Extreme Drought Years Research Articles

A direct comparison of the radial growth response to drought of European and Oriental beech

Climate change-related extreme drought events already have a significant impact on the productivity and mortality of Central European forests. European beech (Fagus sylvatica ssp. sylvatica), one of the most important European broadleaved species, has responded to such drought periods with increasing mortality and reduced volume increment. This has raised concerns about its suitability and adaptive capacity in relation to future climatic conditions and motivated the search for alternative tree species that are suitable for assisted migration into European beech forests. One of the candidates is the Oriental beech species complex (F. sylvatica ssp. orientalis), whose range extends from the Balkan to Iran and, at least in some parts of its range, grows under a warmer and drier climate. In order to evaluate whether Oriental beech is more drought tolerant, we compared the radial growth response to droughts between 1920 and 2018 of a total of 138 European and 122 Oriental beeches growing under identical site conditions in eight different locations in Germany and France. The species identity of all analysed trees was verified by microsatellite analyses, and the origin of the introduced Oriental beech was traced to the Greater Caucasus (7 stands) and the Black Sea coast (1 stand). The drought responses of radial growth were quantified using the indices resistance, resilience, and recovery as suggested by Lloret et al. (2011) and growth recovery time (GRT) (Thurm et al., 2016) and used as response variables in generalized linear mixed effect models.Considering only the average radial growth response to severe and extreme drought events, both the different Lloret indices and the GRT did not show prominent difference between Oriental and European beech. However, the mixed model analyses, which also included interaction terms, revealed interspecific differences in drought tolerance, depending on the intensity and timing of the drought. In extreme summer drought years, values of resistance predicted by the mixed-effect models were significantly higher in Oriental beech than in European beech, whereas its resilience was only slightly better than in European beech, regardless of drought intensities. In contrast, Oriental beech was much more susceptible to spring drought with significantly weaker growth recovery and distinctly longer growth recovery times.Based on these results, Oriental beech provenances from the Caucasus do not appear to be sufficiently more drought tolerant than European beech to justify an assisted migration approach to adapt Central European forests to climate change. To analyse the drought tolerance of Oriental beech more comprehensively, introduced trees representing other genetic clusters need to be analysed, as well as the effects of repeated drought events on growth and mortality.

Damage Inflicted by Extreme Drought on Poyang Lake Delta Wetland and the Establishment of Countermeasures

Due to the joint influence of climate change and human activities, the hydrological rhythm of Poyang Lake has changed in recent years, leading to an increasingly severe drought problem during autumn and winter in this region. Notably, the extreme drought that occurred in 2022 had profound impacts on shipping, water supply and the ecological environment of the wetlands in the Poyang Lake Delta, sparking widespread concern. Based on the historical hydrometeorological data of Poyang Lake, we used statistical models (such as Chow test, correlation analysis, etc.) to analyze the cause of the extreme drought in the Poyang Lake Delta from the perspectives of natural factors and human activity. Through correlation analysis, we found that the water level, discharge, and drought duration of the Poyang Lake Delta were all significantly affected by climate change, particularly rainfall in the Poyang Lake basin. Furthermore, combining the results of Chow test and correlation analysis, we also found that the operation of the Three Gorges Reservoir had a notable impact on the water level of the Poyang Lake Delta. Based on remote sensing images, ecological and environmental sampling monitoring, the damage inflicted by the extreme drought event on the Poyang Lake Delta was analyzed. The results show that the inundated area of the delta wetlands in the extreme-drought year (2022) decreased by 45.75% compared with that in a normal year (2017). In addition, the ecological environment of the wetlands deteriorated significantly. The water quality parameters (TN, TP, NH4+-N) increased by 50.2%, 240% and 64.7%, respectively. The concentrations of TN and TP were 3.8 mg/L and 0.17 mg/L, respectively, while the context values in the delta were 1.2 mg/L and 0.075 mg/L. The density and biomass of algae increased by 87.2% and 557.9%, respectively. In contrast, the density and biomass of benthos decreased by 59.9% and 78.5%, respectively. The control strategy for the Poyang Lake Delta under extreme drought was studied through an experiment on the operation of hydraulic controllers. The results show that under extreme drought conditions, the newly built hydraulic controllers could raise the water level of the delta from 9.1 ± 0.7 m to 14.2 ± 1.8 m, thus effectively solving the water cut-off problem in the four branches of the delta. Furthermore, by adjusting the distributive ratio of the main, north, middle and south branches of the delta to 50%, 4%, 24% and 22% through newly built hydraulic controllers, the water area can be increased by 56%.

