Assessing Nutritional Diversity of Cropping Systems in African Villages

BackgroundIn Sub-Saharan Africa, 40% of children under five years in age are chronically undernourished. As new investments and attention galvanize action on African agriculture to reduce hunger, there is an urgent need for metrics that monitor agricultural progress beyond calories produced per capita and address nutritional diversity essential for human health. In this study we demonstrate how an ecological tool, functional diversity (FD), has potential to address this need and provide new insights on nutritional diversity of cropping systems in rural Africa.
Methods and FindingsData on edible plant species diversity, food security and diet diversity were collected for 170 farms in three rural settings in Sub-Saharan Africa. Nutritional FD metrics were calculated based on farm species composition and species nutritional composition. Iron and vitamin A deficiency were determined from blood samples of 90 adult women. Nutritional FD metrics summarized the diversity of nutrients provided by the farm and showed variability between farms and villages. Regression of nutritional FD against species richness and expected FD enabled identification of key species that add nutrient diversity to the system and assessed the degree of redundancy for nutrient traits. Nutritional FD analysis demonstrated that depending on the original composition of species on farm or village, adding or removing individual species can have radically different outcomes for nutritional diversity. While correlations between nutritional FD, food and nutrition indicators were not significant at household level, associations between these variables were observed at village level.
ConclusionThis study provides novel metrics to address nutritional diversity in farming systems and examples of how these metrics can help guide agricultural interventions towards adequate nutrient diversity. New hypotheses on the link between agro-diversity, food security and human nutrition are generated and strategies for future research are suggested calling for integration of agriculture, ecology, nutrition, and socio-economics.

研究背景：在撒哈拉以南非洲，40%的五岁以下儿童长期处于营养不良状态。随着各类新增投资与关注度推动非洲农业领域减少饥饿的行动蓬勃开展，学界亟需构建能够超越人均粮食产量维度、有效衡量农业进展的指标体系，同时兼顾对人体健康至关重要的营养多样性。本研究阐释了生态工具功能多样性（functional diversity, FD）如何满足这一需求，并为撒哈拉以南非洲乡村种植系统的营养多样性研究提供全新视角。
研究方法与结果：本研究针对撒哈拉以南非洲3个乡村区域的170个农户农场，采集了食用植物物种多样性、粮食安全与膳食多样性相关数据。基于农场物种组成与物种营养成分，计算得到营养功能多样性指标。通过90名成年女性的血液样本，测定其铁与维生素A缺乏状况。营养功能多样性指标可量化农场提供的营养物种类多样性，并反映不同农场与村落间的差异。通过营养功能多样性与物种丰富度、预期功能多样性的回归分析，可识别出对系统营养多样性具有增益作用的关键物种，并评估营养性状的冗余程度。营养功能多样性分析表明，依据农场或村落原有的物种组成，增减单个物种会对营养多样性产生截然不同的影响。尽管营养功能多样性与粮食、营养指标在农户层面未呈现显著相关性，但在村落层面可观测到这些变量间的关联。
研究结论：本研究提出了用于解析种植系统营养多样性的新型指标，并展示了此类指标如何引导农业干预措施朝着保障充足营养多样性的方向推进。本研究生成了关于农业多样性、粮食安全与人类营养之间关联的全新假说，并建议未来研究应整合农业、生态学、营养学与社会经济学等多领域资源，制定跨学科研究策略。