High-resolution record of Holocene erosion patterns in a high altitude lake (Lake Anterne, NW French Alps): a witness of environmental changes, climatic variability and human activities

2012 ◽  
Vol 279-280 ◽  
pp. 167
Author(s):  
Charline Giguet-Covex
Keyword(s):  
High Resolution ◽  
High Altitude ◽  
Human Activities ◽  
Environmental Changes ◽  
Climatic Variability ◽  
French Alps ◽  
High Altitude Lake

Small peatland with a big story: 600-year paleoecological and historical data from a kettle-hole peatland in Western Russia

The Holocene ◽  
2021 ◽  
pp. 095968362110332
Author(s):  
Agnieszka Mroczkowska ◽  
Piotr Kittel ◽  
Katarzyna Marcisz ◽  
Ekaterina Dolbunova ◽  
Emilie Gauthier ◽  
...  
Keyword(s):  
Human Impact ◽  
Human Activities ◽  
Environmental Changes ◽  
Climatic Variability ◽  
Testate Amoebae ◽  
The Past ◽  
Kettle Hole ◽  
Rapid Changes ◽  
History Of ◽  
Physical And Chemical

Peatlands are important records of past environmental changes. Based on a multiproxy analysis, the main factors influencing the evolution of a peatland can be divided into autogenic and allogenic. Among the important allogenic factors, apart from climate change, are deforestation and drainage, which are directly associated with human impact. Numerous consequences arise from these processes, the most important of which are physical and chemical denudation in the catchment and the related hydrological disturbances in the catchment and peatland. The present study determined how human activities and the past climatic variability mutually influenced the development of a small peatland ecosystem. The main goals of the study were: (1) to trace the local changes of the peatland history over the past 600 years, (2) to investigate their relationship with changes in regional hydroclimate patterns, and (3) to estimate the sensitivity of a small peatland to natural and human impact. Our reconstructions were based on a multiproxy analysis, including the analysis of pollen, macrofossils, Chironomidae, Cladocera, and testate amoebae. Our results showed that, depending on the changes in water level, the history of peatland can be divided into three phases as follows: 1/the phase of stable natural conditions, 2/phase of weak changes, and 3/phase of significant changes in the catchment. Additionally, to better understand the importance of the size of catchment and the size of the depositional basin in the evolution of the studied peatland ecosystem, we compared data from two peatlands – large and small – located close to each other. The results of our study indicated that “size matters,” and that larger peatlands are much more resilient and resistant to rapid changes occurring in the direct catchment due to human activities, whereas small peatlands are more sensitive and perfect as archives of environmental changes.

scholarly journals Holocene environmental changes in the highlands of the southern Peruvian Andes (14° S) and their impact on pre-Columbian cultures

2014 ◽  
Vol 10 (2) ◽  
pp. 1707-1746 ◽  
Author(s):  
K. Schittek ◽  
B. Mächtle ◽  
F. Schäbitz ◽  
M. Forbriger ◽  
V. Wennrich ◽  
...  
Keyword(s):  
High Resolution ◽  
High Altitude ◽  
Amazon Basin ◽  
Environmental Changes ◽  
Current Knowledge ◽  
High Temporal Resolution ◽  
Dry Period ◽  
North East ◽  
Xrf Core Scanner ◽  
Poaceae Pollen

Abstract. Within palaeoenvironmental studies, high-altitude peatlands of the Andes still remain relatively unexploited, although they offer an excellent opportunity for high-resolution chronologies, on account of their high accumulation rates and abundant carbon for dating. Especially in the central Andes, additional high-quality proxy records are still needed due to the lack of continuous and well-dated records, which show a significant variability on sub-centennial to decadal precision scales. To widen the current knowledge on climatic and environmental changes in the western Andes of southern Peru, we present a new, high-resolution 8600 year-long record from Cerro Llamoca peatland, a high-altitude Juncaceous cushion peatland in the headwaters of Río Viscas, a tributary to Río Grande de Nasca. A 10.5 m core of peat with intercalated sediment layers was examined for all kinds of microfossils, including fossil charred particles. We chose homogeneous peat sections for pollen analysis at a high temporal resolution. The inorganic geochemistry was analysed in 2 mm resolution using an ITRAX X-ray fluorescence (XRF) core scanner. We interpret the increase of Poaceae pollen in our record as an expansion of Andean grasslands during humid phases. Drier conditions are indicated by a significant decrease of Poaceae pollen and higher abundances of Asteraceae pollen. The results are substantiated by changes in arsenic contents and manganese/iron ratios, which turned out as applicable proxies for in situ palaeo-redox conditions. The mid-Holocene period of 8.6–5.6 ka is characterized by a series of episodic dry spells alternating with spells that are more humid. After a pronounced dry period at 4.6–4.2 ka, conditions generally shifted towards a more humid climate. We stress a humid/relatively stable interval between 1.8–1.2 ka, which coincides with the florescence of the Nasca culture in the Andean foreland. An abrupt turnover to a sustained dry period occurs at 1.2 ka, which coincides with the collapse of the Nasca/Wari society in the Palpa lowlands. Markedly drier conditions prevail until 0.75 ka, providing evidence for the presence of a Medieval Climate Anomaly. Moister but hydrologically highly variable conditions prevailed again after 0.75 ka, which allowed the re-expansion of tussock grasses in the highlands, increased discharge into the Andean foreland and the re-occupation of the settlements in the lowlands during this so-called Late Intermediate Period. On a supraregional scale, our findings can ideally be linked to and proofed by the archaeological chronology of the Nasca-Palpa region as well as other high-resolution marine and terrestrial palaeoenvironmental records. Our findings show that hydrological fluctuations, triggered by the changing intensity of the monsoonal tropical summer rains emerging from the Amazon Basin in the north-east, have controlled the climate in the study area.

