Abrupt change in North African hydroclimate and landscape evolution 3.2 million years ago

Author(s):  
Katharine Grant ◽  
Udara Amarathunga ◽  
Jessica Amies ◽  
Pengxiang Hu ◽  
Yao Qian ◽  
...  

Abstract Dark organic-rich layers (sapropels) have accumulated in Mediterranean sediments since the Miocene due to deep-sea dysoxia and enhanced carbon burial at times of intensified North African run-off during ‘Green’ Sahara Periods (GSPs). The existence of orbital precession-dominated Saharan aridity/humidity cycles is well known, but lack of long-term, high-resolution records hinders understanding of their precise relationships with environmental and hominin evolution. Here we present continuous, high-resolution geochemical and environmental magnetic records for the Eastern Mediterranean that span the past 5.2 million years, which reveal that organic burial in sapropels intensified 3.2 Myr ago. We deduce that fluvial terrigenous sediment inputs during GSPs doubled abruptly at this time, whereas monsoon run-off intensity remained relatively constant. We attribute the increase in sediment mobilisation to an abrupt non-linear North African landscape response associated with a major increase in arid:humid contrasts between GSPs and intervening dry periods. This likely limited hominin (and other animal) inhabitation of, and migration through, the Sahara region to GSPs only.

2022 ◽  
Vol 3 (1) ◽  
Author(s):  
Katharine M. Grant ◽  
Udara Amarathunga ◽  
Jessica D. Amies ◽  
Pengxiang Hu ◽  
Yao Qian ◽  
...  

AbstractDark organic-rich layers (sapropels) have accumulated in Mediterranean sediments since the Miocene due to deep-sea dysoxia and enhanced carbon burial at times of intensified North African run-off during Green Sahara Periods (GSPs). The existence of orbital precession-dominated Saharan aridity/humidity cycles is well known, but lack of long-term, high-resolution records hinders understanding of their relationship with environmental evolution. Here we present continuous, high-resolution geochemical and environmental magnetic records for the Eastern Mediterranean spanning the past 5.2 million years, which reveal that organic burial intensified 3.2 Myr ago. We deduce that fluvial terrigenous sediment inputs during GSPs doubled abruptly at this time, whereas monsoon run-off intensity remained relatively constant. We hypothesize that increased sediment mobilization resulted from an abrupt non-linear North African landscape response associated with a major increase in arid:humid contrasts between GSPs and intervening dry periods. The timing strongly suggests a link to the onset of intensified northern hemisphere glaciation.


2016 ◽  
Vol 371 (1698) ◽  
pp. 20150243 ◽  
Author(s):  
Cassaundra Rose ◽  
Pratigya J. Polissar ◽  
Jessica E. Tierney ◽  
Timothy Filley ◽  
Peter B. deMenocal

East African climate change since the Late Miocene consisted of persistent shorter-term, orbital-scale wet–dry cycles superimposed upon a long-term trend towards more open, grassy landscapes. Either or both of these modes of palaeoclimate variability may have influenced East African mammalian evolution, yet the interrelationship between these secular and orbital palaeoclimate signals remains poorly understood. Here, we explore whether the long-term secular climate change was also accompanied by significant changes at the orbital-scale. We develop northeast African hydroclimate and vegetation proxy data for two 100 kyr-duration windows near 3.05 and 1.75 Ma at ODP Site 967 in the eastern Mediterranean basin, where sedimentation is dominated by eastern Sahara dust input and Nile River run-off. These two windows were selected because they have comparable orbital configurations and bracket an important increase in East African C 4 grasslands. We conducted high-resolution (2.5 kyr sampling) multiproxy biomarker, H- and C-isotopic analyses of plant waxes and lignin phenols to document orbital-scale changes in hydrology, vegetation and woody cover for these two intervals. Both intervals are dominated by large-amplitude, precession-scale (approx. 20 kyr) changes in northeast African vegetation and rainfall/run-off. The δ 13 C wax values and lignin phenol composition record a variable but consistently C 4 grass-dominated ecosystem for both intervals (50–80% C 4 ). Precessional δD wax cycles were approximately 20–30‰ in peak-to-peak amplitude, comparable with other δD wax records of the Early Holocene African Humid Period. There were no significant differences in the means or variances of the δD wax or δ 13 C wax data for the 3.05 and 1.75 Ma intervals studied, suggesting that the palaeohydrology and palaeovegetation responses to precessional forcing were similar for these two periods. Data for these two windows suggest that the eastern Sahara did not experience the significant increase in C 4 vegetation that has been observed in East Africa over this time period. This observation would be consistent with a proposed mechanism whereby East African precipitation is reduced, and drier conditions established, in response to the emergence of modern zonal sea surface temperature gradients in the tropical oceans between 3 and 2 Ma. This article is part of the themed issue ‘Major transitions in human evolution’.


