Impacts of global climate change on terrestrial ecosystems are imperfectly constrained by ecosystem models and direct observations. Pervasive ecosystem transformations occurred in response to warming and associated climatic changes during the last glacial-to-interglacial transition, which was comparable in magnitude to warming projected for the next century under high-emission scenarios. We reviewed 594 published paleoecological records to examine compositional and structural changes in terrestrial vegetation since the last glacial period and to project the magnitudes of ecosystem transformations under alternative future emission scenarios. Our results indicate that terrestrial ecosystems are highly sensitive to temperature change and suggest that, without major reductions in greenhouse gas emissions to the atmosphere, terrestrial ecosystems worldwide are at risk of major transformation, with accompanying disruption of ecosystem services and impacts on biodiversity.

A palynological study based on two 100-m long cores from Lake Urmia in northwestern Iran provides a vegetation record spanning 200 ka, the longest pollen record for the continental interior of the Near East.During both penultimate and last glaciations, a steppe of Artemisia and Poaceae dominated the upland vegetation with a high proportion of Chenopodiaceae in both upland and lowland saline ecosystems. While Juniperus and deciduous Quercus trees were extremely rare and restricted to some refugia, Hippophaë rhamnoides constituted an important phanerophyte, particularly during the upper last glacial sediments. A pronounced expansion in Ephedra shrub-steppe occurred at the end of the penultimate late-glacial period but was followed by extreme aridity that favoured an Artemisia steppe. Very high lake levels, registered by both pollen and sedimentary markers, occurred during the middle of the last glaciation and upper part of the penultimate glaciation. The late-glacial to early Holocene transition is represented by a succession of Hippophaë, Ephedra, Betula, Pistacia and finally Juniperus and Quercus. The last interglacial period (Eemian), slightly warmer and moister than the Holocene, was followed by two interstadial phases similar in pattern to those recorded in the marine isotope record and southern European pollen sequences.1 This work is dedicated to Sytze Bottema for his outstanding contribution to late Quaternary palynology of the Near East.2

International audienceWe present a high-resolution (sub-decadal to centennial), multi-proxy reconstruction of aeolian input and changes in palaeohydrological conditions based on a 13000 Yr record from Neor Lake's peripheral peat in NW Iran. Variations in relative abundances of refractory (Al, Zr, Ti, and Si), redox sensitive (Fe) and mobile (K and Rb) elements, total organic carbon (TOC), delta C-13(TOC), compound-specific leaf wax hydrogen isotopes (delta D), carbon accumulation rates and dust fluxes presented here fill a large gap in the existing terrestrial paleoclimate records from the interior of West Asia. Our results suggest that a transition occurred from dry and dusty conditions during the Younger Dryas (YD) to a relatively wetter period with higher carbon accumulation rates and low aeolian input during the early Holocene (9000-6000 Yr BP). This period was followed by relatively drier and dustier conditions during middle to late Holocene, which is consistent with orbital changes in insolation that affected much of the northern hemisphere. Numerous episodes of high aeolian input spanning a few decades to millennia are prevalent during the middle to late Holocene. Wavelet analysis of variations in Ti abundances as a proxy for aeolian input revealed notable periodicities at 230, 320, and 470 years with significant periodicities centered around 820, 1550, and 3110 years over the last 13000 years. Comparison with palaeoclimate archives from West Asia, the North Atlantic and African lakes point to a teleconnection between North Atlantic climate and the interior of West Asia during the last glacial termination and the Holocene epoch. We further assess the potential role of abrupt climate change on early human societies by comparing our record of palaeoclimate variability with historical, geological and archaeological archives from this region. The terrestrial record from this study confirms previous evidence from marine sediments of the Arabian Sea that suggested climate change influenced the termination of the Akkadian empire. In addition, nearly all observed episodes of enhanced dust deposition during the middle to late Holocene coincided with times of drought, famine, and power transitions across the Iranian Plateau, Mesopotamia and the eastern Mediterranean region. These findings indicate that while socio-economic factors are traditionally considered to shape ancient human societies in this region, the influence of abrupt climate change should not be underestimated. (C) 2015 Elsevier Ltd. All rights reserved