Tracking Free-Ranging Pantaneiro Sheep during Extreme Drought in the Pantanal through Precision Technologies

The Pantanal has been facing consecutive years of extreme drought, with an impact on the quantity and quality of available pasture. However, little is known about how locally adapted breeds respond to the distribution of forage resources in this extreme drought scenario. This study aimed to evaluate the movement of free-grazing Pantaneiro sheep using a low-cost GPS to assess the main grazing sites, measure the daily distance traveled, and determine the energy requirements for walking with body weight monitoring. In a herd of 100 animals, 31 were selected for weighing, and six ewes were outfitted with GPS collars. GPS data collected on these animals every 10 m from August 2020 to May 2021 was analyzed using the Python programming language. The traveled distance and activity energy requirements (ACT) for horizontal walking (Mcal/d of NEm) were determined. The 31 ewes were weighed at the beginning and end of each season. The available dry matter (DM) and floristic composition of the grazing sites were estimated at the peak of the drought. DM was predicted using power regression with NDVI (normalized difference vegetation index) (R2 = 0.94). DM estimates averaged 450 kg/ha, ranging from traces to 3830 kg/ha, indicating overall very low values. Individual variation in the frequency of use of grazing sites was observed (p < 0.05), reflecting the distances traveled and the energetic cost of the activity. The range of distances traveled by the animals varied from 3.3 to 17.7 km/d, with an average of 5.9 km/d, indicating low energy for walking. However, the traveled distance and ACT remained consistent over time; there were no significant differences observed between seasons (p > 0.05). On average, the ewes’ initial weight did not differ from the weight at the drought peak (p > 0.05), indicating that they maintained their initial weight, which is important for locally adapted breeds as it confers robustness and resilience. This study also highlighted the importance of the breed’s biodiverse diet during extreme drought, which enabled the selection of forage for energy and nutrient supplementation. The results demonstrated that precision tools such as GPS and satellite imagery enabled the study of animals in extensive systems, thereby contributing to decision-making within the production system.

Influences of large scale circulation and atmospheric rivers on US winter precipitation beyond ENSO

Abstract This study aims to understand the underlying mechanism of large scale circulation control on atmospheric rivers (AR) and precipitation variability across the Contiguous United States (CONUS) in winter. The El Niño-Southern Oscillation (ENSO), known as a key driver of global circulation, has shown a modest impact on CONUS precipitation, prompting us to focus our attention on other climate drivers. Here, we find that barotropic instability over the exit region of the North Pacific subtropical jet stream plays a critical role in forming a downstream stationary Rossby wave train during winter (referred to as the West Mode). This wave pattern influences CONUS precipitation by affecting AR activity and explains approximately 50% of rainfall changes in the Western US, as well as numerous extreme wet and drought years along the West Coast, such as the wet winter in 2022/23. Over the past eight decades, the West Mode exhibited limited sensitivity to both Sea Surface Temperature (SST) and increasing anthropogenic forcing and was more influential in shaping interannual and interdecadal CONUS precipitation variability than ENSO. This result may explain why ENSO alone can only account for a limited portion of CONUS precipitation variability, thereby imposing an inherent constraint on the precision of seasonal predictions of CONUS precipitation made by climate models. Due to the significance of the West Mode in governing precipitation variability over the Western US, winter precipitation in that region may possess some resilience to the effects of global warming in the coming decades, as supported by large ensemble simulations driven by projected radiative forcing.

