• Energy Research

AbstractLivestock are a critically important component of the food system, although the sector needs a profound transformation to ensure that it contributes to a rapid transition towards sustainable food systems. This chapter reviews and synthesises the evidence available on changes in demand for livestock products in the last few decades, and the multiple socio-economic roles that livestock have around the world. We also describe the nutrition, health, and environmental impacts for which the sector is responsible. We propose eight critical actions for transitioning towards a more sustainable operating space for livestock. (1) Facilitate shifts in the consumption of animal source foods (ASF), recognising that global reductions will be required, especially in communities with high consumption levels, while promoting increased levels in vulnerable groups, including the undernourished, pregnant women and the elderly. (2) Continue work towards the sustainable intensification of livestock systems, paying particular attention to animal welfare, food-feed competition, blue water use, disease transmission and perverse economic incentives. (3) Embrace the potential of circularity in livestock systems as a way of partially decoupling livestock from land. (4) Adopt practices that lead to the direct or indirect mitigation of greenhouse gases. (5) Adopt some of the vast array of novel technologies at scale and design incentive mechanisms for their rapid deployment. (6) Diversify the protein sources available for human consumption and feed, focusing on the high-quality alternative protein sources that have lower environmental impacts. (7) Tackle antimicrobial resistance effectively through a combination of technology and new regulations, particularly for the fast-growing poultry and pork sectors and for feedlot operations. (8) Implement true cost of food and true-pricing approaches to ASF consumption.

AbstractTree radial growth is widely found to respond differently to climate change across altitudinal gradients, but the relative roles of biotic factors (e.g. forest type, height and density) vs. climate gradient remain unclear. We sampled tree rings from 15 plots along a large altitudinal gradient in northeast China, and examined how climate gradient, forest type, height, tree size and density affect: (1) temporal growth variability [mean sensitivity (MS) and standard deviation (SD) of the chronologies], and (2) the relationship of ring width indices (RWI) with historical climate. We used BIC based model selection and variable importance to explore the major drivers of their altitudinal patterns. The results showed that: both growth variability and RWI-climate relationships changed significantly with altitude. Forest height was the most important predictor for altitudinal changes of MS and SD. For RWI-climate relationships, forest type was more important than climate gradient, while height and stem density were weak but necessary predictors. We showed that the altitudinal difference in growth response to climate change cannot be explained by climate gradient alone, and highlight the necessity to examine the influence of biotic factors (which covary with climate across geographic gradient) to better understand forest response to climate change.

Our knowledge on permafrost carbon (C) cycle is crucial for understanding its feedback to climate warming and developing nature-based solutions for mitigating climate change. To understand the characteristics of permafrost C cycle on the Tibetan Plateau, the largest alpine permafrost region around the world, we summarized recent advances including the stocks and fluxes of permafrost C and their responses to thawing, and depicted permafrost C dynamics within this century. We find that this alpine permafrost region stores approximately 14.1 Pg (1 Pg=1015 g) of soil organic C (SOC) in the top 3 m. Both substantial gaseous emissions and lateral C transport occur across this permafrost region. Moreover, the mobilization of frozen C is expedited by permafrost thaw, especially by the formation of thermokarst landscapes, which could release significant amounts of C into the atmosphere and surrounding water bodies. This alpine permafrost region nevertheless remains an important C sink, and its capacity to sequester C will continue to increase by 2100. For future perspectives, we would suggest developing long-term in situ observation networks of C stocks and fluxes with improved temporal and spatial coverage, and exploring the mechanisms underlying the response of ecosystem C cycle to permafrost thaw. In addition, it is essential to improve the projection of permafrost C dynamics through in-depth model-data fusion on the Tibetan Plateau.

