Occurrence Of Extreme Droughts Research Articles

Spatiotemporal dynamics of meteorological and agricultural drought, part of Manbhum-Singhbhum Plateau (India): Four decades study using NASA POWER and MODIS data

Drought is an extremely hazardous situation that predominantly affects ecosystems, hydrological systems, and agricultural mechanisms in different pockets of the world. Management of water resources in dry and semi-arid environments has become a critical challenge in the last few decades. The principal objectives of this study are (i) to categorize the severity and frequency of drought events using the Reconnaissance Drought Index and Rainfall Deviation Index and ii) to evaluate the spatial extension of drought in particular drought times of severe and extreme droughts through Remote Sensing Drought Indices (RSDIs). This drought monitoring index is commonly used index for its high degree of resilience and sensitivity to droughts. The result shows that severe to extreme drought occurred in Bero, Tulin, Sirkabad, Manbazar and Bundwan which are 22, 28, 23, 14 and 25 months correspondingly based on RDI3 whereas RDI12 values indicated 26, 47, 42, 22 and 38 months in the study period (1981 to 2021). Bundwan area faced the most extreme drought occurrence in May month of 1996 with −3.58 values followed by Sirkabad, Bero, Manbazar and Tulin. Manbazar is going through severe to extreme drought months (for short time) whereas ‘extreme drought’ frequency (1.67 % to 1.05 %) is higher in the western part mainly in Jhalda I, Jhalda II, Bagmundi, and Arsha blocks of Purulia district (part of Manbhum Singhbhum Plateau). Additionally, the recurrence of ‘moderate drought’ is much greater in Balarampur along with some portions of Purulia I block. The whole study can be summarized as the northeastern portion being challenged with moderate or severe drought conditions while mild or severe drought is a considerable recurrence in the northern section. The outcome of this study will be helpful for local planners and management officials during implementation strategies related to water resource management.

Characterize and analysis of meteorological and hydrological drought trends under future climate change conditions in South Wollo, North Wollo, and Oromia Zones, in Ethiopia

This research was conducted on North Wollo, South Wollo, and Oromia special zones, in Ethiopia. The study aimed to analyze the temporal and spatial variability of meteorological and hydrological drought trends using the selected drought indices and to predict its future trend in the selected areas. To achieve these objectives, meteorological and hydrological data were collected from the Ethiopian Meteorology Institute and the Ministry of Water and Energy respectively. The historical and future drought condition was analyzed by using the standardized precipitation index (SPI), reconnaissance drought index (RDI), and streamflow drought index (SDI) from the drought indicator calculator (DrinC) software. Based on the availability of the data, for historical drought analysis, ten meteorological stations with thirty-two years of daily data were selected. For the future scenario, RCP 4.5 was used to downscale the future climate data and to forecast SPI and RDI values. Also, an artificial neural network (ANN) was applied to forecast the future streamflow data using Python software, then the future hydrological drought was determined using the forecasted streamflow data. The result indicates that all zones were historically affected by severe to extreme droughts, especially 1984, 1986, 1987, 1989, 1991, 1992, 2003, 2007, 2010, 2013, and 2014 years. From 1984 to 1992 the probability of severe to extreme drought occurrence was on average of two years intervals and from 1992 to 2003 there is a huge gap. From the future drought analysis results, the probability of severe to extreme drought occurrence will be at five-year intervals on average. Based on the analyzed results, the frequency of severe to extreme drought occurrence of historical drought which was two and three years was increased to five years for the future conditions on average. But, these are short intervals and the magnitude of the event is very high. So, the regional water and energy office and other concerned bodies in the area have to plan a good drought mitigation mechanism and should develop a drought early warning system for the communities in and around the study area.

Variation of hydro-climatic extremes in headwater regions of Hei River basin under climate change

Study regionHeadwater regions of Hei River basin, located in the northeast of Tibetan Plateau. Study focusHydro-climatic extremes analysis for historical (1971–2015) and future (2024–2100) period. New hydrological insights for the regionRemarkable climate change has been observed in high mountain areas, which may result in more frequent hydro-climatic extremes. Investigating hydro-climatic extremes variations is important for mitigating hydro-climatic disasters and implementing water resource management. Warm extremes present an increasing trend in frequency and magnitude for historical and future period, while the cold extremes show a decreasing trend in the study area. Meanwhile, frequency and amount of precipitation extremes present an increasing trend for historical and future period. As a result, the intensity of meteorological and hydrological droughts show decreasing trends while floods present an increasing trend, indicating a certain drought relief in the study area. But future occurrence of extreme droughts or floods will increase. Moreover, floods for different return periods will rise with different change rate under different scenarios (SSP 1–2.6, SSP 2–4.5, SSP 3–7.0 and SSP 5–8.5). Therefore, extreme floods or droughts risks should not be underestimated and need be addressed accordingly. The findings highlight the importance of adaptive strategies to cope with more frequent hydro-climatic extremes under climate change.

