Drought Cycles Research Articles

Best of both worlds: hybrids of two commercially important pines (Pinus contorta × Pinus banksiana) combine increased growth potential and high drought tolerance

Over 18 million hectares of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) forests have been affected by a massive mountain pine beetle outbreak in western Canada. The ensuing need for reforestation compels forest managers to deploy more drought-resistant stock in anticipation of a hotter and drier future climate. Recent studies suggest that naturally occurring lodgepole pine × jack pine (Pinus banksiana Lamb.) hybrids may be more drought-resistant than pure lodgepole pine. We used single-nucleotide polymorphism markers to determine the level of jack pine introgression present in the region J lodgepole pine seed orchard, in northwest Alberta, and we identified six hybrid genotypes with 10%–18% jack pine introgression for further study. We compared the performance of open-pollinated seedlings of lodgepole, jack, and hybrid pines under well-watered and drought conditions in a greenhouse experiment. Seedlings were subjected to repeg ated drought cycles, withholding water for either 2 or 3 weeks. We found that hybrid pines grew significantly faster than lodgepole pine under well-watered conditions while retaining the high tolerance to prolonged drought exhibited by lodgepole pine seedlings, a particularly beneficial combination of traits during the critical stage of establishment. We therefore suggest the deployment of hybrid lodgepole pine as a strategy to promote adaptation to hotter and drier future climates.

Food Security and coexistence with the semiarid zone in areas affected by drought in the backlands of Pernambuco

ABSTRACT Objective Between 2010 and 2017, it was registered one of the most intense droughts in the Brazilian Northeastern Semiarid region, when the rainfall was below the historical level for the region. This context was related to water scarcity for human consumption and productive activities in this territory, where the semiarid backlands of the state of Pernambuco are located. The objective of this study was to assess the condition of food security and its associated factors in areas affected by drought in the semiarid zone of Pernambuco, Brazil. Methods It was a cross-sectional study on a populational base. Data were collected by socioeconomic and demographic surveys, and the Brazilian Food Insecurity Scale, which were applied to 252 households, from September to October 2015. The data was analyzed by socioeconomic and demographic characterization of the households, and the identification of the food insecurity prevalence and its associated factors, by Poisson regression. Results The prevalence of food insecurity was high (74.6%). Among those, 9,1% were on starvation, which means severe insecurity. Food insecurity was statistically associated to sanitation, per capita income, and the number of household residents. Lack of money was the main self-reported cause to food insecurity. Conclusion The high prevalence of food insecurity being associated to indicators of great social vulnerability shows the role of social and economic inequities on the inadequate access to food amongst families in the semiarid zone on a nearly generalized low-income context. These findings corroborate to the evident need of expanding and reinforcing public policies, as well sustainable development models to prioritize and promote social inclusion of communities at greater vulnerabilities in the Brazilian semiarid area. Thus, the need of these economic and social public strategies is highlighted by the worsening of historical vulnerable conditions due to the cycles of droughts on this region.

Temporal phytocoenosia and synusiae: should we consider temporal sampling in vegetation classification?

Vegetation classification requires the defining of a hierarchy of types based on a spatial and temporal dimensionality. Spatial variation is achieved by plots being placed across the landscape; however, temporal dimensionality is generally only inferred but not directly tested and is rarely incorporated within the circumscription of types. Here, 108 permanent plots are surveyed across 7 years within the Mulga Lands Bioregion of north-western New South Wales through a drought cycle to assist in incorporating temporal dimensionality within community definition. Herbaceous biomass and species density decreased significantly and species composition changed associated with increasing drought conditions, with a return to closer to original conditions by the end of the study. Here, nine temporal associations and 31 synusiae are defined. The changes noted have significant implications for current vegetation classification methods, benchmarking and threatened community listings. The use of permanent plots in vegetation classification is recommended at least for threatened communities and highly dynamic vegetation types associated with less predictable climates.

Estimating the Rainfall Patterns in Namibia: Are rainfall patterns a myth or fact?