Le but de cette étude est d'évaluer les huit modèles de biome ISIMIP2a par rapport à des estimations indépendantes des flux nets de carbone à long terme (c'est-à-dire la productivité nette du biome, NBP) sur les écosystèmes terrestres au cours des quatre dernières décennies (1971–2010). Nous évaluons le NBP mondial modélisé par rapport à 1) le puits terrestre résiduel mondial (RLS) mis à jour plus les émissions liées à l'utilisation des terres (ELUC) du Global Carbon Project (GCP), présenté comme R + L dans cette étude par Le Quéré et al (2015), et 2) les flux de CO2 terrestre provenant de deux systèmes d'inversion atmosphérique : Jena CarboScope s81_v3.8 et CAMS v15r2, appelés FJena et FCAMS respectivement. L'ensemble de modèles - moyenne NBP (qui comprend sept modèles avec changement d'affectation des terres) est plus élevé que mais dans l'incertitude de R + L, tandis que la tendance NBP positive simulée au cours des 30 dernières années est inférieure à celle de R + L et des deux systèmes d'inversion. Les modèles de biome ISIMIP2a capturent bien la variation interannuelle des flux nets mondiaux de carbone des écosystèmes terrestres. La NBP tropicale représente 31 ± 17 % de la NBP totale mondiale au cours des dernières décennies, et la variation d'une année à l'autre de la NBP tropicale contribue pour l'essentiel à la variation interannuelle de la NBP mondiale. Selon les modèles, l'augmentation de la productivité primaire nette (NPP) a été la principale cause de l'augmentation générale de la NBP. Des anomalies NBP globales significatives à partir de la moyenne à long terme entre les deux phases des événements El Niño Southern Oscillation (ENSO) sont simulées par tous les modèles (p < 0,05), ce qui est cohérent avec l'estimation R + L (p = 0,06), également principalement attribuée à des anomalies NPP, plutôt qu'à des changements dans la respiration hétérotrophique (Rh). Les anomalies mondiales de la centrale nucléaire et de la centrale nucléaire nucléaire pendant les événements ENSO sont dominées par leurs anomalies dans les régions tropicales touchées par la variabilité du climat tropical. Les régressions multiples entre les variations interannuelles de R + L, FJena et FCAMS et les variations du climat tropical révèlent une réponse négative significative des flux nets mondiaux de carbone des écosystèmes terrestres à la variation de la température annuelle moyenne tropicale, et une réponse non significative à la variation des précipitations annuelles tropicales. Selon les modèles, les précipitations tropicales sont un facteur plus important, ce qui suggère que certains modèles ne saisissent pas correctement les rôles des précipitations et des changements de température. El propósito de este estudio es evaluar los ocho modelos de bioma ISIMIP2a contra estimaciones independientes de flujos netos de carbono a largo plazo (es decir, Productividad Neta del Bioma, NBP) sobre ecosistemas terrestres durante las últimas cuatro décadas (1971–2010). Evaluamos el NBP global modelado contra 1) el sumidero de tierra residual (RLS) global actualizado más las emisiones de uso de la tierra (ELUC) del Proyecto Global de Carbono (GCP), presentado como R + L en este estudio por Le Quéré et al (2015), y 2) los flujos de CO2 terrestre de dos sistemas de inversión atmosférica: Jena CarboScope s81_v3.8 y CAMS v15r2, denominados FJena y FCAMS respectivamente. La media del conjunto de modelos NBP (que incluye siete modelos con cambio de uso de la tierra) es mayor que, pero dentro de la incertidumbre de R + L, mientras que la tendencia positiva simulada de NBP en los últimos 30 años es menor que la de R + L y de los dos sistemas de inversión. Los modelos de bioma ISIMIP2a capturan bien la variación interanual de los flujos netos globales de carbono del ecosistema terrestre. El NBP tropical representa el 31 ± 17% del NBP total global durante las últimas décadas, y la variación interanual del NBP tropical contribuye con la mayor parte de la variación interanual del NBP global. Según los modelos, el aumento de la productividad primaria neta (PPN) fue la causa principal del aumento general de la PNB. Todos los