Late Holocene Environmental Changes Research Articles

Lake sediments on the Adamawa Plateau (Central Cameroon) as archives of climate change and the Bantu impact during the last 4000 years BP

AbstractThis study investigates Late Holocene environmental changes in Central Cameroon induced by the combined effects of climate and human impact. For this purpose, sediments from lakes Dang, Massote, Fonjak and Ngaoundaba were studied through lithologic analysis including mineralogical composition and organic geochemistry combined with radiocarbon dates. From these analyses, the sediments at the base of lakes Massote and Dang cores are respectively dated to 4680–3530 and 4220–3580 cal yr BP, whereas the sediments of lakes Fonjak and Ngaoundaba seem to be younger, respectively dated to 3210–3000 and 1870–1740 cal yr BP. Lake sedimentation is dominated by organic matter (OM) poor deposits (OM < 3%) in the lower sections and OM-rich deposits (OM: 5–54%) in the upper sections. This shift from OM-poor to OM-rich sedimentation induced by climate variations occurred at $$\sim $$ ∼ 2800–2400 cal yr BP. The mineral assemblage is predominantly composed of kaolinite with minor contributions from chlorite, smectite, chlorite/smectite, illite/smectite, quartz, K-feldspar, gibbsite, plagioclase, siderite, hematite and goethite. These sediments are clastic, except for Lake Fonjak core sediments which correspond to peat intercalated with carbonate clay and clastic deposits. Age-depth models suggest that the sedimentation rate was 0.2 mm yr-1 for lakes Dang and Massote before $$\sim $$ ∼ 690–560 cal yr BP and $$\sim $$ ∼ 660–470 cal yr BP, respectively. Thereafter, it increased to 0.8 mm yr-1 in Lake Dang and 0.7 mm yr-1 in Lake Massote. Finally, Late Holocene environment changes in Central Cameroon consisted of the shift of open water lakes to marshy fringes with abundant vegetation induced by human activities and facilitated by increasing seasonality.

A high-resolution record of Mid- to Late-Holocene environmental changes from a land-locked lake in Schirmacher Oasis, East Antarctica

We present a high-resolution record of environmental changes during the Mid-Late Holocene obtained from a lake sediment core covering the past 4.87 cal kyr BP in the Schirmacher Oasis, East Antarctica. The magnetic signal of Lake L6 was found to be primarily controlled by catchment-derived ferrimagnetic minerals. The period between 4.87 and 3.35 cal kyr BP is marked by several episodes of cold and warm conditions. Warm and wet conditions prevailed in the region from 3.35 to 2.43 cal kyr BP. Magnetic susceptibility values remained generally low indicating the pedogenic formation of fine magnetic grains. The high values of the chemical weathering indices reflected the warm and wet conditions conducive to chemical weathering. A transition to cold and dry conditions was observed at around 2.43 cal kyr BP, representing the Neoglacial cooling, with high values of magnetic concentration-dependent parameters. Following the Neoglacial period, a return to warm and wet conditions was observed at 1.63 cal kyr BP, coeval with the Medieval Climate Anomaly. Our record shows a Late-Holocene cooling marked by a sudden increase in magnetic susceptibility values, which could represent the Little Ice Age, followed by a shift to warmer conditions near the core top.

Speleothems uncover Late Holocene environmental changes across the Nuragic period in Sardinia (Italy): A possible human influence on land use during bronze to post-Iron Age cultural shifts