Rainfall is generally regarded as the key driver for ecosystem processes, particularly important within the dynamics of semi-arid regions. Since the precipitation impacts the natural environment, human society and the economy, the paper applied rainfall forecasting to avail early warning patterns. The Waterberg rainfall data from 1895 to 2019 was used to determine a better understanding of its pattern. This is necessitated because knowledge of rainfall patterns are required for reviewing production targets and a necessity for decision making in agriculture. Data shows that only 34% of the rainfall years accounted average rainfall, meanwhile 66% of rainfall years is either classified as above or below. Further, results show that the ENSO patterns follow a cyclical pattern, which corresponds to the local Waterberg rainfall. Econometric approaches postulate that there exists volatility of rainfall, effective rainfall, its intensity, cycles and the ENSO data. This paper shows that rainfall forecasting is possible when using a model that takes into account the variation in the ENSO, cyclical pattern and the accumulation of various rainfall cycles. A five year forecast shows that the current experienced drought cycle is coming to an end, and that the prospects of above average years will only persist for 2 years. We recommend that knowledge of the cyclical trend needs to be translated into reliable periodic statements to safeguard Namibia against future famines, possible food shortages and counter rising food prices. Although the methods are robust, they call for further research into the causes of dynamics of observed rainfall variability.

Modern and Holocene microbial mats and associated microbially induced sedimentary structures (MISS) on the southeastern coast of Tunisia (Mediterranean Sea)

AbstractOn the southeastern Tunisian coastline, very diverse living microbial mats colonize the lower supratidal and intertidal zones, and locally may extend into the upper infratidal zone. The interaction between the benthic cyanobacteria and their siliciclastic substratum leads to the development of several types of microbially induced sedimentary structures (MISS). The mapping of the microbial mats has allowed the identification of the types of MISS that characterize the different segments of the coastal environment. The modern microbial mats have been compared with those recorded at the top of the Holocene deposits, which are composed of biodegraded microbial black mats alternating with white laminae made of clastic and evaporitic sediments, indicative of very high frequency cycles of flood and drought. A hypothetic profile showing their occurrences along the different areas bordering the coastline is proposed as a guide for the reconstruction of the ancient depositional environment. The roles of tidal dynamics, storms, and climate in controlling their genesis and spatial distribution, are discussed and highlighted. The modern MISS of southeastern Tunisia are compared with their equivalents that are well documented through the different geological eras.

Distribution and Abundance of Double-crested Cormorants Nesting in the Interior of California, 2009–2012

As part of an 11-state inventory, we censused the Double-crested Cormorant (Phalacrocorax auritus) in the interior of California from 2009 to 2012, using a combination of aerial, ground, and boat surveys. An estimated 8791 pairs breeding in the interior of the state in 2009–2012 exceeded the 7170 pairs estimated in 1998–1999. In both periods, cormorants were breeding in 9 of 11 ecoregions, but three-fourths were at one site—Mullet Island at the Salton Sea in the Sonoran Desert ecoregion (abandoned in 2014). The ecoregions with the next highest proportions were the Sacramento Valley, San Joaquin Valley, and Modoc Plateau. The apparent increase in numbers and colony sites since 1999—consistent with the pattern through much of western North America—reflects the (short-lived) increase in numbers at the Salton Sea, an increasing number of colonies and breeding pairs in the Central Valley, and slightly better coverage on the recent surveys. Because of practical survey constraints and limited data to date, evidence of change in numbers of Doublecrested Cormorants breeding in the interior of California between 1998–1999 and 2009–2012 is inconclusive. Plans for monitoring will need to take into account the effects of substantial annual variation in numbers, which may be associated with large fluctuations in cormorants’ prey base, short-term cycles of drought and flood, shifts of nesting cormorants into or out of the interior of California, and the expectation of greater environmental fluctuations with continuing climate change. The factors most likely to limit the number of cormorants breeding in the interior of the state are habitat loss or alteration (particularly from reallocation of water for human needs), disease, human disturbance, and the long-term effects of climate change.

