scholarly journals Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fabien L. Condamine ◽  
Guillaume Guinot ◽  
Michael J. Benton ◽  
Philip J. Currie
Keyword(s):  
Global Climate ◽  
Extinction Risk ◽  
Physical Factors ◽  
Evolutionary Novelty ◽  
Environmental Pressures ◽  
Diversity Pattern ◽  
Asteroid Impact ◽  
Changing Environments ◽  
Climate Cooling ◽  
The Impact

AbstractThe question why non-avian dinosaurs went extinct 66 million years ago (Ma) remains unresolved because of the coarseness of the fossil record. A sudden extinction caused by an asteroid is the most accepted hypothesis but it is debated whether dinosaurs were in decline or not before the impact. We analyse the speciation-extinction dynamics for six key dinosaur families, and find a decline across dinosaurs, where diversification shifted to a declining-diversity pattern ~76 Ma. We investigate the influence of ecological and physical factors, and find that the decline of dinosaurs was likely driven by global climate cooling and herbivorous diversity drop. The latter is likely due to hadrosaurs outcompeting other herbivores. We also estimate that extinction risk is related to species age during the decline, suggesting a lack of evolutionary novelty or adaptation to changing environments. These results support an environmentally driven decline of non-avian dinosaurs well before the asteroid impact.

Deccan Volcanism or the Chicxulub Impact: The Chicken or Egg Question

2020 ◽  
Author(s):  
Gerta Keller
Keyword(s):  
Mass Extinction ◽  
Impact Crater ◽  
Global Climate ◽  
Mass Extinctions ◽  
Deccan Volcanism ◽  
Asteroid Impact ◽  
Global Climate Warming ◽  
Chicxulub Impact Crater ◽  
Chicxulub Impact ◽  
The Impact

<p>The Cretaceous–Paleogene boundary (KTB or KPB) mass extinction is primarily known for the<br>demise of the dinosaurs, the Chicxulub impact, and the rancorous forty-year-old controversy<br>over the cause of this mass extinction. For the first 30 years, the controversy primarily revolved<br>around the age of the impact claimed as precisely KTB based on the assumption that it caused<br>the mass extinction. The iridium (Ir) anomaly at the KTB was claimed proof of the asteroid<br>impact, but no Ir was ever associated with impact evidence and recent findings reveal no<br>extraterrestrial component in PGEs or the KTB Ir anomaly. Impact melt rock glass spherules are<br>also claimed as indisputable evidence of the KTB age impact, but such spherule layers are<br>commonly reworked from the primary (oldest) layer in late Maastrichtian, KTB and Danian<br>sediments; thus only the oldest impact spherule layer documented near the base of zone CF1<br>~200 ky below the KTB can approximate the impact’s age. Similarly, the impact breccia in the<br>Chicxulub impact crater predates the KTB. The best age derived from Ar/Ar dating of impact<br>glass spherules is within 200 ky of the KTB and thus no evidence for the KTB age. All evidence<br>strongly suggests the Chicxulub impact most likely predates the mass extinction ~ 200 ky and<br>played no role in it.<br>Deccan volcanism (LIP) was dismissed as potential cause or even contributor to the KTB mass<br>extinction despite the fact that all other mass extinctions are associated with Large Igneous<br>Province (LIP) volcanism but none with an asteroid impact. During the last decade, Deccan<br>volcanism gained credence based on a succession of discoveries: 1) the mass extinction in<br>between the longest Deccan lava flows across India; 2) high-precision dating of the entire<br>sequence of Deccan volcanism based on UPb zircon dating; 3) recognition of four distinct<br>eruption pulses all related to global climate warming with the largest pulse beginning 20 ky prior<br>to and ending at the KTB; 4) Identifying the climate link to Deccan volcanism based on age<br>dating and mercury from Deccan eruptions in marine sediments; and 5) Identifying the KTB<br>mass extinction directly related to the major Deccan eruption pulse, hyperthermal warming and<br>ocean acidification all linked to global mercury fallout from Deccan eruptions in marine<br>sediments. Despite this remarkable culmination of evidence, the controversy continues with<br>impact proponents arguing that Deccan volcanism didn’t exist at the KTB – the impact was the<br>sole cause.</p>

scholarly journals Graptolite community responses to global climate change and the Late Ordovician mass extinction