During the Bronze and Iron Age, Sardinia was home of one of the most technologically advanced Mediterranean societies (the Nuragic culture). Given its key geographical location, the island was also the fulcrum of deep cultural exchanges. Toward the end of the Iron Age, Phoenicians, and especially Carthaginians and Romans, massively frequented Sardinia for different purposes. This marks an important cultural transition for the region, as the ancient Nuragic-related society terminated. At the same time, this impacted the subsistence and land use practices. Together with middle to late Holocene climate changes, the novel anthropic activities had a pivotal role in shaping the landscape around the island. However, high resolution climate and environmental records for these culturally important phases are still lacking in Sardinia. Thus, this paper explores palaeoenvironmental changes from the Bronze Age to post Iron Ages times by using carbonate speleothems from Suttaterra de Sarpis Cave (Urzulei, central east Sardinia), strategically located nearby the Or Murales Nuragic Village. U–Th ages (n = 20) indicate that five stalagmites comprehensively span the last ∼7000 years. Peculiarly, they all show an evident stratigraphic discontinuity. Age models attest that hiatuses can be at times associated with the discontinuities, spanning periods of ∼1200 to ∼200 years. Importantly, the discontinuities occurred from the Late Iron Age to the Roman period. Based on fabric observations, trace elements and δ13C- δ18O analyses, the discontinuities are primarily attributed to a progressive change of land use above the cave. We suppose that deforestation aimed to clearance for agriculture and livestock practices probably was the most impacting factor for infiltration dynamics and soil state, thus affecting the studied speleothems, although archaeological and historical data are absent for the specific study area. Instead, this is in line with the cultural transition occurring in Sardinia toward the end of the Iron Age, with novel agricultural practices imported by the overseas populations. The anthropic disturbance to the millennial-long karst equilibrium possibly overprinted the response of speleothem proxies to climate oscillations, although future higher resolution analyses are necessary to better investigate the evolution of climate during the Holocene as well as its role in the development of ancient civilizations. Indeed, this is the first speleothem-based Holocene palaeoenvironmental reconstruction accomplished in Sardinia. Considering the paucity of natural lakes in this key location, speleothems here demonstrate their potential in exploring human-driven palaeoenvironmental changes during times of cultural transitions within the Mediterranean context.

The impact of the Neoglacial and other environmental changes on the raised beaches of Joinville Island, Antarctica

AbstractIn order to reconstruct past environmental conditions along the north-eastern Antarctic Peninsula, we documented changes in grain size, grain roundness, onlap as seen in ground-penetrating radar reflection profiles and ice-rafted debris on a set of 36 raised beaches developed over the last ~7.7 ± 0.9 ka on Joinville Island. The most pronounced changes in beach character occur at ~2.7–3.0 ka. At this time, there appears to have been a reintroduction of less rounded material, the development of stratification within individual beach ridges, an introduction of seaweed and limpets to the beach deposits, a change in clast provenance (although slightly earlier than the change in cobble roundness) and a shallowing of the overall beach plain slope. Prolonged cooling associated with the Neoglacial period may have contributed to these changes, as the readvance of glaciers could have changed the provenance of the beach deposits and introduced more material, leading to the change in roundness of the beach cobbles and the overall slope of the beach plain. This study suggests that late Holocene environmental change left a measurable impact on the coastal zone of Antarctica.

Diatom evidence for late Holocene environmental change in a permafrost peatland in the northern Greater Khingan Mountains, Northeast China

High-latitude permafrost peatlands are sensitive to global warming, and understanding their paleohydrological evolution is critical for assessing future hydrological and environmental changes. This paper presents a diatom record from a peat deposit covering the past 3300 years to reconstruct the moisture and acidity conditions in the Tuqiang permafrost peatland in the northern Greater Khingan Mountains of northeast China. Our findings are integrated with previously published records of plant macrofossils, palynology, and geochemistry from the same profile. From 3300 to 2800 cal yr BP, planktonic and benthic diatoms were equally abundant, indicating relatively high moisture conditions, while the low abundance of acidophilous diatoms reflects relatively high pH during this interval. Pollen data show dominance by sedges with input from the surrounding Pinus forest, while LOI data and lithology suggest that the site was a non-peat accumulating wetland. During the period 2800–1100 cal yr BP, the dominance of planktonic diatoms indicates a wetter local environment, concurrent with the dominance of peat-forming sedges (Eriophorum), indicating the development of a peatland. Between 1100 and 500 cal yr BP, a short-lived increase in acidophilous diatoms (Eunotia) marks a decrease in pH. Since 500 cal yr BP, the dominance of benthic diatoms reflects a drier environment, while a vegetation shift from an Eriophorum-dominated rich fen to a Sphagnum- and Ericaceae-dominated poor fen. An increase in Eunotia diatoms prior to the Sphagnum peak may indicate that diatoms are more sensitive to local acidified habitats than moss. Peatland development in the northern Greater Khingan Mountains was likely induced by the onset of a cooler and wetter climate starting at approximately 2800 cal yr BP, a scenario supported by regional paleoclimate records. Since 700 cal yr BP, the peatland has been affected by both anthropogenic activities and climatic changes, as a drying climate and intensified human activities around the study area reduced diatom species diversity and peat accumulation. Under the background of future global warming and enhanced human activities, the decreasing species diversity and carbon accumulation rate of peatlands in high-latitude permafrost regions need more attention.

