Frequency Of Extreme Climatic Events Research Articles

Setting and smashing extreme temperature records over the coming century

Changes in the intensity or frequency of extreme climate events can profoundly increase the disruption caused by climate change1–4. The more extreme these events, the greater the potential to push ecosystems and communities beyond their ability to cope3,5. The rate at which existing high temperature records have been broken has increased in response to rising global greenhouse gas emissions (GGHGEs)2,6–8, and the rate at which historical records are surpassed is projected to increase further over the coming century1,2,9,10. Here we examine future events that will be so extreme that they will not have been experienced previously. Record setting in 22 climate models11 indicates that, by the end of the twenty-first century, under business-as-usual increases in GGHGEs (representative concentration pathway (RCP) 8.5 (ref. 12)), high monthly mean temperature records will be set in approximately 58% of the world every year, and in 67% of least developed countries and 68% of small island developing states. These figures all drop to 14% under a scenario with much lower GHG concentrations (RCP2.6 (ref. 12)). In any given year, the likelihood of ‘smashing’ at least one monthly record by more than 1.0 °C is much less likely under RCP2.6 than it is under RCP8.5 (1.1 versus 8.9%). Climate change is causing temperature records to be broken around the world with increased frequency. Under a business-as-usual scenario new records will be set every year for 58% of the world, whilst under heavy mitigation (RCP2.6) this would occur for 14% of the world.

Exploring interactive effects of climate change and exotic pathogens on Quercus suber performance: Damage caused by Phytophthora cinnamomi varies across contrasting scenarios of soil moisture

Climate change and exotic pests and pathogens are causing alarming forest declines worldwide. However, we still lack a comprehensive understanding of how damage caused by exotic pests and pathogens might vary under the different scenarios of water availability imposed by a changing climate, particularly in water-limited forests as those that occupy Mediterranean areas. In this paper we aimed to experimentally analyse the interactive effects of the aggressive exotic pathogen Phytophthora cinnamomi and climate change-related reductions in soil moisture on seedling performance of the Mediterranean host Quercus suber. We conducted a full-factorial greenhouse experiment where the physiology and growth of Q. suber seedlings was measured in soils with different combinations of P. cinnamomi inoculum density (0, 30, 60 and 120 colony forming units per gram of dry soil) and soil moisture (15%, 40%, 50% and 100% soil water holding capacity) simulating different invasion and climate change scenarios. We found additive effects of P. cinnamomi and drought on Q. suber performance aboveground, although these effects were not always negative. In fact, seedlings showed a compensatory physiological response to P. cinnamomi infection by increasing their net photosynthetic rates. Our results also supported important interactive effects of pathogens and soil moisture on belowground performance. Thus, the inoculum density in the soil required to cause significant root damage in experimental seedlings decreased as soil moisture increased. From a climate change perspective, these results suggest that an average drier climate might imply sub-optimal conditions for P. cinnamomi infections allowing for a slower advance of the disease in invaded areas. However, this effect will be modulated by the also predicted more frequent extreme climatic events. A higher frequency of extreme rain events that saturate the soil might be particularly beneficial for P. cinnamomi, boosting its soil density beyond any possible response capacity of susceptible hosts.

Scots pine (Pinus sylvestris L.) mortality is explained by the climatic suitability of both host tree and bark beetle populations