2017 ◽  
Author(s):  
Rosa Fregel ◽  
Fernando L. Méndez ◽  
Youssef Bokbot ◽  
Dimas Martín-Socas ◽  
María D. Camalich-Massieu ◽  
...  

ABSTRACTThe extent to which prehistoric migrations of farmers influenced the genetic pool of western North Africans remains unclear. Archaeological evidence suggests the Neolithization process may have happened through the adoption of innovations by local Epipaleolithic communities, or by demic diffusion from the Eastern Mediterranean shores or Iberia. Here, we present the first analysis of individuals’ genome sequences from early and late Neolithic sites in Morocco, as well as Early Neolithic individuals from southern Iberia. We show that Early Neolithic Moroccans are distinct from any other reported ancient individuals and possess an endemic element retained in present-day Maghrebi populations, confirming a long-term genetic continuity in the region. Among ancient populations, Early Neolithic Moroccans are distantly related to Levantine Natufian hunter-gatherers (∼9,000 BCE) and Pre-Pottery Neolithic farmers (∼6,500 BCE). Although an expansion in Early Neolithic times is also plausible, the high divergence observed in Early Neolithic Moroccans suggests a long-term isolation and an early arrival in North Africa for this population. This scenario is consistent with early Neolithic traditions in North Africa deriving from Epipaleolithic communities who adopted certain innovations from neighbouring populations. Late Neolithic (∼3,000 BCE) Moroccans, in contrast, share an Iberian component, supporting theories of trans-Gibraltar gene flow. Finally, the southern Iberian Early Neolithic samples share the same genetic composition as the Cardial Mediterranean Neolithic culture that reached Iberia ∼5,500 BCE. The cultural and genetic similarities of the Iberian Neolithic cultures with that of North African Neolithic sites further reinforce the model of an Iberian migration into the Maghreb.SIGNIFICANCE STATEMENTThe acquisition of agricultural techniques during the so-called Neolithic revolution has been one of the major steps forward in human history. Using next-generation sequencing and ancient DNA techniques, we directly test if Neolithization in North Africa occurred through the transmission of ideas or by demic diffusion. We show that Early Neolithic Moroccans are composed of an endemic Maghrebi element still retained in present-day North African populations and distantly related to Epipaleolithic communities from the Levant. However, late Neolithic individuals from North Africa are admixed, with a North African and a European component. Our results support the idea that the Neolithization of North Africa might have involved both the development of Epipaleolithic communities and the migration of people from Europe.


Author(s):  
Robert Stojanov ◽  
Sarah Rosengaertner ◽  
Alex de Sherbinin ◽  
Raphael Nawrotzki

AbstractDevelopment cooperation actors have been addressing climate change as a cross-cutting issue and investing in climate adaptation projects since the early 2000s. More recently, as concern has risen about the potential impacts of climate variability and change on human mobility, development cooperation actors have begun to design projects that intentionally address the drivers of migration, including climate impacts on livelihoods. However, to date, we know little about the development cooperation’s role and function in responding to climate related mobility and migration. As such, the main aim of this paper is to outline the policy frameworks and approaches shaping development cooperation actors’ engagement and to identify areas for further exploration and investment. First, we frame the concept of climate mobility and migration and discuss some applicable policy frameworks that govern the issue from various perspectives; secondly, we review the toolbox of approaches that development cooperation actors bring to climate mobility; and third, we discuss the implications of the current Covid-19 pandemic and identify avenues for the way forward. We conclude that ensuring safe and orderly mobility and the decent reception and long-term inclusion of migrants and displaced persons under conditions of more severe climate hazards, and in the context of rising nationalism and xenophobia, poses significant challenges. Integrated approaches across multiple policy sectors and levels of governance are needed. In addition to resources, development cooperation actors can bring data to help empower the most affected communities and regions and leverage their convening power to foster more coordinated approaches within and across countries.


