TY - JOUR A1 - Oguntunde, Philip G. A1 - Abiodun, Babatunde Joseph A1 - Lischeid, Gunnar A1 - Abatan, Abayomi A. T1 - Droughts projection over the Niger and Volta River basins of West Africa at specific global warming levels JF - International Journal of Climatology N2 - This study investigates possible impacts of four global warming levels (GWLs: GWL1.5, GWL2.0, GWL2.5, and GWL3.0) on drought characteristics over Niger River basin (NRB) and Volta River basin (VRB). Two drought indices-Standardized Precipitation Index (SPI) and Standardized Precipitation-Evapotranspiration Index (SPEI)-were employed in characterizing droughts in 20 multi-model simulation outputs from the Coordinated Regional Climate Downscaling Experiment (CORDEX). The performance of the simulation in reproducing basic hydro-climatological features and severe drought characteristics (i.e., magnitude and frequency) in the basins were evaluated. The projected changes in the future drought frequency were quantified and compared under the four GWLs for two climate forcing scenarios (RCP8.5 and RCP4.5). The regional climate model (RCM) ensemble gives a realistic simulation of historical hydro-climatological variables needed to calculate the drought indices. With SPEI, the simulation ensemble projects an increase in the magnitude and frequency of severe droughts over both basins (NRB and VRB) at all GWLs, but the increase, which grows with the GWLs, is higher over NRB than over VRB. More than 75% of the simulations agree on the projected increase at GWL1.5 and all simulations agree on the increase at higher GWLs. With SPI, the projected changes in severe drought is weaker and the magnitude remains the same at all GWLs, suggesting that SPI projection may underestimate impacts of the GWLs on the intensity and severity of future drought. The results of this study have application in mitigating impact of global warming on future drought risk over the regional water systems. KW - climate change KW - drought index KW - global warming levels KW - river basins KW - West Africa KW - CORDEX data Y1 - 2019 VL - 40 IS - 13 PB - John Wiley & Sons, Inc. CY - New Jersey ER - TY - JOUR A1 - Stoof-Leichsenring, Kathleen Rosemarie A1 - Pestryakova, Luidmila Agafyevna A1 - Epp, Laura Saskia A1 - Herzschuh, Ulrike T1 - Phylogenetic diversity and environment form assembly rules for Arctic diatom genera BT - a study on recent and ancient sedimentary DNA JF - Journal of Biogeography N2 - Aim This study investigates taxonomic and phylogenetic diversity in diatom genera to evaluate assembly rules for eukaryotic microbes across the Siberian tree line. We first analysed how phylogenetic distance relates to taxonomic richness and turnover. Second, we used relatedness indices to evaluate if environmental filtering or competition influences the assemblies in space and through time. Third, we used distance-based ordination to test which environmental variables shape diatom turnover. Location Yakutia and Taymyria, Russia: we sampled 78 surface sediments and a sediment core, extending to 7,000 years before present, to capture the forest-tundra transition in space and time respectively. Taxon Arctic freshwater diatoms. Methods We applied metabarcoding to retrieve diatom diversity from surface and core sedimentary DNA. The taxonomic assignment binned sequence types (lineages) into genera and created taxonomic (abundance of lineages within different genera) and phylogenetic datasets (phylogenetic distances of lineages within different genera). Results Contrary to our expectations, we find a unimodal relationship between phylogenetic distance and richness in diatom genera. We discern a positive relationship between phylogenetic distance and taxonomic turnover in spatially and temporally distributed diatom genera. Furthermore, we reveal positive relatedness indices in diatom genera across the spatial environmental gradient and predominantly in time slices at a single location, with very few exceptions assuming effects of competition. Distance-based ordination of taxonomic and phylogenetic turnover indicates that lake environment variables, like HCO3- and water depth, largely explain diatom turnover. Main conclusion Phylogenetic and abiotic assembly rules are important in understanding the regional assembly of diatom genera across lakes in the Siberian tree line ecotone. Using a space-time approach we are able to exclude the influence of geography and elucidate that lake environmental variables primarily shape the assemblies. We conclude that some diatom genera have greater capabilities to adapt to environmental changes, whereas others will be putatively replaced or lost due to the displacement of the Arctic tundra biome under recent global warming. KW - ancient sedimentary DNA KW - Arctic lakes KW - assembly rules KW - climate change KW - diatoms KW - environmental filtering KW - phylogenetic diversity KW - Siberian tree line Y1 - 2020 U6 - https://doi.org/10.1111/jbi.13786 SN - 0305-0270 SN - 1365-2699 VL - 47 IS - 5 SP - 1166 EP - 1179 PB - Wiley-Blackwell CY - Oxford ER - TY - JOUR A1 - Pan, Xiaohui A1 - Wang, Weishi A1 - Liu, Tie A1 - Huang, Yue A1 - De Maeyer, Philippe A1 - Guo, Chenyu A1 - Ling, Yunan A1 - Akmalov, Shamshodbek T1 - Quantitative detection and attribution of groundwater level variations in the Amu Darya Delta JF - Water N2 - In the past few decades, the shrinkage of the Aral Sea is one of the biggest ecological catastrophes caused by human activity. To quantify the joint impact of both human activities and climate change on groundwater, the spatiotemporal groundwater dynamic characteristics in the Amu Darya Delta of the Aral Sea from 1999 to 2017 were analyzed, using the groundwater level, climate conditions, remote sensing data, and irrigation information. Statistics analysis was adopted to analyze the trend of groundwater variation, including intensity, periodicity, spatial structure, while the Pearson correlation analysis and principal component analysis (PCA) were used to quantify the impact of climate change and human activities on the variabilities of the groundwater level. Results