• Energy Research

Asseng, S. et al. Crop models are essential tools for assessing the threat of climate change to local and global food production1. Present models used to predict wheat grain yield are highly uncertain when simulating how crops respond to temperature2. Here we systematically tested 30 different wheat crop models of the Agricultural Model Intercomparison and Improvement Project against field experiments in which growing season mean temperatures ranged from 15 °C to 32 °C, including experiments with artificial heating. Many models simulated yields well, but were less accurate at higher temperatures. The model ensemble median was consistently more accurate in simulating the crop temperature response than any single model, regardless of the input information used. Extrapolating the model ensemble temperature response indicates that warming is already slowing yield gains at a majority of wheat-growing locations. Global wheat production is estimated to fall by 6% for each °C of further temperature increase and become more variable over space and time. We thank the Agricultural Model Intercomparison and Improvement Project and its leaders C. Rosenzweig from NASA Goddard Institute for Space Studies and Columbia University (USA), J. Jones from University of Florida (USA), J. Hatfield from United States Department of Agriculture (USA) and J. Antle from Oregon State University (USA) for support. We also thank M. Lopez from CIMMYT (Turkey), M. Usman Bashir from University of Agriculture, Faisalabad (Pakistan), S. Soufizadeh from Shahid Beheshti University (Iran), and J. Lorgeou and J-C. Deswarte from ARVALIS—Institut du Végétal (France) for assistance with selecting key locations and quantifying regional crop cultivars, anthesis and maturity dates and R. Raymundo for assistance with GIS. S.A. and D.C. received financial support from the International Food Policy Research Institute (IFPRI). C.S. was funded through USDA National Institute for Food and Agriculture award 32011-68002-30191. C.M. received financial support from the KULUNDA project (01LL0905L) and the FACCE MACSUR project (031A103B) funded through the German Federal Ministry of Education and Research (BMBF). F.E. received support from the FACCE MACSUR project (031A103B) funded through the German Federal Ministry of Education and Research (2812ERA115) and E.E.R. was funded through the German Science Foundation (project EW 119/5-1). M.J. and J.E.O. were funded through the FACCE MACSUR project by the Danish Strategic Research Council. K.C.K. and C.N. were funded by the FACCE MACSUR project through the German Federal Ministry of Food and Agriculture (BMEL). F.T., T.P. and R.P.R. received financial support from FACCE MACSUR project funded through the Finnish Ministry of Agriculture and Forestry (MMM); F.T. was also funded through National Natural Science Foundation of China (No. 41071030). C.B. was funded through the Helmholtz project ‘REKLIM—Regional Climate Change: Causes and Effects’ Topic 9: ‘Climate Change and Air Quality’. M.P.R. and P.D.A. received funding from the CGIAR Research Program on Climate Change, Agriculture, and Food Security (CCAFS). G.O’L. was funded through the Australian Grains Research and Development Corporation and the Department of Environment and Primary Industries Victoria, Australia. R.C.I. was funded by Texas AgriLife Research, Texas A&M University. E.W. and Z.Z. were funded by CSIRO and the Chinese Academy of Sciences (CAS) through the research project ‘Advancing crop yield while reducing the use of water and nitrogen’ and by the CSIRO-MoE PhD Research Program. Peer reviewed

The conservation of natural resources is the most important key for a sustainable agriculture, especially considering the decreasing conditional subsidies of the Common Agricultural Policy (CAP) of the European Union (EU) for the coming years: the lower economic supports oblige farms to increase efficiency to reduce production costs, whilst given the interaction of agricultural activities with environment quality, appropriate natural resources management will be a crucial aspect for farms. The paper examines the efficiency of agricultural production systems and particularly the efficiency of energy use in a 3-yr soya bean, maize and wheat rotation. The study also aimed to analyse the production cost and the role of EU subsidies on farm strategies for important emerging management systems namely conservation farming (CF) and organic farming (OF) systems. Experiments were carried out in NE Italy, on a farm situated near Rovigo. Energy inputs were generally higher in the CF system but counterbalanced by a higher yield (output), while the OF system had generally reduced energy use (due to no chemical inputs) but lower yield. The economic net return was higher for the CF system, but when the economic subsidies from EU were considered, the integrated net return was higher in the OF system for soya bean and wheat.