2016 ◽  
Vol 113 (30) ◽  
pp. 8380-8385 ◽  
Author(s):  
H. David Sheets ◽  
Charles E. Mitchell ◽  
Michael J. Melchin ◽  
Jason Loxton ◽  
Petr Štorch ◽  
...  
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Mass Extinction ◽  
Climate Changes ◽  
Global Climate ◽  
Extinction Risk ◽  
Late Ordovician ◽  
Ecological Communities ◽  
Mass Extinctions ◽  
The Impact

Mass extinctions disrupt ecological communities. Although climate changes produce stress in ecological communities, few paleobiological studies have systematically addressed the impact of global climate changes on the fine details of community structure with a view to understanding how changes in community structure presage, or even cause, biodiversity decline during mass extinctions. Based on a novel Bayesian approach to biotope assessment, we present a study of changes in species abundance distribution patterns of macroplanktonic graptolite faunas (∼447–444 Ma) leading into the Late Ordovician mass extinction. Communities at two contrasting sites exhibit significant decreases in complexity and evenness as a consequence of the preferential decline in abundance of dysaerobic zone specialist species. The observed changes in community complexity and evenness commenced well before the dramatic population depletions that mark the tipping point of the extinction event. Initially, community changes tracked changes in the oceanic water masses, but these relations broke down during the onset of mass extinction. Environmental isotope and biomarker data suggest that sea surface temperature and nutrient cycling in the paleotropical oceans changed sharply during the latest Katian time, with consequent changes in the extent of the oxygen minimum zone and phytoplankton community composition. Although many impacted species persisted in ephemeral populations, increased extinction risk selectively depleted the diversity of paleotropical graptolite species during the latest Katian and early Hirnantian. The effects of long-term climate change on habitats can thus degrade populations in ways that cascade through communities, with effects that culminate in mass extinction.

Decoding geochemical signals of the Schwalbenberg Loess-Palaeosol-Sequences — A key to Upper Pleistocene terrestrial ecosystem responses in western Central Europe 

2021 ◽  
Author(s):  
Mathias Vinnepand ◽  
Peter Fischer ◽  
Christian Zeeden ◽  
Philipp Schulte ◽  
Sabine Fiedler ◽  
...  
Keyword(s):  
Global Climate ◽  
Terrestrial Ecosystem ◽  
Ecosystem Responses ◽  
Upper Pleistocene ◽  
Linear Discriminant ◽  
Sediment Reworking ◽  
Global Climate Changes ◽  
Depositional Processes ◽  
Climate Cooling ◽  
The Impact

<p>The Schwalbenberg Loess-Palaeosol-Sequences (LPS) in the Middle Rhine Valley, Germany, comprise unprecedented complete records of Upper Pleistocene terrestrial ecosystem response to global climate changes. However, direct correlation of the Schwalbenberg geochemical signals with climate archives of supra-regional northern hemispheric relevance remains complicated. This is due to the complex interplay of pre-, syn-, or post-depositional processes that left their traces in the terrestrial record. In particular, the use of different element ratios to derive weathering indices may be complicated as dust sources change through time, and as ecosystems respond to changing conditions. In this study, we decode interfering geochemical signatures and re-evaluate proxies, commonly applied, regarding their suitability and meaning for understanding the evolution of the Schwalbenberg LPS. We undertake a systematic approach, firstly dividing the 30 m long Schwalbenberg REM3 LPS according to our core description. In a second step, we integrate LOG-ratios indicative of provenance shifts, sediment reworking dynamics and weathering into multivariate analysis. We apply Principle Component Analyses (PCA) and Linear Discriminant Analysis (LDA) to datasets comprising sediments deposited under similar environmental conditions. In doing so, we sensitively quantify subordinate processes and conditions, such as the impact of varying source- and weathering-signals in all proxies. Our results show that in particularly K/Rb and Mg/Ca ratios contain a strong provenance signal in loess deposits, whereas the Ca/Al<sub>d</sub> ratio (Al<sub>d</sub>: dithionite extractable) <sub></sub>best indicates the maturity state of Gelic Gleysols. Integration of our filtered datasets with a high-resolution age model enables direct correlation of the variability of principal components on sub-millennial scales with Atlantic-driven climate oscillations. More specifically, PC2 appears to reflect changes in mineral dust accumulation and indicates increasing dust input in response to climate cooling towards the end of interstadials, highlighting the accretionary nature of the Schwalbenberg LPS during transitional periods from interstadial to stadial depositional modes.</p><p> </p>