INTEGRATION OF THE CRISIS RULES CREATED BY COVID 19 INTO THE EUROPEAN COMMON AGRICULTURAL POLICY AND HUNGARIAN AGRICULTURAL LEGISLATION

After the end of the COVID 19 outbreak, the authors summarise the measures taken by the European Union to ensure the continuity of food supply and the functioning of the food chain during the outbreak. In addition to the EU measures, the specific measures followed by the Member States and their room for manoeuvre are presented using the Hungarian example. In this article we have also tried to elaborate the implications for the European Agricultural Policy and consequently for European Agriculture. The literature we have elaborated also covers the agricultural market processes and the implications for rural areas. However, this article focuses on the Hungarian public law implications of the legislation and the Hungarian judgement practical issues of its application.Our article also discusses the link between the extreme drought year 2022 and the pandemic. We will look at why the extraordinary legal instruments used under COVID '19 were appropriate to deal with the consequences of extreme weather.

Long-term drought effects on landscape water storage and recovery under contrasting landuses

Recent extreme droughts in Europe have highlighted the urgent need to quantify their effects on ecohydrological fluxes (evapotranspiration, groundwater recharge) and water storage (mainly soil moisture) in the landscape. In response, we combined process-based (EcH2O-iso) and machine learning (NARX) models to estimate the enduring effects of long-term drought on water fluxes and storage and to project future short-term groundwater levels and recovery potential under various precipitation scenarios. The work was undertaken at the Demnitz Mill Creek (DMC), a 70 km2 mixed land use (arable crops and forestry) catchment in northern Germany. Our simulations indicated that the extreme drought years of 2018 and 2022 had the most marked impacts, leading to substantial declines in groundwater recharge (>40 %), evapotranspiration (up to 16 %) and soil moisture (up to 6 %). Simulations indicated that groundwater levels may not recover in the next 15 years if recent precipitation anomalies persist. These findings underscore the urgent requirement for enhancing resilience and promoting integrated strategies in managing land and water resources to optimise water retention in landscapes and to better respond to drought.

Growth decline characteristics of Picea schrenkiana at different altitudes in Yili River Basin, western Tian-shan Mountains, Xinjiang, China

Picea schrenkiana is the dominant tree species in Ili River Basin located in the western Tianshan Mountains of Xinjiang. We investigated the growth decline characteristics of P. schrenkiana at different altitudes (1800, 2300 and 2800 m) based on tree-ring index (TRI) and percentage growth change (GC), aiming to understand the growth response of P. schrenkiana to drought events at different altitudes and the impacts of altitude on tree growth decline in this region. The results showed that P. schrenkiana experienced multiple decline events at low-altitude (1800 m). TRI and GC identified inconsistent occurrence time of the decline events. The variations of TRI indicated that P. schrenkiana at low-altitude experienced two large-scale declines during 1927-1933 and 2017-2014, respectively. The variations of GC identified four decline events, including 1891-1893, 1924-1926, 1973-1975, and 2004-2009. The radial growth of P. schrenkiana across altitudes from low to high was significantly affected by the Palmer drought severity index (PDSI) of the previous growing season. The impact of current PDSI on P. schrenkiana during the growing season initially enhanced but later decreased with increasing altitude. In the extreme drought year 1917, the magnitude of growth decline increased with altitude. At low-altitude (1800 m), the TRI was 0.65, which was 35% lower than the normal level. At mid-altitude (2300 m) and high-altitude (2800 m), it was 0.56 and 0.54, respectively, being 40% lower than the average level. The drought event in 1917 had a 2-year legacy effect on the growth of P. schrenkiana at all the altitudes, with the TRI in 1920 recovered to exceeding 0.9, being close to the normal level. The impact of altitude on drought-induced forest decline was significant. Tree growth in low-altitude areas was more vulnerable to drought events due to the relatively poorer water and temperature conditions at low-altitude, which could lead to multiple large-scale decline events. In mid- and high-altitude areas, where hydrothermal conditions were more favorable, trees could experience even more severe decline during extreme droughts.

