• Energy Research

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

Au cours des 50 dernières années, des changements majeurs en agriculture et dans notre alimentation ont généré des effets délétères sur l’environnement et la santé humaine. Pour rendre compte des interdépendances entre les différentes composantes de nos systèmes agricoles et alimentaires, nous avons construit un cadre d’analyse, le « multiscope », en couplant les approches « d’une seule santé », « oneHealth » (l’animal et l’homme dans leur environnement : sol, plante, écosystème), et celles des systèmes alimentaires durables (impacts sur la santé et l’environnement des régimes alimentaires). Ce multiscope nous permet d’identifier les vecteurs de santé (biodiversité, micronutriments) ou de réduction de nuisances (gaz, polluants), puis d’analyser les effets en cascade (de la parcelle ou l’animal à la planète) consécutifs aux choix de production dans les systèmes agricoles et in fine alimentaires. Nous avons défini 3 principes majeurs pour améliorer la santé des différents domaines : i) promouvoir les services écosystémiques par la biodiversité, ii) boucler les cycles biogéochimiques et iii) renforcer le bien-être des animaux et des hommes. Nous appliquons ce cadre d’analyse au cas des légumineuses, fourragères et à graines, qui ont connu une forte régression depuis un demi-siècle malgré leurs importants atouts environnementaux et nutritionnels. Nous montrons que ce multiscope permet d’accompagner les transitions agricoles et alimentaires en favorisant : i) une compréhension intégrée des dynamiques d’innovations et des verrous au développement des légumineuses, ii) une reconception des systèmes de culture et d’élevage, iii) la construction de scénarios territoriaux fondés sur le développement de la culture des légumineuses et de leur utilisation en alimentation humaine. Over the past 50 years, major changes in agriculture and in our diets have had a deleterious effect on the environment and human health. In order to account for the interdependencies between the various components of our agricultural and food systems, we have built an analytical framework, the "multiscope", by combining the "one-health" concept (animals and humans in their environment: soil, plant, ecosystem) and those of sustainable food systems (health and environmental impacts of diets). This multiscope al-lows us to identify the vectors of health (biodiversity, micronutri-ents) or reduction of nuisances (gas, pollutants), and then to ana-lyze the cascade effects (from the plot or the animal to the planet) consecutive to the choices of production in agricultural and food systems. We have identified three major principles for improving the health of the various areas: (i) promoting ecosystem services through biodiversity; (ii) closing biogeochemical cycles, and (iii) enhancing animal and human welfare. We apply this analytical framework to the case of legumes, pulses and forages, which experienced a sharp decline during this period despite their signifi-cant environmental and nutritional assets. We show that this mul-tiscope makes it possible to accompany the agricultural and food transitions by promoting: i) an integrated understanding of the dynamics of innovations and the lockins to the development of the legumes, ii) a re-design of the cropping and livestock systems, (iii) the construction of territorial scenarios based on the development of legume crops and their use in human food.

Abstract In the mountainous areas of South-East Asia, family farms have shifted from subsistence to input-intensified and market-oriented maize-based farming systems, resulting in a substantial increase in farm income, but also in new environmental threats: deforestation, biodiversity loss, soil erosion, herbicide leaching and soil fertility degradation. In this typical case study of cash-strapped farms, where the balance between socio-economic and environmental dimensions of sustainability is complex, we used participatory methods (serious games and Q-methodology), combined with agronomic field monitoring, to identify relevant farm and field-level criteria for sustainability assessment. Serious games at farm level showed that short-term socio-economic dimensions prevailed over environmental dimensions in farmers' objectives. However, farmers also greatly valued their capacity to transfer a viable farm to the next generation and avoid herbicide use. Serious games at field level showed that some farmers were willing to preserve soil fertility for future generations. The agronomic field monitoring showed that maize yield deviations from potential water-limited yield were primarily due to weed infestation favoured by low sowing density, due to uncontrolled moto-mechanized crop establishment. This technical failure at the beginning of the maize cycle led to herbicide overuse, poor returns on investment for fertilizer, and increased exposure to soil erosion. Combining the perspectives of scientists and farmers led to the following set of locally-relevant criteria: i) at farm level: farm income, diversity of activities, farmer autonomy, farmer health, workload peaks, soil fertility transfer between agroecological zones in the landscape, rice and forage self-sufficiency; ii) at field level: resource use efficiency, soil fertility, erosion and herbicide risks, susceptibility to pests, weeds and climate variability, biodiversity, land productivity, economic performance, labour productivity and work drudgery. Our approach helped to identify key relevant sustainability criteria and could be useful for designing alternatives to current maize-based cropping systems, and contributed to informing priority-setting for institutional development and agricultural policies in the region.