Silver and lead in high-altitude lake sediments: Proxies for climate changes and human activities

2012 ◽  
Vol 27 (3) ◽  
pp. 760-773 ◽  
Author(s):  
Marion Garçon ◽  
Catherine Chauvel ◽  
Emmanuel Chapron ◽  
Xavier Faïn ◽  
Mingfang Lin ◽  
...  
Keyword(s):  
High Altitude ◽  
Lake Sediments ◽  
Human Activities ◽  
Climate Changes ◽  
High Altitude Lake

High-altitude varve records of abrupt environmental changes and mining activity over the last 4000 years in the Western French Alps (Lake Bramant, Grandes Rousses Massif)

2007 ◽  
Vol 26 (19-21) ◽  
pp. 2644-2660 ◽  
Author(s):  
Hervé Guyard ◽  
Emmanuel Chapron ◽  
Guillaume St-Onge ◽  
Flavio S. Anselmetti ◽  
Fabien Arnaud ◽  
...  
Keyword(s):  
High Altitude ◽  
Environmental Changes ◽  
Mining Activity ◽  
French Alps

scholarly journals High-resolution sedimentary record of the last deglaciation from a high-altitude lake in Ethiopia

2008 ◽  
Vol 27 (5-6) ◽  
pp. 449-467 ◽  
Author(s):  
J.-J. Tiercelin ◽  
E. Gibert ◽  
M. Umer ◽  
R. Bonnefille ◽  
J.-R. Disnar ◽  
...  
Keyword(s):  
High Resolution ◽  
High Altitude ◽  
Last Deglaciation ◽  
Sedimentary Record ◽  
The Last Deglaciation ◽  
High Altitude Lake

scholarly journals High-resolution Late-holocene Biomarkers Records in Southern Continental Shelf of the Korean Peninsula: Implications for Climate Variations Over the Last 4 Kyr

2021 ◽  
Author(s):  
Sangmin Hyun ◽  
Jeongwon Kang ◽  
Jin Hyung Cho ◽  
Gil Young Kim
Keyword(s):  
High Resolution ◽  
Continental Shelf ◽  
Korean Peninsula ◽  
Environmental Changes ◽  
Climatic Variability ◽  
Source Area ◽  
Carbon Isotope Ratio ◽  
Average Chain Length ◽  
Climate Conditions ◽  
Combined Indices

Abstract High-resolution records for carbon isotopes of organic matter and n-alkane compounds were investigated in two gravity cores (SJP15-2 and SJP15-4) taken from the southern continental shelf of the Korean peninsula to evaluate the influxes of terrestrial biomarkers and their linkage to paleoclimate and marine environmental changes since the last 4 kyr. The total organic carbon contents were < 1%, and the carbon isotope ratio of organic matters (d13Corg) ranged from approximately −21‰ to -22‰ and, they did not highly fluctuate throughout the two cores. However, the vertical distributions of total terrestrial biomarkers, long-chain n-alkanes (nC25-35), and individual n-alkane compounds exhibited distinctive fluctuations. There are two switching points that discriminate patterns of excursion and distribution at ca. 2.5 ka, and 0.5 ka. Several n-alkane combined indices such as average chain length (ACL), carbon preference index (CPI), and paleovegetation index (Paq) were coincident with these switching points, implying that the supply of terrestrial biomarkers was strongly associated with environmental changes at the source area. In particular, variations of compound-specific n-alkanes isotope and the ratios of nC31/nC27 and nC31/nC29 follow those of n-alkanes indices, implying that this millennium records were associated with wetter climate conditions, and thus paleovegetation and paleoclimate variation. Comparison with previous data of the detrital quartz from the East China Sea and aeolian dust in the Cheju (Jeju) Island, South Korea, and Dongge cave oxygen isotope records indicates strong synchronicity with gradual paleoclimate degradation between 2.5 ka and 0.5 ka. Therefore, our high-resolution n-alkane data are very useful for reconstructing past climatic variability, suggesting that paleoclimate system of the East Asian region may have influenced the sediment records of study area since the last 4 kyr.