Different drought indices showed different variations and applicability to dendrochronological studies

In drought studies based on tree-ring data, there is currently no unified drought index that can capture the drought signals contained in tree rings from different climates, habitats, and species. This makes it difficult to compare the results of numerous studies. This paper compared data charactering wet and dry variations in the Ulan Buh Desert in northwestern China from 1962 to 2017, as indicated by different drought indices. We selected the most commonly used drought indices in tree-ring research: precipitation (Pre), self-calibrating Palmer aridity index (scPDSI), and standardized precipitation evapotranspiration index (SPEI), based on observed meteorological data (-obs) and grid data from the Climatic Research Unit (-cru). The results showed that although the different drought indices were significantly correlated with each other, they showed different linear trends. Correlation analyses with the tree-ring width chronology in the study area showed that the applicability of drought indices based on observed data was better than that of drought indices based on CRU data. The correlation between SPEI-cru and chronology was much lower than that of SPEI-obs, scPDSI-obs, scPDSI-cru, Pre-obs and Pre-cru. The extreme drought years identified by SPEI-cru also differed from other indices. These results suggest that SPEI-cru is not applicable to dendrochronological studies in the Ulan Buh Desert, mainly due to the differences between the CRU data and the measured data, and the high sensitivity of SPEI to potential evapotranspiration. This case study illustrates that tree-ring based drought studies must be based on an assessment of the applicability of different drought indices.

Spectral asynchrony as a measure of ecosystem response diversity

AbstractSpecies diversity is crucial for promoting ecosystem resilience and stability. Species diversity promotes complementarity in resource use, resulting in a wider range of responses to adverse conditions. This enables populations of different species to fluctuate asynchronously, maintaining ecosystem functioning during extreme climatic events. However, incorporating such mechanisms into conservation decisions and ecosystem modelling requires scalable metrics that represent species diversity, which is currently lacking. To address this, we introduce spectral asynchrony, a metric that captures the spatial heterogeneity of species’ functional responses occurring in distinct pixels. Here, we use remote sensing datasets to investigate the relationship between spectral asynchrony and productivity responses of seasonally dry tropical forests (SDTF) to climatic fluctuations. Our findings reveal that spectral asynchrony is associated with increased resistance and recovery of SDTF productivity in following extreme drought years, as well as greater productivity stability over two decades. Furthermore, higher spectral asynchrony was associated with relatively wetter regions, suggesting that increasing aridity across SDTF could potentially reduce landscape heterogeneity and limit ecosystem resilience to increasing droughts in the future. Spectral asynchrony provides an easily measurable and monitorable metric for assessing ecosystem responses to global changes, reflecting and scaling‐up the effects of species diversity at the local level.

Extreme drought impacts have been underestimated in grasslands and shrublands globally.

Climate change is increasing the frequency and severity of short-term (~1 y) drought events-the most common duration of drought-globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function-aboveground net primary production (ANPP)-was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought.

Standardized precipitation index analysis and drought frequency tendencies in lower eastern counties of Kenya

The standardized precipitation index (SPI) is a fundamental indicator of meteorological, hydrological, and agricultural droughts in the world. This study aims to evaluate different timescales, 3 months (SPI-3), 6 months (SPI-6), 9 months (SPI-9), and 12 months (SPI-12) indices from meteorological data in quantifying drought characterization in lower eastern counties of Kenya from 1990 to 2018 for observed data and from 1986 to 2018 for Climatic Research Unit Time Series (CRU) data. Precipitation in-situ data (annual) and high-resolution (0.5 × 0.5 degree grid) monthly-scale precipitation data were sought from Kenya Meteorological Department and CRU TS, respectively. Z-Score (SPI) was computed for each year (in-situ data) and month (CRU TS data) using the SPI algorithm, expressed as the departure from the mean in standard deviation units. Quality control of CRU TS data was done by checking outlier values and comparing the data with precipitation data obtained from the meteorological department as well as ERA5 reanalysis data. Results showed that extreme to mild drought was experienced across the Kenyan counties for both annual in-situ and monthly gridded data. Machakos county experienced a year of extreme drought, while Makueni and Taita-Taveta have had 2 and 4 years of severe droughts, respectively. The monthly SPI indices of 3, 6, 9, and 12 months showed a remarkably consistent behavioral pattern detecting extreme droughts across the counties. Considering the uncertainties, unpredictability, and shifting of the long and short rainy seasons in Kenya, results were obtained related to dry and wet episodes and to their relationship with agricultural production as well as water availability and environmental management.