Late Holocene environmental changes inferred from pollen records of Yileimu Lake sediments, southern Altai Mountains, Northwest China

Climate and landscape changes since the late Holocene have received increasing attention. The Altai region, which is located at the intersection of the Inner Asian Mountain Corridor and the Eurasian Steppe Roads, is relatively poorly studied. In this study, based on robust radiocarbon ages and detailed pollen analyses, the history of climate and landscape changes was reconstructed from Yileimu Lake, southern Altai Mountains during the past 3500 years. Four stages of vegetation change are identified: (1) During 1550 BCE–720 BCE, the vegetation was taiga (mainly Picea and Betula) in uplands, and steppe (dominated by Artemisia, Poaceae and Cyperaceae) around the lake, indicating a humid climate, which was favorable for the expansion of human activities including enhanced nomadic pastoralism in Altai Mountains and transcontinental culture exchange along the proto‐Silk Roads. (2) During 720 BCE–390 CE, there was a stepwise decrease in Picea, rapid increase and then decrease in Betula, and gradual increases in contents of Poaceae and Thalictrum pollen, and fern spores, indicating a warm and moderately humid climate, with evidence of more intense human activities during 20 BCE–390 CE. (3) During 390 CE–1560 CE, desert-steppe (with high Amaranthaceae, Caryophyllaceae, Ephedra and Cyperaceae content) developed in response to an increasing arid climate and/or enhanced human activities. (4) After 1560 CE, taiga and steppe recovered due to the humid climate. Human activities have become the key factor affecting vegetation since the past 2000 years. In addition, the vegetation response to an Ms ≥ 8.0 earthquake that occurred around 1550 BCE was characterized by a rapid recovery of Betula, followed by Artemisia and Picea. Restoration of vegetation helps to reduce soil erosion and afforest exposed landslides.

Legacy archaeology: Aboriginal subsistence response to Holocene environmental changes using faunal evidence from archaeological sites on the Lower Murray, South Australia

Ngaut Ngaut (Devon Downs) and Tungawa (Fromm’s Landing) 2 and 6 are located in the Gorge Section of the Lower Murray River. They were excavated more than 60 years ago. Unusually, they preserved fauna over the 6000 or 7000 years of occupation. Assessing this record, it is concluded that Aboriginal agents were responsible for the middens in these rockshelters. Following this, Ngaut Ngaut and the Tungawa sites are compared in terms of their dating, stratigraphy and changes in the fauna through time. While the majority of species are present throughout at all three sites, there are shifts in the number of animals in concert with Holocene environmental changes. After 3000 BP, the trend is to increased attention being given to resources from the riparian and river zones and away from the dryland Murray Plains. An increase in shellfish and the presence of crayfish gastroliths support this contention. Nearby Tartanga Island provides a record of Holocene sedimentary changes in the Murray River associated with altered sea level and flood regimes, particularly the deposition of the Monoman and Coonambidgal formations. The latter creating a landscape of highly productive swamps and backwaters. The information from these legacy excavations supports the conclusion that a shift in the locus of Aboriginal hunting and gathering activities accompanied mid- and late-Holocene environmental changes on the Lower Murray River.

