This study presents, for the first time, an environmental reconstruction of a sequence spanning nearly the entire Mediterranean Epipaleolithic (∼22.0–11.9 ka cal. BP). The study is based on a ...well-dated, high-resolution pollen record recovered from the waterlogged archaeological site Jordan River Dureijat (JRD), located on the banks of Paleolake Hula. JRD's continuous sequence enabled us to build a pollen-based paleoclimate model providing a solid background for the dramatic cultural changes that occurred in the region during this period. Taxonomic identification of the waterlogged wood assemblage collected from JRD was used to fine-tune the paleoenvironmental reconstruction. The chronological framework is based on radiocarbon dating and the typology of archaeological findings. The LGM (∼22–19 ka cal. BP) was found to be the coldest period of the sequence, marked by a distinct decrease in the reconstructed January temperatures of up to 5°C lower than today, while mean annual precipitation was only slightly lower than the present-day average (∼450 vs. 515 mm, respectively). The wettest and warmest period of the record was identified between ∼14.9 and 13.0 ka cal. BP, with maximum values of 545 mm mean annual precipitation reached at ∼14.5 ka cal. BP. This time interval is synchronized with the global warm and moist Bølling-Allerød interstadial as well as with the onset of the Natufian culture and the emergence of sedentism in the Levant. The Younger Dryas began around 12.9 ka cal. BP and was identified as an exceptional period by the JRD sequence with low temperatures and minimal climatic seasonality contrast: an increase in rain contribution during spring, summer, and autumn was documented concurrently with a significant decrease in winter precipitation. The detailed vegetation and climatological reconstruction presented in this study serves as backdrop to seminal events in human history: the transition from small nomadic groups of hunter-gatherers to the sedentary villages of the Natufian, eventually transitioning to the agricultural, complex communities of the Neolithic.
•Pollen-based paleoclimate model (∼22.0–11.9ka) is provided for the southern Levant.•Lowest January temperatures were reconstructed during the LGM (5 °C lower than today).•The lowest climatic seasonality contrast was reconstructed at the Younger Dryas.•A robust environment set is suggested for the rise of sedentism and agriculture.•A confluence of natural changes and cultural developments promoted agriculture.
Olive (Olea europaea L.) was one of the most important fruit trees in the ancient Mediterranean region and a founder species of horticulture in the Mediterranean Basin. Different views have been ...expressed regarding the geographical origins and timing of olive cultivation. Since genetic studies and macro-botanical remains point in different directions, we turn to another proxy – the palynological evidence. This study uses pollen records to shed new light on the history of olive cultivation and large-scale olive management. We employ a fossil pollen dataset composed of high-resolution pollen records obtained across the Mediterranean Basin covering most of the Holocene. Human activity is indicated when Olea pollen percentages rise fairly suddenly, are not accompanied by an increase of other Mediterranean sclerophyllous trees, and when the rise occurs in combination with consistent archaeological and archaeobotanical evidence. Based on these criteria, our results show that the southern Levant served as the locus of primary olive cultivation as early as ~6500 years BP (yBP), and that a later, early/mid 6th millennium BP cultivation process occurred in the Aegean (Crete) – whether as an independent large-scale management event or as a result of knowledge and/or seedling transfer from the southern Levant. Thus, the early management of olive trees corresponds to the establishment of the Mediterranean village economy and the completion of the ‘secondary products revolution’, rather than urbanization or state formation. From these two areas of origin, the southern Levant and the Aegean olive cultivation spread across the Mediterranean, with the beginning of olive horticulture in the northern Levant dated to ~4800 yBP. In Anatolia, large-scale olive horticulture was palynologically recorded by ~3200 yBP, in mainland Italy at ~3400 yBP, and in the Iberian Peninsula at mid/late 3rd millennium BP.
The 4.2 ka BP event in the Levant Kaniewski, David; Marriner, Nick; Cheddadi, Rachid ...
