Ecohydrological Behavior of Semiarid Ecosystems of Chile in Present and Future Climate Scenarios

2021 ◽  
pp. 60-74
Author(s):  
Javier Lo Parra ◽  
Jacinto Garrido Velarde ◽  
Jesus Barrena González ◽  
Manuel Pulido Fernández
Keyword(s):  
Spectral Reflectance ◽  
Climate Change Scenarios ◽  
Climate Scenarios ◽  
Worst Case ◽  
Semiarid Ecosystems ◽  
Demographic Rates ◽  
Rcp 8.5 ◽  
Weather Variations ◽  
Hydrological Variables

Semiarid ecosystems of Chile with Mediterranean climate support high demographic rates and maintain important economies associated with the productivity of the natural environment; however, they strongly depend on the water availability and their future is compromised by climate variations. This study tries to define the role of hydrological variables on the growth of herbaceous biomass under the current climate and under future weather variations. For this, the authors used meteorological stations which let them estimate the water balance at plot scale and spectral reflectance sensors which let them follow the dynamics of the NDVI of herbaceous plants. In this context, the NDVI value was about 0.7, which means approximately 3700 kg DM ha1. However, under the worst-case climate change scenarios (RCP 8.5), annual precipitation showed a reduction of up to 31.6% regarding the present period. In this situation, the NDVI could be reduced up to 80% respect to the current situation. Thus, if climate changes to its worst scenario, it could threaten the maintenance and productivity of these ecosystems.

scholarly journals Global carbon sequestration through continental chemical weathering in a climatic change context

2021 ◽  
Author(s):  
Juan Luis Lechuga-Crespo ◽  
Sabine Sauvage ◽  
Michelle vanVliet ◽  
Estilita Ruiz-Romera ◽  
Jean-Luc Probst ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Chemical Weathering ◽  
Co2 Uptake ◽  
Climate Change Scenarios ◽  
Climate Scenarios ◽  
General Increase ◽  
Change Context ◽  
Rcp 8.5 ◽  
Carbon Dioxide Co2 ◽  
Projected Changes

Abstract Here, we simulate carbon dioxide (CO2) sequestration in 300 major world river basins (about 70% of global surface area) through carbonates dissolution and silicate hydrolysis. For each river basin, the daily timescale impacts under both the RCP 2.6 and RCP 8.5 climate scenarios were assessed relative to a historic baseline (1969-1999) using a cascade of models accounting for the hydrological evolution under climate change scenarios. Here we show that global temporal evolution of the CO2 uptake presents a general increase in the annual amount of CO2 consumed from 0.247 Pg C·y-1 to 0.261 and 0.273 Pg C·y-1, respectively for RCP 2.6 and RCP 8.5. Besides, despite showing a general increase for the global daily carbon sequestration, both climate scenarios present a decrease between June and August. Such projected changes have been mapped and evaluated against changes in hydrology, identifying hot spots and moments for the annual and seasonal periods.

scholarly journals Global carbon sequestration through continental chemical weathering in a climatic change context

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Juan Luis Lechuga-Crespo ◽  
Sabine Sauvage ◽  
Estilita Ruiz-Romera ◽  
Michelle T. H. van Vliet ◽  
Jean-Luc Probst ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Chemical Weathering ◽  
Climate Change Scenarios ◽  
Climate Scenarios ◽  
General Increase ◽  
Change Context ◽  
Rcp 8.5 ◽  
Projected Changes ◽  
Annual Amount ◽  
Global Carbon

AbstractThis study simulates carbon dioxide (CO2) sequestration in 300 major world river basins (about 70% of global surface area) through carbonates dissolution and silicate hydrolysis. For each river basin, the daily timescale impacts under the RCP 2.6 and RCP 8.5 climate scenarios were assessed relative to a historical baseline (1969–1999) using a cascade of models accounting for the hydrological evolution under climate change scenarios. Here we show that the global temporal evolution of the CO2 uptake presents a general increase in the annual amount of CO2 consumed from 0.247 ± 0.045 Pg C year−1 to 0.261 and 0.273 ± 0.054 Pg C year−1, respectively for RCP 2.6 and RCP 8.5. Despite showing a general increase in the global daily carbon sequestration, both climate scenarios show a decrease between June and August. Such projected changes have been mapped and evaluated against changes in hydrology, identifying hot spots and moments for the annual and seasonal periods.

