Holocene Environmental Changes Research Articles

Vegetation-Ice-Bare Land Cover Conversion in the Oceanic Glacial Region of Tibet Based on Multiple Machine Learning Classifications

Oceanic glaciers are one of the most sensitive indicators of climate change. However, remotely sensed evidence of land cover change in the oceanic glacial region is still limited due to the cloudy weather during the growing season. In addition, the performance of common machine learning classification algorithms is also worth testing in this cloudy, frigid and mountainous region. In this study, three algorithms, namely, the random forest, back-propagation neural network (BPNN) and convolutional neural network algorithms, were compared in their interpretation of the land cover change in south-eastern Tibet and resulted in three findings. (1) The BPNN achieves the highest overall accuracy and Kappa coefficient compared with the other two algorithms. The overall accuracy was 97.82%, 98.07%, 98.92%, and 94.63% in 1990, 2000, 2007, and 2016, and the Kappa coefficient was 0.958, 0.959, 0.980, and 0.918 in these four years, respectively. (2) From 1990 to 2000, the dominant land cover was ice at the landscape level. The landscape fragmentation decreased and the landscape aggregation increased. From 2000 to 2016, the dominant land cover transformed from ice to vegetation. The vegetation aggregation increased, while the ice aggregation decreased. (3) When the elevation was less than 4 km, the vegetation was usually transformed into bare land; otherwise, the probability of direct transformation between vegetation and ice increased. The findings on the land cover transformation in the oceanic glacial region by multiple classification algorithms can provide both long-term evidence and methodological indications to understand the recent environmental change in the “third pole”.

How migratory populations become resident.

Migratory behaviour is rapidly changing in response to recent environmental changes, yet it is difficult to predict how migration will evolve in the future. To understand what determines the rate of adaptive evolutionary change in migratory behaviour, we simulated the evolution of residency using an individual-based threshold model, which allows for variation in selection, number of genes, environmental effects and assortative mating. Our model indicates that the recent reduction in migratory activity found in a population of Eurasian blackcaps (Sylvia atricapilla) is only compatible with this trait being under strong directional selection, in which residents have the highest fitness and fitness declines exponentially with migration distance. All other factors had minor effects on the adaptive response. Under this form of selection, a completely migratory population will become partially migratory in 6 and completely resident in 98 generations, demonstrating the persistence of partial migration, even under strong directional selection. Resident populations will preserve large amounts of cryptic genetic variation, particularly if migration is controlled by a large number of genes with small effects. This model can be used to realistically simulate the evolution of any threshold trait, including semi-continuous traits like migration, for predicting evolutionary response to natural selection in the wild.

Aquatic community structure as sentinel of recent environmental changes unraveled from lake sedimentary records from the Atacama Desert, Chile.

The Atacama Desert (21–26°S) is currently one of the driest places on Earth and metal(loid)s are of special concern for this region, which hosts the largest-known porphyry copper deposits produced in Chile. Evidence of past environmental conditions is commonly preserved in natural archives, such as lacustrine sediments. Sediment records obtained from Inca Coya Lake (22°20’S-68°35’W, 2534 m.a.s.l.), a small lake located in the Atacama Desert, reflected the evolution of regional mining activity during the 20th century and sedimentation associated with decadal climate variability. We studied the aquatic community structure changes recorded in sediment records from Inca Coya Lake. By analysis of magnetic properties (susceptibility, hysteresis curves and Curie temperatures), grain size and geochemical composition of the sediments, we identified environmental periods and changes in the community of benthic and planktonic organisms (diatoms and diapausing egg bank). We identified three detrital episodes that we interpret as dry/wet phases during the last 90 years associated with the increase of flash flood events promoting hypoxia oscillations; anthropogenic (mining activity) signals were also identified. Invertebrate community structure (primary consumers) reflected the metal exposure, measured as changes in assemblage composition through species turnover. Diatom community composition was best associated with variables related to wetter/drier alternation and consequent changes in oxygen availability. Bioindicators analyzed (diatoms, diapausing egg bank and invertebrate community) demonstrated to be excellent indicators of the bioavailability of compounds in the aquatic ecosystem of Inca Coya Lake, allowing the environmental impact assessment of the water resources due to flash floods and mining activity in the driest desert of the world.