Working conditions and the formation of health risks among workers of the petrochemical industry engaged in the production of methanol and its derivatives

2019 ◽  
pp. 266-271
Author(s):  
Nina M. Meshchakova ◽  
Marina P. Dyakovich ◽  
Salim F. Shayakhmetov
Keyword(s):  
Working Conditions ◽  
Health Risks ◽  
Quantitative Assessment ◽  
Circulatory System ◽  
Medical Examination ◽  
Physical Factors ◽  
Labor Intensity ◽  
Industrial Noise ◽  
Harmful Substances ◽  
The Impact

Introduction.Methanol and its derivatives occupy one of the leading places among the main organic synthesis intermediates in terms of their importance and scale of production. According to experts, by 2027 the global demand for methanol can reach 135 million tons, the annual growth will be about 5.5%. However, there is little information regarding the assessment of working conditions and occupational risks for workers in modern methanol production and its derivatives.The aim of the studyis hygienic assessment of working conditions and the formation of health risks in workers of modern production of methanol and methylamines.Materials and methods.The assessment of the main adverse factors of production is given. When studying the state of health, objective indicators (the results of an in-depth medical examination) and subjective (the results of a quantitative assessment of the risks of the main pathological syndromes associated with health) are considered.Results.According to long-term observations, the concentration of harmful substances in the air of the working area, indicators of labor severity, parameters of physical factors met hygienic requirements, with the exception of industrial noise exceeding the maximum permissible level, as well as labor intensity of 1 degree. The General assessment of working conditions corresponds to the category of harmful 2 degrees (3.2). According to the results of the medical examination and quantitative assessment of the risks of health disorders in workers, the most significant were functional disorders and diseases of the circulatory system. The levels of somatic pathology on the part of the main body systems were significantly higher in apparatchiks compared to the engineering and technical personnel (ETP).Conclusions:In the production of methyl alcohol and methylamines, the main hygienic importance is the impact on workers of the complex of harmful substances of 1-IV hazard classes in low concentrations, increased levels of industrial noise, labor intensity of 1 degree. According to the subjective assessment of health and medical examination, the greatest prevalence of health risks in workers was observed from the circulatory system, and the levels of the revealed somatic pathology were statistically significantly higher in apparatchiks compared with the ETP.

Impact of LULC Changes on LST in Rajshahi District of Bangladesh: A Remote Sensing Approach

2020 ◽  
Vol 3 (1) ◽  
pp. 11-23 ◽  
Author(s):  
Abdulla Al Kafy ◽  
Abdullah Al-Faisal ◽  
Mohammad Mahmudul Hasan ◽  
Md. Soumik Sikdar ◽  
Mohammad Hasib Hasan Khan ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Surface Temperature ◽  
Land Surface ◽  
Agricultural Land ◽  
Global Climate ◽  
Urban Expansion ◽  
Water Bodies ◽  
Landsat 8 ◽  
Lulc Changes ◽  
The Impact

