Search

The modern Nile delta developed in the Middle and Late Holocene, and at its most northern-central point is situated at the Burullus Lagoon, which is environmentally diverse, including salt marshes, mudflats, and sand plains, and separated from a sea by a sand barrier overtopped with high sand dunes. The lagoon has been fed since the Middle Holocene by the Sebennitic branch of the Nile and marine intrusions through the Bughaz inlet. A sediment core (BO-1) was collected at the northeastern shore of the lagoon and sampled at centennial scale resolution in order to reconstruct the development of the lagoon. The results show that an initial and limited lagoon had developed at the end of the Early Holocene, but after a dry period ca. 7.2 cal ka BP it has been progressively transformed into a marshy area, with occasional inflows of sea water. Lower water level and higher salinity of the Burullus Lagoon at 6.0-5.5 and 4.8-4.2 cal ka BP reflected droughts in the Nile catchment. Thereafter, the river reactivated in the Burullus Lagoon area, and since 2.8 cal ka BP was accompanied by occasional inflows of sea water. Since ca. 0.8 cal ka BP, increased fluvial activity occurred in this part of the Nile delta, which terminated after construction of the Aswan dams in the twentieth century. [ABSTRACT FROM AUTHOR]

The Qarun Lake in the Faiyum Oasis (Egypt) provides a unique record of Holocene environmental and climate change in an arid area largely devoid of fossil proxy records. Multiple lithological, palaeontological and geochemical proxies and 32 radiocarbon dates from the 26-m-long core FA-1 provide a time series of the lake's transformation. Our results confirm that a permanent lake appeared in the Holocene at c. 10 cal. ka BP. The finely laminated lake sediments consist of diatomite, in which diatoms and ostracods together with lower concentrations of ions indicate a freshwater environment at the end of the early and middle Holocene. This freshwater supply was closely associated with regular inflows of the Nile water during flood seasons, when the Intertropical Convergence Zone ( ITCZ) migrated northwards in Africa, although it has probably never reached the Faiyum Oasis. Local rainfall, possibly connected with a northern atmospheric circulation, may have been important during winter. Several phases in the lake's evolution are recognized, represented by oscillations between deep open freshwater conditions during more humid climate and shallow fresh to brackish water during drier episodes. After a long freshwater phase, the lake setting has become more brackish since c. 6.2 cal. ka BP as indicated by diatoms and increasing contents of evaporite ions in the sediment. This clearly shows that since that time the lake has occasionally become partly desiccated. This is a result of reduced discharge of the Nile. In the late Holocene the lake was mostly brackish and then gradually turned into a saline lake. This natural process was interrupted about 2.3 cal. ka BP when a man-made canal facilitated water inflow from the Nile. The examined FA-1 core can be used as a reference age model of climate change in the Holocene and its impact on the development and decline of ancient civilizations in northeastern Africa. [ABSTRACT FROM AUTHOR]

Abstract: Climate change with rising sea levels and possible changes in surge levels and wave climate will have a large impact on how we protect our coastal areas and cities. Here the focus is on estuarine locations not only affected by tide and surge propagation, but also potentially influenced by freshwater discharge. Mitigation measures might be diverse ranging from pure hard ‘engineering’ solutions all the way to significant realignment. The variation in the type/origin and extent of the flood sources greatly influences subsequent risk management measures. At the same time, society is increasingly demanding that we take a holistic view on risk management, embracing and balancing safety, ecological and socio-economic aspects. This requires that all these diverse factors need to be considered together and integrated. In this context, the Source–Pathway–Receptor (SPR) approach offers a powerful holistic tool to investigate changing risk connected to extreme events. The traditional SPR approach with a consecutive treatment of the flood, pathway and receptor is well understood and is widely used in coastal flood risk analysis. Here an enhanced 2D conceptual version of the SPR method is used to better describe the system and to allow flexibility in considering multiple scales, flood sources and pathways. The new approach is demonstrated by three estuarine case studies in western Europe: the Gironde estuary, France; the Dendermonde region in the Scheldt estuary, Belgium; and HafenCity (Hamburg) in the Elbe estuary, Germany. They differ considerably in the surface area considered, in the type of flood sources, and hence also in the SPR configuration. After a brief introduction of the typical characteristics of the three study sites including some lessons learned from past flood protection measures, the differences in application and results of the SPR approach are discussed. Emphasis is on the specific aspects for each study site, but embedded in a generic SPR framework. The resulting generic lessons learned about the flood sources and how this shapes subsequent analysis are transferable to numerous important estuaries worldwide. [Copyright &y& Elsevier]