Projected increases in extreme drought frequency and duration by 2040 affect specialist habitats and species in Scotland

Abstract Climate‐driven increases in drought occurrence are an overlooked risk in temperate climates, which may be less resilient to water scarcity than arid habitats. Scotland provides an example of a temperate oceanic climate in which drought risk is understudied, but could have substantial ecological impacts, particularly in combination with additional stressors. We modelled changes to risk of extreme drought occurrence in Scotland, and considered potential impacts of these changes on two key habitats, ombrotrophic (precipitation fed) wetlands and temperate rainforest. Using temperature and precipitation data from the UK Climate Projections 2018 and the drought index Standardized Precipitation‐Evapotranspiration Index, we calculated and mapped likely changes in extreme drought for the near future (2021–2040) in comparison to a baseline (1981–2001). We found likelihood of extreme drought events increased from an average of one event every 20 years in the baseline period, to one event every 3 years by 2040. Typical events were projected to be up to 2–3 months longer, with an average of 11 extra drought months per decade. Increases were projected throughout the country, but the effect was most severe in the east, and during autumn. Ombrotrophic wetlands have some level of adaptive resilience to drought, but are considered at high risk as several key sites are in drought hotspot areas. In contrast, Scotland's temperate rainforest is located in lower risk areas, but is typically less drought resilient. Potential impacts on these habitats include reductions in ecosystem services including carbon capture, reduced breeding success for multiple taxa and increased competition among plant communities, which threatens drought‐sensitive species. These projections suggest that climate‐driven drought risk is a significant and imminent threat, even in wet climates. In Scotland, the results can direct mitigation and management actions to areas likely to be at greatest risk, as well as informing conservation interventions that can cope with drought. Additionally, other areas with a temperate oceanic climate may be at risk of extreme drought and could experience similar consequences. Therefore, these results have implications both for facilitating improved resilience to extreme drought in Scotland and for potentially overlooked impacts of drought in oceanic climates elsewhere.

Super Drought under Global Warming: Concept, Monitoring Index, and Validation

Abstract Recent decades have witnessed growing frequency and severity of catastrophic droughts in many regions of the world. Despite lots of studies having been dedicated to extreme drought investigation, the fundamental question that has long been ignored is, What is extreme drought? The answer is much more complex than it first appears, because a critical issue in the study of drought is the multiscalar nature. To address the challenge, this study establishes the theoretical basis of the super drought concept, which refers to the simultaneous occurrence of extreme droughts at multiple time scales. The physical significance of super drought represents compound dry extremes in all parts of water resources or equivalently a grand loss in total water storage, which is identified as the essential determinant distinguishing high-impact droughts from those causing mild damage. To have a quantitative representation, a novel monitoring index called comprehensive multiscalar index (CMI) is developed based on the vine copula framework. It turns out that CMI is a plausible measure to determine the overall rarity of multiscalar drought and recognize super drought. Furthermore, the worldwide skill of CMI and super drought identification are testified against Gravity Recovery and Climate Experiment (GRACE) total water storage. Compared to traditional indices that lack comprehensive treatment of drought, CMI performs better in capturing the variation of overall water availability and enables the accurate detection of real water scarcity, with gross improvements in correlation and root-mean-square error scores exceeding the 10−3 significance level. To facilitate end users and policy-makers, near-real-time monitoring and a historical data repository are available through the public website superdrought.com.

