Potential Effects Of Climate Change Research Articles

Permafrost evolution in a mountain catchment near Santiago de Chile

The Chilean Central Andes near Santiago are a semi-arid region with substantial frozen water reserves in their high altitude cryosphere. Millions of people depend on the Andean cryosphere for freshwater supply. Over the last sixty years, global warming has altered the mountains’ water balance, as the temperature rose, precipitation decreased, and deglacierization exposed hundreds of square kilometers. The distribution of solid water stored in soil permafrost and the potential effects of climate change on it are unknown.Here, we map favorable spots for permafrost occurrence at the “Monos de Agua” catchment, Aconcagua basin at 33°S, between 3600 and 5100 m a.s.l.. We identify these “cold spots” based on ground surface temperature and incoming solar radiation between 2017 and 2019. We suggest that these locations currently present permafrost and frozen water might actually be there. We confirmed a body of frozen water at one of these cold spots using an electrical resistivity survey.Our mapping suggests that at least 15 ± 7% of the catchment's surface is underlain by permafrost. Permafrost occurrence begins around 3600 m a.s.l. with low probability and only at locations with favorable conditions of low exposure and isolation. Permafrost occurrence probability increases with altitude, with the largest fraction present above 4200 m a.s.l.Our results suggest that the permafrost area in this region will decrease between 13 and 87% by the end of the century under the future global warming RCP scenarios. This event represents new challenges for the hydrological memory and water security planning in the Chilean Central Andes.

Modelling the potential effects of climate change in the distribution of Xylotrechus arvicola in Spain

Xylotrechus arvicola is an emerging grape pest that generates serious sanitary problems in vineyards and is currently expanding its range throughout Spain. The increasing prevalence of this pest in Spanish vineyards has been detected since 1990. In this study, the relationship between the climate and the actual distribution of the beetle was analysed, as well as how this distribution might change in the future according to several climate change models. The methodology was based on predictive models (SDM; species distribution modelling) using climate variables as explanatory factors, although the relationships were not necessarily causal. Maxent was used as the SDM method. The current climatic niche was calculated, and the actual potential distribution area was estimated. The relationships between the climate variables and the species probability of the presence were projected to various future climate change scenarios. The main conclusions reached were that climate change will favour the expansion of X. arvicola and that the potential infestation zones will be extended significantly. Although the results, because they were based on hypothetical climate frameworks that are under constant revision, were not conclusive, they should be taken into consideration when defining future strategies in the wine industry.

Precipitation declines influence the understory patterns in Nothofagus pumilio old-growth forests in northwestern Patagonia

Forest understories are essential to plant diversity and ecosystem functioning. However, studies about changes in understory patterns as affected by varying precipitation are scarce. Pure Nothofagus pumilio (common name: lenga) forests dominate the eastern side of the Andes mountains in Patagonia across an ample range of precipitation (~1500–500 mm). By studying the same forest type, in the same developmental stage (old-growth), we aimed to isolate the effects of precipitation upon these N. pumilio ecosystems, particularly for the understory. Three sites were selected with annual average precipitations of ~1000 mm (humid), ~800 mm (mesic), and 600 mm (dry), with a distance of 30 km between the humid and the dry sites, and only 18 km between the mesic and the dry sites. In each site, we established three 40 × 40 m plots in 4 blocks, and 30 1 m2 regeneration subplots within each plot. In each subplot we measured vascular plant cover, richness and diversity (alpha and beta), litter cover and coarse woody debris, plus several abiotic variables. We analyzed the data with mixed analysis of variance, differences of understory plant communities through blocked distance-based multivariate analysis of variance, and visualized the groups (sites) with non-metric multidimensional scaling. Indicator species at each site were identified through blocked species indicator analysis. The dry site differed significantly compared to the humid and mesic sites, with the lowest understory cover (4 vs. 82–78%), plant richness (15 vs. 25–26 species), and Simpson diversity index (0.05 vs. 0.66–0.64) . Beta turnover diversity was higher between the dry site with either the humid and the mesic sites (βt = 0.613 and 0.561, respectively), which in turn had more species in common (βt = 0.115). An increase in exposed mineral soil, soil water content, and leaf area index occurred from dry to humid sites, and vice versa for transmitted radiation and litter cover. All sites had different indicator species, but with indicator values increasing from dry to humid sites. The dramatic impoverishment of the plant community once precipitation drops within the range of 800 and 600 mm per year in Northern Patagonia sets a warning to the potential effects of climate change upon N. pumilio-dominated forest ecosystems and their plant diversity. Some forest management and potential adaptation strategies are proposed.