Higher temperatures and extreme drought events are promoting insect-driven tree mortality. However, there is great uncertainty about the impact of extreme climatic variations on the susceptibility to infestation, as this depends on the suitability of climatic conditions to both host trees and insects. For instance, the consequences of infestation could be more intense in tree populations living closer to the limits of tree species’ climatic tolerance, where resource allocation to defenses could be compromised by other functions essential to tree survival. In this article, we explored 22 Scots pine populations (Pinus sylvestris L.) in the northeast of the Iberian Peninsula that experienced a tree mortality episode involving bark beetle infestation and drought. We hypothesized that the infestation and eventual tree mortality varied according to the climatic suitability of a particular location for the host tree and bark beetles. Climatic suitability values were estimated by using species distribution models (MaxEnt). Then, we developed generalized linear mixed-effects models and partial least squares-generalized linear models to study tree mortality and stand bark beetle infestation (proportion of dead trees presenting signs of a successful attack) in relation to: host and insect suitability, intensity of bark beetle attack, tree characteristics, and stand structure. Intensity of bark beetle attack and tree size were the main factors determining the probability of tree mortality. Smaller trees in particular exhibited a higher probability of dying at lower intensities of beetle attack. At stand-level, bark beetle infestation was negatively associated with tree density and basal area of Scots pine, and positively with tree species richness. Taken together, the response of Scots pine populations in relation to the tree characteristics and stand structure suggested low-density attack by bark beetles (i.e., not in eruptive phase) which affected weakened smaller trees. Remarkably, our results showed that Scots pine populations established in higher climatic suitability areas were vulnerable to infestation, particularly when such locations were also suitable for the bark beetle species. Therefore, previous drought events and differential resource allocation for growth and defenses among central and peripheral tree populations seem to regulate infestation patterns, as mediated by the climatic suitability for both hosts and insects. Our study demonstrates the importance of assessing species’ climatic suitability to better understand and anticipate tree mortality episodes driven by bark beetles, particularly under climate scenarios with increasingly frequent extreme climatic events.

Species-Specific Responses of Submerged Macrophytes to Simulated Extreme Precipitation: A Mesocosm Study

More frequent extreme climate events (e.g., extreme precipitation) are to be expected in the future, and such events may potentially have significant effects on freshwater ecosystems. In the present mesocosm study, the effects of simulated extreme precipitation on submerged macrophytes were evaluated for three different macrophyte community (MC) treatments (MC1, MC2 and MC3). MC1 consisted of only Vallisneria denseserrulata, while MC2 and MC3 included three and six species of various growth forms. Two treatments of extreme precipitation (EP) were simulated—an extreme treatment (E) simulating a sudden increase of water level from 75 cm to 150 cm within one day and a gradual treatment (G) simulating an increase to the same water level within 3 months, combined with two control treatments. Total macrophyte community biomass was resilient to the EP and MC treatments, while species-specific variations in responses, in terms of biomass, maximum height, and sexual reproduction, were found. For instance, E led to earlier flowering of Potamogeton lucens and production of more flowers, while it had adverse effects on the flowering of Ottelia alismoides. We conclude that freshwater ecosystems with high coverage of submerged macrophytes may be overall resilient to extreme precipitation under nutrient-limited conditions, especially communities with diverse growth forms.

Compound hot droughts over China: Identification, risk patterns and variations

The increasing concentration of atmospheric greenhouse gases results in not only the consistent tendency of rising temperature but also changes in intensity and frequency of extreme climatic events, and may thereby impact the structure and functioning of terrestrial ecosystems. Increasing concern on increasing global warming has triggered research on extreme climatic events across the globe. In China, existing studies generally focused on single climatic extreme events while the combinations of different climatic events (e.g., high temperatures and droughts) and relevant impacts are rarely studied. To provide a better understanding of compound hot and dry events, in this study we first examined spatial characteristics of the correlations between temperature and drought conditions in the warm season over four different periods (i.e., 1901–1950, 1951–2015, 1951–1980, and 1981–2015). Our results show the negative connection between temperature and droughts encompasses most of China, indicating that high temperatures and droughts are generally concurrent in these regions. We then present a joint dependence model to estimate the occurrence probability of compound hot droughts over the four different periods across the country. Our results demonstrate that likelihood patterns of compound hot droughts vary among different periods. During 1901–1950, the occurrence probability of the compound hot droughts in the eastern part of the country is generally higher than the western part while the likelihood increased significantly in 1951–2015 as compared to pre-1950s over much of western China. A comparison also presents a distinct change in risk patterns between the two sub-periods (1951–1980 and 1981–2015). Given the impact of temperature extremes and drought stress on vegetation and ecosystems, we further examined variations in the likelihood of compound hot droughts regarding different climate zones and terrestrial ecosystems over various periods. Our findings may provide additional insights regarding the climate extremes and risk evaluation over China in a warming world. The proposed framework to evaluate the compound drought and occurrence probability over different climate zones and terrestrial ecosystems could also offer a valuable reference to other regions worldwide.