Herders' adaptation strategies and animal husbandry development under climate change: A panel data analysis

The frequent occurrence of extreme climate events has become an indisputable fact. However, the role of adaptation to extreme climate change in the development of livestock husbandry is still insufficiently understood. This study empirically analyzed the impact of herders' adaptation strategies to extreme drought on livestock husbandry development and aimed to explore the optimal grassland management path under continuous climate change. A panel dataset of surveyed herders from the Xilingol League, a traditional pastoral area in China, was used. The results indicated that the average frequency of extreme drought in the Xilingol League from 1980 to 2020 was 4.94 months/year, and the occurrence of extreme drought showed a slightly upward trend. The average technical efficiency of livestock husbandry was 0.721, which can still be improved. Hay purchases can effectively promote livestock technical efficiency (p<0.01) and is the main adaptation strategy of herders to extreme drought. Further analysis showed that non-farming and pastoral employment has a positive regulatory effect in the impact of purchased hay on livestock technical efficiency. The results of this study deepen the understanding of effective adaptation to extreme weather events in pastoral areas due to climate change and provide useful information to policymakers engaged in grassland management.

Anthropogenic influence on the occurrence of extreme drought like that in eastern China in 2019

Eastern China (EC) experienced extreme drought during August–November 2019, with notable features of a particularly prolonged duration and record-breaking intensity, leading to huge agricultural and economic losses. In the context of anthropogenic climate change, the authors investigated the anthropogenic impacts on the occurrence of extreme drought like that in 2019 (2019Drought-like event) and the related physical mechanism. The authors first selected relatively better-performing models by evaluating their historical simulations, and found that the occurrence probability of a 2019Drought-like event increased by eight times due to anthropogenic forcing. It seems that anthropogenic forcing induces background mean state changes over EC, including a decline in mean moisture content and enhanced mean descending motion. These two mean state changes are favorable for the formation of extreme drought. Diagnosis of the moisture budget showed that the decline in mean moisture mainly stems from the enhanced mean descending motion via the term −δω¯·∂q¯∂p (vertical advection of mean moisture by the change in mean vertical motion). The enhanced descent is linked to the anthropogenic forcing–induced mean sea surface temperature warming pattern, which exhibits a maximum near the equatorial region. This reinforces the mean ascending motion over the Maritime Continent, as in “the rich-get-richer” mechanism, and further causes strengthened subsidence over the EC region through a “regional Hadley circulation”. This study suggests that anthropogenic forcing can sharply increase the occurrence probability of a 2019Drought-like event by modulating large-scale circulations.摘要2019年夏秋季中国东部遭遇了七十年一遇的强持续性极端干旱事件. 本文借助于CMIP6检测归因模式比较计划 (DAMIP) 数据, 量化了人为强迫对类似2019年极端干旱事件发生概率的影响. 通过比较不同外强迫因子作用下此类极端干旱事件的发生概率, 发现人为强迫可使此类极端干旱事件的发生概率提高8倍左右. 进一步研究发现人为强迫引起的海表温度增暖是经向不均匀的, 对应海洋大陆附近存在一个增暖大值中心, 从而增强海洋大陆地区平均上升环流, 通过局地Hadley环流作用导致中国东部地区平均垂直环流出现异常下沉, 最终有利于中国东部极端干旱事件发生概率增加. 该研究表明, 人为强迫通过调制气候平均背景场从而引起极端事件发生频次的变化是人类活动影响极端气候事件的重要途径之一.

Altitudinal variations of hydraulic traits in Faxon fir (Abies fargesii var. faxoniana): Mechanistic controls and environmental adaptability

Global climate change has been seen to result in marked impacts on forest ecosystems such as accelerated tree mortality worldwide due to incidental hydraulic failure caused by intensified and more frequent occurrence of extreme drought and heat-waves. However, it is well understood how the tree hydrological strategies would adjust to environmental variability brough about by climate changes. Here we investigated the hydraulic adjustment as a mechanism of acclimation to different climate conditions along an altitudinal gradient in Faxon fir ( Abies fargesii var. faxoniana ) ― a tree species that plays a key role in conservation of wildlife and maintenance of ecosystem services in subalpine forests. The hydraulic traits and selective morphological and physiological variables were measured seasonally along an altitudinal gradient from 2,800 to 3,600 ​m a.s.l. We found that the native percentage loss of conductivity (PLC) increased with altitude across the seasonal measurements . Both the native sapwood-specific hydraulic conductivity ( K s ) and native leaf-specific hydraulic conductivity ( K l ) significantly decreased with altitude for measurements in July and October, coinciding with the timing for peak growth and pre-dormancy, respectively. The morphological traits varied toward more conservative tree hydrological strategies with increases in altitude, exhibiting trade-offs with hydraulic traits. The total non-structural carbohydrates in both needle (NSC Needle ) and branch (NSC Branch ) as well as photosynthetic capacity of current-year leaves played variable roles in maintaining the integrity of the hydraulic functioning and shaping the hydraulic adjustment under prevailing environmental conditions. Our findings indicate that Faxon fir possesses some degree of hydraulic adaptability to water limitation imposed by climate fluctuations in subalpine region through morphological and physiological modifications.

