ALBERT

Description: Large-scale moisture fluxes and backward air mass trajectories and frequencies were investigated to explain the mechanisms of synoptic-scale seasonal variability of air masses in the Mediterranean basin. For this aim, reanalysis data were used to calculate variations in moisture flux with respect to temperature and stability according to the 8 standard pressure levels between 1000 and 300 hPa. Investigating air mass characteristics changing with pressure levels provided new information in terms of air mass climatology for the Mediterranean basin. Results show that due to the influence of westerly flows, the Atlantic is the main source of moisture higher than 700 hPa. Turbulent transport of moisture from the Mediterranean Sea is the source of moisture close to the surface, which corresponds to levels lower than 700 hPa. According to the trajectory analysis, the continental Arctic (cA) air mass can reach the Mediterranean basin and provide very wet conditions over the Mediterranean basin during winter. In addition, during very dry conditions in summer, all air mass currents originate from surface pressure levels between 1000 and 850 hPa. These relatively warm and dominant air masses cause cloud-free conditions with very low precipitation over the Mediterranean basin. This study showed that air masses should be analyzed not only according to their source and path but also according to pressure levels. Therefore, more studies are needed investigating the contemporary air mass climatology of a specific region.

Description: The impacts of climate change on industrial water demand (IWD) directly affect IWD management. In this study, we propose a framework for evaluating different impacts of climate change on IWD by sector, considering both direct and indirect effects. Data from 34 industrial sectors in Hebei Province, China, showed that the impacts of climate change varied by sector, and IWD in 22 of the 34 sectors was affected, ranging from -15.11 to 37.36% under the average rates of change in precipitation and temperature. The corresponding volumetric change of IWD was between -31.148 and 141.890 million m3, considering the difference in the water demand scale between sectors. The overall impact of climate change on IWD gradually decreased from more than 12.8% to approximately 4.1% from 2007 to 2016 due to the substantial improvement of water use efficiency. The indirect effects caused by the total industrial output value offset about 60-50% of the direct growth impacts. By contrast, the increase in IWD caused by the rise in temperature accounted for nearly 90% of the change, whereas only approximately 10% was caused by the decrease in precipitation. In general, an industrial sector may be directly and indirectly affected by temperature and precipitation, and the different impacts may offset each other. This study provides evidence and explanations for the heterogeneity of climate change impacts, and the research results can provide information for regional industrial water resource managers to adapt to climate change.

Description: Quinoa (Chenopodium quinoa Willd.) is a herbaceous C3 crop that has demonstrated resilience in regions concurrently affected by climate change and food insecurity, such as sub-Saharan Africa (SSA). The photosynthetic rate and productivity of C3 crops are enhanced under increasing CO2 concentrations. We looked at future climate trends in SSA to estimate their impacts on quinoa yields in Burkina Faso. Climate projections show a temperature increase of 1.67-4.90°C under Representative Concentration Pathways (RCP) 4.5 and 8.5, respectively by the end of the century. We demonstrate that any further climate disturbances can either be beneficial or harmful for quinoa, and modulating climate risks will depend on the decisions made at the farm level (e.g. planting date and crop choice). Crop modelling supports the identification of the most suitable transplanting dates based on future climate conditions (RCP 4.5 and 8.5), agroclimatic zones (Sahel, Soudano-Sahelian and Soudanian) and time-horizons (2020, 2025, 2050 and 2075). We show that quinoa yields can improve—when grown under irrigated conditions and transplanted in November—by about 14-20% under RCP 4.5 and by 24-33% under RCP 8.5 by 2075 across the Sahel and Soudanian agroclimatic zones, respectively. For the Soudano-Sahelian zone, the highest yield improvements (19%) are obtained when transplanting is assumed in December under RCP 8.5 by 2075. Overall, the findings of this work encourage policymakers and agricultural extension officers to further promote climate-resilient and highly nutritious crops. Such possibilities are of much interest in SSA, thought to be highly vulnerable to climate change impacts where millions of people are already experiencing food insecurity.

