Non-drought Years Research Articles

Impact of Drought on the Livelihoods of Farmers in Western Odisha: A Comparison Between Drought and Non-Drought Years

The agriculture of our country is increasingly affected due to the irregular climatic variations like drought, flood, etc. which is causing great distress to agriculture farmers financially, socially and emotionally during the period. The present study was undertaken to assess the impact of drought on livelihood of agriculture farmers in drought versus non-drought years in drought prone western Odisha. 194 respondents engaged in agriculture farming as their primary occupation were selected randomly from 3 districts of Western Odisha by stratified random sampling. Ten pertinent questions were selected after due consultation with different stakeholders of the agricultural sector, Govt. officials, University faculties and experts of the field to study the impact of drought. The questions were designed to be answered either in yes or no, which were related to the social, economic, food security and family responsibilities of the agricultural farmer and his family. It was found that the respondents were not able to meet the basic requirements in drought years which could be achieved in non-drought years through agricultural operations. This study also indicated that the basic needs like food, medicine and social needs are severely affected in the drought hit years as compared to the non-drought years. The famers were not even able to purchase medicines in drought hit years. The farmers showed their inability to take care of the basic needs of family during drought. The Government of Odisha may promote secondary sources of livelihood generating options like dairy farming, poultry farming, beekeeping, goat farming, etc., in the drought affected districts of Odisha along with agriculture for meeting basic needs of life during drought period.

Heterogeneity promotes resilience in restored prairie: Implications for the environmental heterogeneity hypothesis.

Enhancing resilience in formerly degraded ecosystems is an important goal of restoration ecology. However, evidence for the recovery of resilience and its underlying mechanisms require long-term experiments and comparison with reference ecosystems. We used data from an experimental prairie restoration that featured long-term soil heterogeneity manipulations and data from two long-term experiments located in a comparable remnant (reference) prairie to (1) quantify the recovery of ecosystem functioning (i.e., productivity) relative to remnant prairie, (2) compare the resilience of restored and remnant prairies to a natural drought, and (3) test whether soil heterogeneity enhances resilience of restored prairie. We compared sensitivity and legacy effects between prairie types (remnant and restored) and among four prairie sites that included two remnant prairie sites and prairie restored under homogeneous and heterogeneous soil conditions. We measured sensitivity and resilience as the proportional change in aboveground net primary productivity (ANPP) during and following drought (sensitivity and legacy effects, respectively) relative to average ANPP based on 4 pre-drought years (2014-2017). In nondrought years, total ANPP was similar between remnant and restored prairie, but remnant prairie had higher grass productivity and lower forb productivity compared with restored prairie. These ANPP patterns generally persisted during drought. The sensitivity of total ANPP to drought was similar between restored and remnant prairie, but grasses in the restored prairie were more sensitive to drought. Post-drought legacy effects were more positive in the restored prairie, and we attributed this to the more positive and less variable legacy response of forb ANPP in the restored prairie, especially in the heterogeneous soil treatment. Our results suggest that productivity recovers in restored prairie and exhibits similar sensitivity to drought as in remnant prairie. Furthermore, creating heterogeneity promotes forb productivity and enhances restored prairie resilience to drought.

Monitoring drought impacts on street trees using remote sensing - Disentangling temporal and species-specific response patterns with Sentinel-2 imagery