Potential of the satellite-based Dynamic Habitat Index (DHI) to capture changes in soil properties and drought conditions across Land Use/Land Cover types in a Central European landscape

This study evaluates the sensitivity of the Dynamic Habitat Index (DHI), utilizing multitemporal Normalized Difference Vegetation Index (NDVI) data, to changing environmental conditions across Land Use/Land Cover (LULC) types in a central European landscape (2017–2020). We observed distinct DHI characteristics for all LULC types, and the DHI responded to an extreme drought year in 2018 with no return to pre-drought conditions except for deciduous forests. The DHI also effectively captured spatio-temporal variability of pedo-climatic conditions. Thus, integrated with ancillary geodata, the DHI enhances traditional categorical LULC maps, offering applications in biodiversity and ecosystem research. Such integrated products could serve as valuable tools for decision makers to formulate sustainable land management strategies and contribute to Sustainable Develop Goal indicators related to land degradation, e.g. by identifying deviations from typical, context-specific DHI profiles as a response to disturbance and environmental stress.

Spatio-temporal drought assessment and comparison of drought indices under climatic variations in drought-prone areas of Pakistan

Abstract Climatic variations cause droughts which badly affect the environment. The study focused on monitoring droughts to aid decision-making and mitigate their negative impacts on water availability for agriculture and livelihoods in the face of increasing water demand and climate change. To assess the agricultural droughts, a new agricultural Standardized Precipitation Index (aSPI) was calculated which is not used earlier in Balochistan. Widely recommended Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) were used for meteorological drought assessment. Drought indices comparison was also conducted to check the applicability. Rainfall, maximum temperature, and minimum temperature data (1992 to 2021) were utilized to calculate SPI, aSPI, and SPEI at different timescales (3, 6, 9, and 12 months) using DrinC software and SPEI calculator. Indices results revealed the following severe to extreme drought years: 1998, 1999, 2000, 2001, 2002, 2004, 2008, 2011, 2014, 2016, and 2017. It was determined that Dalbandin, Quetta, Sibi, Kalat, Khuzdar, and Zhob experienced higher extreme drought frequencies. Both long- and short-term drought durations were observed. Indices comparison showed that SPI is the most efficient drought index compared to aSPI and SPEI. This study offers valuable insights for managing water resources in the face of climate-induced droughts.

Flood and Fire

The intensifying warming of the planet over the past several decades is a manifestation of centuries of uneven and inequitable extractive economies. This warming is well known to be the main force driving shifts in climatological conditions and extreme weather events leading to increasingly severe impacts on planetary systems. Every year, more locations on earth are experiencing heat waves, intense droughts, longer and larger fire seasons, increased tropical storm intensity, and sea level rise at rates that would have been unthinkable a generation ago while near daily news reports document the increasing toll that this changing climate plays in exacerbating social and ecological vulnerabilities. Just this year, at the start of the Northern Hemisphere summer of 2023, a massive tropical cyclone has killed over 145 people in Bangladesh and Myanmar, western Canada has already seen as much forest burned in a few days as it does in an entire summer, drastically diminishing air quality over half a continent, the Po River Valley in Italy has been ravaged by floods after experiencing two years of extreme drought, and California has experienced deadly and pervasive atmospheric rivers after years of record-setting fire seasons and water shortages. In this special issue, rather than prioritizing benign and depoliticized notions of adaptive capacity and resilience, as is far too common within mainstream discussions of climate change, we highlight the theme of flood and fire to examine these events as compounding contemporary crises and responses to phenomena that are devastating, transforming, and reformulating communities, ecologies, and governing processes around the planet.