Compound climate events increase tree drought mortality across European forests

Climate change can lead to the simultaneous occurrence of extreme droughts and heat waves increasing the frequency of compound events with unknown impacts on forests. Here we use two independent datasets, a compiled database of tree drought mortality events and the ICP-Forest level I plots, to study the impacts of the simultaneous occurrence of hot summers, with elevated vapour pressure deficit (VPD), and dry years on forest defoliation and mortality across Europe. We focused on tree drought mortality and background mortality rates, and we studied their co-occurrence with compound events of hot summers and dry years. In total, 143 out of 310 mortality events across Europe, i.e. 46% of cases, corresponded with rare compound events characterized by hot summers and dry years. Over the past decades, summer temperature increased in most sites and severe droughts resulted in compound events not observed before the 1980s. From the ICP-Forest plots we identified 291 (1718 trees) and 61 plots (128 trees) where severe defoliation and mortality, respectively, were caused by drought. The analyses of these events showed that 34% and 27% of the defoliation and mortality cases corresponded with rare compound climate events, respectively. Background mortality rates across Europe in the period 1993–2013 presented higher values in regions where summer temperature and VPD more steeply rose, where drought frequency increased. The steady increase in summer temperatures and VPD in Southern and Eastern Europe may favor the occurrence of compound events of hot summers and dry conditions. Giving that both, local and intense tree drought mortality events and background forest mortality rates, are linked to such compound events we can expect an increase in forest drought mortality in these European regions over the next decades.

Assessing the Contrasting Effects of the Exceptional 2015 Drought on the Carbon Dynamics in Two Norway Spruce Forest Ecosystems

The occurrence of extreme drought poses a severe threat to forest ecosystems and reduces their capability to sequester carbon dioxide. This study analysed the impacts of a central European summer drought in 2015 on gross primary productivity (GPP) at two Norway spruce forest sites representing two contrasting climatic conditions—cold and humid climate at Bílý Kříž (CZ-BK1) vs. moderately warm and dry climate at Rájec (CZ-RAJ). The comparative analyses of GPP was based on a three-year eddy covariance dataset, where 2014 and 2016 represented years with normal conditions, while 2015 was characterized by dry conditions. A significant decline in the forest GPP was found during the dry year of 2015, reaching 14% and 6% at CZ-BK1 and CZ-RAJ, respectively. The reduction in GPP coincided with high ecosystem respiration (Reco) during the dry year period, especially during July and August, when several heat waves hit the region. Additional analyses of GPP decline during the dry year period suggested that a vapour pressure deficit played a more important role than the soil volumetric water content at both investigated sites, highlighting the often neglected importance of considering the species hydraulic strategy (isohydric vs. anisohydric) in drought impact assessments. The study indicates the high vulnerability of the Norway spruce forest to drought stress, especially at sites with precipitation equal or smaller than the atmospheric evaporative demand. Since central Europe is currently experiencing large-scale dieback of Norway spruce forests in lowlands and uplands (such as for CZ-RAJ conditions), the findings of this study may help to quantitatively assess the fate of these widespread cultures under future climate projections, and may help to delimitate the areas of their sustainable production.

Climate-driven desertification and its implications for the ancient Silk Road trade

Abstract. The ancient Silk Road played a crucial role in cultural exchange and commercial trade between western and eastern Eurasia during the historical period. However, the exchanges were interrupted in the early 16th century CE, during the Ming dynasty. Various causes for the decline of the ancient Silk Road have been suggested. Unlike social factors, natural factors have not been adequately addressed. In this study, we use evidence from a sedimentary site (Xishawo, XSW) in Dunhuang oasis, together with analysis of historical archives, to demonstrate the occurrence of extreme droughts and desertification events in the Dunhuang area post ∼ 1450 CE, which persisted at least for decades. The desertification may be closely associated with the accessibility of the ancient Silk Road in the area, which was responsible for a steep fall in the volume of trade, as well as political chaos and mass migrations. Therefore, besides socio-economic factors, climate change may have played an important role in trade exchange between the Ming government and the West and may have even influenced the rise and decline of the ancient Silk Road.