More frequent extreme climate events stabilize reindeer population dynamics

Extreme climate events often cause population crashes but are difficult to account for in population-dynamic studies. Especially in long-lived animals, density dependence and demography may induce lagged impacts of perturbations on population growth. In Arctic ungulates, extreme rain-on-snow and ice-locked pastures have led to severe population crashes, indicating that increasingly frequent rain-on-snow events could destabilize populations. Here, using empirically parameterized, stochastic population models for High-Arctic wild reindeer, we show that more frequent rain-on-snow events actually reduce extinction risk and stabilize population dynamics due to interactions with age structure and density dependence. Extreme rain-on-snow events mainly suppress vital rates of vulnerable ages at high population densities, resulting in a crash and a new population state with resilient ages and reduced population sensitivity to subsequent icy winters. Thus, observed responses to single extreme events are poor predictors of population dynamics and persistence because internal density-dependent feedbacks act as a buffer against more frequent events.

Global warming impairs stock–recruitment dynamics of corals

Changes in disturbance regimes due to climate change are increasingly challenging the capacity of ecosystems to absorb recurrent shocks and reassemble afterwards, escalating the risk of widespread ecological collapse of current ecosystems and the emergence of novel assemblages1-3. In marine systems, the production of larvae and recruitment of functionally important species are fundamental processes for rebuilding depleted adult populations, maintaining resilience and avoiding regime shifts in the face of rising environmental pressures4,5. Here we document a regional-scale shift in stock-recruitment relationships of corals along the Great Barrier Reef-the world's largest coral reef system-following unprecedented back-to-back mass bleaching events caused by global warming. As a consequence of mass mortality of adult brood stock in 2016 and 2017 owing to heat stress6, the amount of larval recruitment declined in 2018 by 89% compared to historical levels. For the first time, brooding pocilloporids replaced spawning acroporids as the dominant taxon in the depleted recruitment pool. The collapse in stock-recruitment relationships indicates that the low resistance of adult brood stocks to repeated episodes of coral bleaching is inexorably tied to an impaired capacity for recovery, whichhighlights the multifaceted processes that underlie the global decline of coral reefs. The extent to which the Great Barrier Reef will be able to recover from the collapse in stock-recruitment relationships remains uncertain, given the projectedincreased frequency of extreme climate events over the next two decades7.

Study on Meteorological Service Policy for Agricultural Insurance in Hebei Province under the Background of Climate Change

Hebei Province is a region sensitive to global climate change. Under the background of climate change and frequent extreme climate events, existing agricultural production structure is facing enormous risk of climate disasters. In order to reduce the risk level of agricultural meteorological disasters, it is imperative to implement effective agro-insurance meteorological services. This paper analyses the facts of climate change, the trend and influence of extreme weather and climate events in recent years. Based on the simulation results of climate models under moderate and high emission scenarios, the distribution characteristics of mean annual and seasonal air temperature in Hebei Province in the first 50 years of the 21st century are given, and the main problems in the practice of agricultural insurance in Hebei Province are pointed out. This paper also puts forward some countermeasures and suggestions for optimizing the agricultural insurance policy and improving the meteorological service effect of agricultural insurance.

Drought-Induced Carbon and Water Use Efficiency Responses in Dryland Vegetation of Northern China.