Doline pond sediments reveal Late Holocene hydro-geomorphological changes in the highlands of the Pantanal, western Brazil

In the southern highlands of the Upper Paraguay River watershed, hundreds of small and shallow ponds exist, but little is known about their origins or potential to record hydroclimate signals in their sediments. Here, we present a multi-proxy evidence that reveals details about the paleolimnological evolution of these shallow tropical lakes. The available data support the conclusion that pond formation resulted from Late Holocene environmental changes that affected the regional hydro-geomorphology. Biological proxies suggest that two distinct environmental phases shaped the regional landscape. In the older phase, sponge spicules and phytoliths are absent, and the sediment geochemistry suggests that karstification processes within the subsurface helped to facilitate topographic closure and doline formation. Sediments of the younger depositional phase are characterized by abundant grass and palm phytoliths. Sponge spicules are also present in these deposits, including the freshwater species Dosilia pydanieli Volkmer-Ribeiro1992, Metania spinata (Carter, 1881), Radiospongilla amazonensis Volkmer-Ribeiro and Becker Maciel, 1983, and Tubella variabilis Bonetto and Ezcurra de Drago1973. These microfossils, especially D. pydanieli, are suggestive of perennial lentic ecosystems. The elemental geochemistry of the youngest sediments is dominated by Si, P, and S; a positive correlation between microfossil content and wt. % S may reflect a linkage between nearshore plant biomass and offshore organic sedimentation. Our results suggest an aquatic transition favoring the formation of stable doline ponds with abundant supra-littoral vegetation occurred over the last millennium, most likely the result of a wetter climate in this region of midwestern Brazil.

A 4000-year paleoenvironmental reconstruction and extreme event record from Laguna Nuxco, Guerrero, Mexico

Reconstructing paleoenvironments on Mexico's Pacific coast is crucial to determine past climate conditions and natural hazard periodicities, vital for predicting future activities. Two sediment cores extracted from Laguna Nuxco, a coastal lagoon in Guerrero, were analyzed to provide a 4000-year paleoenvironmental record. Sediments dominated by shelly clay with low water and organic content, high carbonate content, low Ti/Ca ratio and the presence of Anomalocardia subrugosa suggest that a sheltered bay existed from ~4000–~1300 cal yr BP. During this stage, intermittent beach ridge gaps facilitated the deposition of storm-induced shell deposits, likely from tropical cyclones. Frequent thick shell hash deposition toward the top of the lithologic unit indicates heightened storminess likely from an increase in ENSO activity. An intense tropical cyclone, or perhaps multiple storms during an active period deposited a thick shell hash layer at ~1500 cal yr BP, which helped strengthen the beach ridge system and lead to the modern lagoon phase (~1300 cal yr BP to present), as suggested by the presence of Mytella sp. A more isolated lagoon with significant terrestrial sediment input was reflected by the predominance of lagoonal clay with decreased shell and carbonate contents, increased water and organic contents, and increased Ti/Ca ratio. A quiet period with lower tropical cyclone activity occurred from 1300 to 800 cal yr BP and from 300 cal yr BP to the present, as inferred from no or relatively few shell hash deposits, respectively. A period of hyperactivity occurred from 800 to 300 cal yr BP, as evidenced by seven shell hash layers. During the modern lagoon phase, shell hash deposition was not caused by marine inundation processes, but rather ‘blowout’ events driven by intense precipitation during heightened ENSO activity. Findings shed additional light on Late Holocene environmental changes in a dynamic coastal zone related to regional controlling factors such as tropical cyclone activity, ENSO, and beach ridge development. • A 4000-yr reconstruction at Laguna Nuxco uncovers a transition from bay to lagoon. • Thick shell hash units indicate marine deposition via tropical cyclones. • Thin shell hash layers indicate lagoon “blowouts” from heavy precipitation events. • Activity regimes are largely tied to periods of heightened ENSO. • Notable activity periods occurred from 1500 to 1300 and 800–300 cal yr BP.

Late Holocene Vegetation and Environmental Changes of Coastal Lowlands in Northern Iran: Possible Role of Climate, Human Impact and Caspian Sea Level Fluctuations