Foraminiferal and dinocyst associations as indicators of the Holocene environmental changes at the Cambridge Strait, Franz Josef Land

Herein we report the first decadal to centennial–scale resolution data on foraminiferal and dinocyst assemblages from core AMK-5454 collected in the hard-to-reach Cambridge Strait, Franz Josef Land, and on corresponding paleoenvironments over the last 9.2 ka. The dinocyst and foraminiferal assemblages from the core are rather diverse through the Holocene and represented by 24 and 33 taxa, respectively. The most active hydrodynamics and probably Atlantic Water (AW) inflow are suggested by the enhanced values of autotrophic dinocysts and epibenthic species, as well as Melonis barleeanus, from 9.2 to 6.3 cal ka BP. Specific benthic assemblages indicate high-productivity frontal conditions at site location from 6.3 to 4.1 cal ka BP. AW influx from the Franz Victoria Trough to the Cambridge Strait in subsurface to bottom layer, below the very cold Arctic Water and dense sea ice, is documented by enhanced % Cassidulina teretis over the last 4.5 ka.

Facilitating Judgment Research on Novice Auditors: Academic Perceptions and Auditor Insights into the Work of Novices

Recent environmental changes have led to novice auditors performing tasks traditionally performed by experienced auditors. Yet, our knowledge of novice auditor task responsibilities has not been updated, and research exploring novice judgments does not constitute a large subset of published auditor judgment research. This study facilitates meaningful research on novice auditors by first understanding the perceptions of 113 academics about this type of research. Academics report less than optimistic views regarding the publication likelihood of these studies and express concerns about peers’ views on the importance of novice work and justifying novice participants during the review process. We then inform the study of novices by providing evidence from over 100 audit interns and 30 supervisors on the procedures that interns perform. Supervisors report asking interns to perform tasks historically assigned to higher-ranked auditors including reviewing the work of shared services center staff and performing work in higher-risk accounts such as revenue. To address academic concerns regarding appropriate justifications for novice participants, we use the Kinney Three Paragraphs (and more) approach (Kinney, 2019) to provide insight into key decision points in the participant selection process. In these ways, this study aims to facilitate future research on novice auditors.

Through the Japanese field research in Greenland: A changing natural environment and its impact on human society

Abstract Under the influence of a rapidly warming climate, abrupt changes have been observed along the coast of Greenland. This commentary is based on a Japanese research project initiated in 2012, in which we examined the recent changes in the coastal environment and their impacts on human society in Qaanaaq, a village in northwestern Greenland. Initially, our research sought to quantify the mass loss of glaciers and its interaction with the ocean in the Qaanaaq region. Over the course of the project in collaboration with local communities, we soon realised that the changes in glaciers and the ocean directly impacted the ~600 residents of Qaanaaq. We observed natural disasters triggered by climate change. Environmental changes are also important for local economy and industry because loss of sea ice may lead to growth in transportation, tourism and mineral resource exploration. In order to share the results of our study with the Qaanaaq community, and to gain understanding of local and traditional knowledge, we organised an annual meeting in the village every summer since 2016. Our experience demonstrates the critical importance of performing a long-term multidisciplinary study, including participation of the local communities to understand the changing environment, and to contribute to a sustainable future in Qaanaaq.

