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It is increasingly acknowledged that climate change is influencing terrestrial ecosystems by increased drought and rainfall intensities. Soil microbes are key drivers of many processes in terrestrial systems and rely on water in soil pores to fulfill their life cycles and functions. However, little is known on how drought and rainfall fluctuations, which affect the composition and structure of microbial communities, persist once original moisture conditions have been restored. Here, we study how simulated short-term drying and re-wetting events shape the community composition of soil fungi and prokaryotes. In a mesocosm experiment, soil was exposed to an extreme drought, then re-wetted to optimal moisture (50% WHC, water holding capacity) or to saturation level (100% WHC). Composition, community structure and diversity of microbes were measured by sequencing ITS and 16S rRNA gene amplicons 3 weeks after original moisture content had been restored. Drying and extreme re-wetting decreased richness of microbial communities, but not evenness. Abundance changes were observed in only 8% of prokaryote OTUs, and 25% of fungal OTUs, whereas all other OTUs did not differ between drying and re-wetting treatments. Two specific legacy response groups (LRGs) were observed for both prokaryotes and fungi. OTUs belonging to the first LRG decreased in relative abundance in soil with a history of drought, whereas OTUs that increased in soil with a history of drought formed a second LRG. These microbial responses were spread among different phyla. Drought appeared to be more important for the microbial community composition than the following extreme re-wetting. 16S profiles were correlated with both inorganic N concentration and basal respiration and ITS profiles correlated with fungal biomass. We conclude that a drying and/or an extreme re-wetting history can persist in soil microbial communities via specific response groups composed of members with broad phylogenetic origins, with possible functional consequences on soil processes and plant species. As a large fraction of OTUs responding to drying and re-wetting belonged to the rare biosphere, our results suggest that low abundant microbial species are potentially important for ecosystem responses to extreme weather events.

Activated sludge from municipal wastewater treatment processes can be used directly for the production of biodegradable polyesters from the family of polyhydroxyalkanoates (PHAs). However, municipal activated sludge typically cannot accumulate PHAs to very high levels and often low yields of polymer produced on substrate are observed. In the present work, it was found that the presence of calcium promotes selective growth and enrichment of the PHA-storing biomass fraction and significantly improved both PHA contents and yields. Calcium addition resulted in PHA contents of 0.60 ± 0.03 gPHA/gVSS and average PHA yields on substrate of 0.49 ± 0.03 gCODPHA/gCODHAc compared to 0.35 ± 0.01 gPHA/gVSS and 0.19 ± 0.01 gCODPHA/gCODHAc without calcium addition. After 48 h, three times more PHA was produced compared to control experiments without calcium addition. Higher PHA content and selective biomass production is proposed to be a consequence of calcium dependent increased levels of passive acetate uptake. Such more efficient substrate uptake could be related to a formation of calcium acetate complexes. Findings lead to bioprocess methods to stimulate a short-term selective growth of PHA-storing microorganisms and this enables improvements to the techno-economic feasibility for municipal waste activated sludge to become a generic resource for industrial scale PHA production.

AbstractDengue is hyperendemic in Brazil, with outbreaks affecting all regions. Previous studies identified geographical barriers to dengue transmission in Brazil, beyond which certain areas, such as South Brazil and the Amazon rainforest, were relatively protected from outbreaks. Recent data shows these barriers are being eroded. In this study, we explore the drivers of this expansion and identify the current limits to the dengue transmission zone. We used a spatio-temporal additive model to explore the associations between dengue outbreaks and temperature suitability, urbanisation, and connectivity to the Brazilian urban network. The model was applied to a binary outbreak indicator, assuming the official threshold value of 300 cases per 100,000 residents, for Brazil’s municipalities between 2001 and 2020. We found a nonlinear relationship between higher levels of connectivity to the Brazilian urban network and the odds of an outbreak, with lower odds in metropoles compared to regional capitals. The number of months per year with suitable temperature conditions for Aedes mosquitoes was positively associated with the dengue outbreak occurrence. Temperature suitability explained most interannual and spatial variation in South Brazil, confirming this geographical barrier is influenced by lower seasonal temperatures. Municipalities that had experienced an outbreak previously had double the odds of subsequent outbreaks, indicating that dengue tends to become established in areas after introduction. We identified geographical barriers to dengue transmission in South Brazil, western Amazon, and along the northern coast of Brazil. Although a southern barrier still exists, it has shifted south, and the Amazon no longer has a clear boundary. Few areas of Brazil remain protected from dengue outbreaks. Communities living on the edge of previous barriers are particularly susceptible to future outbreaks as they lack immunity. Control strategies should target regions at risk of future outbreaks as well as those currently within the dengue transmission zone.Author summaryDengue is a mosquito-borne disease that has expanded rapidly around the world due to increased urbanisation, global mobility and climate change. In Brazil, geographical barriers to dengue transmission exist, beyond which certain areas including South Brazil and the Amazon rainforest are relatively protected from outbreaks. However, we found that the previous barrier in South Brazil has shifted futher south as a result of increased temperature suitability. The previously identified barrier protecting the western Amazon no longer exists. This is particularly concerning as we found dengue outbreaks tend to become established in areas after introduction. Highly influential cities with many transport links had increased odds of an outbreak. However, the most influencial cities had lower odds of an outbreak than cities connected regionally. This study highlights the importance of monitoring the expansion of dengue outbreaks and designing disease prevention strategies for areas at risk of future outbreaks as well as areas in the established dengue transmission zone.

