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African mixed crop–livestock systems are vulnerable to climate change and need to adapt in order to improve productivity and sustain people’s livelihoods. These smallholder systems are characterized by high greenhouse gas emission rates, but could play a role in their mitigation. Although the impact of climate change is projected to be large, many uncertainties persist, in particular with respect to impacts on livestock and grazing components, whole-farm dynamics and heterogeneous farm populations. We summarize the current understanding on impacts and vulnerability and highlight key knowledge gaps for the separate system components and the mixed farming systems as a whole. Numerous adaptation and mitigation options exist for crop–livestock systems. We provide an overview by distinguishing risk management, diversification and sustainable intensification strategies, and by focusing on the contribution to the three pillars of climate-smart agriculture. Despite the potential solutions, smallholders face major constraints at various scales, including small farm sizes, the lack of response to the proposed measures and the multi-functionality of the livestock herd. Major institutional barriers include poor access to markets and relevant knowledge, land tenure insecurity and the common property status of most grazing resources. These limit the adoption potential and hence the potential impact on resilience and mitigation. In order to effectively inform decision-making, we therefore call for integrated, system-oriented impact assessments and a realistic consideration of the adoption constraints in smallholder systems. Building on agricultural system model development, integrated impact assessments and scenario analyses can inform the co-design and implementation of adaptation and mitigation strategies.F