This study aims at proposing a new bioclimatic zonation for Iran based on the recently developed Global Bioclimatic Classification System (GBC) and tries to re-appraise this classification system by checking the degree of correspondence between its bioclimatic zones and the distribution of major phytogeographical regions, biomes, and a selection of plant and insect taxa of Iran. After application of the GBC to Iranian meteorological data, three macrobioclimates, ten bioclimates, and three bioclimatic variants were distinguished. The Mediterranean macrobioclimate is the dominant macrobioclimate and correlates with the Irano-Turanian biogeographical region, the Tropical macrobioclimate in southern Iran correlates with the Saharo-Sindian region and finally a small Temperate macrobioclimatic zone in northern Iran correlates with the Euro-Siberian region. Mediterranean macrobioclimate of Iran displays a wide range of bioclimates including Mediterranean pluviseasonal-oceanic, Mediterranean xeric-oceanic, Mediterranean pluviseasonal-continental, Mediterranean xeric-continental, Mediterranean desertic-oceanic, and Mediterranean desertic-continental. Tropical macrobioclimate also shows a range of bioclimates including Tropical xeric, Tropical desertic, and Tropical hyperdesertic. Finally, Temperate macrobioclimate has only one bioclimate i. e. Temperate oceanic. In conclusion, bioclimatic zones identified using the GBC system correlate well with the main phytogeographical regions of Iran at macrobioclimatic level and with major biomes at bioclimatic level. An advantage of the GBC over other bioclimatic classification systems is the inclusion of both seasonal and annual variations in those climatic parameters which are significant for the growth and development of plant populations and communities. GBC distinguishes several types of Mediterranean climate regimes for Iran and helps to differentiate between two different desert climate types i. e. Mediterranean and Tropical deserts in arid parts of the country. Because the climate in the Irano-Turanian region clearly differs from the Mediterranean region in its degree of continentality and seasonality, we propose the term ‘ xero-estival-continental’ or ‘Irano-Turanian’ instead of ‘Mediterranean’ bioclimate when describing the climate of continental Middle East and Central Asia.

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Postglacial expansion of deciduous oak woodlands of the Zagros—Anti-Taurus Mountains, a major biome of the Near East, was delayed until the middle Holocene at ~6300 cal. yr BP. The current hypotheses explain this delay as a consequence of a regional aridity during the early Holocene, slow migration rates of forest trees, and/or a long history of land use and agro-pastoralism in this region. In the present paper, support is given to a hypothesis that suggests different precipitation seasonalities during the early Holocene compared with the late Holocene. The oak species of the Zagros—Anti-Taurus Mts, particularly Quercus brantii Lindl., are strongly dependent on spring precipitation for regeneration and are sensitive to a long dry season. Detailed analysis of modern atmospheric circulation patterns in SW Asia during the late spring suggests that the Indian Summer Monsoon (ISM) intensification can modify the amount of late spring and/or early summer rainfall in western/northwestern Iran and eastern Anatolia, which could in turn have controlled the development of the Zagros—Anti-Taurus deciduous oak woodlands. During the early Holocene, the northwestward shift of the Inter-Tropical Convergence Zone (ITCZ) could have displaced the subtropical anticyclonic belt or associated high pressure ridges to the northwest. The latter could, in turn, have prevented the southeastward penetration of low pressure systems originating from the North Atlantic and Black Sea regions. Such atmospheric configuration could have reduced or eliminated the spring precipitation creating a typical Mediterranean continental climate characterized by winter-dominated precipitation. This scenario highlights the complexity of biome response to climate system interactions in transitional climatic and biogeographical regions.

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