modelos simulan anomalías de NBP globales significativas de la media a largo plazo entre las dos fases de los eventos de El Niño Oscilación del Sur (Enos) (p < 0.05), lo cual es consistente con la estimación de R + L (p = 0.06), también atribuida principalmente a anomalías de NPP, más que a cambios en la respiración heterótrofa (Rh). Las anomalías globales de NPP y NBP durante los eventos Enos están dominadas por sus anomalías en las regiones tropicales afectadas por la variabilidad del clima tropical. Las múltiples regresiones entre las variaciones interanuales de R + L, FJena y FCAMS y las variaciones del clima tropical revelan una respuesta negativa significativa de los flujos netos globales de carbono del ecosistema terrestre a la variación de la temperatura media anual tropical, y una respuesta no significativa a la variación de la precipitación anual tropical. Según los modelos, la precipitación tropical es un impulsor más importante, lo que sugiere que algunos modelos no capturan adecuadamente los roles de la precipitación y los cambios de temperatura. The purpose of this study is to evaluate the eight ISIMIP2a biome models against independent estimates of long-term net carbon fluxes (i.e. Net Biome Productivity, NBP) over terrestrial ecosystems for the recent four decades (1971–2010). We evaluate modeled global NBP against 1) the updated global residual land sink (RLS) plus land use emissions (ELUC) from the Global Carbon Project (GCP), presented as R + L in this study by Le Quéré et al (2015), and 2) the land CO2 fluxes from two atmospheric inversion systems: Jena CarboScope s81_v3.8 and CAMS v15r2, referred to as FJena and FCAMS respectively. The model ensemble-mean NBP (that includes seven models with land-use change) is higher than but within the uncertainty of R + L, while the simulated positive NBP trend over the last 30 yr is lower than that from R + L and from the two inversion systems. ISIMIP2a biome models well capture the interannual variation of global net terrestrial ecosystem carbon fluxes. Tropical NBP represents 31 ± 17% of global total NBP during the past decades, and the year-to-year variation of tropical NBP contributes most of the interannual variation of global NBP. According to the models, increasing Net Primary Productivity (NPP) was the main cause for the generally increasing NBP. Significant global NBP anomalies from the long-term mean between the two phases of El Niño Southern Oscillation (ENSO) events are simulated by all models (p < 0.05), which is consistent with the R + L estimate (p = 0.06), also mainly attributed to NPP anomalies, rather than to changes in heterotrophic respiration (Rh). The global NPP and NBP anomalies during ENSO events are dominated by their anomalies in tropical regions impacted by tropical climate variability. Multiple regressions between R + L, FJena and FCAMS interannual variations and tropical climate variations reveal a significant negative response of global net terrestrial ecosystem carbon fluxes to tropical mean annual temperature variation, and a non-significant response to tropical annual precipitation variation. According to the models, tropical precipitation is a more important driver, suggesting that some models do not capture the roles of precipitation and temperature changes adequately. الغرض من هذه الدراسة هو تقييم نماذج المناطق الأحيائية الثمانية ISIMIP2a مقابل التقديرات المستقلة لصافي تدفقات الكربون طويلة الأجل (أي صافي إنتاجية المناطق الأحيائية) على النظم الإيكولوجية الأرضية على مدى العقود الأربعة الأخيرة (1971–2010). نقوم بتقييم خطة العمل الوطنية العالمية المنمذجة مقابل 1) بالوعة الأراضي المتبقية العالمية المحدثة بالإضافة إلى انبعاثات استخدام الأراضي (ELUC) من مشروع الكربون العالمي (GCP)، والتي تم تقديمها على أنها R + L في هذه الدراسة من قبل Le Quéré et al (2015)، و 2) تدفقات ثاني أكسيد الكربون الأرضية من نظامين لعكس الغلاف الجوي: Jena CarboScope s81_v3.8 و CAMS v15r2، المشار إليها باسم FJena و FCAMS على التوالي. إن مجموعة النماذج - تعني NBP (التي تتضمن سبعة نماذج مع تغيير استخدام الأراضي) أعلى من ولكن ضمن عدم اليقين من R + L، في حين أن اتجاه NBP الإيجابي المحاكي على مدار الثلاثين عامًا الماضية أقل من ذلك