La zone soudano-sahélienne de l'Afrique de l'Ouest a connu des sécheresses récurrentes depuis le milieu des années 1970 et aujourd'hui, on s'inquiète beaucoup de la façon dont cette région sera en mesure de s'adapter au changement climatique futur. Pour développer des stratégies d'adaptation bien ciblées, l'importance relative des facteurs climatiques en tant que moteurs de l'utilisation des terres et du changement des moyens de subsistance doit être mieux comprise. Sur la base des perceptions de 1 249 ménages dans cinq pays à travers un gradient annuel de précipitations de 400 à 900 mm, nous fournissons une estimation de la le poids des facteurs climatiques en tant que facteurs de changement dans les ménages ruraux au cours des 20 dernières années. Les facteurs climatiques, principalement des précipitations insuffisantes, sont perçus par 30 à 50 % des ménages comme une cause de diminution de la production de cultures pluviales, tandis qu'un large éventail d'autres facteurs explique les 50 à 70 % restants. Les facteurs climatiques sont beaucoup moins importants pour la diminution de la production animale et des zones de pâturage. L'augmentation des pâturages est également observée et causée par l'amélioration du régime foncier dans la zone la plus sèche. Les stratégies d'adaptation à la baisse de la production agricole comprennent la « prière » et la migration dans la zone de 400 à 500 mm ; le reboisement, la migration et le gouvernement soutien dans la zone 500-700 mm ; et amélioration des sols dans la zone 700-900 mm. Le déclin des exploitations d'élevage est contré par l'amélioration des ressources fourragères et des services vétérinaires. Il est conclu que, bien que la production de cultures pluviales soit principalement limitée par des facteurs climatiques, le bétail et les pâturages sont moins sensibles au climat dans toutes les zones de précipitations. Cela doit être reflété dans les stratégies nationales d'adaptation dans la région. La zona sudanosaheliana de África occidental ha experimentado sequías recurrentes desde mediados de la década de 1970 y hoy en día existe una preocupación considerable sobre cómo esta región podrá adaptarse al cambio climático futuro. Para desarrollar estrategias de adaptación bien dirigidas, es necesario comprender mejor la importancia relativa de los factores climáticos como impulsores del uso de la tierra y el cambio de los medios de vida. Sobre la base de las percepciones de 1249 hogares en cinco países con un gradiente de lluvia anual de 400-900 mm, proporcionamos una estimación de la el peso de los factores climáticos como impulsores de los cambios en los hogares rurales durante los últimos 20 años. Los factores climáticos, principalmente las precipitaciones inadecuadas, son percibidos por el 30-50% de los hogares como una causa de la disminución de la producción de cultivos de secano, mientras que una amplia gama de otros factores explica el 50-70% restante. Los factores climáticos son mucho menos importantes para la disminución de la producción ganadera y las áreas de pastoreo. Los aumentos en los pastos también se observan y son causados por la mejora de la tenencia en la zona más seca. Las estrategias de adaptación a la disminución de la producción de cultivos incluyen la "oración" y la migración en la zona de 400-500 mm; reforestación, migración y gobierno apoyo en la zona de 500-700 mm; y mejora del suelo en la zona de 700-900 mm. La disminución de las explotaciones ganaderas se contrarresta con la mejora de los recursos forrajeros y los servicios veterinarios. Se concluye que, aunque la producción de cultivos de secano está limitada principalmente por factores climáticos, el ganado y los pastos son menos sensibles al clima en todas las zonas de lluvia. Esto debe reflejarse en las estrategias nacionales de adaptación en la región. The Sudano-Sahelian zone of West Africa has experienced recurrent droughts since the mid-1970s and today there is considerable concern for how this region will be able to adapt to future climate change.To develop well targeted adaptation strategies, the relative importance of climate factors as drivers of land use and livelihood change need to be better understood.Based on the perceptions of 1249 households in five countries across an annual rainfall gradient of 400-900 mm, we provide an estimate of the relative weight of climate factors as drivers of changes in rural households during the past 20 years.Climate factors, mainly inadequate rainfall, are perceived by 30-50% of households to be a cause of decreasing rainfed crop production, whereas a wide range of other factors explains the remaining 50-70%.Climate factors are much less important for decreasing livestock production and pasture areas.Increases in pasture are also observed and caused by improved tenure in the driest zone.Adaptation strategies to declining crop production include 'prayer' and migration in the 400-500 mm zone; reforestation, migration, and government support in the 500-700 mm zone; and soil improvement in the 700-900 mm zone.Declining livestock holdings are countered by improved fodder resources and veterinary services.It is concluded that although rainfed crop production is mainly constrained by climate factors, livestock and pasture are less climate sensitive in all rainfall zones.This needs to be reflected in national adaptation strategies in the region. شهدت المنطقة السودانية الساحلية في غرب إفريقيا موجات جفاف متكررة منذ منتصف السبعينيات، واليوم هناك قلق كبير بشأن كيفية قدرة هذه المنطقة على التكيف مع تغير المناخ في المستقبل. لوضع استراتيجيات تكيف موجهة بشكل جيد، يجب فهم الأهمية النسبية للعوامل المناخية كمحركات لاستخدام الأراضي وتغير سبل العيش بشكل أفضل. بناءً على تصورات 1249 أسرة في خمسة بلدان عبر تدرج هطول الأمطار السنوي من 400-900 ملم، نقدم تقديرًا للنسبة وزن العوامل المناخية كمحركات للتغيرات في الأسر الريفية خلال السنوات العشرين الماضية. ينظر إلى العوامل المناخية، وخاصة عدم كفاية هطول الأمطار، من قبل 30-50 ٪ من الأسر على أنها سبب لانخفاض إنتاج المحاصيل البعلية، في حين أن مجموعة واسعة من العوامل الأخرى تفسر 50-70 ٪ المتبقية. العوامل المناخية أقل أهمية بكثير لانخفاض إنتاج الثروة الحيوانية ومناطق المراعي. كما لوحظت الزيادات في المراعي والناجمة عن تحسين الحيازة في المنطقة الأكثر جفافاً. تشمل استراتيجيات التكيف مع انخفاض إنتاج المحاصيل "الصلاة" والهجرة في منطقة 400-500 مم ؛ إعادة التشجير والهجرة والحكومة الدعم في منطقة 500-700 مم ؛ وتحسين التربة في منطقة 700-900 مم. يتم مواجهة انخفاض حيازات الماشية من خلال تحسين موارد الأعلاف والخدمات البيطرية. تم التوصل إلى أنه على الرغم من أن إنتاج المحاصيل البعلية مقيد بشكل أساسي بعوامل المناخ، إلا أن الثروة الحيوانية والمراعي أقل حساسية للمناخ في جميع مناطق هطول الأمطار. يجب أن ينعكس هذا في استراتيجيات التكيف الوطنية في المنطقة.

Climate change is estimated to exacerbate existing challenges faced by smallholder farmers in Sub-Sahara Africa. However, limited studies quantify the extent of variation in climate change impact under these systems at the local scale. The Decision Support System for Agro-technological Transfer (DSSAT) was used to quantify variation in climate change impacts on maize yield under current agricultural practices in semi-arid regions of Senegal (Nioro du Rip) and Ghana (Navrongo and Tamale). Multi-benchmark climate models (Mid-Century, 2040–2069 for two Representative Concentration Pathways, RCP4.5 and RCP8.5), and multiple soil and management information from agronomic surveys were used as input for DSSAT. The average impact of climate scenarios on grain yield among farms ranged between −9% and −39% across sites. Substantial variation in climate response exists across farms in the same farming zone with relative standard deviations from 8% to 117% at Nioro du Rip, 13% to 64% in Navrongo and 9% to 37% in Tamale across climate models. Variations in fertilizer application, planting dates and soil types explained the variation in the impact among farms. This study provides insight into the complexities of the impact of climate scenarios on maize yield and the need for better representation of heterogeneous farming systems for optimized outcomes in adaptation and resilience planning in smallholder systems.

