vegetation change for 6 case study regions across the Mediterranean and at a pan-Mediterranean scale (described by Fyfe et al., 2018 and Woodbridge et al. 2018). The approach to understanding land cover change employs hierarchical cluster analysis and community classification to derive 16 vegetation clusters from multiple pollen sequences. The results also include reconstructions for a selection of pollen indicator groups e.g. an Anthropogenic Pollen Index (API) and an index for cultivated trees (Olea, Juglans, Castanea and Vitis) (Mercuri et al., 2013). Major patterns in the data sets are summarized by non-metric Multi Dimensional Scaling (nMDS) and Simpson's diversity index. Most of the pollen data derive from the European Pollen Database (Fossil: Leydet, 2007-2018 and modern: Davis et al., 2013), supported by chronologies developed by Giesecke et al (2014) supplemented by additional pollen sites for individual case study regions.
Les transformations de la surface de la terre par l'activité humaine : Géographie : état des lieux. I: La dimension environnementale
Revue Internationale Des Sciences Sociales, 1996
Il est possible, en faisant appel a differentes sources de donnees, d'etudier les transformat... more Il est possible, en faisant appel a differentes sources de donnees, d'etudier les transformations de la surface de la terre par l'activite humaine selon une hierarchie d'echelles de temps. A la fin de la derniere periode glaciaire, l'espece humaine avait colonise la majeure partie de la planete. Les chasseurs-pecheurs-collecteurs etaient integres aux habitats naturels qu'ils occupaient, meme si les traces d'utilisation du feu et l'extinction de la megafaune temoignent tres tot des repercussions de l'activite humaine sur l'environnement naturel. L'exploitation de la nature par l'etre humain changea radicalement de caractere avec l'avenement de l'agriculture, qui entraina le defrichement d'une partie du couvert vegetal et la creation de paysages culturels. Au cours des millenaires suivants, l'ecoumene gagna peu a peu du terrain au detriment des espaces naturels, et ce phenomene s'accelera apres la « decouverte » et la colonisation des Ameriques, de l'Afrique et du Pacifique par les Europeens. Les deux derniers siecles ont ete marques par une profonde modification de l'utilisation des ressources naturelles, en meme temps que se developpait le capitalisme industriel. L'essor des societes industrielles s'explique essentiellement par la substitution de ressources non renouvelables aux ressources qui le sont, en particulier dans le domaine de l'energie. Neanmoins, plutot que l'epuisement des ressources non renouvelables, c'est en premier lieu la degradation des ressources « renouvelables » telles que les forets, les sols et l'eau, et en second lieu la pollution industrielle, qui ont ete les problemes ecologiques majeurs du XX e siecle.
Late Quaternary Hydrologic Changes in the Arid and Semiarid Belt of Northern Africa
Advances in Global Change Research, 2004
The zonal climate pattern associated with the Hadley cell circulation is best exemplified in nort... more The zonal climate pattern associated with the Hadley cell circulation is best exemplified in northern Africa, with its Mediterranean northern tip, subtropi cal Sahara desert, and belts of monsoonal and equatorial climates related to the seasonal migration of the Intertropical Convergence Zone (ITCZ). In the past, astronomical forcing has been the prime factor driving the meridional shifts of these climate belts, but feedback processes from oceans and land surfaces have amplified and modified the direct effects of insolation changes. This chapter uses selected groundwater, paleo lake, and paleobotanic data to illustrate changes in precipitation, moisture sources and trajectories, and wind intensity over the Sahara and its southern semiarid margins (~300N-IOON) over the past 25,000 years. This time interval spans a wet Late Pleistocene phase, followed by two periods of extreme dry and wet conditions, the last glacial maximum (LGM) and the early to mid-Holocene, respectively. During the cool Late Pleistocene wet period, data indicate a strengthening and a southward displacement of extratropical cyclonic disturbances associated with an equatorial shift of the subtropical westerly jet and of the Saharan anti cyclone. During the LGM, the generally dry conditions are in good agreement with model simulations. Northern Africa climates responded to reduced sum mer insolation over the Northern Hemisphere, associated with a stronger northern branch of the Hadley cell circulation, tropical cooling, and a global decrease in water vapor. Data from the early to mid-Holocene wet period show a northward migration of the tropical rainfall belts as far as 200N-24 oN. They suggest a strengthen ing of the ITCZ, a northward migration of 5°-6° of the core of the upper-level