Healthy street trees provide important ecosystem services to cities, but are under increasing stress from urbanisation and climate change, including drought. Traditional field observations are limited in their ability to provide city-wide and regular monitoring of the drought response of street trees, which is essential for their effective management. To overcome this, we propose a novel workflow using freely available remote sensing imagery from Sentinel-2 to identify temporal and species-specific drought response patterns of street trees. We evaluate the workflow on a sample of 2514 mature street trees of the seven most common street tree species in Leipzig, Germany. For each tree, we generate time series of eight vegetation indices from 2017 to 2022, namely enhanced vegetation index (EVI), normalised burn ratio (NBR) and normalised difference vegetation index (NDVI), each using the 10 m and 20 m resolution near-infrared band (EVI-10, EVI-20, NBR-10, NBR-20, NDVI-10, NDVI-20), as well as red edge normalised difference vegetation index (RENDVI) and red-green vegetation index (RGVI). They form the basis for a correlation analysis with the meteorological drought indicator standardised precipitation evapotranspiration index (SPEI) and for annual growing season integrals, which we subtract from those of the base year 2017. We use boxplots and statistical hypothesis testing to examine differences between and within tree species and years. The results show positive relationships between the eight vegetation indices and the SPEI, with the NBR-20 having the highest correlation coefficients. We also find significant differences in the drought response of several tree species, with Quercus robur being the most drought responsive and Platanus x acerifolia being the least. While most tree species have significantly smaller growing season integrals in the drought years 2018 and 2020 than in the non-drought years 2017 and 2021, the effects are not as pronounced in the drought years 2019 and 2022. Uncertainties arise, for example, from spectral signal variations caused by adjacent land use. Nevertheless, the proposed workflow holds promise for incorporation into holistic urban green management solutions and mixed-method approaches for further research into the causes and consequences of drought-induced damage to street trees.

Impact of drought on Oncomelania hupensis snails breeding in the Poyang Lake area

To examine the impact of arid climates on distribution of Oncomelania hupensis snails in the Poyang Lake area, so as to provide insights into precision control of O. hupensis snails in the Poyang Lake area. O. hupensis snails-infested grass islands in Hukou County, Lianxi District and Lushan City in the northern Poyang Lake area, and Jinxian County, Nanchang County and Poyang County in the southern Poyang Lake area were selected as the study areas, and the occurrence of frames with living snails and the mean density of living snails were captured from snail surveys in the study areas in spring and autumn each year from 2006 to 2023. Five years 2007, 2011, 2013, 2019 and 2022 were selected as drought years, and the mean daily water levels were collected at the Xingzi hydrological station in the drought years, normal flow year (2012) and flood year (2020). The numbers of days with water levels ranging from the lower elevation (11 m) to the upper elevation (16 m) for snail survival and the numbers of days with water levels of 11 m and below were collected in the Poyang Lake area, and the changes of snail indicators were compared in different grass islands in the Poyang Lake area before and after drought. The numbers of days with water levels ranging from 11 to 16 m were 110, 88, 136 d and 125 d at the Xingzi hydrological station in four drought years 2007, 2011, 2013 and 2019, which were less than in the flow year and flood year, and the days with water levels of 11 m and below were 242, 277, 220 d and 198 d in four drought years 2007, 2011, 2013 and 2019, which were longer than in the flow year and flood year. A total of 416 snails-infested marshlands were surveyed in the Poyang Lake area from 2006 to 2021, and the survey marshlands accounted for 43.12% (307/712) and 46.98% (109/232) of total marshlands in the southern and northern Poyang Lake areas, respectively. The median occurrence of frames with living snails and mean density of living snails were 0.60% (interquartile range, 4.04%) and 0.010 1 snail/0.1 m2 (interquartile range, 0.076 1 snail/0.1 m2) in drought years, which were both lower than those [1.33% (5.19%) and 0.022 8 (0.098 9) snail/0.1 m2] in non-drought years (χ2= 42.170 and 44.911, both P values < 0.01). The proportion of grass islands with a continuous decline in snail indicators was higher in the southern Poyang Lake area than in the northern Poyang Lake area after the next year of drought (24.24% vs. 2.33%; χ2 = 10.633, P < 0.01), and the proportion of grass islands with rebounding snail indicators was higher in the northern Poyang Lake area than in the southern Poyang Lake area (53.49% vs. 15.76%; χ2 = 26.966, P < 0.01). A longitudinal analysis of snail indicators in marshlands with rebounding snail indicators after drought showed 1 to 5 years for return to pre-drought snail status, with a median of 2 (interquartile range, 1) years, and snail status was more likely to rebound if the occurrence of frames with living snails and the mean density of living snails were 2.11% and 0.025 5 snail/0.1 m2 and greater in snails-infested grass islands. Drought causes a remarkable decline in O. hupensis snail indicators in the Poyang Lake area, with a more remarkable impact in the southern Poyang Lake area, and 1 to 5 years are required for return to pre-drought snail status.