Description: Choosing the right harvesting strategy is crucial for sustainable utilization of biological resources but is challenging in real systems with fluctuating environments. This challenge is expected to become even greater with global warming, as environmental variability is predicted to increase. Additionally, harvesting strategies based on single-species models have been shown to carry a severe risk of species extinctions when species interactions are ignored, particularly in systems with more than one harvested species. As the climate continues to warm, we therefore need new reference points for harvesting in an ecosystem context with environmental fluctuations. In this paper, we discuss the development of harvesting strategies and suggest that a proportional threshold harvesting framework could be a useful starting point for developing such reference points and tackling the challenge of sustainable harvesting in the future.

Description: Climate change can manifest in many ways, including impacts on the start, end, and duration of the frost-free season. We examined the climatology and variability of the first fall frost day (FFFD), last spring frost day (LSFD), and length of the frost-free season (LFFS) across Iran for the period 1978-2017. Trend analysis revealed that FFFD shifted later by 6.4 d over the study period while LSFD shifted earlier by slightly over 2 wk, and LFFS is now 〉3 wk longer than it was only 4 decades ago. Since land-use changes around meteorological stations may affect the temperature measured at these stations (especially the magnitudes of nocturnal cooling rates), atmospheric thickness changes, which reflect temperature changes and are independent of station-based measurements, were used as a secondary dataset to investigate minimum temperature trends. The analysis revealed a very strong relationship between frost-related indices and atmospheric thickness. Sequential Mann-Kendall statistical analysis revealed abrupt changes in the applied frost-related indices, minimum temperatures, and atmospheric thicknesses. The first abrupt changes in FFFD and LFFS occurred around 1996, which matched the timing of abrupt changes in atmospheric thickness over Iran. Interestingly, seasonal trend analyses of minimum temperature over the Northern Hemisphere using Era5 reanalysis data indicated consistent regional patterns of warming over the last 4 decades. The results suggest that the increase in LFFS is largely driven by regional-scale warming as opposed to local urbanization and/or land-use changes. Our results document an important and ongoing change of potentially considerable interest to agriculturalists in Iran and elsewhere.

Description: We investigated the time evolution of heat waves and warm nights over the 7 agro-climatic zones of Tamil Nadu, India, during the period 1951-2016, including the spatiotemporal patterns of concurrent hot day and hot night (CHDHN) episodes and the concurrent warm spells in daytime temperature and drought (CWD) episodes. The research relied upon gridded temperature and rainfall observations from the India Meteorological Department. We used the Heat-Wave Magnitude Index daily to study the warm spells in daytime and nighttime temperature, while the analysis of droughts was based on the Standardized Precipitation Evapotranspiration Index. We observed a considerable increase in the count, intensity and duration of heat waves and warm night episodes across Tamil Nadu between the periods 1951-1983 and 1984-2016. Particularly, the number of heat wave events almost doubled in the second half of the study period. We observed a west-east gradient in the severity of heat waves. The intensity and duration of warm night events increased up to 3-fold in the second half of the study period, especially over central Tamil Nadu. The study recorded a multi-fold increase in the number and frequency of CHDHN episodes and the number of CWD episodes during 1984-2016 compared to the base period 1951-1983. More importantly, the incidence of compound events that coexisted with anomalous phases of sea surface temperatures registered a statistically significant spike in many locations. These changes in temperature-induced extremes pose an exceptional public health threat that can increase morbidity and mortality, disproportionately affecting vulnerable sections of Tamil Nadu’s populace engaged in outdoor work.

Description: Freshwater species are particularly vulnerable to emerging threats linked to climate change because they are often already heavily impacted by habitat destruction, pollution, and exploitation. For many harvested populations of freshwater fish, these combined impacts have been mitigated for decades through stocking with captive-bred individuals. However, stocking may lead to loss of genetic variation, which may be crucial for adaptation under climate change. Exploration of sustainable alternatives is therefore paramount. We used a female-based integral projection model (IPM) to assess the consequences of terminating a long-term stocking programme for a population of landlocked, migratory brown trout Salmo trutta, and to evaluate relative effectiveness of alternative management strategies involving harvest regulations and river habitat improvement. The IPM classified individuals by body size, life history stage, and location relative to a hydropower dam, and was parameterised with 50 yr of individual-based data, supplemented with literature values. Model simulations indicated a strong population decline of 22-29% per year without stocking, much of which was attributed to high harvest mortality. Consequently, drastic reductions in fishing pressure were predicted to be necessary to ensure population viability without stocking. Mitigation measures reducing mortality associated with the hydropower dam or restoring spawning areas could further contribute to population viability when combined with changes in harvest regulations. Our results thus emphasise that large changes in management strategies, such as termination of long-term stocking programmes, require a thorough assessment of potential consequences and alternative mitigation strategies using data and models, or, at the very least, a precautionary approach under consideration of on-going climate change.