Coastal forests and wetlands play an important role in supporting biodiversity, protecting the hinterlands and shorelines from erosion and also contributing to carbon sequestration and freshwater storage. To reconstruct late Holocene vegetation and environmental dynamics in the coastal lowlands of northern Iran and to detect the possible role of climate, human and Caspian Sea level fluctuation on coastal ecosystems, multi-proxy analysis was applied on the sediment cores from the inland Eynak (EYK) lagoon and near coast Bibi Heybat (BBH) alder swamp. Results shows that in the last 170 years, strong reduction of alder forest occurred around Eynak lagoon, while an expansion occurred in the coastal area in the last 100 years. This indicates that human impact shifted from the near coast to elevated inland, which might be due to the raised water level from the Caspian Sea and the coastal area of BBH region was flooded by brackish water from the Caspian Sea, and was not so suitable for agriculture anymore. This study indicate that alder swamp extent is different between coastal and inland sites, suggesting that further studies of multiple records across the region are needed. Moreover, this study helps to distangle human impacts from wetland processes and thus will be an important contribution to effective climate mitigation and conservation strategies. This multi-proxy study presents important palynological records, which helps to understand past and future impacts of various drivers, such as climate, human impact and sea level changes on wetland ecosystems both regionally and globally.

Refining Late-Holocene environmental changes of the Akko coastal plain and its impacts on the settlement and anchorage patterns of Tel Akko (Israel)

Akko/Acre, a UNESCO World Heritage site since 2001, is one of the oldest continuously inhabited sites in the eastern Mediterranean. Tel Akko was a major maritime centre of the southern Levant from the Middle Bronze to the Late Persian period. The city was then moved 1500 m to the west on the Akko promontory where the ‘Old City’ of Saint-Jean d'Acre is located. The natural and anthropogenic evolution of Tel Akko area is reflected by persistent geographical and habitation pattern changes. We combine sedimentological and faunal analyses of radiocarbon dated cores as well as identification of ceramic sherds found in the cores with ground penetrating radar investigations to propose an up-to-date palaeogeographical reconstruction of landscape/environmental changes of the Akko coastal plain in order to understand the extent to which environmental pressures have played a role on the position of anchorage and habitation patterns. We highlight how the local population make use of the natural advantages of the area and adapted to environmental pressures. Following a constant sedimentary input and simultaneous coastal progradation of the Akko coastal plain the main anchorage areas where forced to move. While the 2nd Millennium BCE anchorage was on the southern area of the tell, the late-1st Millennium BCE (Phoenician-Persian) anchorage was relocated on the western area. Vicissitudes in settlement pattern noted in archaeological excavations and surveys on Tel Akko have, most likely, been the consequence of the changes in the position of the coastline.

Late Holocene environmental change in Celestun Lagoon, Yucatan, Mexico

Epikarst estuary response to hydroclimate change remains poorly understood, despite the well-studied link between climate and karst groundwater aquifers. The influence of sea-level rise and coastal geomorphic change on these estuaries obscures climate signals, thus requiring careful development of paleoenvironmental histories to interpret the paleoclimate archives. We used foraminifera assemblages, carbon stable isotope ratios (δ13C) and carbon:nitrogen (C:N) mass ratios of organic matter in sediment cores to infer environmental changes over the past 5300 years in Celestun Lagoon, Yucatan, Mexico. Specimens (> 125 µm) from modern core top sediments revealed three assemblages: (1) a brackish mangrove assemblage of agglutinated Miliammina and Ammotium taxa and hyaline Haynesina (2) an inner-shelf marine assemblage of Bolivina, Hanzawaia, and Rosalina, and (3) a brackish assemblage dominated by Ammonia and Elphidium. Assemblages changed along the lagoon channel in response to changes in salinity and vegetation, i.e. seagrass and mangrove. In addition to these three foraminifera assemblages, lagoon sediments deposited since 5300 cal yr BP are comprised of two more assemblages, defined by Archaias and Laevipeneroplis, which indicate marine Thalassia seagrasses, and Trichohyalus, which indicates restricted inland mangrove ponds. Our data suggest that Celestun Lagoon displayed four phases of development: (1) an inland mangrove pond (5300 BP) (2) a shallow unprotected coastline with marine seagrass and barrier island initiation (4900 BP) (3) a protected brackish lagoon (3000 BP), and (4) a protected lagoon surrounded by mangroves (1700 BP). Stratigraphic (temporal) changes in core assemblages resemble spatial differences in communities across the modern lagoon, from the southern marine sector to the northern brackish region. Similar temporal patterns have been reported from other Yucatan Peninsula lagoons and from cenotes (Nichupte, Aktun Ha), suggesting a regional coastal response to sea level rise and climate change, including geomorphic controls (longshore drift) on lagoon salinity, as observed today. Holocene barrier island development progressively protected the northwest Yucatan Peninsula coastline, reducing mixing between seawater and rain-fed submarine groundwater discharge. Superimposed on this geomorphic signal, assemblage changes that are observed reflect the most severe regional wet and dry climate episodes, which coincide with paleoclimate records from lowland lake archives (Chichancanab, Salpeten). Our results emphasize the need to consider coastal geomorphic evolution when using epikarst estuary and lagoon sediment archives for paleoclimate reconstruction and provide evidence of hydroclimate changes on the Yucatan Peninsula.