Climate change and the distribution of two Ficus spp. in Bangladesh – predicting the spatial shifts

Climate change acts as a major cause of species extinction by impacting the distribution and abundance of species. The impact of global climate change on ecosystems, especially at the species level, is already being observed across the world. Species distribution models can help to assess the potential effects of climate change on the spatial redistribution of species under different climate scenarios which is crucial for the management of habitat for endangered and critically endangered flora and fauna. Considering this, the present study aimed to predict the effect of climate change on two ecologically important species viz. Ficus benghalensis and Ficus hispida in Chattogram, Cox's Bazar and Bandarban Districts of Bangladesh using Maximum Entropy platform. Under the RCP2.6 and RCP8.5 scenario, the model predicted the future suitable habitat by 2050 and 2070. The study predicted insignificant changes in terms of suitable habitat for the selected species under climate change scenarios indicating higher climate resilience of both Ficus benghalensis and Ficus hispida. The findings of the study may contribute to the policymaking regarding wildlife conservation and forest management as both these species are crucial for a range of fauna.

Impacts of climate change and increasing carbon dioxide levels on yield changes of major crops in suitable planting areas in China by the 2050s

Maize, rice, and wheat are the major staple food crops in China and are crucial components of national food security and economic development. The cultivation and production of these crops are expected to be affected by climate change and elevated atmospheric carbon dioxide (CO2) concentration, and have drawn considerable public attention. The objective of this experiment was to understand the impact of future climate change (including increased temperature and changed precipitation patterns) and elevated CO2 concentration on variations of crop yields in their suitable planting areas. We conducted a spatial grid-based analysis of maize, rice, and wheat yields using projections of future climate generated by a multi-model ensemble of global climate models for three representative concentration pathway scenarios (RCP2.6, RCP4.5, and RCP8.5) in suitable planting areas in China for the 2030s (2021–2040) and the 2050s (2041–2060). Suitable areas for the planting of maize, rice, and wheat under the high-emission scenarios migrated slightly northward over time. Yield of all three crops would be expected to remain stable or to slightly increase across China in the future. A possible reason for this result may be because the positive effects of increased precipitation and CO2 offset the negative effect of increased temperature on crop yields, resulting in a much more appropriate growth environment and increased biomass accumulation and crop yield. In addition, this study also indicated that changes in crop yields were mainly driven by temperature and CO2 factors. The potential effects of climate change and elevated CO2 concentration on migration of planting areas and yield fluctuations for crops should be given greater attention in the future.

Design process in the urban context - Mobility and health in Special Flood Hazard Area

Resume In developing countries, unplanned urban growth, lack of infrastructure services, pollution, diseases, and flooding generate urgent needs. Floods cause diseases and damage to countries at all levels of development because they usually lack the preparedness for current climate variability. In Brazil, Municipal Civil Defense (JMCD) – in a 600,000 inhabitants city-, together with other city agencies, established a safe route (SRP) to be implemented during flood occurrences. This map is available for download as a PDF. This work aims to present the developed methodology, tools, and ways to design, in a collaborative way, a conceptual, innovative system model capable of bringing together needs like resilience, safety and sustainability, contributing to urban resilience, mobility, risks communication and health. Different design processes: design thinking, wayfinding system, signage, norms, and laws were used to create a dynamic conceptual design in the urban development. As a result, visual identity, pictograms icons, totems and luminous panels are presented. Luminous system is projected to be linked to rivers height (measured in hydrological gauging stations) to guide users to safe routes. The information technology which can link water height in rivers, to the different levels of flood in the designed system is not among the objectives of this study. Developing strategies to face the potential effects of climate change in the transportation sector poses a major significant challenge. Proper tools are required to prepare to change and provide meaningful environmental, health, social, and security solutions with the quickness the modern cities demand.