The vast Dongting Lake in the middle Yangtze River basin, China, was occupied by Chinese Neolithic settlements starting 10 000 years ago, and rice cultivation there is probably the earliest in the world. The numerous Neolithic settlements identified by previous archaeological surveys represent the five major Neolithic cultural stages, i.e. the Pengtoushan (9000–7900 cal. yr BP), Zaoshixiaceng (7900–6800 cal. yr BP), Daxi (6800–5500 cal. yr BP), Qujialing (5500–5000 cal. yr BP), and Shijiahe (5000–4000 cal. yr BP). Using sedimentological and geoarchaeological approaches, this paper analyses the drivers of basin-scale settlement relocation in relation to lake-level fluctuations and monsoon climate variations in the Holocene. The relocation of Neolithic sites around the lake shoreline and on the adjacent floodplain, together with radiocarbon-dated stratigraphy, clearly indicates that the shape of the lake basin was an incised and elongated valley occupied by a lake in the early Holocene, which became a broader and shallower depression in the mid to late Holocene. The established lowest habitable base of the settlements positioned on the lake shore assists reconstruction of the change in lake level from 22 m at 9000 cal. yr BP to 26 m at 5500–4000 cal. yr BP, although higher and lower lake levels occurred during the intervening cultural stages. The pollen spectra reveal a warming trend throughout the Holocene with at least four major temperature cycles, driven by monsoon variations between temperate- and warm-humid conditions. In the early Holocene the climate changed from cool-dry to warm-humid, and this played a key role in developing the earliest Pengtoushan culture in the region. Subsequent climate fluctuations fit well with the advance and retreat of the lake shore, also coevally with Neolithic site movements in the lake region. In this study we show how geoarchaeological evidence can be used in environmental reconstruction during the Holocene. [ABSTRACT FROM AUTHOR]

Due to increasing water use, diversion and salinization, along with subsidence and sea-level rise, deltas in arid regions are shrinking worldwide. Some of the most ecologically important arid deltas include the Colorado, Indus, Nile, and Tigris-Euphrates. The primary stressors vary globally, but these deltas are threatened by increased salinization, water storage and diversion, eutrophication, and wetland loss. In order to make these deltas sustainable over time, some water flow, including seasonal flooding, needs to be re-established. Positive impacts have been seen in the Colorado River delta after flows to the delta were increased. In addition to increasing freshwater flow, collaboration among stakeholders and active management are necessary. For the Nile River, cooperation among different nations in the Nile drainage basin is important. River flow into the Tigris-Euphrates River delta has been affected by politics and civil strife in the Middle East, but some flow has been re-allocated to the delta. Studies commissioned for the Indus River delta recommended re-establishment of some monthly water flow to maintain the river channel and to fight saltwater intrusion. However, accelerating climate impacts, socio-political conflicts, and growing populations suggest a dire future for arid deltas. [ABSTRACT FROM AUTHOR]

An important focus in research over the past decade is the relationship between climatic/environmental change and human cultural evolution during the Holocene. This decade saw an increasing number of natural scientists involved in this research, which led to debates and collaborations between natural scientists and archaeologists/anthropologists. This decade also witnessed an increase in multidisciplinary research across these subjects, which has improved significantly the understanding of the human–environment relationship. As part of this research drive, this Special Issue highlights the importance of multidisciplinary studies, mainly from China, on early rice agriculture, impacts of environmental change in Neolithic communities, and new approaches for environmental reconstruction. [ABSTRACT FROM AUTHOR]