Evaluation of the drought resilience of indigenous irrigation water systems: a case study of dry zone Sri Lanka

The wave of modernization and globalization in the last century has rapidly involved a technological paradigm shift from indigenous irrigation water systems to modern systems in arid regions. Despite interest in the drought resilience of indigenous water systems, the impact of this paradigm shift on drought resilience remains poorly understood because previous studies have focused on fixed irrigation water systems. To fill this gap, we investigated the drought resilience of an indigenous and modern irrigation water system that coexists in the drought-prone Mahaweli H region of the Sri Lankan dry zone. To explain drought resilience, we quantified the historical irrigation system performance (1985–2021) of both water systems using the water duty indicator (i.e., the volume of water required to cultivate a unit land area). The statistical Pettitt test was used to detect significant change points in the time series of water duty, and we divided the time line into few periods based on the change points. Furthermore, a quantitative trend analysis of several socio-hydrological variables and a qualitative analysis of their socio-hydrological backgrounds with triggers of water duty were conducted to explain drought resilience path dependency in modern and indigenous water systems. The results indicated a higher drought resilience is embedded in the indigenous system as the mean water duty increment in drought years compared to non-drought years is 16.4% for the indigenous system and 58.3% for the modern system. In addition, drought resilience pathways that elucidated by water duty change points also demonstrated that indigenous water system features a higher drought resilience compared to the modern water system. The findings of this comparative study can contribute to the design of drought resilience improvement strategies in arid region irrigation water systems in a more comprehensive manner.

The time since land-use transition drives changes in fire activity in the Amazon-Cerrado region

AbstractDeforestation and climate change are expected to alter fire regimes along the Cerrado-Amazon transition, one of the world’s most active agricultural frontiers. Here we tested the hypothesis that the time since land-use transition (age of frontier) and agricultural intensification also drive changes in the region’s fire regimes by reducing fire probability in both drought and non-drought years. We modeled fire probability as a function of the time since land-use transitions based on MapBiomas Project datasets from 1986 to 2020. We find that, while burned area declined as pasturelands aged and croplands advanced, deforestation abruptly increased fire activity before (Amazon: 4 years; Cerrado: 3 years) and after (Amazon: 8 years; Cerrado: 7 years) land clearing for pasture, especially in the Amazon. Additionally, the combination of ignition risk, drought, and air-dryness increased the likelihood of large extents of burned areas associated with deforestation. Incorporating frontier age as a proxy for governance in fire modeling is crucial, given the ecological implications of changing fire regimes despite declining rates of fire probability. Most importantly, protecting against deforestation and preserving native vegetation are vital.

Assessing the relative importance of dry-season incoming solar radiation and water storage dynamics during the 2005, 2010 and 2015 southern Amazon droughts: not all droughts are created equal

Three severe droughts impacted the Amazon in 2005, 2010, and 2015, leading to widespread above-average land surface temperature (LST) (i.e. positive thermal anomalies) over the southern Amazon in the dry season (Aug–Sep) of these years. Below-average dry-season incoming solar radiation (SW↓) and terrestrial water storage anomaly (TWSA) were simultaneously observed in 2005 and 2010, whereas the opposite was observed in 2015. We found that anomalies in precipitation (P), SW↓, and TWSA combined can well explain dry-season thermal anomalies during these droughts (average R2–0.51). We investigated the causes for opposing anomalies in dry-season SW↓ and TWSA, and found different hydro-climatological conditions preceding the drought-year dry seasons. In 2005 and 2010, P was considerably below average during the wet-to-dry transition season (May–July), causing below-average TWSA in the dry season that was favorable for fires. Increased atmospheric aerosols resulting from fires reduced solar radiation reaching the ground. In 2015, although below-average dry-season P was observed, it was above the average during the wet-to-dry transition season, leading to reduced fires and aerosols, and increased dry-season SW↓. To further examine the impact of opposite hydro-climatological processes on the drought severity, we compared dry-season LST during droughts with the maximum LST during non-drought years (i.e. LSTmax) for all grid cells, and a similar analysis was conducted for TWSA with the minimum TWSA (i.e. TWSAmin). Accordingly, the regions that suffered from concurrent thermal and water stress (i.e. LST > LSTmax and TWSA < TWSAmin) were identified. These regions are mainly observed over the southeast in 2005 and southern Amazon in 2010. In 2015, large-scale dry-season thermal stress was found over central and southeast Amazon with little water stress. This study underlines the complex interactions of different hydro-climatological components and the importance of understanding the evolution of droughts to better predict their possible impacts on the Amazon rainforest.