Given the context of global warming and the increasing frequency of extreme climate events, concerns have been raised by scientists, government, and the public regarding drought occurrence and its impacts, particularly in arid and semi-arid regions. In this paper, the drought conditions for the forest and grassland areas in the northern region of China were identified based on 12 years of satellite-based Drought Severity Index (DSI) data. The impact of drought on dryland vegetation in terms of carbon use efficiency (CUE) and water use efficiency (WUE) were also investigated by exploring their correlations with DSI. Results indicated that 49.90% of forest and grassland experienced a dry trend over this period. The most severe drought occurred in 2001. In general, most forests in the study regions experienced near normal and wet conditions during the 12 year period. However, grasslands experienced a widespread drought after 2006. The forest CUE values showed a fluctuation increase from 2000 to 2011, whereas the grassland CUE remained steady over this period. In contrast, WUE increased in both forest and grassland areas due to the increasing net primary productivity (NPP) and descending evapotranspiration (ET). The CUE and WUE values of forest areas were more sensitive to droughts when compared to the values for grassland areas. The correlation analysis demonstrated that areas of DSI that showed significant correlations with CUE and WUE were 17.24 and 10.37% of the vegetated areas, respectively. Overall, the carbon and water use of dryland forests was more affected by drought than that of dryland grasslands.

Effect of In Situ short-term temperature increase on carbon metabolism and dissolved organic carbon (DOC) fluxes in a community dominated by the seagrass Cymodocea nodosa.

Seagrasses form one of the most productive and threatened ecosystems worldwide because of global change and anthropogenic pressures. The frequency of extreme climatic events, such as heat waves, are expected to increase and may drive even more adverse effects than gradual warming. This study explores for the first time the effects of a sudden and temporary increase of temperature in situ on carbon metabolism and dissolved organic carbon (DOC) fluxes in a community dominated by a seagrass (Cymodocea nodosa) during two contrasting seasons (winter and summer). Results showed a positive correlation between temperature and seagrass production between seasons, while the experimental sudden and temporary increase in water temperature did not produce significant differences in carbon community metabolism and DOC fluxes in winter. In contrast, high temperature conditions in summer enhanced significantly the net community production and affected positively to DOC fluxes. Hence, this study indicates that a sudden and temporary increase in water temperature, which characterize marine heat waves, in temperate areas may enhance the autotrophic metabolism of seagrass communities and can yield an increase in the DOC released, in contrast to previous researches suggesting solely negative effects on seagrasses.

Using otolith chronologies to understand long‐term trends and extrinsic drivers of growth in fisheries

AbstractIdentifying trends and drivers of fish growth in commercial species is important for ongoing sustainable management, but there is a critical shortage of long‐term datasets in marine systems. Using otolith (ear bone) sclerochronology and mixed‐effects modeling, we reconstructed nearly four decades (37 yr) of growth across four oceanographically diverse regions in an iconic fishery species, snapper (Chrysophrys auratus). Growth was then related to environmental factors (sea surface temperature, chlorophyll‐a, and Southern Oscillation Index) and population performance indicators (recruitment and commercial catch). Across the decades, growth rates declined in the two most productive fishery regions. Chlorophyll‐a (a measure of primary productivity) was the best predictor of growth for all regions, but direction and magnitude of the relationships varied, indicating regional‐specific differences in intra‐specific competition. Sea surface temperature was positively correlated with fish growth, but negatively correlated after temperature reached optimum thermal maxima, which suggests individuals in warmer regions may be under thermal stress. Growth also decreased at the extremes of the Southern Oscillation Index, indicating fish growth is impeded in significant climatic events. Contrasting relationships between growth, catch, and recruitment indicated regional‐specific density‐dependent effects, with growth positively correlated with population size in one region but negatively correlated in another. Our results indicate that under future ocean warming and increased frequency of extreme climate events, fish growth and fisheries productivity are likely to be affected. Furthermore, the interactive effects of extrinsic factors also indicated that stressors on fisheries should be managed collectively. We show that otolith chronologies are an effective method to assess long‐term trends and drivers of growth in fishery species. Such informed ecological predictions will help shape the sustainable management of fisheries under future changing climates.