Late Holocene environmental change and anthropogenic: Ecosystem interaction on the Laikipia Plateau, Kenya

East African ecosystems have been shaped by long-term socio-ecological–environmental interactions. Although much previous work on human–environment interrelationships have emphasised the negative impacts of human interventions, a growing body of work shows that there have also often been strong beneficial connections between people and ecosystems, especially in savanna environments. However, limited information and understanding of past interactions between humans and ecosystems of periods longer than a century hampers effective management of contemporary environments. Here, we present a late Holocene study of pollen, fern spore, fungal spore, and charcoal analyses from radiocarbon-dated sediment sequences and assess this record against archaeological and historical data to describe socio-ecological changes on the Laikipia Plateau in Rift Valley Province, Kenya. The results suggest a landscape characterised by closed forests between 2268 years before present (cal year BP) and 1615 cal year BP when there was a significant change to a more open woodland/grassland mosaic that continues to prevail across the study area. Increased amounts of charcoal in the sediment are observed for this same period, becoming particularly common from around 900 cal year BP associated with fungal spores commonly linked to the presence of herbivores. It is likely these trends reflect changes in land use management as pastoral populations improved and extended pasture, using fire to eradicate disease-prone habitats. Implications for contemporary land use management are discussed in the light of these findings.

Late-Holocene landscape evolution and human presence in the northern Danube delta (Chilia distributary lobes)

This paper documents the Late-Holocene environmental changes and human presence in the northern Danube delta using a multidisciplinary approach that combines geoscientific data with archaeological findings, historical texts, and maps. It follows the formation and progression of the Chilia distributary and the reconfiguration of socioeconomic activities. Sedimentary facies identified on five new cores by changes in texture properties, magnetic susceptibility, geochemistry, and macro- and microfauna composition together with the newly obtained chronology constrain the complex evolution of the Chilia branch as filling in a long-lasting bay and then of a giant lagoon (Thiagola) which covered most of the northern delta since the Old Danube lobe inception (ca. 7500 yrs BP) till modern Chilia development. It initiated during the Greek Antiquity (ca. 2500 yrs ar BP) at the delta apex, while in Roman times (ca. 1800 yrs BP) it pursued its slow flowing into the vast Thiagola Lagoon. The most dramatic transformations occurred in the last 800 years when the river passed east of the Chilia promontory, rapidly went through the present-day Matița-Merhei basin (several decades), and created its first open-sea outlet. Solid discharge increased in two distinct periods, once in the Middle Ages (ca. 750 yrs BP) and then in the Modern Period (ca. 150 yrs BP) due to human-induced land-use changes in the Danube watershed. The chronology of the cultural remains on the pre-deltaic Chilia promontory and the multiproxy analysis of a sediment core retrieved nearby downstream suggest the terrestrial connection of the island with the mainland in ancient times. The hitherto contended issue of the old Thiagola Lagoon and its location are redefined here, as are the original identifications of ancient and medieval toponyms and hydronyms, especially for Chilia-Licostomo, Byzantine, Genoese, Moldavian, Ottoman, and Russian trading point of great importance in the political and economic history of the Black Sea and neighboring regions.