Crop growth simulation models can differ greatly in their treatment of key processes and hence in their response to environmental conditions. Here, we used an ensemble of 26 process-based wheat models applied at sites across a European transect to compare their sensitivity to changes in temperature (-2 to +9°C) and precipitation (-50 to +50%). Model results were analysed by plotting them as impact response surfaces (IRSs), classifying the IRS patterns of individual model simulations, describing these classes and analysing factors that may explain the major differences in model responses.The model ensemble was used to simulate yields of winter and spring wheat at four sites in Finland, Germany and Spain. Results were plotted as IRSs that show changes in yields relative to the baseline with respect to temperature and precipitation. IRSs of 30-year means and selected extreme years were classified using two approaches describing their pattern.The expert diagnostic approach (EDA) combines two aspects of IRS patterns: location of the maximum yield (nine classes) and strength of the yield response with respect to climate (four classes), resulting in a total of 36 combined classes defined using criteria pre-specified by experts. The statistical diagnostic approach (SDA) groups IRSs by comparing their pattern and magnitude, without attempting to interpret these features. It applies a hierarchical clustering method, grouping response patterns using a distance metric that combines the spatial correlation and Euclidian distance between IRS pairs. The two approaches were used to investigate whether different patterns of yield response could be related to different properties of the crop models, specifically their genealogy, calibration and process description.Although no single model property across a large model ensemble was found to explain the integrated yield response to temperature and precipitation perturbations, the application of the EDA and SDA approaches revealed their capability to distinguish: (i) stronger yield responses to precipitation for winter wheat than spring wheat; (ii) differing strengths of response to climate changes for years with anomalous weather conditions compared to period-average conditions; (iii) the influence of site conditions on yield patterns; (iv) similarities in IRS patterns among models with related genealogy; (v) similarities in IRS patterns for models with simpler process descriptions of root growth and water uptake compared to those with more complex descriptions; and (vi) a closer correspondence of IRS patterns in models using partitioning schemes to represent yield formation than in those using a harvest index.Such results can inform future crop modelling studies that seek to exploit the diversity of multi-model ensembles, by distinguishing ensemble members that span a wide range of responses as well as those that display implausible behaviour or strong mutual similarities.

AbstractEnergy crops for biofuel production, especially switchgrass (Panicum virgatum), are of interest from a climate change perspective. Here, we use outputs from a crop growth model and life cycle assessment (LCA) to examine the global warming intensity (GWI; g CO2 MJ−1) and greenhouse gas (GHG) mitigation potential (Mg CO2 year−1) of biofuel systems based on a spatially explicit analysis of switchgrass grown on marginal land (abandoned former cropland) in Michigan, USA. We find that marginal lands in Michigan can annually produce over 0.57 hm3 of liquid biofuel derived from nitrogen‐fertilized switchgrass, mitigating 1.2–1.5 Tg of CO2 year−1. About 96% of these biofuels can meet the Renewable Fuel Standard (60% reduction in lifecycle GHG emissions compared with conventional gasoline; GWI ≤37.2 g CO2 MJ−1). Furthermore, 73%–75% of these biofuels are carbon‐negative (GWI less than zero) due to enhanced soil organic carbon (SOC) sequestration. However, simulations indicate that SOC levels would fail to increase and even decrease on the 11% of lands where SOC stocks >>200 Mg C ha−1, leading to carbon intensities greater than gasoline. Results highlight the strong climate mitigation potential of switchgrass grown on marginal lands as well as the needs to avoid carbon rich soils such as histosols and wetlands and to ensure that productivity will be sufficient to provide net mitigation.