The Environmental History of a Climate-Sensitive Lake in the Former 'White Highlands' of Central Kenya
Paleolimnological analyses of sediment cores from Lake Oloidien in Kenya's central Rift Valle... more Paleolimnological analyses of sediment cores from Lake Oloidien in Kenya's central Rift Valley produced a detailed chronology of climate-driven environmental change since the early 1800s. During much of the 19th century and between about 1940 and 1991, Lake Oloidien was shallow and inhabited by algal and invertebrate communities typical of saline lakes. Confluence with Lake Naivasha between about 1890 and the late 1930s flushed dissolved salts out of Lake Oloidien and created a temporary freshwater phase with papyrus swamp, well-developed submerged macrophyte beds, and reduced algal production. The timing and magnitude of ecological change in Lake Oloidien implies that early agricultural development of the Rift Valley by British colonial settlers coincided with an unusually favorable water-resource availability, out of balance with long-term trends in rainfall and evaporation. Recent lake-level decline and rising salinity are in part a natural consequence of the lake's hydrological response to interannual and decade-scale climate variability. However, ongoing diversion of Rift Valley river inflows for cropland irrigation and industry accelerates the salinization of Lake Oloidien, and may result in deterioration of precious freshwater resources throughout the region.
Diatoms from the annually-laminated sediments of Nar crater lake in central Turkey are used to in... more Diatoms from the annually-laminated sediments of Nar crater lake in central Turkey are used to investigate climatic changes throughout the last 1720 years at decadal time resolution. A diatom-conductivity transfer function is employed to infer past water balance. Further information has been extracted from the palaeo-record through calculation of diatom biovolume, rarefaction (species diversity) and concentration, and through the identification of diatom bloom events in core thin sections. The Nar diatom sequence is compared with oxygen isotope (d 18 O) and pollen records from the same sediment cores in order to test the respective roles of changes in climate and land cover. Diatom-inferred (DI) conductivity excluding bloom taxa and d 18 O show very good correspondence for the first half of the record and demonstrate that this region experienced a period of century-scale drought prior to AD 540, with a subsequent rapid and simultaneous shift to fresher lake conditions and wetter climate. After a drier phase in the Nar record from AD 800e950, the period of the Medieval Climate Anomaly (AD 950 e1400) was generally well watered. During the subsequent Little Ice Age (wAD 1700e1900), DI-conductivity and d 18 O become decoupled. Thin sections reveal between 20 and 40 distinct diatom bloom events per century since AD 1100, with increasing frequency between AD 1700 and 2000. Human land-use changes evident in the pollen sequence may have influenced the diatom relationship with lake water conductivity in the later part of the record. None the less, diatom DCA axes do show a clear response to multi-decadal drought events within the last six centuries. Differences between the proxy-climate records from Nar Lake may be associated with the dissimilar thresholds to environmental fluctuations and non-stationarity in the response of different proxies through time. The palaeoclimate records from Nar show that arid periods occurred in the Eastern Mediterranean during the last two millennia that were more prolonged and extreme than those experienced in the last century.