Effects of drought on the abundance and distribution of non-breeding shorebirds in central California, USA

Conservation of migratory species requires anticipating the potential impacts of extreme climatic events, such as extreme drought. During drought, reduced habitat availability for shorebirds creates the potential for changes in their abundance and distribution, in part because many species are highly mobile and rely on networks of interior and coastal habitats. Understanding how shorebirds responded to a recent drought cycle that peaked from 2013 to 2015 in central California, USA, will help optimize management of wetlands and fresh water for wildlife. In the Central Valley, a vast interior region that is characterized by a mosaic of wetlands and agricultural lands, we found 22% and 29% decreases in the annual abundance of shorebirds during periods of 3-year drought (2013-2015) and 2-year extreme drought (2014-2015), respectively, when compared to non-drought years. Lower abundance of shorebirds coincided with significant decreases in the mean proportion flooded of survey units (7% and 9%, respectively) that were reliant on fresh water. Drought was associated with lower abundance within both the interior Central Valley and coastal San Francisco Bay for greater and lesser yellowlegs (Tringa melanoleuca and T. flavipes) and long- and short-billed dowitchers (Limnodromus scolopaceus and L. griseus). Only dunlins (Calidris alpina) had patterns of abundance that suggested substantial shifts in distribution between the Central Valley and coastal regions of San Francisco Bay and Point Reyes. Our results indicate that drought has the potential to reduce, at least temporally, shorebird populations and flooded habitat in the Central Valley, and the ability to respond to drought by taking advantage of nearby coastal habitats may limit the long-term effects of drought on some species. Successful conservation strategies must balance the impacts of reduced habitat availability at interior sites with the ability of some migratory shorebirds to adapt rapidly to shifting distributions of resources.

A Geographic Information System for Managing and Mapping Irrigation Infrastructure

Indonesia is one of the world's major agricultural nation which offers wide diversity of tropical products and agricultural commodities produced in substantial number of agricultural areas. Some of these areas are equipped with irrigation infrastructures which delivers water management throughout the land. Irrigation helps grow agricultural crops, maintain landscapes, and revegetation disturbed soils in dry areas. Water resources are finite while cyclic droughts on agricultural areas affecting the amount of water remains, thus creating unbalanced water demand and supply. Therefore, building an effective plan and management for irrigation infrastructure must be conducted using reliable information. The objective of this study is to develop a geographic information system to help managing and mapping process of irrigation infrastructure, such as flood gate and water ways. This system also helps to manage all the irrigation area and infrastructure data by providing geological information, search, and managing database function. We developed a web application for system interactivities. We also work together with Dinas Pekerjaan Umum dan Penataan Ruang of Kabupaten Kubu Raya, as they are managing nearest irrigation land which available to be inspected for research. The system has been tested in a real-life case study. As a result, the system enhances the efficient management of irrigation area and infrastructure data. Users stated that this geographic information system has many benefits to irrigation area management., i.e, ensuring data authorization with user information when data is recorded, real time image capture for each irrigation infrastructure, and digital maps to gain a wide overview of irrigation area information on Kabupaten Kubu Raya

Evidence of drought memory in Dipteryx alata indicates differential acclimation of plants to savanna conditions

The remarkable phytogeographic characteristics of the Brazilian savanna (Cerrado) resulted in a vegetation domain composed of plants with high structural and functional diversity to tolerate climate extremes. Here we used a key Cerrado species (Dipteryx alata) to evaluate if species of this domain present a mechanism of stress memory, responding more quickly and efficiently when exposed to recurrent drought episodes. The exposure of D. alata seedlings to drought resulted in several changes, mainly in physiological and biochemical traits, and these changes differed substantially when the water deficit was imposed as an isolated event or when the plants were subjected to drought cycles, suggesting the existence of a drought memory mechanism. Plants submitted to recurrent drought events were able to maintain essential processes for plant survival when compared to those submitted to drought for the first time. This differential acclimation to drought was the result of orchestrated changes in several metabolic pathways, involving differential carbon allocation for defense responses and the reprogramming and coordination of primary, secondary and antioxidant metabolism. The stress memory in D. alata is probably linked the evolutionary history of the species and reflects the environment in which it evolved.