Consequences of drought for grassland songbird reproduction

AbstractAbiotic stressors can be major sources of selection, resulting in diverse demographic responses operating via multiple direct and indirect mechanisms. However, unusual weather events are notoriously difficult to study due to their spatial and temporal unpredictability. A severe drought affected the Flint Hills of Kansas in 2018, occurring during the ongoing population‐level studies of three species of declining grassland songbirds: Eastern Meadowlarks (Sturnella magna), Grasshopper Sparrows (Ammodramus savannarum), and Dickcissels (Spiza americana). We compared nest survival, nest initiation date, and potential behavioral drivers of reproductive differences (i.e., nest orientation, investment) between the 2018 drought year and 2–6 years of average‐to‐wet years. Nest initiation in the drought year was concentrated early in the season, suggesting that birds did not renest or attempt second broods. The two species that build domed nests shifted the orientation of nest entrances away from early morning sun and toward the direction of prevailing winds in the drought year. Multiple nest‐level metrics of investment and success were similar in drought and nondrought years. These results suggest that demographic changes during droughts can reflect both direct responses and may also involve biotically mediated trophic consequences.

Irrigation scheduling has limited effects on productivity of field-grown pak choi (Brassica rapa L. spp. chinensis) in non-drought years

Irrigation scheduling has limited effects on productivity of field-grown pak choi (<i>Brassica rapa</i> L. spp. <i>chinensis</i>) in non-drought years

Attribution of Extreme Drought Events and Associated Physical Drivers across Southwest China Using the Budyko Framework

Drought is a meteorological phenomenon that negatively impacts agricultural production. In recent years, southwest China has frequently experienced agricultural droughts; these have significantly impacted the economy and the ecological environment. Although several studies have been conducted on agricultural droughts, few have examined the factors driving agricultural droughts from the perspective of water and energy balance. This study aimed to address this gap by utilizing the Standardized Soil Moisture Index (SSMI) and the Budyko model to investigate agricultural drought in southwest China. The study identified four areas in Southwest China with a high incidence of agricultural drought from 2000 to 2020. Yunnan and the Sichuan-Chongqing border regions experienced drought in 10% of the months during the study period, while Guangxi and Guizhou had around 8% of months with drought. The droughts in these regions exhibited distinct seasonal characteristics, with Yunnan experiencing significantly higher drought frequency than other periods from January to June, while Guizhou and other areas were prone to severe droughts in summer and autumn. The Budyko model is widely used as the mainstream international framework for studying regional water and energy balance. In this research, the Budyko model was applied to analyze the water and energy balance characteristics in several arid regions of southwest China using drought monitoring data. Results indicate that the water and energy balances in Yunnan and Sichuan-Chongqing are more moisture-constrained, whereas those in Guizhou and Guangxi are relatively stable, suggesting lower susceptibility to extreme droughts. Furthermore, during severe drought periods, evapotranspiration becomes a dominant component of the water cycle, while available water resources such as soil moisture decrease. After comparing the causes of drought and non-drought years, it was found that the average rainfall in southwest China is approximately 30% below normal during drought years, and the temperature is 1–2% higher than normal. These phenomena are most noticeable during the spring and winter months. Additionally, vegetation transpiration is about 10% greater than normal during dry years in Southwest China, and soil evaporation increases by about 5% during the summer and autumn months compared to normal conditions.