Description: For species with individual variation in reproductive success, experience in breeding and the distribution of different breeders is important for population productivity and viability. Human impacts, such as climate change and harvesting, can alter this distribution and thus population dynamics. Here, we investigated the effect of spawning experience on population growth in a population of migratory brown trout Salmo trutta subject to stressors including migration barriers, harvesting, and climate change. We described the population dynamics with a structured integral projection model that differentiates between first-time and repeat spawners. We then took a scenario-based approach to test to which extent spawning experience has a positive effect on the population growth of brown trout by running 3 different model simulations: a baseline scenario with no changes to the reproductive output of the population, a non-selective scenario in which the reproductive output of all spawners was reduced, and a selective scenario where the reproductive output of only first-time spawners was reduced. We found that the reproductive output of repeat spawners is more important than that of first-time spawners for population growth, in line with other studies. Moreover, the contribution of first-time spawners to the population growth through their own survival is more important than their contribution to growth through reproduction. To ensure the continued existence of the study population, survival of first-time spawners and reproductive success of repeat spawners should be prioritised. More generally, including breeding experience adds more mechanistic detail, which ultimately can aid management and conservation efforts.

Description: Scientists and wildlife managers implementing adaptive monitoring and management schemes, are tasked with providing predictions of population responses to harvest and environmental changes. Such predictions are useful not only to forecast direct effects of climate, productivity, land use, or habitat degradation, but also changes in the food web, such as expanding/�increasing species that are predators, prey, and competitors of populations of concern. Explicit consideration of food webs and their dynamics in more complex models could provide better predictions of future changes, and allow us to better assess the influence of management actions. Here, we present our perspective on what we have learned from conducting a number of case studies using such a food web approach with a focus on climate and harvest impacts and their implications for management. We found empirical support for many of our hypothesized food web effects, and were able in some cases to obtain short-term forecasts with slightly lower prediction error using models that account for food web dynamics compared with simpler models. Predictions are the foundation of adaptive management because they allow quantitative assessment of the effects of management actions; however, evaluating predictions requires adequate and high-quality monitoring data. Results from our case studies show that a combination of long-term monitoring and different types of study designs coupled with models of adequate complexity are likely required to better understand populations’ responses to environmental changes and harvest, as well as the consequences for food webs.

Description: The impact of climate change on the dynamics of populations has been well documented and is widespread. However, weather variability influences populations both directly and indirectly, and is mediated by species interactions. This complexity may impede proper climate impact assessments. Hence, predicting the consequences of climate change may require including processes that occur both with time lags and across trophic levels. Based on our current understanding of the mechanisms linking local climate and trophic interactions in tundra ecosystems, we used a state-space formulation of a mediation model that allowed for assessing the relative contribution of direct and indirect environmental (weather and trophic) effects on reindeer Rangifer tarandus reproductive success. Our study showed that the mediator effect of body condition caused delayed but predictable effects of weather, plant productivity, and reindeer densities on reproductive success. Furthermore, these predictors also affected reproductive success directly and with the same sign, suggesting that direct and indirect effects pulled in the same direction with respect to their combined total effect on reproductive success. Hence, poor weather conditions not only affect calf production negatively the same year, but also increase the likelihood of poor reproductive success the subsequent year. The results support the expectation that calf slaughter mass (as a proxy for herd body condition) is an important indicator of the state of reindeer herds with respect to their production potential and resilience to weather events and climate change. Finally, the model framework employed in the present study can be further developed as a potential vehicle for near-term forecasting, and thereby constitutes a useful tool for adaptive management.