A question of scale? A review of interpretations of Irish peatland archaeology in relation to Holocene environmental and climate change

A question of scale? A review of interpretations of Irish peatland archaeology in relation to Holocene environmental and climate change

A question of scale? A review of interpretations of Irish peatland archaeology in relation to Holocene environmental and climate change

A question of scale? A review of interpretations of Irish peatland archaeology in relation to Holocene environmental and climate change

‘Nomad savage’ and herder–farmer conflicts in Nigeria: the (un)making of an ancient myth

Conflicts between sedentary farmers and nomadic pastoralists (herders) are a common phenomenon in Africa. In recent scholarship, environmental change, structural violence and capital flows to agro-pastoral communities are identified as the core conflict drivers. Although scholars differ on the exact causal pathways, most arguments ultimately centre around competition over access to water and land. Yet there is a lot more to learn about the ecology of these conflicts, especially people’s perception of pastoral nomads and its implication for conflict resolution. The tendency among researchers is to explore the conflict as if it comprises only objective realities devoid of subjective beliefs. Yet my research shows that popular representations of Fulani herders in Nigeria today reflect ancient stereotypes of nomadic peoples. By ignoring this subjective dimension of the conflict, we limit our understanding of its causes and the reason(s) behind its protraction, and, by extension, are blinded to the need for prejudice reduction. This paper argues that the perception of pastoral nomads as savages is a factor in the conflict because it shapes people’s relationship with, and reception of, Fulani herders. Hence, it must be grasped, probed and included in the visioning of conflict resolution.

Younger Dryas and Holocene environmental change at the Atlantic fringe of Europe derived from lake‐sediment stable‐isotope records from western Ireland

Western Ireland lies at the Atlantic fringe of Europe and is thus well positioned to record changes in climate linked to North Atlantic circulation. Lake‐sediment oxygen and carbon isotopes are sensitive to changes in the atmosphere, the lake catchment and the lake itself, and thus are valuable proxies for long‐term environmental change. Here we present Younger Dryas and Holocene stable‐isotope records from endogenic and biogenic carbonates from An Loch Mór, a karstic lake on Inis Oírr, Aran Islands, western Ireland. The bulk carbonate and ostracod‐derived stable‐isotope records are a complex response to regional climatic and local factors. Low oxygen‐isotope and high carbon‐isotope values in the Younger Dryas most likely reflect low air temperatures and dominance of bedrock‐derived carbon from the poorly vegetated catchment, but input of detrital carbonate cannot be ruled out. Holocene variations in oxygen‐isotope values are likely a response mainly to changes in the isotopic composition of rainfall, evaporative enrichment of lake water and, during the past millennium, incursion of seawater as a result of regional sea‐level rise. A reduction in carbon‐isotope values at the Younger Dryas/Early Holocene transition reflects increased input of soil‐derived carbon to the lake, modified by changes in aquatic productivity. During the past millennium a shift to less negative values is attributed mainly to increasing saline influence. Broad similarities with stable‐isotope records from other sites in western Ireland suggest regional climatic controls dominated by North Atlantic atmospheric circulation patterns, although abrupt events, that were possibly unique to An Loch Mór, point to local factors also being important.

Integration of lean accounting techniques and balanced scorecard to evaluate the performance of economic units: An exploratory or applied study in Iraq

Received Jun 12th, 201x Recent technological developments and environmental changes that have occurred in recent decades have affected the economic environment and significantly affected the accounting field, where a large spread of industrial enterprises has emerged, which led to increased competition and complexity of the wishes and needs of customers. The research adopted on the topic of Lean accounting, which recognizes the importance of integration between Lean accounting techniques and sustainable balanced scorecard, and how the application of these techniques will reflect the views. This study aimed to determine the role of Lean accounting. There are many results and, more importantly, there is an integral relationship between Lean accounting methods and sustainable balanced scorecard views, reflecting the use of meager methods (value stream, continuous improvement) in a positive way on sustainable scorecard views, and as a result of achieving Balanced and sustainable strategic performance. The study concluded some recommendations such as activating the use of the value principle of accounting Lean was higher to eliminate waste and loss, as well as to maximize the benefits of economic units by finding solutions to problems and obstacles facing the production process

The inhibitory control of pheasants (Phasianus colchicus) weakens when previously learned environmental information becomes unpredictable