Goldilocks forbs: survival is highest outside—but not too far outside—of Wyoming big sagebrush canopies

In arid and semiarid systems, positive effects of nurse shrubs generally occur immediately underneath and around shrub canopies, creating microsites that can be targeted to promote plant establishment in restoration settings. Alternatively, the best microsites may occur in the interspace zone immediately surrounding nurse shrubs if positive abiotic effects extend beyond nurse shrub canopy boundaries and if competition with nurse shrubs is reduced in that zone. In the Intermountain West, U.S.A., we investigated survival of transplanted herbaceous seedlings at different distances from Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) canopies. We planted two native perennial forb species, Munro's globemallow (Sphaeralcea munroana) and common yarrow (Achillea millefolium), and two native perennial grass species, bluebunch wheatgrass (Pseudoroegneria spicata) and bottlebrush squirreltail (Elymus elymoides), at four distances from sagebrush canopies at six sites across the Intermountain West, repeated across 2 years. Under above‐normal precipitation, proximity to sagebrush influenced first‐year survival of the forb, but not grass, species. Globemallow and yarrow survival were highest mid‐way between the canopy dripline and maximum interspace distance between neighboring sagebrush plants. Ground cover characteristics and globemallow survival covaried with respect to distance from shrub, suggesting ground cover characteristics as indicators of suitable planting microsites. Under drier conditions, survival of all species was low and unaffected by distance from canopies. Our results demonstrate the value of fine‐tuning the canopy‐interspace paradigm to more carefully consider how plant performance may differ across zones within the interspace region between plants, especially when the goal is to maximize plant establishment in nondrought years.

Forest edge effects on moss growth are amplified by drought.

Forest fragmentation increases the amount of edges in the landscape. Differences in wind, radiation, and vegetation structure create edge-to-interior gradients in forest microclimate, and these gradients are likely to be more pronounced during droughts and heatwaves. Although the effects of climate extremes on edge influences have potentially strong and long-lasting impacts on forest understory biodiversity, they are not well understood and are not often considered in management and landscape planning. Here we used a novel method of retrospectively quantifying growth to assess biologically relevant edge influences likely caused by microclimate using Hylocomium splendens, a moss with annual segments. We examined how spatio-temporal variation in drought across 3 years and 46 sites in central Sweden, affected the depth and magnitude of edge influences. We also investigated whether edge effects during drought were influenced by differences in forest structure. Edge effects were almost twice as strong in the drought year compared to the non-drought years, but we did not find clear evidence that they penetrated deeper into the forest in the drought year. Edge influences were also greater in areas that had fewer days with rain during the drought year. Higher levels of forest canopy cover and tree height buffered the magnitude of edge influence in times of drought. Our results demonstrate that edge effects are amplified by drought, suggesting that fragmentation effects are aggravated when droughts become more frequent and severe. Our results suggest that dense edges and buffer zones with high canopy cover can be important ways to mitigate negative drought impacts in forest edges.

Ancient fires enhance Amazon forest drought resistance

Drought and fire reduce productivity and increase tree mortality in tropical forests. Fires also produce pyrogenic carbon (PyC), which persists in situ for centuries to millennia, and represents a legacy of past fires, potentially improving soil fertility and water holding capacity and selecting for the survival and recruitment of certain tree life-history (or successional) strategies. We investigated whether PyC is correlated with physicochemical soil properties, wood density, aboveground carbon (AGC) dynamics and forest resistance to severe drought. To achieve our aim, we used an Amazon-wide, long-term plot network, in forests without known recent fires, integrating site-specific measures of forest dynamics, soil properties and a unique soil PyC concentration database. We found that forests with higher concentrations of soil PyC had both higher soil fertility and lower wood density. Soil PyC was not associated with AGC dynamics in non-drought years. However, during extreme drought events (10% driest years), forests with higher concentrations of soil PyC experienced lower reductions in AGC gains (woody growth and recruitment), with this drought-immunizing effect increasing with drought severity. Forests with a legacy of ancient fires are therefore more likely to continue to grow and recruit under increased drought severity. Forests with high soil PyC concentrations (third quartile) had 3.8% greater AGC gains under mean drought, but 33.7% greater under the most extreme drought than forests with low soil PyC concentrations (first quartile), offsetting losses of up to 0.68 Mg C ha–1yr–1 of AGC under extreme drought events. This suggests that ancient fires have legacy effects on current forest dynamics, by altering soil fertility and favoring tree species capable of continued growth and recruitment during droughts. Therefore, mature forest that experienced fires centuries or millennia ago may have greater resistance to current short-term droughts.