Climate of the past,
10/2018, Letnik:
14, Številka:
10
Journal Article
Recenzirano
Odprti dostop
The 4.2 ka BP event is defined as a phase of environmental stress characterized by severe and prolonged drought of global extent. The event is recorded from the North Atlantic through Europe to Asia ...and has led scientists to evoke a 300-year global mega-drought. For the Mediterranean and the Near East, this abrupt climate episode radically altered precipitation, with an estimated 30 %–50 % drop in rainfall in the eastern basin. While many studies have highlighted similar trends in the northern Mediterranean (from Spain to Turkey and the northern Levant), data from northern Africa and the central-southern Levant are more nuanced, suggesting a weaker imprint of this climate shift on the environment and/or different climate patterns. Here, we critically review environmental reconstructions for the Levant and show that, while the 4.2 ka BP event also corresponds to a drier period, a different climate pattern emerges in the central-southern Levant, with two arid phases framing a wetter period, suggesting a W-shaped event. This is particularly well expressed by records from the Dead Sea area.
The objective of this study is to contribute to the conservation of upland tree species in the face of climate change. We used a conservation index to prioritize the areas and populations of three ...conifer species in the mountains of Lebanon. This conservation index integrates (1) mountain topography to identify areas that could provide a suitable microclimate, (2) genetic diversity to assess the adaptive capacity of populations in these mountain areas, and (3) a hypothetical climate change scenario that could affect this Mediterranean region. The idea of this index is to prioritize protected areas based on a match between the relevance of the area to be protected and the populations that need local and long-term protection. The stronger the match, the higher the priority of the area to be protected. We applied this conservation index to 36 populations of 15 fir, 15 cedar, and 6 juniper. These populations were genotyped by different authors whose published data we used. The results show that 10 populations of the 3 species have a very high index and 9 others have a lower but still high index, indicating a high conservation priority. These 19 populations occur in 5 different areas that we delineated and that form a network along the Lebanon Mountains. We hypothesize that the conservation of these 19 populations across the Lebanon Mountains could contribute to the long-term sustainability of the 3 species in the face of a 2 °C increase in mean seasonal temperature and a 20% decrease in seasonal precipitation compared to the current climate.
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 with environmental proxies for assessing the interplay of biotic and abiotic factors in shaping the Holocene landscapes in the Levant.
Quaternary Refugia and Persistence of Biodiversity Taberlet, Pierre; Cheddadi, Rachid
Science (American Association for the Advancement of Science),
09/2002, Letnik:
297, Številka:
5589
Journal Article
Recenzirano
In order to preserve biodiversity, we need to understand the mechanisms that sustain it. In their perspective, Taberlet and Cheddadi describe work (Tzedakis et al.) that illustrates the importance of ...southern refugia for the persistence of some temperate tree species during the last glacial-interglacial cycles. Interdisciplinary efforts to identify other putative refugia, could be important in long-term conservation planning.
The threatened conifer Abies cilicica currently persists in Lebanon in geographically isolated forest patches. The impact of demographic and evolutionary processes on population genetic diversity and ...structure were assessed using 10 nuclear microsatellite loci. All remnant 15 local populations revealed a low genetic variation but a high recent effective population size. FST -based measures of population genetic differentiation revealed a low spatial genetic structure, but Bayesian analysis of population structure identified a significant Northeast-Southwest population structure. Populations showed significant but weak isolation-by-distance, indicating non-equilibrium conditions between dispersal and genetic drift. Bayesian assignment tests detected an asymmetric Northeast-Southwest migration involving some long-distance dispersal events. We suggest that the persistence and Northeast-Southwest geographic structure of Abies cilicica in Lebanon is the result of at least two demographic processes during its recent evolutionary history: (1) recent migration to currently marginal populations and (2) local persistence through altitudinal shifts along a mountainous topography. These results might help us better understand the mechanisms involved in the species response to expected climate change.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Cedrus atlantica (Atlas cedar) is a relict and endemic endangered species from northwestern African mountains, whose distribution range has undergone a dramatic reduction over recent decades. ...Long-term studies are needed for a better understanding of the development of its range as well as for assisting in the implementation of sustainable conservation measures. The multi-proxy analysis of a high-resolution fossil record of 180 cm depth allowed us to depict the final demise of an Atlas cedar population from the western Rif Mountains (Jbel Khesana), despite its high resilience during the last ~4000 years. Currently, Atlas cedar trees are not observed in Jbel Khesana but they still occur in the nearby area as scattered populations on a few mountain tops at altitudes higher than 1400 m a.s.l. Our data show an initial relatively stable period (~4000–2400 cal. yr BP) followed by a phase where both climatic and human-induced disturbances cause an alternate dominance of oaks and Atlas cedars (2400~1550 cal. yr BP). Then, the increasing aridity and human activities favoured the depletion of Atlas cedar forests (~1550–800 cal. yr BP). Our record shows that Atlas cedar forests have recovered after each deforestation event, which reveals a high resilience of the species until the mid-20th century, when they became extinct in the study area. The main driver of their local extinction may be attributed to the strong human pressure. Management measures of Atlas cedar in the Rif Mountains should aim at limiting intensive loggings and protecting the existing populations for their local regeneration.