Human Influence on the Increasing Drought Risk Over Southeast Asian Monsoon Region

AbstractSoutheast Asian monsoon region is regularly stricken by drought, but less attention is paid due to its slow‐onset and less visual impact. This study investigated the observed drought changes over Southeast Asian monsoon region and impacts of anthropogenic forcing using the Coupled Model Intercomparison Project Phase 6 models. We revealed an increasing drought risk for 1951–2018 due to more frequent and wide‐spread droughts. The influence of anthropogenic forcing is successfully detected, which has increased the likelihood of the extreme droughts in historical simulation by reducing precipitation and enhancing evapotranspiration. The time of emergence of anthropogenic forcing in extreme drought occurrence and affected area occurs around the 1960s. The future projected severe and extreme drought risks are still beyond natural only forced changes under all scenarios. Our findings demonstrate a robust impact of anthropogenic forcing on drought risk over Southeast Asia, and highlight the importance of future pathway choice.

Projected Changes in Reference Evapotranspiration in California and Nevada: Implications for Drought and Wildland Fire Danger

AbstractRecent high impact wildfires and droughts in California and Nevada have been linked to extremes in the Evaporative Demand Drought Index (EDDI) and Standardized Precipitation Evapotranspiration Index (SPEI), respectively. Both indices are dependent on reference evapotranspiration (ET0). Future changes in ET0 for California and Nevada are examined, calculated from global climate model simulations downscaled by Localized Constructed Analogs (LOCA). ET0 increases of 13–18% at seasonal timescales are projected by late century (2070–2099), with greatest relative increases in winter and spring. Seasonal ET0 increases are most strongly driven by warmer temperatures, with increasing specific humidity having a smaller, but noteworthy, counter tendency. Extreme (95th percentile) EDDI values on the 2‐week timescale have coincided with recent large wildfires in the area. Two‐week EDDI extremes are projected to increase by 6–10 times during summer and 4–6 times during autumn by the end of the century. On multiyear timescales, the occurrence of extreme droughts based on 3‐year SPEI below the historical fifth percentile, similar to that experienced during the 2012–2016 drought across the region, is projected to increase 3–15 times by late century. Positive trends in extreme multiyear droughts will further increase seasonal fire potential through degraded forests and increased fuel loads and flammability. Understanding how these drought metrics change on various climate timescales at the local level can provide fundamental information to support the development of long‐term adaptation strategies for wildland fire and water resource management.

Farmers\u2019 perceptions and matching climate records jointly explain adaptation responses in four communities around Lake Tana, Ethiopia

Farmers’ climate perceptions are responsible for shaping their adaptive responses and are thus essential to consider for the design of strategies to reduce vulnerability and increase resilience. In this study, we collected social data in four communities in the central Ethiopian Highlands on farmers’ climate perceptions and adaptations using group discussions and PRA tools. We related these to climate data spanning 30 years (1981 to 2010), consisting of daily minimum temperature, maximum temperature and precipitation, modelled for the four communities using global databases and regional meteorological data. We found that farmers’ climate perceptions showed considerable spatial and gender differences. Perceptions matched well with records describing climate variability, particularly in terms of the shortening and the increased variability of the rainy season, as well as the occurrence of extreme drought in recent years. Climate change, described by long-term average increases in temperature and decreases in precipitation, was perceived, but with subordinate priority. Perceived climate impacts included reduced crop yield, increased occurrence of pests and diseases and increased crop damage by extreme events and poverty. Adaptations were mainly land based and included agronomic measures, land management and ecosystem restoration. Furthermore, important gender differences in adaptation could be traced back to typical gender roles. Results highlight the risk of broadcast adaptation programs, such as the government-propagated combination of mineral fertilizers and early maturing crop varieties. Most importantly, they point to the need to consider climate variability, site- and gender-specific perceptions and priorities.