Visitation to national parks in California shows annual and seasonal change during extreme drought and wet years

This study examines the influence of drought indicators on recreational visitation patterns to National Park Service units in California (USA) from 1980 to 2019. We considered mountain, arid, and coastal park types across a climate gradient where seasonal recreational opportunities are directly or indirectly dependent on water resources. Significant departures from the normal hydroclimate, reflected by drought or unusually wet conditions, can lead visitors to change their behavior, including recreating at a different time or place. Drought conditions can facilitate earlier seasonal access at higher elevation parks, but displace visitors in other seasons and parks. Wetter-than-average conditions can displace visitors due to snowpack or flooding, but also facilitate other activities. We found a decrease in annual visitation at popular mountain parks including Yosemite (-8.6%) and Sequoia and Kings Canyon (-8.2%) during extreme drought years due to lower-than-average attendance in peak summer and fall months. Extreme wet years also had significantly reduced annual visitation in Sequoia and Kings (-8.5%) and Lassen Volcanic (-13.9%) due to declines in spring and summer use as snowpack restricts road access. For arid parks, drought status did not have a statistically significant effect on annual visitation, although extreme drought led to less use during the hottest months of summer at Death Valley, and extreme wet conditions at Pinnacles led to less visitation throughout the year (-16.6%), possibly from impacts to infrastructure associated with flooding. For coastal park units, extreme drought led to year-round higher levels of use at Redwood (+27.7%), which is typically wet, and less year-round use at Channel Islands (-23.6%), which is relatively dry, while extreme wet years led to higher levels of annual use at Channel Islands (+29.4%). Collectively, these results indicate the effect of extreme drought or wet years on park visitation varies by park depending on geography and recreational activities offered.

Tree rings in Tsuga dumosa reveal increasing drought variability in subtropical southwest China over the past two centuries

High-resolution palaeoclimate proxy records have been lacking for the subtropical region of southwest China. To gain insights into hydroclimate variability in central Yunnan Province, we constructed a tree ring-width chronology of Tsuga dumosa from the Wuliang Mountain area. Correlation analysis shows that moisture availability is predominantly the limiting factor on radial growth, particularly during the spring-early summer season. Using a well-calibrated regression model (R2 = 0.36, p < 0.001), we reconstructed the March–June Standardized Precipitation-Evapotranspiration Index (SPEI) for the period from 1826 to 2020 CE. Eleven extreme drought years (1860, 1897, 1958, 1960, 1979, 1984, 1987, 2006, 2010, 2013, and 2019) were identified, with most of them confirmed by historical evidence. The reconstruction series shows inter-annual to inter-decadal variations and an increasing occurrence of severe dry or wet events in the recent past, particularly during the last 50 years. Our drought reconstruction series shows high frequency cycle of 2–8 years. Spatial correlations indicate that our drought reconstruction captures hydrological signals over a larger area. In line with this, the reconstructed dry periods exhibit broad consistency with other tree-ring based drought reconstructions conducted in nearby regions. Our findings demonstrate the potential of tree-ring proxies for hydroclimate reconstruction in the subtropical areas of southwest China and provide crucial information for evaluating long-term climate change in this region.

Dry and Wet Period Analysis using Meteorological Drought Indices in Sabarkantha district Gujarat, India

Drought assessment is very important to manage water resources in lean period. In the present study, identification of drought years and extent of deficit of annual rainfall is accomplished by use of three meteorological based drought indices like the Standardized Precipitation Evapotranspiration index (SPEI), China-Z index (CZI) and Modified China-Z index (MCZI) on 1, 3, 6, 9 and 12 month (short term and long term) timescales using monthly precipitation and temperature data from 1901 to 2002 at Sabarkantha to specify the drought conditions in present study area. The analysis of multiple time steps in drought indices make it harder to decide the best time step to show the drought conditions. The months of January, March, November and December have been identified 76, 79, 77 and 80 times as drought months respectively in the 20th century, indicating that these months must be provided with assured Irrigation. It is observed that 1904, 1911, 1915, 1923, 1974, 1987 and 2002 affected by severe drought condition in SPEI-12. The China Z Index and Modified China Z index shows that’s 1904, 1911, 1915, 1918, 1923, 1948, 1951, 1965, 1968, 1969, 1972, 1974, 1985, 1987, 1991, 1995 and 2002 affected by extreme drought. The study also reveals that only 1% year obtain as extreme wet conditions. From result it shows that 23% years are categorised into moderate to extreme drought years, which includes 15% Moderate dry, 8% severe dry years.