Historical, current, and future climate niche of the red dwarf honey bee across its native range

Knowledge of spatial patterns of climatically suitable habitats, and species range contractions/expansions, or shifts due to changing climate are important to improve the effectiveness of conservation efforts. Ecological niche models (ENMs) are the primary tools currently available for evaluating species’ response to anthropogenic or natural changes. We used ENMs to evaluate potential effects of future climate changes on the distribution range of a keystone pollinator, Apis florea Fabricius 1787 (Apidae: Apini), across its native range. We also provided a picture of the potential paleodistribution range of this species to complement future genetic/phylogenetic studies. In all assessed scenarios (i.e past, current, and future), the species was limited to its current native range and the mean temperature of the coldest season was the most key determinative factor affecting the species’ climate niche. The projection results revealed that the extent of climatically suitable habitats of the species was probably more than current in the past time periods and will increase in the future. Our findings of the consequences of climate changes on geographical distributions of this pollinator facilitate future management efforts for the species conservation by the identification of potential habitats where A. florea may already exist, prioritizing key habitats within the species’ native range under the current and future conditions, and recognizing regions where it is likely to spread its range.

Climate Change Effects on Aquaculture Production: Sustainability Implications, Mitigation, and Adaptations

Aquaculture continues to significantly expand its production, making it the fastest-growing food production sector globally. However, the sustainability of the sector is at stake due to the predicted effects of climate change that are not only a future but also a present reality. In this paper, we review the potential effects of climate change on aquaculture production and its implications on the sector's sustainability. Various elements of a changing climate, such as rising temperatures, sea-level rise, diseases and harmful algal blooms, changes in rainfall patterns, the uncertainty of external inputs supplies, changes in sea surface salinity, and severe climatic events have been discussed. Furthermore, several adaptation options have been presented as well as some gaps in existing knowledge that require further investigations. Overall, climate change effects and implications on aquaculture production sustainability are expected to be both negative and positive although, the negative effects outweigh the positive ones. Adapting to the predicted changes in the short-term while taking mitigation measures in the long-term could be the only way toward sustaining the sector's production. However, successful adaptation will depend on the adaptive capacity of the producers in different regions of the world.

Effects of the Climate Change on Peripheral Populations of Hydrophytes: A Sensitivity Analysis for European Plant Species Based on Climate Preferences

Biogeographical theory suggests that widespread retractions of species’ rear edges are expected due to anthropogenic climate change, affecting in a particularly intense way those linked to fragile habitats, such as species’ rear edges closely dependent on specific water conditions. In this way, this paper studies the potential effects of anthropogenic climate change on distribution patterns of threatened rear edge populations of five European hydrophyte plants distributed in the Iberian Peninsula. We explored (i) whether these populations occur at the limit of the species’ climatic tolerance, (ii) we quantified their geographic patterns of vulnerability to climate change, and in addition, (iii) we identified in a spatially explicit way whether these threatened populations occur in vulnerable environments to climate change. To do this, we simulated the climatic niche of five hydrophyte species using an ecological modelling approach based on occurrences and a set of readily available climatic data. Our results show that the Iberian populations studied tended to occur in less suitable environments relative to each of the species’ optimal climates. This result suggests a plausible explanation for the current degree of stagnancy or regression experienced by these populations which showed high sensitivity and thus vulnerability to thermal extremes and high seasonality of wet and temperature. Climatic predictions for 2050 displayed that most of the examined populations will tend to occur in situations of environmental risk in the Iberian Peninsula. This result suggests that the actions aimed at the conservation of these populations should be prioritized in the geographic locations in which vulnerability is greatest.