Inhibitory control (IC) is the ability to intentionally restrain initial, ineffective responses to a stimulus and instead exhibit an alternative behaviour that is not pre-potent but which effectively attains a reward. Individuals (both humans and non-human animals) differ in their IC, perhaps as a result of the different environmental conditions they have experienced. We experimentally manipulated environmental predictability, specifically how reliable information linking a cue to a reward was, over a very short time period and tested how this affected an individual’s IC. We gave 119 pheasants (Phasianus colchicus) the opportunity to learn to associate a visual cue with a food reward in a binary choice task. We then perturbed this association for half the birds, whereas control birds continued to be rewarded when making the correct choice. We immediately measured all birds’ on a detour IC task and again 3 days later. Perturbed birds immediately performed worse than control birds, making more unrewarded pecks at the apparatus than control birds, although this effect was less for individuals that had more accurately learned the initial association. The effect of the perturbation was not seen 3 days later, suggesting that individual IC performance is highly plastic and susceptible to recent changes in environmental predictability. Specifically, individuals may perform poorly in activities requiring IC immediately after information in their environment is perturbed, with the perturbation inducing emotional arousal. Our finding that recent environmental changes can affect IC performance, depending on how well an animal has learned about that environment, means that interpreting individual differences in IC must account for both prior experience and relevant individual learning abilities.

Body size and diet–related morphological variation of bats over the past 65 years in China

Abstract We examined both historical (1960s) and recent (2017) specimens of an insectivorous bat species (Hipposideros armiger) and a phytophagous bat (Rousettus leschenaultii) from the same latitudinal range to explore phenotypic responses to environmental change in China over the past 65 years. Hipposideros armiger exhibited significant increases in forearm length and three diet-related cranial traits, as well as carbon and nitrogen stable isotope composition, suggesting that modern H. armiger must travel farther for food and may now use different food resources. In contrast, R. leschenaultii showed no change in forearm length but displayed significant increases in diet-related cranial traits. This study provides evidence for differential responses to recent environmental changes in bat species with different diets. The changes in diet-related traits of the two species and the forearm length change on the insectivorous bats suggest that recent phenotypic changes may be adaptions to land-use changes rather than to climate change.

Stable isotopes reveal differential patterns of Holocene environmental change among tuco-tucos (Rodentia: Ctenomyidae, Ctenomys) from Patagonia

To explore the role of past environmental changes in shaping interspecific differences in genetic structure among tuco-tucos (Rodentia: Ctenomyidae, Ctenomys) from the Limay Valley of northern Patagonia, we compared δ13C and δ18O values for modern and historical tooth enamel from the colonial tuco-tuco (C. sociabilis) and the parapatric Patagonian tuco-tuco (C. haigi). Specifically, we sought to test the hypothesis that a mid-Holocene loss of genetic variation in C. sociabilis was associated with environmental change. For both species, the δ13C composition of tooth enamel differed significantly (~ 5.1‰ difference in mean δ13C values) between modern and Holocene (0.5–12 kyr B.P.) samples, suggesting marked temporal changes in the vegetation consumed. For C. sociabilis, no statistically significant differences in the δ13C composition of teeth were found among individuals from the early, middle, and late Holocene. In contrast, significant differences in δ13C values were found between middle and late Holocene samples from C. haigi. None of our analyses revealed statistically significant differences in δ18O values. Thus, although the diets of both study species have changed from the Holocene to the present, only C. haigi experienced significant dietary changes during the Holocene. We suggest that the ecologically more specialized C. sociabilis continued to consume the same food resources even as changing Holocene conditions caused preferred habitats to disappear. In contrast, the more generalized C. haigi altered its diet, allowing populations of this species to remain widespread despite changing Holocene environments.