Plant species richness in mountainous regions generally follows a unimodal distribution with lower values at both low and high altitudes in relation to precipitation. In the Atlas mountains, Morocco, ...plant species richness is currently highest at 800–1200 m elevation, but the extent and altitudinal limits of this species-rich belt have shifted in the past with climate change.
Here, we trace the evolution of pollen taxonomic richness (PTR) as a proxy for plant species richness, with the aim of understanding the relationship with climatic changes over the past 19,000 years, and make some assumptions about future changes in species richness. Past PTR was inferred through an analogy with an extensive modern pollen dataset, and past climatic variables were reconstructed from a fossil record collected in the Middle Atlas, Morocco.
We found that the current PTR distribution in Morocco is more closely associated with precipitation than with temperature. During the last glacial period, both PTR and annual precipitation were low, and the analogs were located at lower altitudes than the altitude of the fossil record. During the early Holocene, the PTR increased by approximately 15%, and the modern analogs were found approximately 600–800 m higher than the analogs of the last glacial period. After 6000 years BP, we observe a steady decline in annual precipitation of approximately 30%, resulting in a species richness loss of approximately 18% and a retreat of the upper boundary of the species-rich belt.
Climate projections suggest that annual precipitation in Northwest Africa will decrease by 20–30% over the next 50 years, an annual amount comparable to that of the last glacial period, but under much warmer conditions and in a significantly shorter time. Such a decline in precipitation could result in an unprecedented loss of plant species richness of approximately 15% in just a few decades and put 35% of the protected areas at risk. The forested mountains above 1600 m could then resemble the treeless and less diverse steppes found at higher altitudes above today's tree line.
The aim of this work is to reconstruct the periods of growth and decline of human populations in Morocco and their potential impacts on the landscape over the past 10,000 years. In order to estimate ...the trends in the human population size between 10,000 and 3000 years ago, we used a summed probability distribution (SPD) of radiocarbon dates from a wide range of archaeological sites throughout Morocco. Landscape changes were identified and quantified from a dataset of fossil pollen records. Different anthropogenic pollen markers, as well as natural vegetation groups and taxonomic richness were used to analyse the relationship between long-term trends in human population expansion or regression and type of impact on the landscape. The sub-regions of Morocco have different topographies and climates, which have either favoured or prevented the establishment and/or spread of human populations. In order to identify the areas most significantly impacted by humans and the timing of such impacts, we have reconstructed and compared the same past anthropogenic and landscape proxies along with the population trends within the lowlands and mountainous areas. The lowlands were more strongly impacted earlier in the Holocene than the mountainous areas. Anthropogenic markers indicate that farming expanded in the lowlands during the first major expansion of human populations between ca. 7200 and 6700 cal. yr BP at the start of the Neolithic period. In the Atlas and Rif Mountains, anthropogenic impact is not clearly detectable in any of these areas before 4000 cal. BP.
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