By the year 2050, agriculture will have to provide the food and nutrition requirements of some 9 billion people. Moreover, to maintain that level of productivity indefinitely it must do so using environmentally sustainable production systems. This task will be profoundly complicated by the effects of climate change, increasing competition for water resources and loss of productive lands. Agricultural production methods will also need to recognize and accommodate ongoing rural to urban migration and address a host of economic, ecological and social concerns about the 'high inputs/high outputs' model of present-day industrial agriculture. At the same time, there is a need to confront the unacceptable levels of continuing food and nutrition insecurity, greatest in the emerging economy countries of Africa and Asia where poverty, rapid population growth and climate change present additional challenges and where agriculture is practiced primarily by small-scale farmers. Within this context, we here review science-based evidence arguing that diversification with greater use of highly valuable but presently under-valorised crops and species should be an essential element of any model for sustainable smallholder agriculture. The major points of these development opportunity crops are presented in four sections: agricultural farming systems, health and nutrition, environmental sustainability and prosperity of the populations. For each section, these crops and their associated indigenous knowledge are reported to bring benefits and services when integrated with food systems. In this paper, we conclude that not only a change in policy is needed to influence behaviours and practices but also strong leadership able to synergize the various initiatives and implement an action plan. (Résumé d'auteur
Seedlings sourced through tree nurseries are expected to form an important component of future tree cover on farms. As such, the genetic composition of nursery seedlings is expected to impact on the productivity and sustainability of agroforestry ecosystems. By surveying current practices of nursery managers in five areas from Kenya, Tanzania and Uganda, we quantified parameters associated with the collection, production and distribution of tree germplasm in East Africa. Considerable variation for seed-propagated nursery species was observed in the number of maternal parents ͑mother trees͒ sampled to establish nursery lots, the quantity of seedlings raised in nursery lots and the projected number of clients for nursery lots. Current seed collection practice was the most obvious limiting bottleneck in delivering high levels of genetic diversity to farmers. In the 143 cases analysed, seed to establish nursery lots was collected from a mean of only 6.4 maternal parents. In 22% of cases, nursery lots were established from a single maternal parent. On average, each maternal parent produced sufficient progeny to provide all the seedlings received by an individual nursery client. Consequently, the potential impact on farm and landscape genetic diversity of possible non-randomisation of progeny within nurseries is serious. In two instances, pair-wise analysis of transformed data suggested significant differences between geographic areas in the projected number of clients for nursery lots. We discuss improved nursery practices likely to promote genetic diversity, in particular increased maternal parent sampling and germplasm exchange.
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