Responses of the mangrove ecosystem to Holocene environmental change in the Sundarban Biosphere Reserve, India

Abstract The Sundarban Mangrove Forest in the Sundarban Biosphere Reserve, located at the mouth of the Ganga–Brahmaputra Delta in India, is the most diverse mangrove ecosystem in the world. Sediment cores were taken from two widely separated islands in that reserve: Chamta (CMT) and Sudhyanyakhali (SDK). Pollen analysis and radiocarbon dating were used to study the Holocene development and dynamics of this unique ecosystem. Modern pollen rain study reveals a strong relation between modern pollen rain and the present vegetation, as well as a high rate of Phoenix palludosa pollen production.The pollen records indicate that man-grove existed at CMT from ~5960 and at SDK from ~1520 cal yr BP. Changes in relative sea level, including the frequency and intensity of inundation as well as fluctuating precipitation, have been the major factors along with geomorphic processes that control the development and dynamics of the mangrove in the area during the Holocene. The mid Holocene mangrove at CMT declined, to be progressively replaced by successive communities, and eventually reached climax stage, while the SDK site is transitional in nature. The mangrove responds rapidly to changes in environmental conditions at both locations. Because of large-scale anthropogenic interventions, it is unlikely that similar rapid responses will occur in the future.

Late Miocene origin and recent population collapse of the Malagasy savanna olive tree (Noronhia lowryi)

Abstract Debates regarding the origin of tropical savannas have attempted to disentangle the role of human, biotic and abiotic factors. Understanding the origins of savanna remains essential to identifying processes that gave rise to habitat mosaics, particularly those found in the Central Plateau of Madagascar. Documenting the evolutionary history and demography of native trees occurring in open habitats may reveal footprints left by past and recent environmental changes. We conducted a population genetic analysis of an endangered Malagasy shrub (Noronhia lowryi, Oleaceae) of the Central Plateau. Seventy-seven individuals were sampled from three sites and genotyped at 14 nuclear and 24 chloroplast microsatellites. We found a highly contrasting nuclear and plastid genetic structure, suggesting that pollen-mediated gene flow allows panmixia, while seed-based dispersal may rarely exceed tens of metres. From a phylogeny based on full plastomes, we dated the surprisingly old crown age of maternal lineages back to ~6.2 Mya, perhaps co-occurring with the global expansion of savanna. In contrast, recent demographic history inferred from nuclear data shows a bottleneck signature ~350 generations ago, probably reflecting an environmental shift during the Late Pleistocene or the Holocene. Ancient in situ adaptation and recent demographic collapse of an endangered woody plant highlight the unique value and vulnerability of the Malagasy savannas.

Estimation of lucerne yield stability for enabling effective cultivar selection under rainfed conditions

AbstractEvaluation of crop and forage yield stability is of increasing relevance in the context of current and recent environmental changes but, in contrast to other field crops, there are no published systematic analyses among forage crops in Europe. A study of stability performance was conducted with 13 Czech cultivars of lucerne at four locations over a 2‐year period with the following aims: (a) to evaluate yield stability of varieties across different environments and (b) to calculate measurable benefits of variety selection in relation to the specific environment. The cultivar Vlasta was identified as the highest yielding cultivar (annual yield 16.0 t DM/ha), whereas the lowest yielding cv. Magda, Tereza and Oslava averaged around 14.9 t DM/ha. Effect of genotype × environment interaction (G × E) was two times higher than for genotype alone. Additive main effects and the multiplicative interaction (AMMI) model showed that the highest yielding cultivars may not be stable across environments. This study demonstrated further that significant yield improvement could be detected, even among a relatively homogenous group of domestic cultivars, and this was driven mainly by site productivity: the improvement was +10% in low‐yielding sites, compared with +3% in high‐yielding sites. Results highlight that advanced agronomy should also consider stability parameters such as AMMI stability value or superiority measures for forage crops in response to the challenges associated with climate change.