scholarly journals Robust Universal Inference

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 773
Author(s):  
Amichai Painsky ◽  
Meir Feder
Keyword(s):  
Robust Estimation ◽  
Minimax Estimator ◽  
Worst Case ◽  
Capacity Theory ◽  
Alternative Approach ◽  
True Model ◽  
Finite Set ◽  
Universal Prediction ◽  
Estimation Scheme

Learning and making inference from a finite set of samples are among the fundamental problems in science. In most popular applications, the paradigmatic approach is to seek a model that best explains the data. This approach has many desirable properties when the number of samples is large. However, in many practical setups, data acquisition is costly and only a limited number of samples is available. In this work, we study an alternative approach for this challenging setup. Our framework suggests that the role of the train-set is not to provide a single estimated model, which may be inaccurate due to the limited number of samples. Instead, we define a class of “reasonable” models. Then, the worst-case performance in the class is controlled by a minimax estimator with respect to it. Further, we introduce a robust estimation scheme that provides minimax guarantees, also for the case where the true model is not a member of the model class. Our results draw important connections to universal prediction, the redundancy-capacity theorem, and channel capacity theory. We demonstrate our suggested scheme in different setups, showing a significant improvement in worst-case performance over currently known alternatives.

scholarly journals Water Temperature and Hydrological Modelling in the Context of Environmental Flows and Future Climate Change: Case Study of the Wilmot River (Canada)

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2101
Author(s):  
Christian Charron ◽  
André St-Hilaire ◽  
Taha B.M.J. Ouarda ◽  
Michael R. van den Heuvel
Keyword(s):  
Climate Change ◽  
Water Temperature ◽  
Environmental Flows ◽  
Low Flow ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Water Abstraction ◽  
Surface Water Flow ◽  
Modelling Studies ◽  
Rcp 8.5

Simulation of surface water flow and temperature under a non-stationary, anthropogenically impacted climate is critical for water resource decision makers, especially in the context of environmental flow determination. Two climate change scenarios were employed to predict streamflow and temperature: RCP 8.5, the most pessimistic with regards to climate change, and RCP 4.5, a more optimistic scenario where greenhouse gas emissions peak in 2040. Two periods, 2018–2050 and 2051–2100, were also evaluated. In Canada, a number of modelling studies have shown that many regions will likely be faced with higher winter flow and lower summer flows. The CEQUEAU hydrological and water temperature model was calibrated and validated for the Wilmot River, Canada, using historic data for flow and temperature. Total annual precipitation in the region was found to remain stable under RCP 4.5 and increase over time under RCP 8.5. Median stream flow was expected to increase over present levels in the low flow months of August and September. However, increased climate variability led to higher numbers of periodic extreme low flow events and little change to the frequency of extreme high flow events. The effective increase in water temperature was four-fold greater in winter with an approximate mean difference of 4 °C, while the change was only 1 °C in summer. Overall implications for native coldwater fishes and water abstraction are not severe, except for the potential for more variability, and hence periodic extreme low flow/high temperature events.

scholarly journals A hydrological modelling-based approach for vulnerable area identification under changing climate scenarios

2020 ◽  
Author(s):  
Sonam S. Dash ◽  
Dipaka R. Sena ◽  
Uday Mandal ◽  
Anil Kumar ◽  
Gopal Kumar ◽  
...  
Keyword(s):  
Assessment Tool ◽  
Fold Increase ◽  
Maximum Temperature ◽  
Climate Scenarios ◽  
Vulnerable Area ◽  
Temperature And Precipitation ◽  
Monthly Streamflow ◽  
Rcp 8.5 ◽  
Streamflow Data ◽  
Critical Zones