Extreme climatic events down-regulate the grassland biomass response to elevated carbon dioxide

Terrestrial ecosystems are considered as carbon sinks that may mitigate the impacts of increased atmospheric CO2 concentration ([CO2]). However, it is not clear what their carbon sink capacity will be under extreme climatic conditions. In this study, we used long-term (1998–2013) data from a C3 grassland Free Air CO2 Enrichment (FACE) experiment in Germany to study the combined effects of elevated [CO2] and extreme climatic events (ECEs) on aboveground biomass production. CO2 fertilization effect (CFE), which represents the promoted plant photosynthesis and water use efficiency under higher [CO2], was quantiffied by calculating the relative differences in biomass between the plots with [CO2] enrichment and the plots with ambient [CO2]. Down-regulated CFEs were found when ECEs occurred during the growing season, and the CFE decreases were statistically significant with p well below 0.05 (t-test). Of all the observed ECEs, the strongest CFE decreases were associated with intensive and prolonged heat waves. These findings suggest that more frequent ECEs in the future are likely to restrict the mitigatory effects of C3 grassland ecosystems, leading to an accelerated warming trend. To reduce the uncertainties of future projections, the atmosphere-vegetation interactions, especially the ECEs effects, are emphasized and need to be better accounted.

Impact of extreme drought on tree-ring width and vessel anatomical features of Chukrasia tabularis

Multiple sources of evidence suggest an increasing frequency of extreme climatic events during the past century. In Bangladesh, a country strongly influenced by the South Asian monsoon climate, the years 1999 and 2006 were the most severe droughts among the ten drought events identified over the last four decades. We investigated the impact of these two drought events on radial growth and xylem anatomical features of the brevi-deciduous tree species Chukrasia tabularis in a moist tropical forest in Bangladesh. Tree radial growth declined by 54% during the 1999 and 48.7% during the 2006 droughts, respectively. Among the wood anatomical features, the number of vessels (NV) showed the highest sensitivity to drought, with a 45% decrease in the 1999 drought year, followed by total vessel area (TVA) and mean vessel area (MVA). On the other hand, Vessel density (VD) increased by 13% during the 1999 drought but the increase in VD was very low in the drought year 2006. The decreasing vessel area and increasing vessel density indicate xylem hydraulic adaptation of C. tabularis to minimize drought induced cavitation risk and to avoid hydraulic failure. The significant correlations between the Standardized Precipitation Evapotranspiration Index (SPEI) and time series of tree-ring width and vessel variables imply that decline in radial growth and changes in vessel features in C. tabularis are likely to be caused by drought induced water stress. Our analyses suggest that radial growth and wood anatomical features of C. tabularis are highly sensitive to extreme drought events in South Asian moist tropical forests and can be used to reconstruct past droughts and to model tree response to drought stress under future climate conditions.

Effects of snow pack reduction and drought on litter decomposition in subalpine grassland communities

In subalpine grasslands, litter decomposition controls soil nutrient availability and is highly sensitive to increasing intensity and frequency of extreme climate events, potentially impacting grasslands diversity and functioning. Here, we assessed the effects of early snowmelt and summer drought on decomposition, and how these were modulated by agricultural management. In a common garden, conservative and exploitative assembled communities were submitted for two years to combined snow removal and drought, and to cutting and fertilization. We measured decomposition rates of standard and native leaf material from each plant communities on their respective soils. We observed relatively weak climatic stress effects on decomposition rates. Management increased decomposition rates and remaining litter N contents through leaf quality improvement rather than changed soil biotic activity. Climate events impacted the decomposer community and limited litter N immobilization in conservative communities. Less recalcitrant litter of exploitative species facilitated decomposition and counterbalanced the negative effects of climate stress. Our results suggest that drought and earlier snowmelt could decrease N availability in subalpine grasslands due to reduced litter biomass and decomposition. In the long-term climate change may shift subalpine grasslands towards more conservative plant composition and lower soil fertility.

Assessment of Climate Change Impacts on Extreme Precipitation Events: Applications of CMIP5 Climate Projections Statistically Downscaled over South Korea

Climate change may accelerate the water cycle at a global scale, resulting in more frequent extreme climate events. This study analyzed changes in extreme precipitation events employing climate projections statistically downscaled at a station-space scale in South Korea. Among the CMIP5 climate projections, based on spatial resolution, this study selected 26 climate projections that provide daily precipitation under the representative concentration pathway (RCP) 4.5. The results show that a 20-year return period of precipitation event during a reference period (1980∼2005) corresponds to a 16.6 yr for 2011 to 2040, 14.1 yr for 2041 to 2070, and 12.8 yr for 2071 to 2100, indicating more frequent extreme maximum daily precipitation may occur in the future. In addition, we found that the probability density functions of the future periods are located out of the 10% confidence interval of the PDF for the reference period. The result indicates that the design standard under the reference climate is not managed to cope with climate change, and accordingly the revision of the design standard is required to improve sustainability in infrastructures.