Urbanization has been contributing more in global climate warming, with more than 50% of the population living in cities. Rapid population growth and change in land use / land cover (LULC) are closely linked. The transformation of LULC due to rapid urban expansion significantly affects the functions of biodiversity and ecosystems, as well as local and regional climates. Improper planning and uncontrolled management of LULC changes profoundly contribute to the rise of urban land surface temperature (LST). This study evaluates the impact of LULC changes on LST for 1997, 2007 and 2017 in the Rajshahi district (Bangladesh) using multi-temporal and multi-spectral Landsat 8 OLI and Landsat 5 TM satellite data sets. The analysis of LULC changes exposed a remarkable increase in the built-up areas and a significant decrease in the vegetation and agricultural land. The built-up area was increased almost double in last 20 years in the study area. The distribution of changes in LST shows that built-up areas recorded the highest temperature followed by bare land, vegetation and agricultural land and water bodies. The LULC-LST profiles also revealed the highest temperature in built-up areas and the lowest temperature in water bodies. In the last 20 years, LST was increased about 13ºC. The study demonstrates decrease in vegetation cover and increase in non-evaporating surfaces with significantly increases the surface temperature in the study area. Remote-sensing techniques were found one of the suitable techniques for rapid analysis of urban expansions and to identify the impact of urbanization on LST.

scholarly journals Endemic Juniperus Montane Species Facing Extinction Risk under Climate Change in Southwest China: Integrative Approach for Conservation Assessment and Prioritization

Biology ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 63
Author(s):  
Mohammed A. Dakhil ◽  
Marwa Waseem A. Halmy ◽  
Walaa A. Hassan ◽  
Ali El-Keblawy ◽  
Kaiwen Pan ◽  
...  
Keyword(s):  
Climate Change ◽  
Potential Distribution ◽  
Extinction Risk ◽  
In Situ Conservation ◽  
Integrative Approach ◽  
Conservation Assessment ◽  
Distribution Models ◽  
Area Of Occupancy ◽  
Annual Range ◽  
The Impact

Climate change is an important driver of biodiversity loss and extinction of endemic montane species. In China, three endemic Juniperus spp. (Juniperuspingii var. pingii, J.tibetica, and J.komarovii) are threatened and subjected to the risk of extinction. This study aimed to predict the potential distribution of these three Juniperus species under climate change and dispersal scenarios, to identify critical drivers explaining their potential distributions, to assess the extinction risk by estimating the loss percentage in their area of occupancy (AOO), and to identify priority areas for their conservation in China. We used ensemble modeling to evaluate the impact of climate change and project AOO. Our results revealed that the projected AOOs followed a similar trend in the three Juniperus species, which predicted an entire loss of their suitable habitats under both climate and dispersal scenarios. Temperature annual range and isothermality were the most critical key variables explaining the potential distribution of these three Juniperus species; they contribute by 16–56.1% and 20.4–38.3%, respectively. Accounting for the use of different thresholds provides a balanced approach for species distribution models’ applications in conservation assessment when the goal is to assess potential climatic suitability in new geographical areas. Therefore, south Sichuan and north Yunnan could be considered important priority conservation areas for in situ conservation and search for unknown populations of these three Juniperus species.

scholarly journals A multilevel carbon and water footprint dataset of food commodities

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Tashina Petersson ◽  
Luca Secondi ◽  
Andrea Magnani ◽  
Marta Antonelli ◽  
Katarzyna Dembska ◽  
...  
Keyword(s):  
Water Footprint ◽  
Greenhouse Gas Emission ◽  
Grey Literature ◽  
Climate Mitigation ◽  
Food Sector ◽  
Environmental Pressures ◽  
Global Environmental ◽  
Dietary Shifts ◽  
Food Commodities ◽  
The Impact

AbstractInforming and engaging citizens to adopt sustainable diets is a key strategy for reducing global environmental impacts of the agricultural and food sectors. In this respect, the first requisite to support citizens and actors of the food sector is to provide them a publicly available, reliable and ready to use synthesis of environmental pressures associated to food commodities. Here we introduce the SU-EATABLE LIFE database, a multilevel database of carbon (CF) and water (WF) footprint values of food commodities, based on a standardized methodology to extract information and assign optimal footprint values and uncertainties to food items, starting from peer-reviewed articles and grey literature. The database and its innovative methodological framework for uncertainty treatment and data quality assurance provides a solid basis for evaluating the impact of dietary shifts on global environmental policies, including climate mitigation through greenhouse gas emission reductions. The database ensures repeatability and further expansion, providing a reliable science-based tool for managers and researcher in the food sector.

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