Warm winters challenge the cultivation of temperate species in South America—a spatial analysis of chill accumulation

Winter chill accumulation plays a crucial role in determining the moment of bud burst in temperate fruit and nut trees, and insufficient chill can greatly limit yield potentials. To assess future cultivation options for such species in South America, we estimated winter chill through a spatial analysis. We used historical data (1980–2017) from 158 weather stations to calibrate a weather generator and produce temperature data for 10 historical and 60 future scenarios. We computed Safe Winter Chill (SWC, corresponding to the 10th quantile of a chill distribution) for the period 1980–2017 and for all historical and future weather scenarios and developed a framework to interpolate SWC for the continent using the Kriging method. To improve the interpolation, we applied a 3D correction model based on two co-variables (means of daily temperature extremes in July). Our results suggest important chill declines in southern Brazil and central Chile. By 2050 under the global warming scenario RCP4.5 (Representative Concentration Pathway), absolute SWC in these regions may reach a median of 18.7 and 39.6 Chill Portions (CP), respectively. Projections are most alarming for a strong global warming scenario (RCP8.5). In southern South America, adequate SWC levels of about 60 CP may be expected even under the RCP8.5 scenario. Our results highlight the need for climate change adaptation measures to secure temperate fruit production in important growing regions of South America. The procedure we developed may help farmers and practitioners across South America estimate future SWC to adapt their orchards to future challenges.

Changes in the microbial community structure triggered by permafrost peat thawing

An increase in permafrost temperature, accompanied by the melting and release of buried organic carbon, is one of the elements of the global warming scenario. To understand the way ecosystems respond to environmental changes, it is necessary to elucidate the factors affecting the distribution and activity of microbes in permafrost soils, which have been poorly studied so far. Meanwhile, they can have significant implications for nutrient cycling and related processes. Our research is devoted to assessing changes in the structure of the microbial community due to the melting of the palsa permafrost layer caused by the fire in 2007. The ecological-trophic groups of microorganisms of the territories changed under the influence of a natural fire in comparison with undisturbed analogs have been studied. It was revealed that the number of microorganisms in most groups on the palsa, affected by fire, is statistically significantly higher than the number of microorganisms in the undisturbed area.

Higher temperatures reduce the number of Trypanosoma cruzi parasites in the vector Triatoma pallidipennis

Background Relatively little is known about how pathogens transmitted by vector insects are affected by changing temperatures analogous to those occurring in the present global warming scenario. One expectation is that, like their ectothermic vectors, an increase in temperature could reduce their fitness. Here, we have investigated the effect of high temperatures on the abundance of Trypanosoma cruzi parasites during infection in the vector Triatoma pallidipennis. Methods We exposed T. pallidipennis nymphs to two strains (Morelos and Chilpancingo) of T. cruzi. Once infected, the fifth-instar bugs were distributed among three different temperature groups, i.e. 20, 30, and 34 °C, and the resulting parasites were counted when the bugs reached adulthood. Results The number of parasites increased linearly with time at 20 °C and, to a lesser extent, at 30 °C, especially in the Chilpancingo compared to the Morelos strain. Conversely, at 34 °C, the number of parasites of both strains decreased significantly compared to the other two temperatures. Conclusions These results suggest negative effects on the abundance of T. cruzi in T. pallidipennis at high temperatures. This is the first evidence of the effect of high temperatures on a pathogenic agent transmitted by an insect vector in the context of global warming. Further tests should be done to determine whether this pattern occurs with other triatomine species and T. cruzi strains. Graphical abstract

Response of the Indian summer monsoon to global warming, solar geoengineering and its termination

The response of the Indian Summer Monsoon (ISM) to global warming, solar geoengineering and its termination is examined using the multi-model mean of seven global climate model simulations from G2 experiment of the Geoengineering Model Intercomparison Project. Under the global warming scenario, land–ocean temperature contrasts and low-level monsoon circulation progressively strengthen accompanied by enhanced precipitation over the Indian subcontinent. Notably, in the solar geoengineered scenario, marginal surface cooling is projected over the majority of the ISM region, and there is strengthening of both upper and lower level circulation. However, preferential precipitation near Western Ghats leads to dry bias over majority of Indian land. Upon the termination of the geoengineering, the climatic conditions—temperature, precipitation, winds and moisture would abruptly change to what it would have been under the global warming scenario. Thus, this may be important to note that such changes may need attention for the future mitigation and adaptation purposes if solar geoengineering is required to implement in future.

Major ion composition and 87Sr/86Sr of groundwater in the coastal Gujarat alluvial plain, India

<p>Major ions, Sr concentration, and <sup>87</sup>Sr/<sup>86</sup>Sr have been analyzed in groundwater of the coastal Gujarat Alluvial Plain, collected during monsoon, post-monsoon, and pre-monsoon seasons of 2016–2017. The major objective of this study was to understand the regional groundwater salinization mechanism. In the study area, the groundwater is mostly characterized by Na-Cl facies, with few samples of Ca-Cl, Ca-Mg-Cl, Na-Ca-HCO<sub>3</sub>, and Ca-Mg-HCO<sub>3</sub> types. Whereas, the Narmada and the Tapi river water samples are particularly of Ca-Mg-HCO<sub>3</sub> type. The hydrogeochemical facies evolution (HFE) diagram depicts the coastal groundwater freshening irrespective of the season ruling out the lateral seawater intrusion far inland. However, the <sup>87</sup>Sr/<sup>86</sup>Sr and Br/Cl ratios strongly suggest the modern marine influence on the regional groundwater. In the plot of 1/Sr versus <sup>87</sup>Sr/<sup>86</sup>Sr, most of the groundwater samples fall on the binary mixing line between the seepage groundwater and modern seawater endmembers. Therefore, we suspect that the up-coning of recently trapped seawater by groundwater over-extraction is the most plausible reason for the groundwater salinization, which indicate the vulnerability of the coastal Gujarat alluvial plain to the near future sea ingress under the global warming scenario. A few exceptional groundwater samples far north of the Narmada River show more radiogenic <sup>87</sup>Sr/<sup>86</sup>Sr indicative of silicate weathering.</p>

No evidence for short-term evolutionary response to a warming environment in Drosophila

Adaptive evolution is key in mediating responses to climate change. Such evolution will expectedly lead to changes in the populations’ thermal reaction norm and improve their ability to cope with stressful conditions. Conversely, constraints of different nature might limit the adaptive response. Here, we test these expectations by performing a real-time evolution experiment in historically differentiated Drosophila subobscura populations. We address the phenotypic changes of flies evolving for nine generations in a daily fluctuating environment with average constant temperature, or a warming environment with increasing average and amplitude temperature across generations. Our results showed that (1) evolution under a global warming scenario has not led, so far, to a noticeable change in the thermal response; (2) historical background appears to be affecting the responses of populations under the warming environment, particularly at higher temperatures; (3) thermal reaction norms are trait-dependent: while lifelong exposure to low temperature decreases fecundity and productivity but not viability, high temperature causes negative transgenerational effects on productivity and viability, even though fecundity remains high. These findings raise concerns about the short-term efficiency of adaptive responses to the current changing climate.