Abstract Developing relevant decision-support tools for policymakers to support large-scale implementation of climate-smart agriculture in the Global South is challenging given the great diversity in biophysical, socio-technical, and organizational conditions. This article describes a pilot exercise inspired by the recommendation domain literature that aimed at mapping, beyond “classical” biophysical and socio-technical variables, the institutional variables (i.e., the existence of policy incentives in national policy documents) that could influence the large-scale implementation of climate-smart agricultural practices. Four practices were considered: cereal-legume intercropping, fodder legume cultivation, farmer managed natural regeneration (FMNR) of Parkia biglobosa, and crop residue mulching. The biophysical and socio-technical variables were classified based on thresholds identified in the literature and mapped with a geographic information system. The policy documents considered were investment plans, adaptation plans for climate change, nationally determined contributions, and Technology Needs Assessments project reports. Sixteen policy documents for four countries were thoroughly reviewed and classified as unfavorable, intermediate, and favorable for the four selected practices, based on a decision tree built for that purpose. Our analysis shows that areas where biophysical, socio-technical, and institutional variables are aligned for the four practices considered are small, particularly for fodder legume cultivation and crop residue mulching. For cereal-legume intercropping, incentives from national policies strongly differ from one country to another while for FMNR of Parkia biglobosa policies are more homogeneously conducive across countries. Nonetheless, it was possible to identify areas where biophysical, socio-technical, and institutional dimensions of the transition toward climate-smart agriculture (CSA) were aligned, for example, cereal-legume intercropping in southern Mali. The delineating of favorable and unfavorable areas allows specific recommendations to be made for policymakers as levers for action differ in favorable, intermediate, and unfavorable zones. Based on the exploration made for the four practices, this study highlights the need for further articulations from local to national scale to implement CSA.

AbstractSmallholder farmers in sub‐Saharan Africa (SSA) currently grow rainfed maize with limited inputs including fertilizer. Climate change may exacerbate current production constraints. Crop models can help quantify the potential impact of climate change on maize yields, but a comprehensive multimodel assessment of simulation accuracy and uncertainty in these low‐input systems is currently lacking. We evaluated the impact of varying [CO2], temperature and rainfall conditions on maize yield, for different nitrogen (N) inputs (0, 80, 160 kg N/ha) for five environments in SSA, including cool subhumid Ethiopia, cool semi‐arid Rwanda, hot subhumid Ghana and hot semi‐arid Mali and Benin using an ensemble of 25 maize models. Models were calibrated with measured grain yield, plant biomass, plant N, leaf area index, harvest index and in‐season soil water content from 2‐year experiments in each country to assess their ability to simulate observed yield. Simulated responses to climate change factors were explored and compared between models. Calibrated models reproduced measured grain yield variations well with average relative root mean square error of 26%, although uncertainty in model prediction was substantial (CV = 28%). Model ensembles gave greater accuracy than any model taken at random. Nitrogen fertilization controlled the response to variations in [CO2], temperature and rainfall. Without N fertilizer input, maize (a) benefited less from an increase in atmospheric [CO2]; (b) was less affected by higher temperature or decreasing rainfall; and (c) was more affected by increased rainfall because N leaching was more critical. The model intercomparison revealed that simulation of daily soil N supply and N leaching plays a crucial role in simulating climate change impacts for low‐input systems. Climate change and N input interactions have strong implications for the design of robust adaptation approaches across SSA, because the impact of climate change in low input systems will be modified if farmers intensify maize production with balanced nutrient management.