The Record-Breaking Extreme Drought in Yunnan Province, Southwest China during Spring-Early Summer of 2019 and Possible Causes

In spring and early summer of 2019, Yunnan Province experienced the most severe seasonal drought on record, with days of extreme drought area exceeding 105 km2 far more than normal. Consistently, the precipitation in each month from February to June is over 30% less than normal, and about 50% less in the most severe drought period (April–June). The rainy season in Southwest China (SWC) started on the third pentad in June 2019, which is the second latest in history. The rainy season in Yunnan started on 24 June, which is the latest (29 days later than normal). On the contrary, the onset of the South China Sea summer monsoon (SCSSM) is abnormally early. The lag time between the start of the rainy season in SWC and the onset of the SCSSM in 2019 is 7 pentads, which is the largest since 1961, much longer than the climate mean (less than 1 pentad). The present study analyzes the possible reasons why the rainy season came extremely late and the drought disaster persisted and intensified after a much early SCSSM, at both seasonal and subseasonal timescales. The abnormally late onset of the rainy season and the second greatest potential evapotranspiration (PET) since 1981 are the direct reasons for the persistent drought. Statistical results show that the water vapor from southwest of Yunnan in April-June contributes more than that from the east at the seasonal scale. In April-June 2019, however, the southern branch trough (SBT) was abnormally weak, the large and strong anticyclonic wind anomaly prevailed over the Bay of the Bengal (BOB), and the meridional water vapor transport to Yunnan was weak. At the subseasonal scale, the weaker SBT lasted the longest, and the strong convection over the BOB came up late despite of an early onset of the SCSSM, which resulted in reduced low-level moisture convergence in Yunnan and development of drought prior to the SCSSM onset. From the onset of SCSSM to the start of rainy season in SWC, the SBT and meridional water vapor transport from the BOB were still weak, and the water vapor was mainly transported into the coastal area of South and Southeast China rather than Yunnan. After the start of the rainy season in SWC, the SBT was still weak. This led to less moisture transport in the westerlies to the west of Yunnan and the persistent extreme drought. Both the statistical results and case analysis indicate that the stronger Australian high in spring and early summer of 2019 was associated with the abnormally strong anticyclone over the BOB and the always weak SBT. In sum, the anomalous weakness of SBT played a critical role in the extreme drought occurrence and persistence in Yunnan of Southwest China in 2019.

Frameworks on Patterns of Grasslands’ Sensitivity to Forecast Extreme Drought

Climate models have predicted the future occurrence of extreme drought (ED). The management, conservation, or restoration of grasslands following ED requires a robust prior knowledge of the patterns and mechanisms of sensitivity—declining rate of ecosystem functions due to ED. Yet, the global-scale pattern of grasslands’ sensitivity to any ED event remains unresolved. Here, frameworks were built to predict the sensitivity patterns of above-ground net primary productivity (ANPP) spanning the global precipitation gradient under ED. The frameworks particularly present three sensitivity patterns that could manipulate (weaken, strengthen, or erode) the orthodox positive precipitation–productivity relationship which exists under non-drought (ambient) condition. First, the slope of the relationship could become steeper via higher sensitivity at xeric sites than mesic and hydric ones. Second, if the sensitivity emerges highest in hydric, followed by mesic, then xeric, a weakened slope, flat line, or negative slope would emerge. Lastly, if the sensitivity emerges unexpectedly similar across the precipitation gradient, the slope of the relationship would remain similar to that of the ambient condition. Overall, the frameworks provide background knowledge on possible differences or similarities in responses of grasslands to forecast ED, and could stimulate increase in conduct of experiments to unravel the impacts of ED on grasslands. More importantly, the frameworks indicate the need for reconciliation of conflicting hypotheses of grasslands’ sensitivity to ED through global-scale experiments.

Quantification of drought severity change in Ethiopia during 1952–2017

Drought is considered as a frequent environmental disaster that persists long enough to adversely influence economic and social development for the last few decades, particularly in Ethiopia. Here, we examined the occurrence of drought severity change in Ethiopia using standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), China Z Index (CZI) and percent of normal precipitation (PNP). Mann Kendal and Sen’s method tests also used to compute trends and magnitudes of drought occurrences. The years 1953, 1961–1964, 1972–1976, 1984–1987, 2002–2004 and 2011–2014 were recorded as the most intense drought episodes ranging from − 1.58 to − 4.31. With some exceptions, the years 1984, 1986, 2002 and 2014/15 were the direst extreme drought occurrence across all locations. The interpolated spatial extent of drought frequency was highest in central, north and southern regions of the country, respectively. More extreme and severe droughts are identified from SPI and SPEI time series than CZI and PNP at many stations across the domain. In 3-month time scales, severe/extreme drought incidences are intra-annual and 12- and 24-month time scales are inter-annual. SPI and SPEI have stronger correlation than SPI and CZI at all timescales. This kind of inventory drought characterization can be used as a basis to quantitatively prioritize specific intervention at the regional level in responding to drought impacts due to climate change with available resources. By large, it will help to foster a vital shift in the way drought is perceived and coped in the region, taking into account the country’s economic, social and environmental context.