High resilience to extreme climatic changes in the CAM epiphyte Tillandsia utriculata L. (Bromeliaceae)

Climate change is expected to increase the frequency of extreme climatic events, yet few studies have addressed the capacity of plant species to deal with such events. Species that are widespread are predicted to be highly plastic and able to acclimate to highly changing conditions. To study the plasticity in physiological responses of the widely distributed epiphyte Tillandsia utriculata, we transplanted individuals from a coastal scrub and broadleaf evergreen forest to a similar coastal scrub site and forest. After a 45-day acclimation, the plants were moved to a semi-controlled greenhouse at each site, and then subjected to a 20-day drought. Physiological variables were measured during the acclimation and the drought. The individuals of scrub and forest populations had similar relative water content and carbon assimilation in the contrasting conditions of the two transplantation sites despite the high discrepancy between the environments at their original site. Electron transport rates were higher in individuals from the scrub population. Electron transport rates were also higher than estimated from carbon assimilation, suggesting that photorespiration was present. The individuals of the coastal scrub population had a higher capacity to dissipate excess energy this way. The relative distance index of plasticity was high overall, indicating that some traits are highly plastic (titratable acidity, carbon assimilation) in order to maintain the stability of others (maximum quantum yield Fv /Fm and relative water content). We conclude that T. utriculata is a highly plastic species with a high capacity to tolerate extreme environmental changes over a short time.

Reflection of near-infrared light confers thermal protection in birds

Biologists have focused their attention on the optical functions of light reflected at ultraviolet and human-visible wavelengths. However, most radiant energy in sunlight occurs in ‘unseen’ near-infrared (NIR) wavelengths. The capacity to reflect solar radiation at NIR wavelengths may enable animals to control heat gain and remain within their critical thermal limits. Here, using a continent-wide phylogenetic analysis of Australian birds, we show that species occupying hot, arid environments reflect more radiant energy in NIR wavelengths than species in thermally benign environments, even when controlling for variation in visible colour. Biophysical models confirm that smaller species gain a greater advantage from high NIR reflectivity in hot, arid environments, reducing water loss from compensatory evaporative cooling by up to 2% body mass per hour. These results highlight the importance of NIR reflectivity for thermal protection, which may become increasingly critical as the frequency of extreme climatic events increases.

[Impacts of climate and land use change on water and sediment load in the Northwest arid region, China: With Xiaonanchuan River Basin as a case.]

Understanding regional water and sediment transport patterns and their responses to climate and land use changes can provide a theoretical basis for the prevention and control of soil erosion, and is an important prerequisite for the integrated development of land and water resources. Based on monthly monitoring meteorological, runoff, and sediment data from 1963 to 2013, combined with the land use data in the 1980s and 2000 and NDVI data, using the Mann-Kendall trend analysis and abrupt change test method, we systematically analyzed the long-term variations of the climate, runoff and sediment transport, with the changes of land use and vegetation coverage being identified in the Xiaonanchuan (XNC) River basin, a typical watershed in the Northwest arid region. Based on the analysis of single element change, the impacts of climate and land use change on water and sediment transport were quantified by the multiple linear regression analysis. Simultaneously, the key action factors were identified. Results showed that air temperature was developing to the polarization, the precipitation increased gradually. A generally warm and wet tendency of climate change and an increased frequency of extreme climate events were found in the XNC River basin. Moreover, the speed and magnitude of climate change were intensified after the 1990s, which was the abrupt change point of the climate. Since the 1980s, with economic and social development, the area of arable land and built land expanded, that of the forest area increased, and the ecological environments were improved in the XNC River basin. Under the dominant driving effects of land use and vegetation coverage change, the runoff and sediment load gradually reduced with the average rate of 1.7×106 m3·(10 a)-1 and 1.5×108 m3·(10 a)-1, respectively. Quantifying the influence of land use and climate change on the water and sediment transport indicated that vegetation cove-rage and mean daily maximum temperature were the two key factors affecting the runoff change, while the vegetation coverage and maximum daily precipitation were the two key factors affecting the sediment load change. Under the condition of current climate change, ecological restoration could be one of the most effective ways to prevent water and soil losses in the arid area.