A novel framework for investigating the mechanisms of climate change and anthropogenic activities on the evolution of hydrological drought

Climate change and anthropogenic activity are the primary drivers of water cycle changes. Hydrological droughts are caused by a shortage of surface and/or groundwater resources caused by climate change and/or anthropogenic activity. Existing hydrological models have primarily focused on simulating natural water cycle processes, while limited research has investigated the influence of anthropogenic activities on water cycle processes. This study proposes a novel framework that integrates a distributed hydrological model and an attribution analysis method to assess the impacts of climate change and anthropogenic activities on hydrological drought The distributed dualistic water cycle model was applied to the Fuhe River Basin (FRB), and it generated a Nash–Sutcliffe efficiency coefficient > 0.85 with a relative error of <5 %. Excluding the year with extreme drought conditions, our analysis revealed that climate change negatively impacted the average drought duration (−105.5 %) and intensity (−23.6 %) because of increasing precipitation. However, anthropogenic activities continued to contribute positively to the drought, accounting for 5.5 % and 123.6 % of the average drought duration and intensity, respectively, because of increased water consumption. When accounting for extreme drought years, our results suggested that climate change has contributed negatively to the average duration of drought (−113.2 %) but positively to its intensity (7.8 %). Further, we found that anthropogenic activities contributed positively to both the average drought duration and intensity (13.2 % and 92.2 %, respectively). While climate change can potentially mitigate hydrological drought in the FRB by boosting precipitation levels, its overall effect may exacerbate drought through the amplification of extreme climate events resulting from global climate change. Therefore, greater attention should be paid to the effects of extreme drought.

Carbon starvation following a decade of experimental drought consumes old reserves in Pinus edulis.

Shifts in the age or turnover time of non-structural carbohydrates (NSC) may underlie changes in tree growth under long-term increases in drought stress associated with climate change. But NSC responses to drought are challenging to quantify, due in part to large NSC stores in trees and subsequently long response times of NSC to climate variation. We measured NSC age (Δ14 C) along with a suite of ecophysiological metrics in Pinus edulis trees experiencing either extreme short-term drought (-90% ambient precipitation plot, 2020-2021) or a decade of severe drought (-45% plot, 2010-2021). We tested the hypothesis that carbon starvation - consumption exceeding synthesis and storage - increases the age of sapwood NSC. One year of extreme drought had no impact on NSC pool size or age, despite significant reductions in predawn water potential, photosynthetic rates/capacity, and twig and needle growth. By contrast, long-term drought halved the age of the sapwood NSC pool, coupled with reductions in sapwood starch concentrations (-75%), basal area increment (-39%), and bole respiration rates (-28%). Our results suggest carbon starvation takes time, as tree carbon reserves appear resilient to extreme disturbance in the short term. However, after a decade of drought, trees apparently consumed old stored NSC to support metabolism.

Assessing Climate-Driven Salinity Intrusion through Water Accounting: A Case Study in Ben Tre Province for More Sustainable Water Management Plans

This scientific paper delves into sustainable water management strategies for Ben Tre Province of the Vietnamese Mekong Delta (VMD) in light of water-infrastructure plans that have been impacted by climate change-induced salinity intrusion. Specifically, we aim to mitigate the effects of salinity intrusion for the province while promoting long-term environmental sustainability. In doing so, a water accounting framework was applied, mostly based on the MIKE11 hydrodynamic modeling and water balance calculations, to determine current and future water stress issues based on two main scenarios of extreme drought year 2016 (baseline) and the future year 2030 under climate change for a medium-low emission scenario (RCP4.5). The study found that salinity intrusion significantly causes severe water stress in the future year 2030 compared to the baseline year 2016, while the existing water management methods are relatively inadequate to control salinity intrusion, leading to over 57% of the area affected by medium to critical water stress levels, although it will go along with planned water infrastructures. Additionally, a system of triple rice cropping converted two rice cropping and upland cropping with 40% water demand cutoff was found to be the most suitable measure for 2030. Particularly, water-saving and water demand reduction should be incorporated into infrastructural planning for sustainable water management. Our study provides valuable insights for policymakers and stakeholders, not only for the province and the VMD, but also other regions facing similar challenges.