Climate Change Shocks Exposure Index to Drought on the Livelihoods of the Smallholder Farmers in Kinakomba Ward, Tana River County, Kenya

Being susceptible to climate change means being unable to cope with the adverse effects of climate change especially droughts and a likelihood of experiencing harm due to its occurrence. The study sought to evaluate the effects of exposure to Climate related shocks on the livelihoods of the smallholder farmers with the intent of formulating appropriate policies to enable them cope with its impacts. A descriptive survey research design was used. Stratified random sampling was employed to select 390 households. Two methods were used to analyse exposure. Firstly the fuzzy logic in assessing susceptibility to drought involving a selection of input variables, Fuzzification, inference modelling and defuzzification and secondly DrinC Model software. The results revealed that the final value of the negative consequences of drought was 0.35.The study also established a single index as 0.45 for exposure for the entire study period of 35 years for Kinakomba Ward .The study showed that exposure was statistically significant at (0.000066). The study further revealed that the periods between occurrence of extreme droughts were reducing and at the same time that droughts were moving from being severe to being extreme within shorter periods of time leaving smallholder farmers who depend on rain fed agriculture with high exposures and risks as well as experiencing longer hunger periods with severe implications on their food and nutritional security for the vast populations in the study area. The Study concluded that the exposure to drought of the smallholder farmers in Kinakomba Ward is significantly related to their farming livelihood systems. This study recommends that the County Government in partnership with the National Government and other stakeholders develop a comprehensive disaster risk management framework to address the drought hazards and undertake mitigation and adaptation measures by equipping the smallholder farmers with knowledge on how to cope with the cyclic and vicious droughts’ impacts that have led to serious irreversible harm to humans and livestock in the area. Keywords: Exposure, Drought, Mitigation, Adaptation, Food security DOI: 10.7176/FSQM/94-07 Publication date: February 29 th 2020

The effects of river-level oscillations on the macroinvertebrate community in a river–floodplain system

Extreme climatic events, such as flooding and drought, can abruptly modify the amplitude of the river level of a river, promoting new environmental conditions and impacting aquatic communities. Furthermore, an increasing frequency of extreme droughts in dammed rivers is expected because dams homogenize the flood pulse and decrease the river level. In this study, we evaluated the effects of extreme river-level oscillations on the benthic macroinvertebrate communities in a floodplain river. We analysed 47 years of river-level data and 17 years of benthic macroinvertebrate data. Our findings indicated that (1) extreme river-level oscillations promoted environmental conditions that were distinct from the regular oscillation; moreover, environmental characteristics were more heterogeneous in extreme oscillations than regular oscillations; (2) extreme oscillations were associated with a decreased richness, density, and diversity of benthic macroinvertebrates, promoting the dominance of tolerant taxa. Furthermore, in the studied river, a large hydroelectric power plant was built 19 years ago, which (3) decreased the river-level downstream, accentuating the occurrence of extreme drought, which has become more common after damming. We emphasize the importance of long-term biological monitoring considering the more frequent occurrence of extreme river-level oscillations in response to factors such as dam building and climate change.

Plant community stability results from shifts in species assemblages following whole community transplants across climates

Climate change will decrease precipitation and increase rainfall variability in eastern Mediterranean regions, with responses of plant communities largely uncertain. Here, we tested short‐term responses of dryland plant communities to contrasting rainfall regimes using reciprocal transplants of soil and seed banks. We exposed three annual plant communities to very different climatic conditions along a steep rainfall gradient. We tested for the role of climate versus community origin on community response and resistance. In parallel, we asked whether origin‐specific climatic adaptations predict compositional shifts across climates. Due to an extreme drought, all plants in the driest climate failed to reach maturity. For the remaining two community origins, the most dry‐adapted species in each community increased in dry climate and the wet‐adapted species increased in wet climate. Dry community origins showed large compositional shifts while maintaining stable plant density, biomass and species richness across climates. Conversely, wet communities showed smaller compositional shifts, but larger variation in biomass and richness. This asynchrony in species abundances in response to rainfall variability could maintain structural community stability. This, in combination with seed dormancy, has the ability to delay extinction in response to climate change. However, increasing occurrence of extreme droughts may, in the long‐term, lead to loss of wet‐adapted species.