The Holocene ◽  
2021 ◽  
pp. 095968362199464
Author(s):  
Katarzyna Marcisz ◽  
Krzysztof Buczek ◽  
Mariusz Gałka ◽  
Włodzimierz Margielewski ◽  
Matthieu Mulot ◽  
...  

Landslide mountain fens formed in landslide depressions are dynamic environments as their development is disturbed by a number of factors, for example, landslides, slopewash, and surface run-off. These processes lead to the accumulation of mineral material and wood in peat. Disturbed peatlands are interesting archives of past environmental changes, but they may be challenging for providing biotic proxy-based quantitative reconstructions. Here we investigate long-term changes in testate amoeba communities from two landslide mountain fens – so far an overlooked habitat for testate amoeba investigations. Our results show that abundances of testate amoebae are extremely low in this type of peatlands, therefore not suitable for providing quantitative depth-to-water table reconstructions. However, frequent shifts of dominant testate amoeba species reflect dynamic lithological situation of the studied fens. We observed that high and stable mineral matter input into the peatlands was associated with high abundances of species producing agglutinated (xenosomic) as well as idiosomic shells which prevailed in the testate amoeba communities in both analyzed profiles. This is the first study that explores testate amoebae of landslide mountain fens in such detail, providing novel information about microbial communities of these ecosystems.


2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Melissa Ong ◽  
Mark Gibson ◽  
Gerald Coakley