Abstract The hydrologic behaviour of the Brahmani River basin (BRB) (39,633.90 km2), India was assessed for the base period (1970–1999) and future climate scenarios (2050) using the Soil and Water Assessment Tool (SWAT). Monthly streamflow data of 2000–2009 and 2010–2012 was used for calibration and validation, respectively, and performed satisfactorily with Nash-Sutcliffe Efficiency (ENS) of 0.52–0.55. The projected future climatic outcomes of the HadGEM2-ES model indicated that minimum temperature, maximum temperature, and precipitation may increase by 1.11–3.72 °C, 0.27–2.89 °C, and 16–263 mm, respectively, by 2050. The mean annual streamflow over the basin may increase by 20.86, 11.29, 4.45, and 37.94% under RCP 2.6, 4.5, 6.0, and 8.5, respectively, whereas the sediment yield is likely to increase by 23.34, 10.53, 2.45, and 27.62% under RCP 2.6, 4.5, 6.0, and 8.5, respectively, signifying RCP 8.5 to be the most adverse scenario for the BRB. Moreover, a ten-fold increase in environmental flow (defined as Q90) by the mid-century period is expected under the RCP 8.5 scenario. The vulnerable area assessment revealed that the increase in moderate and high erosion-prone regions will be more prevalent in the mid-century. The methodology developed herein could be successfully implemented for identification and prioritization of critical zones in worldwide river basins.

South Africa at a Turning Point?

2015 ◽  
Vol 53 (3) ◽  
pp. 477-486 ◽  
Author(s):  
Elke Zuern
Keyword(s):  
South Africa ◽  
Turning Point ◽  
Case Scenario ◽  
State Collapse ◽  
Worst Case ◽  
South Africans ◽  
Nelson Mandela ◽  
Wide Range ◽  
Electricity Provision

South Africa is at a crossroads. The state has not adequately addressed dire human development needs, often failing to provide the services it constitutionally guarantees. As a result, citizens are expressing their frustrations in a variety of ways, at times including violence. These serious challenges are most readily apparent in poverty, inequality and unemployment statistics, but also in electricity provision, billing and affordability as well as a recent spate of racially motivated attacks which highlight the tension both among South Africans and between South Africans and darker skinned foreigners. The country has, however, been on the brink before and avoided the worst-case scenario of full-scale civil war and state collapse. Far too often South Africa's past successes have been attributed to the role of one man, Nelson Mandela. While Mandela was indeed an extraordinary human being who rightly deserved the international awards and accolades as well as the deep admiration of so many, South Africa's triumphs as a society and a state are the product of both cooperative and conflicting contributions by a wide range of actors. A central question at the present juncture is how well equipped domestic actors and institutions are to address the crisis. The following pages seek to provide some insights and through the perspectives of three authors to consider causes and possible responses.

scholarly journals Trends in Adoption of Farm Technology: An Overview of Survey in Bhagalpur District of Bihar

2020 ◽  
pp. 56-62
Author(s):  
Shivam Kumar ◽  
S. R. Singh ◽  
Chaitali Kumari ◽  
Aabha .
Keyword(s):  
Rural Areas ◽  
Primary Source ◽  
Marketing Channel ◽  
Structured Interview ◽  
Large Area ◽  
New Techniques ◽  
New Crops ◽  
High Yielding Varieties ◽  
Weather Variations

Agriculture is the primary source of livelihood for rural areas in Bihar. Agriculture being mostly dependent on monsoon is highly affected by scanty rainfall, weather variations, flood, etc. The study was conducted in Bhagalpur district of Bihar to assess role of different technologies in enhancing income and mitigate challenges faced by farmers. Three villages of Sabour block in Bhagalpur district namely Farka, Ghospur and English were selected for study. A total of 150 farmers (50 from each village) were selected randomly and data was collected using semi-structured interview schedule. Production innovations like high yielding varieties, new techniques, and home-made remedies of costly designs were identified, along with a marketing channel to sell vegetables from diara region. Some new crops like strawberry and fruits plantation in large area seemed to have good scope; poultry business also appeared to be promising. Some constraints were also identified which when rectified can give new potentials to agricultural production in this area.

scholarly journals Stochastic Flips on Dimer Tilings

2010 ◽  
Vol DMTCS Proceedings vol. AM,... (Proceedings) ◽  
Author(s):  
Thomas Fernique ◽  
Damien Regnault
Keyword(s):  
Fixed Point ◽  
Markov Process ◽  
Upper Bound ◽  
Numerical Experiments ◽  
Triangular Grid ◽  
Expected Number ◽  
Worst Case ◽  
Average Case ◽  
International Audience