AbstractSoil micronutrients are capital for the delivery of ecosystem functioning and food provision worldwide. Yet, despite their importance, the global biogeography and ecological drivers of soil micronutrients remain virtually unknown, limiting our capacity to anticipate abrupt unexpected changes in soil micronutrients in the face of climate change. Here, we analyzed >1300 topsoil samples to examine the global distribution of six metallic micronutrients (Cu, Fe, Mn, Zn, Co and Ni) across all continents, climates and vegetation types. We found that warmer arid and tropical ecosystems, present in the least developed countries, sustain the lowest contents of multiple soil micronutrients. We further provide evidence that temperature increases may potentially result in abrupt and simultaneous reductions in the content of multiple soil micronutrients when a temperature threshold of 12–14°C is crossed, which may be occurring on 3% of the planet over the next century. Altogether, our findings provide fundamental understanding of the global distribution of soil micronutrients, with direct implications for the maintenance of ecosystem functioning, rangeland management and food production in the warmest and poorest regions of the planet.

Los escenarios se han convertido en una herramienta clave para apoyar la investigación de sostenibilidad sobre el cambio regional y global. En este estudio evaluamos cuatro evaluaciones de escenarios regionales: primero, para explorar una serie de desafíos de investigación relacionados con la ciencia de la sostenibilidad y, segundo, para contribuir a la investigación de sostenibilidad en los estudios de casos específicos. Los cuatro estudios de casos utilizaron enfoques de escenarios comúnmente aplicados que son (i) un enfoque de historia y simulación con participación de las partes interesadas en la cuenca hidrográfica de Oum Zessar, Túnez, (ii) una exploración participativa de escenarios en la región de Rwenzori, Uganda, (iii) un estudio de prepolíticas basado en modelos en el Delta Interior del Níger, Malí, y (iv) un análisis de escenarios basado en modelos de acoplamiento en la cuenca alta de Thukela, Sudáfrica. Las evaluaciones de escenarios se evalúan frente a un conjunto de desafíos conocidos en la ciencia de la sostenibilidad, con cada desafío representado por dos indicadores, complementados por una encuesta realizada sobre la percepción de las evaluaciones de escenarios dentro de las regiones de estudio de caso. Los resultados muestran que todos los tipos de evaluaciones de escenarios abordan muchos desafíos de sostenibilidad, pero que los más complejos basados en la historia y la simulación y el acoplamiento de modelos son: el más completo. El estudio destaca la necesidad de investigar los cambios abruptos del sistema, así como los factores gubernamentales y políticos como fuentes importantes de incertidumbre. Para un análisis en profundidad de estos problemas, se sugiere el uso de enfoques cualitativos y una participación activa de las partes interesadas locales. Se recomienda estudiar los umbrales ecológicos a escala regional para apoyar la investigación sobre la sostenibilidad regional. La evaluación de los procesos y resultados de los escenarios por parte de los investigadores locales indica que las evaluaciones de escenarios más transparentes son las más útiles. Las evaluaciones de escenarios centradas, directas e iterativas pueden ser muy relevantes al aportar información a los problemas de sostenibilidad seleccionados. Les scénarios sont devenus un outil clé pour soutenir la recherche sur la durabilité des changements régionaux et mondiaux. Dans cette étude, nous évaluons quatre évaluations de scénarios régionaux : premièrement, explorer un certain nombre de défis de recherche liés à la science de la durabilité et, deuxièmement, contribuer à la recherche sur la durabilité dans les études de cas spécifiques. Les quatre études de cas ont utilisé des approches de scénarios couramment appliquées qui sont (i) une approche d'histoire et de simulation avec la participation des parties prenantes dans le bassin versant d'Oum Zessar, en Tunisie, (ii) une exploration participative de scénarios dans la région de Rwenzori, en Ouganda, (iii) une étude pré-politique basée sur des modèles dans le delta intérieur du Niger, au Mali, et (iv) une analyse de scénarios basée sur le couplage de modèles dans le bassin supérieur de Thukela, en Afrique du Sud. Les évaluations de scénarios sont évaluées par rapport à un ensemble de défis connus en science de la durabilité, chaque défi étant représenté par deux