Abstract Case report - Introduction Severe acute respiratory coronavirus 2 (SARS-CoV-2) is a novel virus that can lead to an excessive immune activation and cytokine response known as Coronavirus disease 2019 (COVID-19) which predominantly affects the lungs. Patients with chronic inflammatory disease on biological immunosuppressive treatments may be at a higher risk of contracting SARS-CoV-2. However, it is yet to be determined whether immunomodulatory medications used in inflammatory diseases have protective capabilities against severe outcomes. Case report - Case description A 51-year old female with a 13-year history of rheumatoid arthritis (RA) presented to hospital with fever, exertional breathlessness, and a non-productive cough. She was diagnosed with seropositive erosive RA at the age of 38 and was on 6-monthly Rituximab infusions and Leflunomide on admission. She had relatively stable pulmonary fibrosis (diagnosed in 2010). Her chest CTs in 2010 and 2018 noted bilateral basal subpleural ground glass change with limited honeycombing and spirometry study revealed FEV1 of 2.2 (82% predicted), VC of 2.7 (87% predicted), DLCO of 7.0 (78% predicted) and kCO of 1.6 (78% predicted). On admission in March 2020, she was hypoxic (oxygen saturation of 88% in room air) and had raised inflammatory markers (CRP 341mg/dL, d-Dimer 914ng/ml, Ferritin 3141ng/ml, LDH 672U/L). Her last Rituximab infusion was 3 months prior and leflunomide was withheld on admission. SARS-CoV-2 PCR nasopharyngeal swab was positive, and she was recruited to the RECOVERY trial, being randomized to Lopinavir-Ritonavir for 10 days. Her oxygen requirements increased, and a CT pulmonary angiogram excluded pulmonary embolism but revealed ground glass changes and extensive multilobar consolidation. She was eligible for recruitment into RECOVERY-2 (tocilizumab) given the ongoing oxygen requirement and elevated CRP, but she was randomised to usual care. She was commenced on 80mg of IV methylprednisolone, a dose chosen because of its proven effectiveness in Acute Respiratory Distress Syndrome. She clinically improved and was discharged from hospital 20 days after starting Methylprednisolone with a CRP of 17mg/dL. Two months after discharge, the patient had repeat spirometry study which noted FEV1 of 1.4 (57% predicted), VC of 1.5 (52% predicted), DLCO of 2.4 (28% predicted) and kCO of 1.0 (47% predicted). A repeat high-resolution chest CT reported significant improvement of peripheral ground glass changes and consolidation, but she is still fatigued and more breathless than previously. Case report - Discussion The RECOVERY trial concluded that Dexamethasone reduced mortality in intubated patients and in hospitalised patients with COVID-19 with a high oxygen requirement. The results were published after this patient was discharged. A hyperinflammatory response to COVID-19 is seen in a subset of patients, and our own hospital data suggest that this condition affects around 5% of admitted COVID-19 patients, but that extreme hyperferritinaemia above 10,000 is extremely rare. Similar responses (known as Haemophagocytic Lymphohistiocytosis [HLH]) are seen with a variety of viral and bacterial infections, in malignancy and in inflammatory rheumatic diseases (Macrophage Activation Syndrome [MAS]), but typically HLH and MAS patients have ferritin > 10,000. It appears unlikely that true HLH is a significant manifestation of COVID-19 infection, but moderate hyperferritinaemia is not uncommon and the results of this study, taken together with case reports and series from China and Italy suggest that similar treatments to those used in HLH may transform the prognosis for COVID-19 patients in this subset. It is unknown whether the recent Rituximab infusion had a role in reducing the “cytokine storm” and delaying progression to severe COVID-19. However, it may be argued that the remaining T cells in B cell depleted patients are sufficient for viral clearance. The long-term impact of SARS-CoV-2 on pulmonary function is still unclear. Our patient had a major deterioration in her lung function when compared to her baseline. There was severe reduction in gas transfer post COVID-19. However, her repeat high resolution CT chest reported substantial improvement in ground glass changes and consolidation. The long-term prognosis is still uncertain. Initial fears that patients on DMARDs and biological therapies for inflammatory rheumatic disease would be extremely vulnerable to COVID-19 have not been confirmed, but patients with extra-articular manifestations on combinations of DMARDs and biological therapies may be a subset at higher risk. Case report - Key learning points Our Intensivist colleagues, early in the COVID-19 outbreak, were understandably cautious about using heavily immunosuppressive treatments for a life-threatening viral infection. Using a multi-disciplinary approach at a time when knowledge of how to treat this condition was rudimentary, along with informed consent from an intelligent and thoughtful patient, we were able to plot a middle path to suppress hyperinflammation without using massively immunosuppressive doses of steroid, with a successful outcome. This patient illustrates one aspect of the hyper-inflammatory response seen in a subset of the most critically ill patients with COVID-19. At the time of writing, the RECOVERY 2 trial is yet to be published, but the rapid improvement in inflammatory markers including CRP and Ferritin, along with a dramatic improvement in clinical state, suggest that relatively modest doses of parenteral steroid have life-saving potential at far lower cost and greater worldwide availability than biological therapies such as Tocilizumab or Anakinra. Trials of Tocilizumab in RECOVERY2 and of Anakinra coordinated by the Hyperinflammation Histio UK Haemophagocytosis Across Specialty Collaboration (HASC), as well as international randomised controlled trials will be critical in determining the optimal treatment strategy for this subset of critically ill COVID-19 patients. The experience of our patient suggests that one arm of such studies should include a relatively modest dose of parenteral steroid, be that Dexamethasone or Methylprednisolone, particularly given that COVID-19 is affecting countries across the developing, as well as the developed, world.


Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 37
Author(s):  
Martial Amou ◽  
Amatus Gyilbag ◽  
Tsedale Demelash ◽  
Yinlong Xu

As global temperatures continue to rise unabated, episodes of heat-related catastrophes across the world have intensified. In Kenya, heatwave phenomena and their associated impacts are ignored and neglected due to several reasons, including unreliable and inconsistent weather datasets and heatwave detection metrics. Based on CHIRTS satellite infrared estimates and station blended temperature, this study investigated the spatiotemporal distribution of the heatwave events over Kenya during 1987–2016 using the Heatwave Magnitude Index daily (HWMId). The results showed that contrary to the absence of heatwave records in official national and international disaster database about Kenya, the country experienced heatwaves ranging from less severe (normal) to deadly (super-extreme) between 1987 and 2016. The most affected areas were located in the eastern parts of the country, especially in Garissa and Tana River, and in the west-northern side around the upper side of Turkana county. It was also found that the recent years’ heatwaves were more severe in magnitude, duration, and spatial extent. The highest magnitude of the heatwaves was recorded in 2015 (HWMId = 22.64) while the average over the reference period is around 6. CHIRTS and HWMId were able to reveal and capture most critical heatwave events over the study period. Therefore, they could be used respectively as data source and detection metrics, for heatwaves disaster emergency warning over short period as well as for long-term projection to provide insight for adaptation strategies.


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