Micro-geographic variation in burrow use of Agassiz’s desert tortoises in the Sonoran Desert of California

Little has been published regarding the burrowing habits of Agassiz’s desert tortoises (Gopherus agassizii) in the Sonoran Desert of California. We monitored the interactions of tortoises with their burrows, and other tortoises, via radio-telemetry at two nearby sites between the Cottonwood and Orocopia Mountains, from 2015-2018. We examined how annual cycles of drought and non-drought years, behaviourally affected how tortoises use their burrows (i.e., burrow fidelity, cohabitation, and location), including the timing of the tortoise brumation period. Burrow locations were strongly dependent on local geology and topography, with a tendency to orientate in conformance with the general aspect of the landscape. The timing of brumation was similar to records for G. agassizii throughout their range (with a few exceptions). There was no difference in the estimated number of burrows used per 30 days between the active seasons (2017 and 2018) at the Orocopia site, despite the occurrence of drought in 2018.

Potential management practices of saltwater intrusion impacts on soil health and water quality: a review

AbstractSeveral studies have documented the multifaceted impacts of climate change and variability on agricultural and environmental sustainability, and social and economic development. Climate change and variability contribute to increased warmer conditions, increased frequency of heavy rain that accounts for an increasing proportion of total rainfall, extreme weather characterized by spatially variable cycles of drought and wetness, increased frequency of tropical storms/hurricanes, increased frequency of storm surges, and accelerated rate of sea-level rise (SLR). As SLR continues, it is expected that salinity due to saltwater intrusion (SWI) will impact soil health and agricultural production. As such, the significant threats of salinity necessitate more work to be done to better understand its impact on soil health and associated functional ecosystem processes. This is of even greater importance in areas such as South Florida where the surface and groundwater resources are hydrologically connected due to the shallow and highly permeable limestone soils. A better understanding of the impacts of salinity due to SWI on soil health is critical to design effective mitigation strategies. Healthy soil has multifaceted benefits to enhance agricultural productivity, i.e. regulates the flow of water; serves as a source and sink of nutrients; minimizes greenhouse gas emissions and provides optimal biological and chemical conditions for the transformation of nutrients into plant-available forms. Improved understanding of the processes and impacts of SWI on soil health will assist in guiding management decisions and policies to mitigate the impacts of SWI and salinity on agricultural soils. This review paper provides a comprehensive overview of the impacts of SWI and soil salinity on agricultural soil health and water quality.

Evolutional Characteristics of Regional Meteorological Drought and Their Linkages with Southern Oscillation Index across the Loess Plateau of China during 1962–2017

The Loess Plateau of China (CLP) is located in the transition zone from a semi-humid climate zone to semi-arid and arid climate zones. It is influenced by the westerly circulation, plateau monsoon, and East Asian monsoon circulation, and the drought disasters across the CLP have obvious regional characteristics. In this study, climate regionalization was performed by a spatial hierarchical cluster approach based on the gridded datasets of monthly precipitation across the CLP from 1961 to 2017. Then, the standardized precipitation index (SPI) was used to explore the temporal evolution of regional meteorological droughts. Finally, wavelet methods were used to investigate the drought cycles in each homogeneous subregion and the linkages between SPI and the Southern Oscillation Index (SOI). The results show that: (1) Spatially, the CLP can be divided into four homogeneous regions, namely, Ordos Plateau semi-arid area (Region I), Northern Shanxi hilly semi-humid area (Region II), Longzhong plateau cold-arid area (Region III), and Fenwei Plain and Shaanxi-Shanxi hilly semi-humid area (Region IV). (2) There are apparent differences in the temporal evolution of meteorological droughts in different subregions, but two wet periods from the 1960s to 1980s and 2010s, and a drought period in the 1990s, can be found in each subregion. (3) There is a significant drought cycle of 3–8 years in the four subregions, and the first main cycles of drought variation are not completely consistent. (4) The linkages between SPI and SOI are time- and space-dependent and the phase differences are dominated by in-phase. The strongest correlations between the two time series occur in the 1980s in the four subregions. The results of this research have important implications for the establishment of drought monitoring programs in homogeneous climate regions, and informed decision making in water resource management.