International audience This paper introduces a Markov process inspired by the problem of quasicrystal growth. It acts over dimer tilings of the triangular grid by randomly performing local transformations, called $\textit{flips}$, which do not increase the number of identical adjacent tiles (this number can be thought as the tiling energy). Fixed-points of such a process play the role of quasicrystals. We are here interested in the worst-case expected number of flips to converge towards a fixed-point. Numerical experiments suggest a $\Theta (n^2)$ bound, where $n$ is the number of tiles of the tiling. We prove a $O(n^{2.5})$ upper bound and discuss the gap between this bound and the previous one. We also briefly discuss the average-case.

scholarly journals EARLY FLOWERING 3 controls temperature responsiveness of the circadian clock

2020 ◽  
Author(s):  
Zihao Zhu ◽  
Marcel Quint ◽  
Muhammad Usman Anwer
Keyword(s):  
Circadian Clock ◽  
Biological Rhythms ◽  
Early Flowering ◽  
Climate Change Scenarios ◽  
Temperature Changes ◽  
Physiological Processes ◽  
Average Global Temperature ◽  
Clock Component ◽  
Rhythmic Growth

SummaryPredictable changes in light and temperature during a diurnal cycle are major entrainment cues that enable the circadian clock to generate internal biological rhythms that are synchronized with the external environment. With the average global temperature predicted to keep increasing, the intricate light-temperature coordination that is necessary for clock functionality is expected to be seriously affected. Hence, understanding how temperature signals are perceived by the circadian clock has become an important issue, especially in light of climate change scenarios. In Arabidopsis, the clock component EARLY FLOWERING 3 (ELF3) not only serves as an essential light Zeitnehmer, but also functions as a thermosensor participating in thermomorphogenesis. However, the role of ELF3 in temperature entrainment of the circadian clock is not fully understood. Here, we report that ELF3 is essential for delivering temperature input to the clock. We demonstrate that in the absence of ELF3, the oscillator was unable to properly respond to temperature changes, resulting in an impaired gating of thermoresponses. Consequently, clock-controlled physiological processes such as rhythmic growth and cotyledon movement were disturbed. Together, our results reveal that ELF3 is an essential Zeitnehmer for temperature sensing of the oscillator, and thereby for coordinating the rhythmic control of thermoresponsive physiological outputs.

scholarly journals Climatic suitability predictions for the cultivation of macadamia in Malawi using climate change scenarios.

2021 ◽  
Author(s):  
Emmanuel Junior Zuza ◽  
Yoseph Negusse Araya ◽  
Kadmiel Maseyk ◽  
Shonil A Bhagwat ◽  
Kaue de Sousa ◽  
...  
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
General Circulation Models ◽  
Food Sources ◽  
Climate Change Scenarios ◽  
Crop Species ◽  
Cascading Effects ◽  
Northern Regions ◽  
Rcp 8.5 ◽  
Model Approach

Climate change is altering suitable areas of crop species worldwide, with cascading effects on people and animals reliant upon those crop species as food sources. Macadamia is one of Malawi's most important and profitable crop species. Here, we used an ensemble model approach to determine the current distribution of macadamia producing areas across Malawi in relation to climate. For future distribution of suitable areas, we used the climate outputs of 17 general circulation models (GCM's) based on two climate change scenarios (RCP 4.5 and RCP 8.5). We found that the precipitation of the driest month and isothermality were the climatic variables that strongly influenced macadamia's suitability in Malawi. These climatic requirements were fulfilled across many areas in Malawi under the current conditions. Future projections indicated that large parts of Malawi's macadamia growing regions will remain suitable for macadamia, amounting to 36,910 km2 (39.1%) and 33,511 km2 (35.5%) of land based on RCP 4.5 and RCP 8.5, respectively. Of concern, suitable areas for macadamia production are predicted to shrink by −18% (17,015 km2) and −22% (20,414 km2) based on RCP 4.5 and RCP 8.5, respectively, with much of the suitability shifting northwards. Although a net loss of area suitable for macadamia is predicted, some currently unsuitable areas will become suitable in the future. Notably, suitable areas will increase in Malawi's central and northern regions, while the southern region will lose most of its suitable areas. In conclusion, our study provides critical evidence that climate change will significantly affect the macadamia sub-sector in Malawi. Therefore area-specific adaptation strategies are required to build resilience.

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