Evaluation of conventional and AMS radiocarbon dates, obtained for 65 Holocene sediment samples in 20 cores collected in the Yangtze delta, China, indicates that only about one in 4 dates falls within an expected time range. In this Holocene deltaic system, most radiocarbon-dated samples do not become progressively younger upcore, and there is no direct relationship between age and depth. About one in 6 dates is too young, recording locally truncated stratigraphic sections. Of particular note are the nearly two-thirds of all radiocarbon dates that record ages that are much too old, by 1000 to 10,000 years (23% are of Pleistocene age). This phenomenon results from the introduction of old carbon during sediment storage and reworking along the dispersal path between headlands and the coast. Thus, rather than recording final time of Holocene deposition at deltaic core sites, dates in Yangtze delta sediment appear to indicate a time lapse that occurred during storage and transport cycles in the fluvial valley and delta plain. There is no simple, obvious or universal solution to this radiocarbon-dating problem in deltaic sequences. The problem warrants attention since reliable dating of Holocene sequences is essential for measurement of rates of sediment accumulation and delta margin subsidence relative to sea level, two of the parameters needed to help implementprotection measures along the vulnerable low-lying Yangtze delta coast. At present, a multi-method dating approach (amino acid racemization, isotopic analyses, archaeological determination, and others) would constrain sediment age, and provide a more reliable measure of deposition time in such settings than by radiocarbon dating alone. [ABSTRACT FROM AUTHOR]

This study reports the high-resolution (50–100 yr) temporal variations of quartz roundness used as a climate proxy in the sediment core FA-1 recovered in the Faiyum Basin of the lower Nile. A higher proportion of transparent angular quartz can be found in sediment transported from the upper to the lower Nile via runoff when the Intertropical Convergence Zone (ITCZ) migrated northwards during the Holocene. The stained rounded quartz in the core sediment can be linked to windblown input into the Faiyum Basin from the Sahara Desert when the ITCZ shifted southwards. Using this theory, we reconstructed the series of Holocene climate changes in relation to the ITCZ migration. Our quartz evidence revealed: 1) the African Humid Period (AHP) occurring in the basin at 9200–4200 cal. yrs BP; 2) a short-term (5800–5400 cal. yrs BP) aridification occurred during the AHP; and 3) the rapid onset of hyper-aridification at ca. 4200–4000 years ago, which then persisted. These ITCZ related climate pulses, have basin-wide implications supporting relevant paleoclimate studies in North Africa. In addition, our results suggested at least 3 times when hydro-geoengineering works were implemented to source water from the Nile for local farming during the hyper-aridification period. [ABSTRACT FROM AUTHOR]

High-resolution climate variations since the last 4500 years in the monsoonal-arid transition zone of north-central China were revealed through the integration of proxies from sediment cores in the Lake Daihai basin. Human occupations in the lake basin deduced from archeological findings and historical literatures were then incorporated into the climate sequence to demonstrate the patterns of human responses to the climate changes, and the recent anthropogenic effects. It indicated that: (1) Climate dominated human-environment adaptations prevailed prior to ∼2700 cal yr BP. An amicable climate setting before ∼4100 cal yr BP would facilitate the growth of the Laohushan Culture (LC) in the lake basin, while a pronounced deterioration of water thermal condition after that had led to human exodus and the collapse of the LC. The reduced human activity in the lake basin indicated at ∼3800–3500 cal yr BP and a subsequent cultural blank at ∼3500–2700 cal yr BP, were both in response to the climate and lake level fluctuations during ∼3800–2800 cal yr BP. (2) Transition to a positive human adaptation was seen at ∼2700–1100 cal yr BP, represented by the exploitation of arable land for cultivation and animal husbandry as the lake contracted. (3) An increasing human presence that affected environmental processes became more severe over the last ∼1100 cal yr BP. This was basically due to the ongoing lake shore reclamation for cropping, and more recently heavy metals emissions from fossil fuel combustion and local industries. [ABSTRACT FROM AUTHOR]