Low Densities of the Ghost Crab Ocypode quadrata Related to Large Scale Human Modification of Sandy Shores

Sandy beaches are the most common ecosystems of coastal regions and provide direct and indirect essential services for millions of people, such as coastal protection, fishing, tourism, and recreational activities. However, the natural habitats of sandy shores are being modified at rates never experienced before, making beaches key monitoring sites of marine ecosystems worldwide. The ghost crab species Ocypode quadrata is the most conspicuous crustacean of sandy beaches along the Western Atlantic coast and has been successfully used as an indicator of anthropogenic disturbance and environmental variability. To investigate the potential role of a “triple whammy” [(1) urbanization; (2) use of resources; (3) decreasing resilience] on the most common bioindicator of sandy shores, we compiled a dataset including 214 records of burrows density from 94 microtidal sandy beach sectors covering a range of over 65° of latitude. The response of burrows density to synergetic effects of human modification of natural systems and environmental changes was investigated using linear models. We used the cumulative Human Modification (HMc) index, a standardized geographic projection of changes of natural systems, as a predictor of urbanization, industrialization and use of resources. The predictor wave energy, tidal range and temperature (sea surface and air) were included as potential effects of climate changes. Literature review showed records mainly concentrated at sub-tropical and temperate regions. HMc values were clearly negatively related to burrows density, thereby supporting an effect of modification of natural habitat at large spatial scale. Sea surface temperature and air temperature were positive related with density and the lack of a general pattern of the relationship between burrows density, interactions between wave energy and tide range, supported unclear patterns reported at regional scales. Finally, we argue that ghost crabs are valuable targets for protection actions on sandy beaches that can benefit coexisting species and provide natural habitat conservation.

Changes in haemolymph parameters and insect ability to respond to immune challenge during overwintering.

Overwintering is a challenging period in the life of temperate insects. A limited energy budget characteristic of this period can result in reduced investment in immune system. Here, we investigated selected physiological and immunological parameters in laboratory‐reared and field‐collected harlequin ladybirds (Harmonia axyridis). For laboratory‐reared beetles, we focused on the effects of winter temperature regime (cold, average, or warm winter) on total haemocyte concentration aiming to investigate potential effects of ongoing climate change on immune system in overwintering insects. We recorded strong reduction in haemocyte concentration during winter; however, there were only limited effects of winter temperature regime on changes in haemocyte concentration in the course of overwintering. For field‐collected beetles, we measured additional parameters, specifically: total protein concentration, antimicrobial activity against Escherichia coli, and haemocyte concentration before and after overwintering. The field experiment did not investigate effects of winter temperature, but focused on changes in inducibility of insect immune system during overwintering, that is, measured parameters were compared between naïve beetles and those challenged by Escherichia coli. Haemocyte concentration decreased during overwintering, but only in individuals challenged by Escherichia coli. Prior to overwintering, the challenged beetles had a significantly higher haemocyte concentration compared to naïve beetles, whereas no difference was observed after overwintering. A similar pattern was observed also for antimicrobial activity against Escherichia coli as challenged beetles outperformed naïve beetles before overwintering, but not after winter. In both sexes, total protein concentration increased in the course of overwintering, but females had a significantly higher total protein concentration in their hemolymph compared to males. In general, our results revealed that insect’s ability to respond to an immune challenge is significantly reduced in the course of overwintering.

Southern coastal subtropical shallow lakes skin temperature driven by climatic and non-climatic factors.

Subtropical coastal shallow lakes (SCSL) are sensitive ecosystems. The lake-skin-water temperature (LSWT) is an average lake temperature proxy and responds to changes in surroundings, affecting biological and physical lake processes. In this study, M*D11A1 products are used to develop daytime and nighttime LSWT time series for 20 SCSL in South America. The influence of climatic (air temperature, surface net solar radiation, wind speed, and wind direction) and non-climatic (latitude, lake area, perimeter, width, length, and morphology) factors are evaluated from 2001 to 2017. Pearson's coefficients (ρ) and auto- and cross-correlations are used to establish the relation between LWST and the selected factors. We identify that the dynamic of LSWT is sensitive to geomorphological factors (latitude and lake width) throughout the year, especially in summer. In winter, the LSTW regime is mainly affected by wind direction (ρ = -0.66, p value < 0.01). Linear models are fitted to the temperature series to check the trend changes in the inflection points and the warming or cooling trend for LSWT. Considering the complete series, the maximum warming rate of LSWT is 0.25 °C per decade (°C/dec). The analysis of the identified sub-periods reveals that warming and cooling can occur (significantly) in shorter periods. The average trends within sub-periods for skin temperature-daytime (± 0.0105 °C/dec), skin temperature-nighttime (0.0041 °C/dec), and air temperature (- s0.006 °C/dec; 0.007 °C/dec) are estimated. Our approach has the potential to be applied in future studies due to the expansion of knowledge about the behavior of SCSL and the understanding of the current and potential effects of climate change in association with physical and geomorphological traits.