scholarly journals Extended Distributed Framework for Feature Extraction in Remote Sensing Imagery with High Resolution

Webology ◽  
2021 ◽  
Vol 18 (2) ◽  
pp. 1035-1046
Author(s):  
T. Naga Raju ◽  
Dr. Chittineni Suneetha
Keyword(s):  
Remote Sensing ◽  
Feature Extraction ◽  
High Resolution ◽  
Spatial Data ◽  
Human Activities ◽  
Environmental Changes ◽  
Total System ◽  
Remote Sensing Imagery ◽  
Distributed Framework ◽  
The Given

Remote Sensing imagery is used vastly in the areas of human activities investigation, environmental changes monitoring and geo-spatial data updation in a rapidly increasing way. Humans can easily and appropriately interpret the normally shot pictures but this is a difficult task for the computer to automatically interpret information from the given images. One of the prominent phases is in finding the way to extract the projected information from the given imagery and its conversion to wrath-ful data which can be used for further research. The motto is the generation of an algorithm which aims to be very efficient during of processing of huge images that include enhancement of efficiency in processing, correlation finding amongst given data and extraction of continuous features. In order to accomplish all these purposes as stated above, we hereby put forward an algorithm Extended Feature Extraction and Detection in High Resolution Remote Sensing (HRRS) Imagery to detect rivers. The proposed system is established with Hadoop Distributed Framework in order to enhance the efficiency of total system.

Desertification and Re-Greening of the Sahel

2017 ◽  
Author(s):  
Rasmus Fensholt ◽  
Cheikh Mbow ◽  
Martin Brandt ◽  
Kjeld Rasmussen
Keyword(s):  
Human Activities ◽  
Environmental Changes ◽  
Spatial Scales ◽  
Climatic Variability ◽  
Anthropogenic Factors ◽  
Land Resource ◽  
Positive Trend ◽  
Vegetation Greenness ◽  
Positive Effects ◽  
Semi Arid

In the past 50 years, human activities and climatic variability have caused major environmental changes in the semi-arid Sahelian zone and desertification/degradation of arable lands is of major concern for livelihoods and food security. In the wake of the Sahel droughts in the early 1970s and 1980s, the UN focused on the problem of desertification by organizing the UN Conference on Desertification (UNCOD) in Nairobi in 1976. This fuelled a significant increase in the often alarmist popular accounts of desertification as well as scientific efforts in providing an understanding of the mechanisms involved. The global interest in the subject led to the nomination of desertification as focal point for one of three international environmental conventions: the UN Convention to Combat Desertification (UNCCD), emerging from the Rio conference in 1992. This implied that substantial efforts were made to quantify the extent of desertification and to understand its causes. Desertification is a complex and multi-faceted phenomenon aggravating poverty that can be seen as both a cause and a consequence of land resource depletion. As reflected in its definition adopted by the UNCCD, desertification is “land degradation in arid, semi-arid[,] and dry sub-humid areas resulting from various factors, including climate variation and human activities” (UN, 1992). While desertification was seen as a phenomenon of relevance to drylands globally, the Sahel-Sudan region remained a region of specific interest and a significant amount of scientific efforts have been invested to provide an empirically supported understanding of both climatic and anthropogenic factors involved. Despite decades of intensive research on human–environmental systems in the Sahel, there is no overall consensus about the severity of desertification and the scientific literature is characterized by a range of conflicting observations and interpretations of the environmental conditions in the region. Earth Observation (EO) studies generally show a positive trend in rainfall and vegetation greenness over the last decades for the majority of the Sahel and this has been interpreted as an increase in biomass and contradicts narratives of a vicious cycle of widespread degradation caused by human overuse and climate change. Even though an increase in vegetation greenness, as observed from EO data, can be confirmed by ground observations, long-term assessments of biodiversity at finer spatial scales highlight a negative trend in species diversity in several studies and overall it remains unclear if the observed positive trends provide an environmental improvement with positive effects on people’s livelihood.

Sign in / Sign up

Export Citation Format

Share Document