Book reviews : Bradley, R.S., editor, 1991: Global changes in the past. Boulder, CO: UCAR/Office for Interdisciplinary Earth Studies. iv + 514 pp. $38.00 paper
Southern Anatolia can be broadly divided into three main subregions, namely, the coastal zone, th... more Southern Anatolia can be broadly divided into three main subregions, namely, the coastal zone, the Taurus Mountains with intramontane lake basins and the inner Anatolian plateau (Iyigun et al., 2013). The modern landscape of Anatolia has developed over many millennia as a result of complex interactions between climate, human land use, natural and anthropogenic fire, and other factors, such as competition and species interactions. The landscape of inner Anatolia at the start of the Holocene was characterised by species-rich savannah-type grassland, which was replaced by Quercus-dominated parklands and wood pastures of lower diversity (Asouti and Kabukcu, 2014) into the mid-Holocene. In the wetter uplands of southwest Turkey, mixed conifer-deciduous forests replaced the Artemisia-chenopod steppe of the last glacial period (Van Zeist and Bottema, 1991). Archaeobotanical and archaeozoological evidence demonstrates that plant and animal domestication developed earlier in Southwest Asia than in Europe, in particular within the Levant, showing that this was an important centre of agricultural origins
This paper explores long-term trends in human population and vegetation change in the Levant from... more This paper explores long-term trends in human population and vegetation change in the Levant from the Early to the Late Holocene in order to assess when and how human impact has shaped the region's landscapes over the millennia. To do so, we employed multiple proxies and compared archaeological, pollen and palaeoclimate data within a multi-scalar approach in order to assess how Holocene landscape dynamics change at different geographical scales. We based our analysis on 14 fossil pollen sequences and applied a hierarchical agglomerative clustering and community classification in order to define groups of vegetation types (e.g. grassland, wetland, woodland, etc.). Human impact on the landscape has been assessed by the analysis of pollen indicator groups. Archaeological settlement data and Summed Probability Distribution (SPD) of radiocarbon dates have been used to reconstruct long-term demographic trends. In this study, for the first time, the evolution of the human population is estimated statistically and compared to environmental proxies for assessing the interplay of biotic and abiotic factors in shaping the Holocene landscapes in the Levant.
As part of the Changing the Face of the Mediterranean Project, we consider how human pressure and... more As part of the Changing the Face of the Mediterranean Project, we consider how human pressure and concomitant erosion has affected a range of Mediterranean landscapes has between the Neolithic
This paper offers a comparative study of land use and demographic development in northern and sou... more This paper offers a comparative study of land use and demographic development in northern and southern Greece from the Neolithic to the Byzantine period. Results from summed probability densities (SPD) of archaeological radiocarbon dates and settlement numbers derived from archaeological site surveys are combined with results from cluster-based analysis of published pollen core assemblages to offer an integrated view http://mc.manuscriptcentral.com/holocene HOLOCENE Long-term trends of land use and demography in Greece: a comparative study
A high resolution proxy record of precipitation and evaporation variability through the past 1700... more A high resolution proxy record of precipitation and evaporation variability through the past 1700 yr from δ 18 O analysis of a varved lake sequence from central Turkey shows rapid shifts between dry periods (AD 300-500 and AD 1400-1950) and wetter intervals (AD 560-750 and AD 1000-1350). Changes are consistent with changes in instrumental and proxy records of the Indian monsoon, dry summers in the Eastern Mediterranean being associated with periods of enhanced monsoon rainfall. In addition major shifts in the record are coherent with changes in North Atlantic winter climate with cold, wet periods in the Alps occurring at times of dry Turkish climate.
A multi-proxy intercomparison of environmental change in two maar lake records from central Turkey during the last 14 ka
EGU General Assembly Conference Abstracts, Apr 1, 2016
(1) University of Plymouth, Geography, Earth and Environmental Sciences, Plymouth, United Kingdom... more (1) University of Plymouth, Geography, Earth and Environmental Sciences, Plymouth, United Kingdom , (2) CNRS EDYTEM Laboratory, University of Savoie, Chambéry, France, (3) NERC Isotope Geosciences Facilities, British Geological Survey, Keyworth, NG12 5GG, UK, (4) School of Geography, Earth and Environmental Sciences, University of Birmingham, B15 2TT, UK, (5) School of Geography, University of Nottingham, NG7 2RD, UK, (6) Department of Geography, Ankara University, Turkey
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