indicateurs, complétés par une enquête réalisée sur la perception des évaluations de scénarios dans les régions d'étude de cas. Les résultats montrent que tous les types d'évaluations de scénarios répondent à de nombreux défis de durabilité, mais que les plus complexes basés sur l'histoire et la simulation et le couplage de modèles sont la plus complète. L'étude souligne la nécessité d'enquêter sur les changements brusques du système ainsi que sur les facteurs gouvernementaux et politiques en tant que sources importantes d'incertitude. Pour une analyse approfondie de ces questions, l'utilisation d'approches qualitatives et un engagement actif des parties prenantes locales sont suggérés. L'étude des seuils écologiques à l'échelle régionale est recommandée pour soutenir la recherche sur la durabilité régionale. L'évaluation des processus et des résultats des scénarios par les chercheurs locaux indique que les évaluations de scénarios les plus transparentes sont les plus utiles. Des évaluations de scénarios ciblées, simples, mais itératives peuvent être très pertinentes en fournissant des informations à des problèmes de durabilité sélectionnés. Scenarios have become a key tool for supporting sustainability research on regional and global change.In this study we evaluate four regional scenario assessments: first, to explore a number of research challenges related to sustainability science and, second, to contribute to sustainability research in the specific case studies.The four case studies used commonly applied scenario approaches that are (i) a story and simulation approach with stakeholder participation in the Oum Zessar watershed, Tunisia, (ii) a participatory scenario exploration in the Rwenzori region, Uganda, (iii) a model-based prepolicy study in the Inner Niger Delta, Mali, and (iv) a model coupling-based scenario analysis in upper Thukela basin, South Africa.The scenario assessments are evaluated against a set of known challenges in sustainability science, with each challenge represented by two indicators, complemented by a survey carried out on the perception of the scenario assessments within the case study regions.The results show that all types of scenario assessments address many sustainability challenges, but that the more complex ones based on story and simulation and model coupling are the most comprehensive.The study highlights the need to investigate abrupt system changes as well as governmental and political factors as important sources of uncertainty.For an in-depth analysis of these issues, the use of qualitative approaches and an active engagement of local stakeholders are suggested.Studying ecological thresholds for the regional scale is recommended to support research on regional sustainability.The evaluation of the scenario processes and outcomes by local researchers indicates the most transparent scenario assessments as the most useful.Focused, straightforward, yet iterative scenario assessments can be very relevant by contributing information to selected sustainability problems. أصبحت السيناريوهات أداة رئيسية لدعم أبحاث الاستدامة حول التغيير الإقليمي والعالمي. في هذه الدراسة، نقوم بتقييم أربعة تقييمات للسيناريوهات الإقليمية: أولاً، لاستكشاف عدد من تحديات البحث المتعلقة بعلوم الاستدامة، وثانياً، للمساهمة في أبحاث الاستدامة في دراسات الحالة المحددة. استخدمت دراسات الحالة الأربع مناهج السيناريوهات المطبقة بشكل شائع والتي هي (1) نهج القصة والمحاكاة بمشاركة أصحاب المصلحة في مستجمعات مياه أم زسار، تونس، (2) استكشاف سيناريو تشاركي في منطقة روينزوري، أوغندا، (3) دراسة سياسة مسبقة قائمة على نموذج في دلتا النيجر الداخلية، مالي، و (4) تحليل سيناريو قائم على نموذج الاقتران في حوض ثوكيلا العلوي، جنوب أفريقيا. يتم تقييم تقييمات السيناريو مقابل مجموعة من التحديات المعروفة في علم الاستدامة، مع تمثيل كل تحدٍ بمؤشرين، يكملهما مسح تم إجراؤه على تصور تقييمات السيناريو داخل مناطق دراسة الحالة. تظهر النتائج أن جميع أنواع تقييمات السيناريو تعالج العديد من تحديات الاستدامة، ولكن التحديات الأكثر تعقيدًا القائمة على القصة والمحاكاة واقتران النموذج هي الأكثر شمولاً. تسلط الدراسة الضوء على الحاجة إلى التحقيق في التغييرات المفاجئة في النظام وكذلك العوامل الحكومية والسياسية كمصادر مهمة لعدم اليقين. للحصول على تحليل متعمق لهذه القضايا، يُقترح استخدام النهج النوعية والمشاركة النشطة لأصحاب المصلحة المحليين. يوصى بدراسة العتبات البيئية على المستوى الإقليمي لدعم البحوث المتعلقة بالاستدامة الإقليمية. يشير تقييم عمليات ونتائج السيناريو من قبل الباحثين المحليين إلى أن تقييمات السيناريو الأكثر شفافية هي الأكثر فائدة. يمكن أن تكون تقييمات السيناريو المركزة والمباشرة والمتكررة ذات صلة كبيرة من خلال المساهمة بالمعلومات في مشاكل الاستدامة المختارة.