Cutaneous Leishmaniasis outbreaks and management

‘Cutaneous Leishmaniasis’ (CL) term includes a broad range of clinical expressions, etiological agents of the genus Leishmania, and environmental and epidemiological scenarios, distributed mainly in the inter-tropical belt around the world. The outbreak events involve a couple of unexpected cases to more than 60,000 cases by year. There are ‘perfect waves’ or eco-epidemiological momenta of interwoven socio-economic, political and cultural, biological and physical causes, and also inter-linked consequences. However, we can figure out a typology of the outbreaks to think on the better strategies to control them, discriminating levels because in the large-long duration ones, climate change, economic trends or immune compromise by malnutrition, require actually structural changes. On the other hand, in space-time scales from foci up to individual exposure two mains processes could be discriminated: the human moving toward the primarily zoonotic cycle or the zoonotic cycle moving toward the humans. In the former case the contact could be: 1) Transient: soldiers, fleeing populations, illegal traffic, forest-related works as deforestation; 2) temporary: soldier, refugees and workers camps as gold miners settled on potential foci; 3) permanent: immigration of susceptible people, peripheral new neighborhoods (deforestation-peaks) or settlements in ‘low rent’ lands (unplanned urbanization-borders-new endemic areas). The zoonotic cycle toward human outbreaks, even if afterward the cycle become anthroponotic, are usually related to environment modification, vector-reservoir dispersion or exceptional population growth, and frequency of extreme climatic events. Many control measures were assayed for these scenarios as active surveillance, physical and chemical blocking or ‘barrier’ interventions, reservoir elimination directly or by food deprivation, although there are scarce rigorous impact evaluations. However, the better strategy to control outbreaks is to avoid them wherever possible, each past outbreak is a lesson to learn. Development, urbanization, military and law-enforcement projects should include CL epidemiological risk assessment with forecasting statistical modeling in time and space; the corporate and the state accountability should be explicitly stated and evaluated ‘a priori’ in terms of cost-community acceptable risk, and if the outbreak happens the system besides treatment, personal protection, and vector-reservoir control should also think in the psychological, social and economic consequences for individuals, families and collectives (refugees).

Early monsoon failure and mid-summer dryness induces growth cessation of lower range margin Picea crassifolia

The frequency of stem-growth cessation in Picea crassifolia has increased significantly as the frequency of extreme climate events has increased. Extreme climatic events are increasingly recognized as important drivers of tree growth, forest dynamics, and range contractions. Understanding tree growth responses to extreme events is important for forest conservation and management, especially under climate change. Here, we studied the patterns of growth cessation of Picea crassifolia Kom., an endemic species to Central Asia, across its distributional range in the Helan Mountains of Northwestern China, to test the hypotheses that (1) tree growth and growth cessations are limited by moisture availability, and (2) that this relationship is constant over the diverse set of conditions covered in our elevational gradient. While tree growth across our gradient was significantly limited by low precipitation in June, we found growth cessation events at the lower distributional margin to increase in severity and frequency in recent decades. We found that the combination of low precipitation early in the monsoon season (June) and high mid-summer (July) vapor pressure deficit likely caused the increased frequency of growth cessation events. Because these populations are already experiencing a high frequency of growth cessation events, the mortality rate of the lower distributional margin trees could further increase if the current trends of decreasing moisture and increasing heat stress continue into the future. Our results strongly suggest that growth cessation events are more than the dendrochronological curiosity they are usually considered to be, and can be important indicators of increased tree growth stress and be potentially useful in identifying tipping points prior to forest change.