من R + L ومن نظامي الانعكاس. تلتقط نماذج المناطق الأحيائية ISIMIP2a بشكل جيد التباين السنوي لتدفقات الكربون الصافية للنظام الإيكولوجي الأرضي العالمي. يمثل الناتج القومي الاستوائي 31 ± 17 ٪ من إجمالي الناتج القومي العالمي خلال العقود الماضية، ويساهم التباين من سنة إلى أخرى في الناتج القومي الاستوائي في معظم التباين السنوي في الناتج القومي العالمي. وفقًا للنماذج، كانت زيادة صافي الإنتاجية الأولية هي السبب الرئيسي لزيادة صافي الإنتاجية الأولية بشكل عام. تتم محاكاة حالات الشذوذ العالمية الكبيرة من المتوسط طويل الأجل بين مرحلتي أحداث التذبذب الجنوبي لظاهرة النينيو (ENSO) من خلال جميع النماذج (P < 0.05)، وهو ما يتوافق مع تقدير R + L (P = 0.06)، والذي يعزى أيضًا بشكل أساسي إلى حالات الشذوذ في NPP، بدلاً من التغيرات في التنفس غيري التغذية (Rh). تهيمن الشذوذات العالمية لمحطات الطاقة النووية ومحطات الطاقة الوطنية خلال أحداث ENSO على شذوذاتها في المناطق المدارية المتأثرة بتقلب المناخ المداري. تكشف الانحدارات المتعددة بين الاختلافات السنوية بين R + L و FJENA و FCAMS والتغيرات المناخية المدارية عن استجابة سلبية كبيرة لصافي تدفقات الكربون في النظام الإيكولوجي الأرضي العالمي لمتوسط التغير السنوي في درجة الحرارة المدارية، واستجابة غير كبيرة لتغير هطول الأمطار السنوي المداري. وفقًا للنماذج، يعد هطول الأمطار الاستوائية محركًا أكثر أهمية، مما يشير إلى أن بعض النماذج لا تلتقط أدوار هطول الأمطار وتغيرات درجة الحرارة بشكل كافٍ.

AbstractPast assessments report negative impacts of the climate crisis in boreal areas; but milder and shorter winters and elevated atmospheric CO2may provide opportunities for agricultural productivity potentially playing a significant role in future food security. Arable cropping systems are expanding in boreal areas, but the regional mainstay will likely continue to be livestock production. Agroecological models can when appropriately calibrated and evaluated, facilitate improved productivity while minimising environmental impacts by identifying system interactions, and quantifying greenhouse gas emissions, soil carbon stocks and fertiliser use. While models designed for temperate and tropical zones abound, few are developed specifically for boreal zones, and there is uncertainty around the performance of existing models in boreal areas. We reviewed model performance across boreal environments and management systems. We identified a dearth of modelling studies in boreal regions, with the publication of three or less papers per year since the year 2000, constituting a significant research gap. Models IFSM and BASGRA_N performed best in grassland production, DNDC best in predicting soil N2O and NH3emissions. No model outperformed all others, strengthening the case for ensemble modelling. Existing agroecological models would be worthy of further evaluation, providing model improvements designed for boreal systems.

Abstract Global terrestrial vegetation is greening, particularly in mountain areas, providing strong feedbacks to a series of ecosystem processes. This greening has been primarily attributed to climate change. However, the spatial variability and magnitude of such greening do not synchronize with those of climate change in mountain areas. By integrating two data sets of satellite-derived normalized difference vegetation index (NDVI) values, which are indicators of vegetation greenness, in the period 1982–2015 across the Tibetan Plateau (TP), we test the hypothesis that climate-change-induced greening is regulated by terrain, baseline climate and soil properties. We find a widespread greening trend over 91% of the TP vegetated areas, with an average greening rate (i.e. increase in NDVI) of 0.011 per decade. The linear mixed-effects model suggests that climate change alone can explain only 26% of the variation in the observed greening. Additionally, 58% of the variability can be explained by the combination of the mountainous characteristics of terrain, baseline climate and soil properties, and 32% of this variability was explained by terrain. Path analysis identified the interconnections of climate change, terrain, baseline climate and soil in determining greening. Our results demonstrate the important role of mountainous effects in greening in response to climate change.