Lake Ecosystem Robustness and Resilience Inferred from a Climate-Stressed Protistan Plankton Network.

Network analyses of biological communities allow for identifying potential consequences of climate change on the resilience of ecosystems and their robustness to resist stressors. Using DNA metabarcoding datasets from a three-year-sampling (73 samples), we constructed the protistan plankton co-occurrence network of Lake Zurich, a model lake ecosystem subjected to climate change. Despite several documentations of dramatic lake warming in Lake Zurich, our study provides an unprecedented perspective by linking changes in biotic association patterns to climate stress. Water temperature belonged to the strongest environmental parameters splitting the data into two distinct seasonal networks (October–April; May–September). The expected ecological niche of phytoplankton, weakened through nutrient depletion because of permanent thermal stratification and through parasitic fungi, was occupied by the cyanobacterium Planktothrix rubescens and mixotrophic nanoflagellates. Instead of phytoplankton, bacteria and nanoflagellates were the main prey organisms associated with key predators (ciliates), which contrasts traditional views of biological associations in lake plankton. In a species extinction scenario, the warm season network emerged as more vulnerable than the cold season network, indicating a time-lagged effect of warmer winter temperatures on the communities. We conclude that climate stressors compromise lake ecosystem robustness and resilience through species replacement, richness differences, and succession as indicated by key network properties.

The role of disturbance in invasive plant establishment in a changing climate: insights from a drought experiment

Climate change and disturbance are two major factors affecting the establishment of invasive species, yet few studies to date have assessed the individual and interactive effects of these two factors in a common setting. Disturbance has often been found to facilitate the establishment of invading species, while climate change may affect them positively or negatively through altering abiotic conditions, or indirectly by modifying species interactions. In a full-factorial field experiment in a semiarid temperate grassland in Central Hungary, we studied the effects of drought (40% rain exclusion throughout the year) and soil disturbance on the emergence, survival and aboveground biomass of four invasive plant species that represent different life forms and that are of concern in the region and at a broader scale. We added seeds of Ambrosia artemisiifolia (annual forb), Cenchrus incertus (annual grass), Asclepias syriaca (perennial forb) and Ailanthus altissima (deciduous tree) in drought and non-drought plots with and without soil disturbance. Ailanthus germinated poorly irrespective of treatments. Disturbance facilitated while drought suppressed seedling emergence in the other three species. Ambrosia was more sensitive to disturbance, while Cenchrus was more responsive to drought. Asclepias achieved substantial emergence in disturbed non-drought plots only, as drought strongly suppressed its emergence even in the presence of disturbance. Seedling survival and late-season aboveground biomass of Ambrosia and Cenchrus were positively affected by disturbance but were unaffected by drought, while no Asclepias seedling survived until late summer. Our results highlight that both drought and disturbance may considerably impact the establishment of invasive plants, with potential interactive effects, but responses may greatly differ among species and life stages. Overall, our findings in this study suggest that although drought may negatively affect seedling establishment, a drier climate may not suppress or eliminate invasive species if soil disturbance is present. They also highlight the importance of including disturbance in studies assessing the potential effects of climate change on plant invasions.