Transformation of maritime desert to an agricultural center: Holocene environmental change and landscape engineering in Chicama River valley, northern Peru coast

Some of the earliest Andean populations settled in the region's arid coastal river valleys, supported by abundant marine life despite having domesticated plant cultigens as early as ∼10 ka. In the Chicama River valley, this maritime economy dominated at the Preceramic site, Huaca Prieta, until ∼6 ka, after which agricultural production began to increase significantly. This agricultural expansion was motivated in part by the development of arable fine-grained soils along the coast as the result of slowing sea-level rise, enhanced river floods, and unique basin lithology. Local populations made use of the stabilized floodplain and wetland settings to conduct raised-terrace farming. By ∼3.5 ka, growth in agriculture and the new fine-grained sediment resources led to several major cultural developments, including the production of fired-ceramic pottery and adobe-brick monument construction associated with the Cupisnique culture. Populations thereafter expanded into the middle valley, where the Salinar and Gallinazo cultures used small water-control structures to farm local ravines. These cultural and technological developments all parallel natural environmental changes driven by increasing ENSO-related water and sediment discharge. By ∼1.8 ka, though, further expansion of agriculture –and arable land– was driven primarily by direct human manipulation of the environment. The construction of an ever-expanding network of irrigation canals diverted increasing volumes of water and sediment to distal reaches of the Chicama valley, supporting the great Moche and Chimu civilizations, and persisting through the Inka and Colonial periods. This history of Chicama valley traces strongly coupled interactions between the human and natural environments, supporting significant socio-cultural, economic, demographic, and technological advances.

Paleontological Records of Holocene Environmental Changes offshore, Egypt

Paleontological and sedimentological analyses were carried out in sediment core from southeastern Mediterranean Sea, offshore Egypt to reconstruct the past environmental changes in trophic state and temperature during Holocene. To achieve our goals, grain size, total organic carbon, planktic and benthic foraminifera, dinoflagellate cysts have been investigated. Few micropalaentological studies have been done in the studied area and none of them used the combined proxies of benthic foraminifera and dinoflagellate cyst. Theses combined proxies reflects more comprehensive paleoenvironmental view. Biotic and abiotic data have been analysed with multivariate technique including Redundancy Analysis (RDA). Diversity indices such as: Fisher alpha index (α) and Shannon index (H) have been applied. The foraminiferal study yields 9 planktic species and 10 benthic species. Foraminiferal assemblages have low species diversity indices especially at sapropel layer S1. Mediterranean sapropels are layers with elevated organic carbon concentrations that contrast with surrounding organic poor sediments. Sapropels occur periodically in sedimentary sequences of the last millions years, which have been the subject of extensive previous study. Redundancy Analysis (RDA) yields two groups of foraminiferal assemblages depending on the changes of total organic carbon and clay content. The dinocysts study yields 15 species, the majority of cyst types belonging to the order Gonyaulacales. The association of dinoflagellate cyst shows two depositional phases in the sediment. The sapropel layer S1, with anoxic condition and warmer temperature, is recorded at depth 28–46 cm where heterotrophic taxa dominate and the post-sapropel layer is recorded at depth 0–28 cm; where autotrophic taxa dominate.

Phenotypic selection mosaic for flower length influenced by geographically varying hawkmoth pollinator proboscis length and abiotic environment.

Biotic and abiotic context may affect the intensity of interspecific interactions and subsequently drive locally particular phenotypic selection patterns on interacting traits. We evaluated the geographical variation of matching traits of the brush-type flowers of Caesalpinia gilliesii and of the proboscis length of its guild of hawkmoth pollinators, as well as their relationship with environmental variables. We assessed the geographical variation of interacting traits (style and filament vs mean proboscis length of the guild of hawkmoths) across seven populations and estimated phenotypic selection on the plant side. Interacting traits showed similar relationships with environmental variables. Phenotypic selection on the plant side was influenced by proboscis length and by environmental conditions. Mean proboscis length of the guild was shorter than previously recorded for the same study area, thus probably shifting the selective optima of flower length. We observed two presumptive coevolutionary cold spots where one-sided negative directional selection is acting on style length. The lack of selection on the pollinator side should be further confirmed. We provided joint evidence, mostly lacking, about the geographical variation of selective pressures on the plant side associated with both proboscis length and abiotic conditions. We suggest that recent environmental change may be shifting floral length optima.