Mid‐ to late Holocene environmental changes and human‐environment interactions in the surroundings of La Silla del Papa, SW Spain

AbstractIn southern Iberia, the surroundings of the Strait of Gibraltar are known as a crossroad for population movements, cultural exchanges, and trade from Late Prehistory to modern times. However, questions remain about the impact of this historical development on the environment. The settlement of La Silla del Papa, an important hillfort in southern Andalusia (Cádiz), was occupied during the entire Iron Age, replaced by the coastal town Baelo Claudia during Roman times, and re‐occupied during Early Medieval times. As such, La Silla del Papa and its territory represent an ideal location for long‐term studies on human‐environment interactions. Within the framework of the interdisciplinary project “Archeostraits,” geoarchaeological investigations in the surroundings of La Silla del Papa aimed at constraining ecological conditions and human‐environment interactions during the mid‐ and late Holocene and during major human occupation phases. Our results document an early mid‐Holocene marine embayment in the lower floodplain of the Río del Cachón, rapidly turning into a coastal lagoon and later into freshwater‐dominated wetlands. After approximately 2100 BP (c. 150 BC), fluvial and alluvial deposition i600ing a high anthropogenic impact on the local landscape during Roman or post‐Roman times. Palynological results reveal fluctuating agricultural and pastoral activities and distinct periods of landscape opening during the Neolithic and Iron Age.

New insights into Late Devensian Lateglacial and early Holocene environmental change: Two high-resolution case studies from SE England

The Late Devensian Lateglacial to early Holocene transition across north-west Europe was characterized by a rapid shift in climate from the cold, harsh conditions of the Loch Lomond Stadial to the warmer climate of the early Postglacial. However, our knowledge of this transition in south-east England has been hampered by the paucity of mires with sedimentary records spanning this period. We present two new high-resolution paleoenvironmental records from Langshot Bog and Elstead Bog B (Surrey, UK), which provide a clear signature of vegetation succession and fire history. Organic sedimentation at Langshot Bog commenced prior to 12,640–12,410 cal. BP (95% probability) and continued until 8430–8350 cal. BP (95% probability). Providing a robust chronology for Elstead Bog B proved to be problematic, although available dates suggest sediment accumulation commenced prior to 11,820–11,400 cal. BP (WM-168, 2σ). The sites are characterized by similar vegetation records, indicating a regional signal from locations over 20 km apart. Scrubby tundra-style vegetation is characteristic of cold conditions associated with the Lateglacial. The identification of Alnus and Corylus, taxa not normally associated with this period, indicates that microclimates may have permitted the survival of these species. Expansion of Betula followed by Pinus dates to the onset of the Holocene, forming mixed coniferous-deciduous woodland, during a period which is punctuated by short climatic events identified from stable isotope analysis. Subsequent expansion of thermophilous taxa Corylus, Ulmus and Quercus results in the formation of deciduous woodland. A rise in micro-charcoal, heathland and herbaceous taxa indicates development of heathy-scrubby clearings within this Holocene landscape.

Late Holocene environmental and climatic changes in the Western Sayan Mountains based on high‐resolution multi‐proxy data

Southern Siberia is characterized by complex climatic and vegetation patterns, and the late‐Quaternary evolution of climate and vegetation in this vast region is still poorly understood. This study uses pollen, spores, testate amoebae and plant macrofossils to characterize environmental and climatic changes at Bezrybnoe Mire (Western Sayan Mountains, southern Central Siberia). Pollen data indicate permanent forest cover in the region during the Late Holocene and subtle variations in abundances of dominant taxa (Pinus sibirica,Abies sibirica,Larix,Pinus sylvestris and Betula pendula). Higher values of Betula and Artemisia at the beginning of the record (>2500 cal. a BP, probably c. 3300 cal. a BP) and c. 420–140 cal. a BP suggest slight expansion of birch forest and steppe. The intervening period has higher values of dark taiga taxa, suggesting a shift to higher moisture levels. Superimposed on this longer‐term variation, the testate amoeba record of mire wetness reveals 12 sub‐millennial episodes of drier conditions (with a sample resolution of c. 50–90 years). Mire plant communities reacted to the high‐frequency fluctuations in moisture but with a delayed response of c. 30–40 years. Both the short‐ and long‐term variations in moisture show general concordance with neighbouring regional records and align with observed cultural changes of the Eurasian steppe region. These variations in moisture probably relate to the degree of penetration of the moisture‐bearing Westerlies into southern Siberia.