Les zones urbaines telles que les mégapoles (celles dont la population est supérieure à 10 millions d'habitants) sont des points chauds de l'utilisation mondiale de l'eau et sont donc confrontées à d'intenses défis en matière de gestion de l'eau.Les zones urbaines sont influencées par les interactions locales entre les systèmes humains et naturels et interagissent avec les systèmes distants par le biais des flux d'eau, de nourriture, d'énergie, de personnes, d'information et de capitaux.Toutefois, les analyses de la durabilité de l'eau et de la gestion des flux d'eau dans les zones urbaines sont souvent fragmentées.Il est fortement nécessaire d'appliquer des cadres intégrés pour analyser systématiquement les zones urbaines la dynamique de l'eau et les facteurs qui influencent ces dynamiques.Nous appliquons le cadre du télécouplage (interactions socio-économiques et environnementales sur des distances) pour analyser les problèmes d'eau urbaine, en utilisant Pékin comme mégapole de démonstration.Pékin illustre le défi mondial de la durabilité de l'eau pour les milieux urbains.Comme de nombreuses autres villes, Pékin a connu des réductions drastiques de la quantité et de la qualité des eaux de surface et souterraines au cours des dernières décennies ; il dépend de l'importation d'eau réelle et virtuelle provenant de systèmes d'envoi pour répondre à sa demande d'eau propre et rejette de l'eau polluée dans d'autres systèmes (systèmes de débordement).Le Le cadre intégratif que nous présentons démontre l'importance de prendre en compte les interactions socio-économiques et environnementales entre les systèmes humains et naturels télécouplés, qui comprennent non seulement Pékin (le système de réception de l'eau), mais aussi les systèmes d'envoi d'eau et les systèmes de débordement. Ce cadre aide à intégrer des composantes importantes des interactions locales et lointaines entre l'homme et la nature et intègre un large éventail de couplages et de télécouplages locaux qui affectent la dynamique de l'eau, ce qui génère à son tour des conséquences socio-économiques et environnementales importantes, y compris des effets de rétroaction. L'application du cadre à Pékin révèle de nombreuses lacunes dans la recherche et de nombreux besoins en matière de gestion. Nous fournissons également une base pour appliquer le cadre de télécouplage afin de mieux comprendre et gérer la durabilité de l'eau dans d'autres villes du monde. Las áreas urbanas como las megaciudades (aquellas con poblaciones superiores a 10 millones) son puntos críticos del uso global del agua y, por lo tanto, enfrentan intensos desafíos de gestión del agua. Las áreas urbanas están influenciadas por las interacciones locales entre los sistemas humanos y naturales e interactúan con sistemas distantes a través de flujos de agua, alimentos, energía, personas, información y capital. Sin embargo, los análisis de la sostenibilidad del agua y la gestión de los flujos de agua en las áreas urbanas a menudo están fragmentados. Existe una gran necesidad de aplicar marcos integrados para analizar sistemáticamente la dinámica del agua y factores que influyen en esta dinámica. Aplicamos el marco del teleacoplamiento (interacciones socioeconómicas y ambientales a distancia) para analizar los problemas del agua urbana, utilizando a Beijing como una megaciudad de demostración. Beijing ejemplifica el desafío global de sostenibilidad del agua para los entornos urbanos. Al igual que muchas otras ciudades, Beijing ha experimentado reducciones drásticas en la cantidad y calidad de las aguas superficiales y subterráneas en las últimas décadas; depende de la importación de agua real y virtual de los sistemas de envío para satisfacer su demanda de agua limpia y libera agua contaminada a otros sistemas (sistemas de derrame). El marco integrador que presentamos demuestra la importancia de considerar las interacciones socioeconómicas y ambientales entre los sistemas humanos y naturales teleacoplados, que incluyen no solo Beijing (el sistema de recepción de agua) sino también los sistemas de envío de agua y los sistemas de desbordamiento. Este marco ayuda a integrar componentes importantes de las interacciones locales y distantes entre el ser humano y la