Droughts Reduce Growth Rates and Increase Vulnerability to Increasingly Frequent and Severe Drying Events in an Aquatic Ectotherm

Many aquatic organisms are experiencing increasingly severe and frequent droughts and drying events. Simultaneously, drought effects are carrying over to nondrought years as ecosystems remain in incomplete states of recovery. Aquatic organisms are thus faced with fewer sequential years under degraded environmental conditions to prepare for increasingly severe droughts and potential drying events. We assessed the effect of droughts and sex on the growth, mass, and mass-dependent estivation potential of long-lived aquatic salamanders (Greater Sirens, Siren lacertina) that estivate during drying events brought on by severe droughts. We calculated growth rates of S. lacertina based on mark–recapture data spanning 11 yr of a severe drought local minimum (of past 50 yr) in the southeastern United States. Sirens showed a distinct seasonal gain in body length and mass from March through September and little growth for the rest of the year. Gains during the growth season were strongly reduced by drought conditions. Although male and female sirens were predicted to reach a similar maximum body size, females grew much slower. Recruitment into drying event “size refugia” is constrained by drying event severity (determines minimum size required), frequency (determines available time between events to grow), and environmental conditions between drying events (determines the rate of growth). Thus, increases in drying event severity and frequency will require faster growth to a larger body size for successful recruitment into a size class that is resistant to drying events. The slower growth of females and reduction of growth during suboptimal years (mild to moderate droughts) suggest that the life history strategy of Greater Sirens for persisting through drying events potentially increases their demographic susceptibility to the predicted effects of climate change.

Water-soluble saponins accumulate in drought-stressed switchgrass and may inhibit yeast growth during bioethanol production

BackgroundDeveloping economically viable pathways to produce renewable energy has become an important research theme in recent years. Lignocellulosic biomass is a promising feedstock that can be converted into second-generation biofuels and bioproducts. Global warming has adversely affected climate change causing many environmental changes that have impacted earth surface temperature and rainfall patterns. Recent research has shown that environmental growth conditions altered the composition of drought-stressed switchgrass and directly influenced the extent of biomass conversion to fuels by completely inhibiting yeast growth during fermentation. Our goal in this project was to find a way to overcome the microbial inhibition and characterize specific compounds that led to this inhibition. Additionally, we also determined if these microbial inhibitors were plant-generated compounds, by-products of the pretreatment process, or a combination of both.ResultsSwitchgrass harvested in drought (2012) and non-drought (2010) years were pretreated using Ammonia Fiber Expansion (AFEX). Untreated and AFEX processed samples were then extracted using solvents (i.e., water, ethanol, and ethyl acetate) to selectively remove potential inhibitory compounds and determine whether pretreatment affects the inhibition. High solids loading enzymatic hydrolysis was performed on all samples, followed by fermentation using engineered Saccharomyces cerevisiae. Fermentation rate, cell growth, sugar consumption, and ethanol production were used to evaluate fermentation performance. We found that water extraction of drought-year switchgrass before AFEX pretreatment reduced the inhibition of yeast fermentation. The extracts were analyzed using liquid chromatography–mass spectrometry (LC–MS) to detect compounds enriched in the extracted fractions. Saponins, a class of plant-generated triterpene or steroidal glycosides, were found to be significantly more abundant in the water extracts from drought-year (inhibitory) switchgrass. The inhibitory nature of the saponins in switchgrass hydrolysate was validated by spiking commercially available saponin standard (protodioscin) in non-inhibitory switchgrass hydrolysate harvested in normal year.ConclusionsAdding a water extraction step prior to AFEX-pretreatment of drought-stressed switchgrass effectively overcame inhibition of yeast growth during bioethanol production. Saponins appear to be generated by the plant as a response to drought as they were significantly more abundant in the drought-stressed switchgrass water extracts and may contribute toward yeast inhibition in drought-stressed switchgrass hydrolysates.