Benchmarking Data-Driven Rainfall-Runoff Models in Great Britain: A comparison of LSTM-based models with four lumped conceptual models

Long short-term memory models (LSTMs) are recurrent neural networks from the emerging field of Deep Learning (DL), which have shown recent promise when predicting time-series especially when data are abundant. Rainfall-runoff modelling presents a challenge, yet accurate hydrological models are vital for flood forecasting, hazard impact assessment, and to assess the potential effects of climate change on floods and water resources. In this study, we compare the performance of two DL-based models, a LSTM and an Entity Aware LSTM (EA LSTM). The DL models were trained using a newly published data set, CAMELS-GB, for a sample of 518 catchments across Great Britain. To identify spatial and seasonal patterns in model performance, we compare the DL models against benchmark outputs from four lumped conceptual models recently configured for rainfall-runoff modelling in Great Britain. Our findings show that the LSTM models simulate discharge with consistently high model performance scores, including in catchments typically considered difficult to model. The LSTM achieves a mean catchment NSE of 0.88 (0.86 for the EALSTM), which represents a performance improvement of 10 %–16 % compared with the benchmark conceptual models. Seasonal and spatial patterns indicate that the largest performance improvement relative to the benchmark is in the drier summer months and in drier catchments in the South East of England. By comparing LSTMs with conceptual models, we diagnose possible reasons for their different performance. We suggest that LSTMs offer useful predictive capability for rainfall-runoff modelling in Great Britain and elsewhere and note their value to support process understanding in locations where processes are less well understood.

Estimating the potential effects of climate change on GDP in the agriculture sector by countries in the ASEAN region

This study estimates the potential effects of climate change on GDP in the agriculture sector in the ASEAN region based on historic data from 1995-2018. An econometric panel model is applied to examine the impact of the changing climatic and non-climate variables AGDP. The empirical estimation results show that some significant and insignificant. Based on estimation results, if the policymaker is concerned about climate change actions, it helps more comprehensive risk decision-making, and policy exertions should be concentrated toward climate change to the total gross domestic product in the ASEAN region. Under projections of the future climate change, the simulation results reveal that the substantial change in GDP in agriculture in the ASEAN region arises due to the fluctuation of temperature and precipitation. For instance, GDP in the agriculture sector would be decreased by 0.27% to 0.90% in response to different scenarios over the century. Therefore, it is necessary to take immediate adaptive actions appropriately to mitigate the decrease in GDP in the agriculture sector in the ASEAN region.

Ensembpecies distribution modeling of Salvia hydrangea under future climate change scenarios in Central Zagros Mountains, Iran

Medicinal and aromatic plants, such as Salvia hydrangea DC. Ex Benth., have been highly popular all over the world throughout the time. Future climate change is believed to be one of the great threats to the range and resilience of these species. Therefore, recognizing the extensive spatial distribution and potential effects of global climate change on S. hydrangea in its major habitats (Chaharmahal Va Bakhtiari province: CVBP, Central Zagros Mountains: CZMs, Iran) is of considerable importance. We recorded the data concerning occurrence points data using the global positioning system (GPS). We also collected bioclimatic and topographic variables from the WorldClim-global climate dataset to model the current and future (under RCP4.5 and RCP8.5 within two global circulation models HadGEM2-CC and MRI-CGCM3 for 2050 and 2070) habitat suitability for S. hydrangea employing an ensemble species distribution modeling (ESDM) on BIOMOD2 package. The visualization of an ensemble forecasting model of the true skill statistic (TSS) > 0.8 models revealed that the majority of suitable habitats for this species were situated in the east and southeast of this province. Generally, precipitation of coldest season, temperature annual range, and elevation variables were of great importance for our study model. Comparing the current and future habitat suitability distribution of S. hydrangea, it could be concluded that the plant distribution is migrating between different latitudes and altitudes. The results suggested that the scenarios of MIRI-CGCM3 probably create serious effects and implications on the future distribution of S. hydrangea habitats. The loss of habitat of this species in the southeast of this province was considerably more visible, indicating a significant diminution in the distribution area. However, the potential distribution of S. hydrangea in this province would face alarming conditions between 2050 and 2070. Consequently, S. hydrangea could be particularly in need of conservation plans, which is urgently needed in order to reduce climate change-associated impacts.