naturaleza e incorpora una amplia gama de acoplamientos y teleacoplamientos locales que afectan la dinámica del agua, que a su vez generan importantes consecuencias socioeconómicas y ambientales, incluidos los efectos de retroalimentación. La aplicación del marco a Beijing revela muchas lagunas de investigación y necesidades de gestión. También proporcionamos una base para aplicar el marco de teleacoplamiento para comprender y gestionar mejor la sostenibilidad del agua en otras ciudades del mundo. Urban areas such as megacities (those with populations greater than 10 million) are hotspots of global water use and thus face intense water management challenges.Urban areas are influenced by local interactions between human and natural systems and interact with distant systems through flows of water, food, energy, people, information, and capital.However, analyses of water sustainability and the management of water flows in urban areas are often fragmented.There is a strong need to apply integrated frameworks to systematically analyze urban water dynamics and factors that influence these dynamics.We apply the framework of telecoupling (socioeconomic and environmental interactions over distances) to analyze urban water issues, using Beijing as a demonstration megacity.Beijing exemplifies the global water sustainability challenge for urban settings.Like many other cities, Beijing has experienced drastic reductions in quantity and quality of both surface water and groundwater over the past several decades; it relies on the import of real and virtual water from sending systems to meet its demand for clean water, and releases polluted water to other systems (spillover systems).The integrative framework we present demonstrates the importance of considering socioeconomic and environmental interactions across telecoupled human and natural systems, which include not only Beijing (the water-receiving system) but also water-sending systems and spillover systems.This framework helps integrate important components of local and distant human-nature interactions and incorporates a wide range of local couplings and telecouplings that affect water dynamics, which in turn generate significant socioeconomic and environmental consequences, including feedback effects.The application of the framework to Beijing reveals many research gaps and management needs.We also provide a foundation to apply the telecoupling framework to better understand and manage water sustainability in other cities around the world. المناطق الحضرية مثل المدن الكبرى (تلك التي يزيد عدد سكانها عن 10 ملايين نسمة) هي نقاط ساخنة للاستخدام العالمي للمياه وبالتالي تواجه تحديات مكثفة في إدارة المياه. تتأثر المناطق الحضرية بالتفاعلات المحلية بين النظم البشرية والطبيعية وتتفاعل مع النظم البعيدة من خلال تدفقات المياه والغذاء والطاقة والناس والمعلومات ورأس المال. ومع ذلك، غالبًا ما تكون تحليلات استدامة المياه وإدارة تدفقات المياه في المناطق الحضرية مجزأة. هناك حاجة قوية لتطبيق أطر متكاملة لتحليل المناطق الحضرية بشكل منهجي ديناميكيات المياه والعوامل التي تؤثر على هذه الديناميكيات .نطبق إطار الاقتران عن بعد (التفاعلات الاجتماعية والاقتصادية والبيئية عبر المسافات) لتحليل قضايا المياه في المناطق الحضرية، باستخدام بكين كمدينة ضخمة .تجسد بكين التحدي العالمي لاستدامة المياه في المناطق الحضرية .مثل العديد من المدن الأخرى، شهدت بكين تخفيضات جذرية في كمية ونوعية كل من المياه السطحية والمياه الجوفية على مدى العقود العديدة الماضية ؛ وهي تعتمد على استيراد المياه الحقيقية والافتراضية من أنظمة الإرسال لتلبية طلبها على المياه النظيفة، وتطلق المياه الملوثة إلى أنظمة أخرى (أنظمة غير مباشرة). يوضح الإطار التكاملي الذي نقدمه أهمية النظر في التفاعلات الاجتماعية والاقتصادية والبيئية عبر الأنظمة البشرية والطبيعية المقترنة عن بعد، والتي لا تشمل بكين فقط (نظام استقبال المياه) ولكن أيضًا أنظمة إرسال المياه وأنظمة الامتداد. يساعد هذا الإطار على دمج المكونات المهمة للتفاعلات المحلية والبعيدة بين الطبيعة البشرية ويتضمن مجموعة واسعة من الوصلات المحلية والوصلات عن بعد التي تؤثر على ديناميكيات المياه، والتي بدورها تولد عواقب اجتماعية واقتصادية وبيئية كبيرة، بما في ذلك تأثيرات التغذية الراجعة. يكشف تطبيق الإطار على بكين عن العديد من الثغرات البحثية والاحتياجات الإدارية. كما نوفر أساسًا لتطبيق إطار الاقتران عن بعد لفهم وإدارة استدامة المياه بشكل أفضل في مدن أخرى حول العالم.