Collapse of Breeding Success in Desert-Dwelling Hornbills Evident Within a Single Decade

Rapid anthropogenic climate change potentially severely reduces avian breeding success. While the consequences of high temperatures and drought are reasonably well-studied within single breeding seasons, their impacts over decadal time scales are less clear. We assessed the effects of air temperature (Tair) and drought on the breeding output of southern yellow-billed hornbills (Tockus leucomelas; hornbills) in the Kalahari Desert over a decade (2008–2019). We aimed to document trends in breeding performance in an arid-zone bird during a time of rapid global warming and identify potential drivers of variation in breeding performance. The breeding output of our study population collapsed during the monitoring period. Comparing the first three seasons (2008–2011) of monitoring to the last three seasons (2016–2019), the mean percentage of nest boxes that were occupied declined from 52% to 12%, nest success from 58% to 17%, and mean fledglings produced per breeding attempt from 1.1 to 0.4. Breeding output was negatively correlated with increasing days on which Tmax (mean maximum daily Tair) exceeded the threshold Tair at which male hornbills show a 50% likelihood of engaging in heat dissipation behavior [i.e., panting (Tthresh; Tair = 34.5°C)] and the occurrence of drought within the breeding season, as well as later dates for entry into the nest cavity (i.e., nest initiation) and fewer days post-hatch, spent incarcerated in the nest by the female parent. The apparent effects of high Tair were present even in non-drought years; of the 115 breeding attempts that were recorded, all 18 attempts that had ≥ 72% days during the attempt on which Tmax &amp;gt; Tthresh failed (equivalent to Tmax during the attempt ≥ 35.7°C). This suggests that global warming was likely the primary driver of the recent, rapid breeding success collapse. Based on current warming trends, the Tmax threshold of 35.7°C, above which no successful breeding attempts were recorded, will be exceeded during the entire hornbill breeding season by approximately 2027 at our study site. Therefore, our findings support the prediction that climate change may drive rapid declines and cause local extinctions despite the absence of direct lethal effects of extreme heat events.

Drivers of drought-induced shifts in the water balance through a Budyko approach

Abstract. An inconsistent relationship between precipitation and runoff has been observed between drought and non-drought periods, with less runoff usually observed during droughts than would be expected based solely on precipitation deficit. Predictability of these shifts in the precipitation–runoff relationship is still challenging, largely because the underlying hydrologic mechanisms are poorly constrained. Using 30 years of data for 14 basins in California, we show how the Budyko framework can be leveraged to decompose shifts in precipitation versus runoff during droughts into “regime” shifts, which result from changes in the aridity index along the same Budyko curve, and “partitioning shifts”, which imply a change in the Budyko parameter ω and thus in the relationship among water balance components that governs partitioning of available water. Regime shifts are primarily due to measurable interannual changes in precipitation or temperature, making them predictable based on drought conditions. Partitioning shifts involve further nonlinear and indirect catchment feedbacks to drought conditions and are thus harder to predict a priori. We show that regime shifts dominate changes in absolute runoff during droughts but that gains or losses due to partitioning shifts are still significant. Low aridity, high baseflow, a shift from snow to rain, and resilience of high-elevation runoff correlate with higher annual runoff during droughts than would be predicted by the precipitation–runoff ratio during non-drought years. Differentiating between these shifts in the precipitation–runoff relationship using a Budyko approach will help water resource managers, particularly in arid, drought-prone regions, to better project runoff magnitudes during droughts based on available climate data and, furthermore, understand under what circumstances and to what extent their forecasts may be less reliable due to nonlinear basin–climate feedbacks.

Effect of drought on wheat production in Poland between 1961 and 2019

AbstractThe impact of drought on wheat (Triticum aestivum L.) production is shown, using an example data set of almost 60 yr from six climate‐specific regions in Poland. Drought was measured using the standardized precipitation index (SPI) and the hydro‐thermal coefficient of Selyaninov (HTC). Yield trends were estimated by Bayesian linear regression over two periods, 1961–1991 and 1992–2019, identified by a changepoint detection method. Bayesian inference is used as it allows the estimation of a credible interval of regression coefficients instead of point estimates and asymptotic confidence intervals, thus comparisons between regression coefficients are more meaningful. We detected an increase in yield in both time periods and in all regions. The average winter wheat yield increased by 97% in the first period and by 35% in the second (19.8–39.1 dt ha−1 and 32.9–44.5 dt ha−1, respectively). Spring wheat yield increased by 96% in the first period and by 42% in the second (16.8–37.9 and 22.9–32.5 dt ha−1, respectively). Yield losses in drought years were estimated using the paired t test to compare mean difference between real yields and yields estimated from regression lines for nondrought years. The highest yield losses due to drought were in regions I (–19.3% spring wheats, –6.3% winter ones) and III (–16.1% spring and –8.3% winter wheats) over the 1992–2019 period.