How climate change is affecting the transitional natural zones of the Northern and Arctic regions of Russia

Continued global warming and the increase in climate extremes have mostly been identified in Northern and Arctic areas of Russia. Investigation of natural and climatic conditions in these regions was conducted using the method of zoning that is based on the environmental conditions of human life. This method estimates the relatively slowly changing landscape component and the rapidly changing climate component of the discomfort. Transitional natural zones represent an open system for the impact of climatic changes. A positive trend in the number of active temperatures and a negative precipitation trend was observed in these regions. At present, the climate conditions of some areas in the tundra, forest-tundra, and northern taiga correspond to the more southerly landscape zones. This situation is conducive to changes in the landscape vegetation and could lead to a shift in the transitional landscape zone borders towards higher latitudes. The relevancy of the study results is that they help to establish the potential consequences of climate change for landscape structures, as well as for the environment and the population of the Northern and Arctic areas. They can be used for developing the regulatory documents that govern the population's life in the Northern and Arctic areas.

Multi-century tree-ring anatomical evidence reveals increasing frequency and magnitude of spring discharge and floods in eastern boreal Canada

Abstract In eastern boreal Canada, variability in river discharge is poorly understood at the multi-century scale due to short instrumental records. In recent decades, increased magnitude and frequency of spring floods have raised concerns about the potential effects of climate change on flood risk. Unlike tree-ring width, flood rings have a demonstrated dendrochronological utility for reconstructing high discharge in boreal environments. In this study, twelve chronologies of earlywood vessel cross-sectional area (a new hydrological proxy) and ring width were developed from riparian Fraxinus nigra trees periodically flooded in spring. These chronologies were used as predictors of Harricana River spring discharge, which was reconstructed for the period 1771–2016. The reconstruction captured 69% of the variance over a 102-year calibration period. The reconstruction indicates that the magnitude and frequency of spring high discharge has increased since the end of the Little Ice Age (1850–1870 CE) and since 1950. The change from a multi-decadal frequency in the late 19th century to a decadal and then interannual frequency in the late 20th century is associated with an increase in snow cover over much of central-eastern Canada. The association between the reconstructed spring discharge and spring atmospheric circulation indices NINO3.4, AMO, NAO may also have changed in these periods and further work is needed to assess the stability of these associations. The correlation between reconstructed and instrumental spring discharge at the regional scale, as well as the shared features in reconstructed discharge and other paleorecords from subarctic Quebec suggest a common hydrological signal across the study area and for the early 20th to 21st centuries. The unprecedently low and high spring discharge in recent decades compared to the historical natural variability of the last 250 years also suggests that the increase in flood frequency and magnitude originates from climate change.

The Role of Climate Changes in the Spread of Freshwater Fishes: Implications for Alien Cool and Warm-Water Species in a Mediterranean Basin

In running waters, under climate change conditions, the combined effect of water warming and decreasing flow rates may encourage colonisation by invasive cool and warm-water fish species. The aim of the study was to analyze the potential climate change effects on the spread of four invasive alien fishes in the Tiber River basin, taking into account the effects of river fragmentation. Fish and environmental data collected in 91 sites over the years 1998–2018, were used to analyze temporal changes in their habitat requirements. A multivariate analysis was conducted, and the hypothesis of a range expansion towards the upstream reaches has been tested. For Barbus barbus, Gobio gobio, Padogobius bonelli and Pseudorasbora parva population abundances and body condition were analyzed. Detectability, occupancy, local extinction and colonization probabilities were estimated. We showed that B. barbus and P. bonelli have significantly extended their range toward upstream. P. parva did not move toward higher altitudes significantly, suggesting that, at this stage, the species has probably reached an equilibrium. River fragmentation, elevation, water temperature and average current speed seem to be major determinants in colonization processes, affecting the dispersal ability of the species. Not surprisingly for species introduced in relatively recent times, the colonization probabilities were much higher than extinction probabilities. Our results provided evidence for some synergistic effects between climate changes and alien fish species invasions, in terms of species range shifts mediated by rising water temperatures, although they should be interpreted cautiously, taking into account that these species most likely were not yet stabilized.