Climate History of Southern Mongolia Since 17 ka: The Ostracod, Gastropod and Charophyte Record From Lake Ulaan

Late glacial and Holocene environmental and climate change in the Gobi Desert is poorly understood due to the lack of appropriate geological archives and commonly faced difficulties in establishing reliable chronologies. Here, the relatively well-dated sediment record from the terminal Lake Ulaan is used to reconstruct the lake history and climate in the region. Most abundant calcareous fossils in the lake sediments are ostracod (micro-crustacean) valves. The ostracod assemblage is dominated by Limnocythere inopinata, and generally very shallow conditions and sodium-dominated waters are inferred for Lake Ulaan. A single period of significantly increased silt accumulation in the late glacial was recorded at ca. 16 ka, probably as a result of melting glaciers in the uppermost reaches of the lake’s main tributary, the Ongin River, and the influx of glacially-ground, fine materials. Lake Ulaan had a higher salinity afterwards during the Greenland Interstadial 1, and dry climate prevailed in the region. The lake level started to rise and the salinity decreased since ca. 12.3 ka, leading to the establishment of freshwater conditions in the early Holocene. Highest inflows and highest productivity in and around the lake, and wettest climate conditions in the region were recorded in the early Holocene. Lake conditions, most favourable for the aquatic fauna, culminated ca. 10 ka. Afterwards, Lake Ulaan experienced a step-wise lake-level decline and salinity increase at 9.4 and 6.8 ka. The further shrinkage of the lake and the approaching Ongin River mouth near the central part of the basin is recorded since 3.2 ka.

Late-Holocene environmental change on the Nullarbor Plain, southwest Australia, based on speleothem pollen records

Fossil pollen from two stalagmites is examined to reconstruct a c. 2400-year history of vegetation change on the Nullarbor Plain. Environmental changes are reflected by variation in chenopod species abundance, and by a peak in woody taxa between 1000 and 800 years ago which is interpreted as evidence of increased moisture conditions associated with a positive phase of the Southern Annular Mode. While no strong palynological signal is observed at the time of European colonization of Australia, a significant change occurs in the past 40 years, which is interpreted as a vegetation response to a recorded fire event. As speleothems (secondary cave carbonates including stalagmites, stalactites and flowstones) rarely contain enough fossil pollen for analysis, the taphonomic biases of speleothem archives remain poorly understood. This study, as well as being a high-resolution record of environmental change, presents an opportunity to examine these taphonomic filters. The record is shown to be sensitive to episodic deposition of presumably insect-borne pollen, but overall appears to provide a faithful representation of local and regional vegetation change. There is a need for greater research into taphonomic processes, if speleothem palynology is to be developed as a viable alternative to lacustrine sediments in the investigation of past environmental change.

Mid to late Holocene environmental change and human impact: A view from Central China

Dajiuhu, a rare peatland in Central China, has attracted several studies. There are differences in the interpretations of its Holocene record, and little has been written on landscape transformation by human impact. A 6100 yr palynologic record, together with TOC and charcoal data, from Dajiuhu peatland is assessed to provide a new perspective on mid-late Holocene environmental change and human activity. We found that wetland herb pollen is a sensitive marker of effective precipitation, and the ratio of evergreen and deciduous tree pollen can be a proxy for temperature variability at the site. A mixed evergreen and deciduous forest dominates the record. Peak warming was at 2900 cal yr BP and cool events occurred around 5100, 4100 and 2700 cal yr BP. The cooling at 5100 and 2700 cal yr BP may be related to decreased solar activity. There was a long-term drying trend punctuated by episodic droughts around 3000 to 2800 cal yr BP and following 1500 cal yr BP; we argue that these relate to the southward retreat of the ITCZ. A low level of regional fires was present as background. At 800 cal yr BP there were declines in forest taxa, increases in ferns, herbs, burning and inorganic inputs into the sediment; these signal sustained human impact in the area. The relatively late human impact is probably related to the rugged mountain landscape and river systems prone to frequent flooding, or may be due to a late expansion in human population and land resource pressures at Dajiuhu.