Neighbor identity affects growth and survival of Mediterranean plants under recurrent drought.

The increasing intensity and frequency of droughts predicted for the Mediterranean basin with ongoing climate change will impact plant communities and ecosystem functioning. This study investigated the effect of severe recurrent droughts and the role of the neighbor plant identity on the growth and survival of three abundant and co-existing species of a typical Mediterranean shrubland. Two juvenile plants, either of the same species or in all possible combinations of the two woody species Quercus coccifera and Cistus albidus and the perennial grass species Brachypodiumretusum were grown together in rhizotrons under controlled watering regimes for two years. Compared to a treatment with only one drought cycle, three successive droughts reduced the relative growth rates (RGR) of shoots and roots in B. retusum, but not in woody species, and increased the mortality of the woody species, but not that of the grass. The survival of C. albidus and of B.retusum, but not of Q. coccifera, increased when the neighbor individual was a different species than when it was the same species. Our data suggest that both species composition and frequency of drought events will impact the dynamics of plant communities in Mediterranean shrublands under ongoing climate change. The abundance of dehydration sensitive woody species will likely decrease under more frequent drought events at the expense of dehydration-tolerant grass species, resulting in potentially strong changes in the functioning of these ecosystems.

Anomalous Weather Events in Central Himalaya: Real-World Observations and Some Questions

The central sector of the Himalayan province is witnessing inordinately frequent incidences of extreme weather, unending cycles of prolonged droughts and very short spells of excessive rainfall over geographically limited areas, absence of ‘April Showers’ before the onset of summer monsoon, and delayed arrival of the Indian summer monsoon. Are these happenings related to merely the rise in atmospheric and surface temperatures due to global warming, or are they caused by the excess presence of biogenic carbon generated by rampant burning of agricultural residues and wastes, and uncontrolled forest fires? One would also like to know whether the western disturbances and/or the mid-latitude interactions have a role in these distressing developments. The simplistic answer that all these anomalous happenings are ‘the combined effect of global warming enhanced by anthropogenic influences’ is hardly convincing to the laymen who solicit answers to these questions from experts – in a language free from technical jargon.

La variabilidad hídrica en la cuenca del río Atuel, desde la climatología histórica: siglo XVIII a mediados del XX

Desde mediados del siglo XX, se ha desarrollado un conflicto a escala nacional, entre las provincias de La Pampa y Mendoza (Argentina), cuya causa es una supuesta disminución en la cantidad de agua proveniente del río Atuel. El objetivo principal del estudio es tratar de reconstruir las condiciones hidrológicas del río Atuel, desde finales del siglo XVIII hasta mediados del siglo XX, para analizar el reclamo pampeano sobre la disminución del volumen hídrico, la cual se le atribuye al uso agrícola intensivo que realizó Mendoza en la cuenca media. Para ello, se elaboró una “línea de tendencia” de los caudales del río Atuel, a partir de documentos de archivo, relatos de viajeros, estudios de naturalistas e incursiones militares, en los que se tuvo en cuenta especialmente el periodo preinstrumental. Después, se realizó una comparación, a partir de reconstrucciones elaboradas para áreas vecinas, desde la dendrocronología, la glaciología y la meteorología. Los resultados comprueban que el río Atuel presenta una disminución sostenida de su caudal —aunque con pulsos de crecidas y sequías cíclicas— desde finales del siglo XIX. En los pulsos observados aparecen importantes periodos secos durante el siglo XIX, los cuales incluso habrían impedido que la cuenca volcara sus aguas al río Colorado, como se supone que era normal antes de 1900.Ideas destacadas: artículo de revisión que propone una reconstrucción hidroclimática del río Atuel, a partirdel análisis de documentación histórica; aporta al debate sobre el conflictointerprovincial entre Mendoza y La Pampa, y a la investigación sobre la apropiación del agua de los “oasis” vs “desiertos”.