Human perturbation and its impact on vegetation and plant diversity during the Holocene have caused serious concerns for the biogeological and geoarchaeological communities. As a centre of origin of rice agriculture, the lower Yangtze region (LYR) has a long history of human occupation over most of the Holocene. However, early anthropogenic impacts on the ecosystem of the region remain elusive. Here we present a multidisciplinary study including pollen and charcoal analysis on three different sediment cores (TJA, YJ1503 and PW) along a gradient of human interference to disentangle human and climatic influences on vegetation in the coastal area of the LYR. The results show that rice farming which developed after an environmental transition from salt marsh to freshwater wetland was mainly assisted by fire, particularly slash-and-burn practices by the Neolithic people between 7 and 4 kyr BP. Both the vegetation composition and plant diversity of the mixed forests of the LYR responded to these early human perturbations with a threshold effect. However, whereas plant diversity rapidly recovered when human activity ceased/weakened, the vegetation composition showed differences from the pre-fire condition, indicating a lasting effect. We propose that the varied post-fire recovery strategies of different species, e.g. Quercus evergreen comp. versus Pinus massonania , would account for this discrepancy. • Pollen and charcoal were analyzed for three sediment cores along a gradient of human interference. • Human impact on vegetational change occurred since 6.6 kyr BP with a lasting effect. • Fire interference reduced plant diversity with a threshold effect. [ABSTRACT FROM AUTHOR]

Highlights: [•] Annual precipitation and runoff variability in the Yangtze River are very low. [•] No significant trend in annual precipitation and runoff over the period 1955–2011. [•] Mean annual temperature shows significant increasing trend over the period 1955–2011. [•] Annual runoff shows little response to major developments over the period 1955–2011. [•] No climate change effect on annual precipitation or runoff in the period 1955–2011. [ABSTRACT FROM AUTHOR]

To investigate how Holocene climate patterns influenced the development of early Egyptian agriculture at the archaeological site of Sais on the Nile Delta, we conducted a palynological study. Seven palynological zones were defined to reveal Holocene climate fluctuations. Zone I (ca. 9000–7000 cal yr BP) was a period of warming climate, succeeded by a progressive drying climate phase in Zones II–VII (ca. 7000–2000 cal yr BP). Pollen records indicate Nile flooding prevailed before 7000 years ago, making the study area uninhabitable, before it later developed into a wetland setting. The earliest farming started at ca. 6700 cal yr BP, as indicated by the abrupt appearance of cereal (Poaceae > 35 μm), during a time of climate warming (Zone III), This material can be differentiated from wild Poaceae (<35 μm), which occurs throughout the profile, indicating the cereal was introduced to this area for agriculture. Results further reveal the transformation of human activities, from passive adaptation to climate, to actively remolding the environment against the background of long-term drying. During the early farming stage (ca. 6700–5500 cal yr BP), climate-human indicators were synchronous in distribution, suggesting lower pressure from climate change on population growth; however, this reversed from ca. 5500 cal yr BP, as intensive agriculture was required to meet shortages of natural resources during climate drying. Perhaps, the best evidence for adaptation is the increased abundance of Azolla from ca. 4000 years ago, a fern that favours growing in still-water bodies, hinting that much more irrigation was required at the time to sustain societal development. • A palynological profile is described at the Sais archaeological site, Nile Delta. • High-resolution studies reveal centennial fluctuations in pollen-climate through Holocene times. • The earliest farming and adaptation to climate change commenced 6700 cal yrs. BP. • Two mechanisms of climate-societal development are proposed. [ABSTRACT FROM AUTHOR]

Although archaeological findings show the synchronous collapses of major well-documented Chinese Neolithic cultures around 4000 cal. yr BP, the driving mechanism for the phenomenon is still unclear and debatable. Spatial climatic features in China spanning this time period suggest a generally cold-dry setting. This is evidenced by 130 well-dated geological records at 97 sites located in climatically and topographically diverse regions, with occurrences of some extreme hydrological events like severe floods in the Chinese Loess Plateau, and in basins of the lower Yellow River and the middle-to-lower Yangtze River. The weakening of the Asian Summer Monsoon (ASM) since the mid-Holocene would have made Neolithic subsistence living unfavourable by decreasing the warmth and wetness in arid and semi-arid regions. However, it might not have been the sole factor that destroyed the Neolithic cultures in the vast territories of China ca. 4000 cal. yr BP. Environmental alterations in the major cultural territories of China reacted in response to precipitation anomalies caused by high variability of the ASM and the westerlies, which were modulated by centennial- to inter-annual- scale driving factors such as solar insolation, the North Atlantic Oscillation (NAO), the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillations (ENSO). This most likely accounted for the nearly synchronous Chinese Neolithic cultural collapses. [ABSTRACT FROM AUTHOR]