AbstractCrop improvement efforts aiming at increasing crop production (quantity, quality) and adapting to climate change have been subject of active research over the past years. But, the question remains ‘to what extent can breeding gains be achieved under a changing climate, at a pace sufficient to usefully contribute to climate adaptation, mitigation and food security?’. Here, we address this question by critically reviewing how model‐based approaches can be used to assist breeding activities, with particular focus on all CGIAR (formerly the Consultative Group on International Agricultural Research but now known simply as CGIAR) breeding programs. Crop modeling can underpin breeding efforts in many different ways, including assessing genotypic adaptability and stability, characterizing and identifying target breeding environments, identifying tradeoffs among traits for such environments, and making predictions of the likely breeding value of the genotypes. Crop modeling science within the CGIAR has contributed to all of these. However, much progress remains to be done if modeling is to effectively contribute to more targeted and impactful breeding programs under changing climates. In a period in which CGIAR breeding programs are undergoing a major modernization process, crop modelers will need to be part of crop improvement teams, with a common understanding of breeding pipelines and model capabilities and limitations, and common data standards and protocols, to ensure they follow and deliver according to clearly defined breeding products. This will, in turn, enable more rapid and better‐targeted crop modeling activities, thus directly contributing to accelerated and more impactful breeding efforts.

In West Africa’s highly weathered soils, plant-available soil-P levels determine sorghum performance and yield to a far greater extent than projected variability in climate. Despite local landrace varieties having excellent adaptation to the environment and a relatively stable yield, sorghum grain yield remains quite low, averaging less than 1 t ha−1. Low P availability in West African soils has significant effects on crop development and growth with potential grain yield losses of more than 50%. Use of mechanistic models, which integrate physiological processes, could assist with understanding the differences in P-uptake among varieties and guide effective P management. Yet only few crop models include a soil-plant P model for simulating crop yield response to P management. A generic soil-plant P module was developed for crop models in the Cropping System Model (CSM) of the Decision Support System for Agrotechnology Transfer (DSSAT) but the module was adapted and tested only on two crops, groundnut and maize. The aim of the study was to adapt the soil-plant P module for sorghum and perform initial testing on highly weathered soils in West Africa. Data used in adapting and testing the soil-plant P model for sorghum consisted of in-season P concentrations and dry weights of stems, leaves and grain from four sorghum varieties covering a range of maturities and photoperiod sensitivities and grown in high-P and P-deficient soils at ICRISAT-Mali. Results showed that the coupled CERES-Sorghum − P module reasonably reproduced the vegetative and grain yield reductions experienced in the field experiments with an average RMSE of 1561 and 909 kg ha−1 under high P conditions and 1168 and 466 kg ha−1 under low P conditions, respectively. The simulations are in most cases within the observation error. We also confirmed that contrasting variety types differ in their P-uptake dynamics relative to above-ground growth change over time, and hence respond differently to available P.

In recent decades, mechanisms for observation and information production have proliferated in an attempt to meet the growing needs of stakeholders to access dynamic data for the purposes of informed decision-making. In the land sector, a growing number of land observatories are producing data and ensuring its transparency. We hypothesize that these structures are being developed in response to the need for information and knowledge, a need that is being driven by the scale and diversity of land issues. Based on the results of a study conducted on land observatories in Africa, this paper presents existing and past land observatories on the continent and proposes to assess their diversity through an analysis of core dimensions identified in the literature. The analytical framework was implemented through i) an analysis of existing literature on land observatories, ii) detailed assessments of land observatories based on semi-open interviews conducted via video conferencing, iii) fieldwork and visits to several observatories, and iv) participant observation through direct engagement and work at land observatories. We emphasize that the analytical framework presented here can be used as a tool by land observatories to undertake ex-post self-evaluations that take the observatory’s trajectory into account, or in the case of proposed new land observatories, to undertake ex-ante analyses and design the pathway towards the intended observatory.