Mechanisms of Cold Region Hydrologic Change to Recent Wetting in a Northern Glaciated Landscape

AbstractThe Northern Great Plains (NGP) experienced a transition from a long drought cycle to a deluge cycle in the late 1900s. Embedded within this long‐term transition were shorter‐term decadal‐scale dry and wet periods. A recent NGP drought (1999–2004) was followed in 2005 by a wet period that continues to present day. However, how surface hydrology in a northern glaciated landscape responds to increased precipitation is poorly understood and a physically based modeling framework is needed to clarify the underlying processes. This study utilizes a physically based hydrologic model to investigate the impacts of increased precipitation on the water budget by examining its partition into intermediate processes from 2004–2017 in the Mauvais Coulee Basin (MCB). The MCB model evaluations against snow observations (2016–2017) and outlet streamflow observations (2004–2017) imply strong model performance. Simulated snow exhibits high spatiotemporal variation due to variability in precipitation, snow redistribution from stubble fields to wooded areas, and snow accumulation in small depressions. Our modeling results identify two major phases (before and after 2011) exhibiting different hydrologic responses. The period before 2011 is dominated by streamflow and evapotranspiration (ET), while extreme ET dominance is observed after 2011. This switch is due to climatic conditions involving changes in the vapor density difference and depressional and subsurface storage by intermediate processes. A clear contrast in the prewinter soil moisture‐streamflow relationship between before and after 2011 is reported. Our findings help illuminate the important influences of increased precipitation upon the intermediate processes in controlling streamflow in a northern glaciated prairie landscape.

Analysis of groundwater and river stage fluctuations and their relationship with water use and climate variation effects on Alto Grande watershed, Northeastern Brazil

Sustainable use of water resources on the behavior of groundwater table and surface water level variations, especially in phreatic sedimentary aquifers, where a strong interaction between stream flow and groundwater normally takes place. In the present study, precipitation, water level fluctuation, river flow and pivot installation data from an important agricultural frontier with an increasing water use for irrigated agriculture and a downward precipitation trend were compared with surface and water level fluctuation monitoring data. The main purpose was to assess possible impacts on the aquifers and to analyze the variation in groundwater table and surface water levels due to long-term downward precipitation trend (climate variation effects) and increasing water demand (irrigation). A growing number of central pivots installed for irrigation are withdrawing water from the Urucuia Aquifer System (UAS) in western Bahia State, Northeastern Brazil, one of the leading agricultural frontiers of the world. Field surveys provided hydrogeological aspects that led to the construction of a hydrogeological conceptual model. Monitoring groundwater and surface water through Brazilian Geological Survey's Integrated Groundwater Monitoring Network (RIMAS-CPRM), satellite images and Hydrological Information System (HidroWeb-ANA) network formed the databases for the study. This data was compared with rainfall data and evolution of irrigated areas captured by satellite image analysis. Results indicate that reduction of rainfall volumes from 1990 to 2018 in the headwaters of Alto Grande basin, due to cyclic droughts, and an increase in surface and groundwater exploitation due to flourishing agribusiness activity has caused a considerable groundwater level drawdown. The drawdown of up to 6.63 m points to the need of strong management actions, which should provide a long-term sustainable use of water resources (superficial and underground) within Alto Grande watershed. This study is part of the actions undertaken to provide the scientific and technical basis to secure the availability of water and a sustainable agricultural activity, since an important part of the Cerrado, the Brazilian savanna ecosystem, and considerable proportion of São Francisco river flow, lies in the study area.