reveal that the local groundwater dynamic has varied considerably. From 1999 to 2002, the groundwater level dropped from -189 cm to -350 cm. Until 2017, the groundwater level rose back to -211 cm with fluctuation. Seasonally, the fluctuation period of groundwater level and irrigation water was similar, both were about 18 months. Spatially, the groundwater level kept stable within the irrigation area and bare land but fluctuated drastically around the irrigation area. The Pearson correlation analysis reveals that the dynamic of the groundwater level is closely related to irrigation activity within the irrigation area (Nukus: -0.583), while for the place adjacent to the Aral Sea, the groundwater level is closely related to the Large Aral Sea water level (Muynak: 0.355). The results of PCA showed that the cumulative contribution rate of the first three components exceeds 85%. The study reveals that human activities have a great impact on groundwater, effective management, and the development of water resources in arid areas is an essential prerequisite for ecological protection. KW - groundwater level variation KW - climate change KW - human activities KW - statistical analysis KW - Amu Darya Delta Y1 - 2020 U6 - https://doi.org/10.3390/w12102869 SN - 2073-4441 VL - 12 IS - 10 PB - MDPI CY - Basel ER - TY - JOUR A1 - Tesselaar, Max A1 - Botzen, W. J. Wouter A1 - Haer, Toon A1 - Hudson, Paul A1 - Tiggeloven, Timothy A1 - Aerts, Jeroen C. J. H. T1 - Regional inequalities in flood insurance affordability and uptake under climate change JF - Sustainability N2 - Flood insurance coverage can enhance financial resilience of households to changing flood risk caused by climate change. However, income inequalities imply that not all households can afford flood insurance. The uptake of flood insurance in voluntary markets may decline when flood risk increases as a result of climate change. This increase in flood risk may cause substantially higher risk-based insurance premiums, reduce the willingness to purchase flood insurance, and worsen problems with the unaffordability of coverage for low-income households. A socio-economic tipping-point can occur when the functioning of a formal flood insurance system is hampered by diminishing demand for coverage. In this study, we examine whether such a tipping-point can occur in Europe for current flood insurance systems under different trends in future flood risk caused by climate and socio-economic change. This analysis gives insights into regional inequalities concerning the ability to continue to use flood insurance as an instrument to adapt to changing flood risk. For this study, we adapt the "Dynamic Integrated Flood and Insurance" (DIFI) model by integrating new flood risk simulations in the model that enable examining impacts from various scenarios of climate and socio-economic change on flood insurance premiums and consumer demand. Our results show rising unaffordability and declining demand for flood insurance across scenarios towards 2080. Under a high climate change scenario, simulations show the occurrence of a socio-economic tipping-point in several regions, where insurance uptake almost disappears. A tipping-point and related inequalities in the ability to use flood insurance as an adaptation instrument can be mitigated by introducing reforms of flood insurance arrangements. KW - climate change KW - flood risk management KW - insurance KW - socio-economic KW - tipping-point KW - adaptation KW - partial equilibrium modeling Y1 - 2020 U6 - https://doi.org/10.3390/su12208734 SN - 2071-1050 VL - 12 IS - 20 PB - MDPI CY - Basel ER - TY - JOUR A1 - Huber, Veronika A1 - Krummenauer, Linda A1 - Peña-Ortiz, Cristina A1 - Lange, Stefan A1 - Gasparrini, Antonio A1 - Vicedo-Cabrera, Ana Maria A1 - Garcia-Herrera, Ricardo A1 - Frieler, Katja T1 - Temperature-related excess mortality in German cities at 2 °C and higher degrees of global warming JF - Environmental Research N2 - Background: Investigating future changes in temperature-related mortality as a function of global mean temperature (GMT) rise allows for the evaluation of policy-relevant climate change targets. So far, only few studies have taken this approach, and, in particular, no such assessments exist for Germany, the most populated country of Europe. Methods: We assess temperature-related mortality in 12 major German cities based on daily time-series of all-cause mortality and daily mean temperatures in the period 1993-2015, using distributed-lag non-linear models in a two-stage design. Resulting risk functions are applied to estimate excess mortality in terms of GMT rise relative to pre-industrial levels, assuming no change in demographics or population vulnerability. Results: In the observational period, cold contributes stronger to temperature-related mortality than heat, with overall attributable fractions of 5.49% (95%CI: 3.82-7.19) and 0.81% (95%CI: 0.72-0.89), respectively. Future projections indicate that this pattern could be reversed under progressing global warming, with heat-related mortality starting to exceed cold-related mortality at 3 degrees C or higher GMT rise. Across cities, projected net increases in total temperature-related mortality were 0.45% (95%CI: -0.02-1.06) at 3 degrees C, 1.53% (95%CI: 0.96-2.06) at 4 degrees C, and 2.88% (95%CI: 1.60-4.10) at 5 degrees C, compared to today's warming level of 1 degrees C. By contrast, no significant difference was found between projected total temperature-related mortality at 2 degrees C versus 1 degrees C of GMT rise. Conclusions: Our results can inform current adaptation policies aimed at buffering the health risks from increased heat exposure under climate change. They also allow for the evaluation of global mitigation efforts in terms of local health benefits in some of Germany's most populated cities. KW - temperature-related mortality KW - climate change KW - Future projections KW - Germany KW - global mean temperature Y1 - 2020 U6 - https://doi.org/10.1016/j.envres.2020.109447 SN - 0013-9351 SN - 1096-0953 VL - 186 SP - 1 EP - 10 PB - Elsevier CY - San Diego, California ER -