Mapping of crop types and crop sequences with combined time series of Sentinel-1, Sentinel-2 and Landsat 8 data for Germany

Monitoring agricultural systems becomes increasingly important in the context of global challenges like climate change, biodiversity loss, population growth, and the rising demand for agricultural products. High-resolution, national-scale maps of agricultural land are needed to develop strategies for future sustainable agriculture. However, the characterization of agricultural land cover over large areas and for multiple years remains challenging due to the locally diverse and temporally variable characteristics of cultivated land. We here propose a workflow for generating national agricultural land cover maps on a yearly basis that accounts for varying environmental conditions. We tested the approach by mapping 24 agricultural land cover classes in Germany for the three years 2017, 2018, and 2019, in which the meteorological conditions strongly differed. We used a random forest classifier and dense time series data from Sentinel-2 and Landsat 8 in combination with monthly Sentinel-1 composites and environmental data and evaluated the relative importance of optical, radar, and environmental data.Our results show high overall accuracy and plausible class accuracies for the most dominant crop types across different years despite the strong inter-annual meteorological variability and the presence of drought and non-drought years. The maps show high spatial consistency and good delineation of field parcels. Combining optical, SAR, and environmental data increased overall accuracies by 6% to 10% compared to single sensor approaches, in which optical data outperformed SAR. Overall accuracy ranged between 78% and 80%, and the mapped areas aligned well with agricultural statistics at the regional and national level. Based on the multi-year dataset we mapped major crop sequences of cereals and leaf crops. Most crop sequences were dominated by winter cereals followed by summer cereals. Monocultures of summer cereals were mainly revealed in the Northwest of Germany. We showcased that high spatial and thematic detail in combination with annual mapping will stimulate research on crop cycles and studies to assess the impact of environmental policies on management decisions. Our results demonstrate the capabilities of integrated optical time series and SAR data in combination with variables describing local and seasonal environmental conditions for annual large-area crop type mapping.

Population genetic structure and dispersal patterns of a cooperative breeding bird in variable environmental conditions

Understanding the effects of environmental conditions in cooperatively breeding species helps reveal the nature of evolutionary forces leading to this type of social system. In particular, environmental variability may affect demographic processes such as mortality and dispersal which can ultimately define the fine-scale genetic structure of cooperatively breeding populations, including direct and indirect fitness opportunities for individuals. We investigated the population genetic structure and dispersal patterns of obligately cooperative white-winged choughs, Corcorax melanorhamphos , exploring within-group relatedness and genetic differentiation among groups sampled over several years of above average rainfall. We compared our results with data from a previous study in the surrounding area, conducted during a drought period. White-winged chough groups showed similar significant genetic differentiation among groups during both drought and nondrought periods. However, we found female-biased dispersal during abundant rainfall years, which contrasts with the previous study conducted during a drought. We also examined differences in genetic structure in the present study, between groups breeding in suburbs versus native woodlands, finding higher within-group relatedness in woodland birds. Dispersal was female biased in both suburban and woodland habitat but subadult females in suburban habitat were more likely to disperse than adult females. We suggest that higher mortality in chough populations (both during a drought and in suburban habitats) led to more breeding opportunities, resulting in higher dispersal, and reflecting lower group stability. Our study suggests ecological conditions are important drivers of social structure in a cooperatively breeding bird, which are likely to be impacted by environmental change, including climate and urbanization. • Chough groups show significant genetic variation in drought and nondrought years. • In nondrought years, in both suburbs and woodland, dispersal is female biased. • Among suburban females, subadults are more likely to disperse than adults. • In drought years dispersal is not sex biased.