Response of growth and drought tolerance of Acacia seyal Del. seedlings to arbuscular mycorrhizal fungi

Considering the improvement of acacia species growth in arid and semi-arid environment, a pot experiment was conducted to evaluate the role of arbuscular mycorrhizal fungi (AMF); Funneliformis mosseae (syn. Glomus mosseae), Rhizophagus intraradices (syn. Glomus intraradices) and Claroideoglomus etunicatum (syn. Glomus etunicatum) on growth and drought tolerance of Acacia seyal Del. seedlings under drought cycles (7, 14, 21 and 28 days). AMF-inoculated seedlings showed a clear colonisation percentage (36–68%). AMF treatment significantly improved seedlings shoot and root growth under all drought cycles compared to non-AMF control seedlings. Moreover, AMF treatment enhanced seedlings drought resistance by increasing root surface area (root length increased by 483.76% and root tips number increased by 1 463.94% under 28 days of drought cycle), there was a strong linear relation between proline accumulation, AMF and drought stress (proline content decreased in treated seedlings by 31.3% and 14.3% and increased by 97.5% and 80.4% in untreated seedlings under drought cycles of 21 and 28 days, respectively). In conclusion, the AMF inoculation improved growth and enhanced drought tolerance of A. seyal seedlings and can be used as a natural biostimulator for acacias seedlings establishment in arid areas.

Drought Cycles Over the Last 8,200 Years Recorded in Maar Lake Twintaung, Myanmar

AbstractThe tropical Asian regions are particularly prone to catastrophic droughts due to high temperature and evaporation and their sensitivity to variable oceanic‐atmospheric circulation. The extent to which future global warming may intensify droughts in this populous region is a matter of utmost concern. Palaeoclimatic data can help inform scientists learn more about the temporal patterns and drivers of monsoon change over geological timescales. In this paper, we present a new 8,200 year biomarker record preserved in the annually laminated sediments of Maar Lake Twintaung, Myanmar. The δ13C27‐35 sedimentary record is mainly derived from leaf wax lipids in the lake catchment, which is presently dominated by C3 vegetation in the modern lake catchment. The δ13C27‐35 is mainly regulated by plant physiological and biochemical responses to drought stress and, as such, can be used as a proxy of past changes in moisture. The δ13C27–35 record reveals distinct decadal‐to‐centennial‐scale droughts superimposed on a trend of gradually decreasing summer monsoon intensity from the mid‐Holocene to late Holocene. Within the limits of the dating uncertainties, these decadal‐to‐centennial‐scale droughts are found to be well correlated with the southward shift of the Intertropical Convergence Zone. It highlights the importance of the Intertropical Convergence Zone shift (tropical monsoon trough) in regulating monsoon rainfall in the region. In addition, most of the droughts are likely to be linked with active volcanism and solar minima and suggest a coupled process between external drivers and internal climate dynamics.

Nefarious Agents of Ecological Collapse: “The Desert Makers” by Euclides da Cunha

Cycles of drought and images of human suffering, starvation, and displacement have animated Brazil’s national identity since the nineteenth century. Yet, though the tragic effects of drought extend to every geographic region of Brazil, literary and cultural representations of drought remain firmly tied to the Brazilian Northeast.1 Indeed, drought and its human costs have in large measure defined Brazil’s Northeastern geographic and cultural identity. In his thoroughly researched study Disaster Writing: The Cultural Politics of Catastrophe in Latin America, Mark Anderson notes that over a fifty-year period, from roughly the 1880s to the 1930s, “the nation undertook a process of assessment that classified the Northeast and its residents as a security risk, a threat to its program of modernization, and an economic liability” (58). Unquestionably, literary production helped galvanize the identification of the Northeast with drought,2 yet one consequence of this literary and cultural tradition is that drought has been consigned to the Northeast—that is, literature and other media often present drought as an unavoidable natural occurrence that, while tragic, remains distant, remote, and otherwise removed from the concentrated population centers of the Southeast.3 Nevertheless, the real effects of drought impact other regions of Brazil as well. For example, severe dry weather resulting from an El Niño phenomenon in 2014–17 led to a devastating drought in the states of São Paulo and Mato Grosso do Sul, delaying or greatly reducing planting and agricultural operations.4 This drought similarly crippled the city of São Paulo, the metropolitan and financial capital of the country, by reducing the Cantareira Reservoir system, which provides greater São Paulo with the majority of its water, to its lowest levels on record. These acute effects ask us to consider the scarcity of literary representations of drought and its causes and effects that are situated in Brazil’s Southeast region.