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Current Opinion in
Developing more productive African agroforestry systems and improving food and nutritional security through tree domestication
Daniel A Ofori1, Amos Gyau1, Ian K Dawson1, Ebenezer Asaah2, Zac Tchoundjeu3 and Ramni Jamnadass1
The domestication of new tree crops is one means for improving food and nutritional security. In the last decade, a participatory domestication approach involving scientists and farmers in close collaboration has been developed in sub-Saharan Africa, based on satisfying household needs for tree foods and then growing to meet wider demands. The approach, when practiced in mixed agroforestry regimes that promote yields and resilience, has resulted in significant improvements in incomes, diets and in rural business development. In the next decade, successful agroforestry tree domestication approaches require scaling-up and better engagement is needed with markets. The domestication of the edible oil-producing tree allanblackia provides a model for the involvement of private-public partnerships in sustainable business development.
Addresses
1 The World Agroforestry Centre (ICRAF), Headquarters, United Nations Avenue, Gigiri, P.O. Box 30677, Nairobi 00100, Kenya
2 The World Agroforestry Centre (ICRAF), Sierra Leone Office, 5 Presidential Lodge Rd, Makeni, Northern Province, Sierra Leone 3The World Agroforestry Centre (ICRAF), West and Central Africa Regional Programme, Box 16377, Yaounde, Cameroon
Corresponding author: Ofori, Daniel A. (d.ofori@cgiar.org)
Introduction
Solving the problem of food and nutritional security in sub-Saharan Africa, where nine of the 20 nations with the highest burden of child under-nutrition worldwide are found [1], and where fruit and vegetable consumption are well below global averages [2], requires a range of interconnected approaches, including improvements in crop yields, the bio-fortification of food staples and the cultivation of a wider range of edible plants [3]. As well as the
greater use of a wider range of exotic crops, potential for agricultural diversification lies in the great range of lesser-used indigenous foods found naturally and traditionally managed in African forests and wooded lands, foods which are often richer in micronutrients, fibre and protein than staple crops [4] [Box 1]. In addition to providing human foods' directly, tree domestication provides animal fodder (important to support dairy and meat production) [5], improves soils (thereby supporting staple crop yields) [6], provides energy needs (important for the proper processing and cooking of food) [7] and supports incomes (for the purchase of foods) [8*,9].
The process of domestication — bringing plants into cultivation and adapting them to meet human needs — began over 10 000 years ago for annual crops [10], and for a few selected food trees has already occurred over several millennia, most obviously in Latin America [11-14]. The great majority of the world's >80 000 tree species are, however, still essentially wild or exist only as early stage, incipient domesticates [15], and in particular the domestication of African food trees has been limited, with few documented examples [16,17**] and limited characterisation work undertaken [18]. Access to wild food trees in Africa is however declining due to deforestation, and attention to bring species into wider cultivation provides opportunities to improve livelihoods, increase productivity, combat malnutrition and adapt to anthropogenic climate change [19,20]. This paper outlines our opinion and describes recent tree domestication progress in the region.
Tree domestication methods
Two basic approaches to tree domestication have been described. The first is a centralised approach involving field trials, controlled crosses and, in some cases, biotech-nological breeding methods to carry out genetic improvement [21,22], while the second makes use of more decentralised community-driven strategies [23]. The first approach is straightforward to coordinate, and has been applied to exotic fruits planted in sub-Saharan Africa [17**], but the results do not always filter down to small-scale farmers, who face high transaction costs in obtaining external farm inputs such as tree planting material and the information needed on the management of cultivars [24]. The first approach is also a narrow view of domestication in that it focuses on genetic improvement,
Current Opinion in Environmental Sustainability 2014, 6:123-127
This review comes from a themed issue on Sustainability challenges
Edited by Cheikh Mbow, Henry Neufeldt, Peter Akong Minang, Eike Luedeling and Godwin Kowero
For a complete overview see the Issue and the Editorial
Received 14 June 2013; Accepted 16 November 2013
Available online 12th December 2013
1877-3435/$ - see front matter, © 2013 Daniel A Ofori. Published by Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.cosust.2013.11.016
Box 1 Examples of indigenous food trees important for domestication in sub-Saharan Africa (for further information on these and other important tree species for smallholders, see www.worldagroforestry.org/resources/databases/ agroforestree)
Baobab: The edible white, powdery pulp found in the fruit of Adansonia digitata is very rich in vitamins C and B2. Young leaves are rich in vitamin C and are in high demand in West Africa as a soup vegetable.
Ber: The fruit of Ziziphus mauritiana is eaten fresh or dried and can be made into a floury meal, butter, or a cheese-like paste, and is a good source of carotene, vitamins A and C, and oils. Also native to Asia, large-fruited cultivars are found there.
Bush mango: The fruit mesocarp of Irvingia gabonensis, sweet bush mango, is appreciated as a fresh fruit snack. Ground kernels of I. gabonensis and I. wombolu are used to thicken and flavour soups.
Desert date: The fleshy pulp of Balanites aegyptiaca fruit is eaten dried or fresh, and oil from the kernel is used for cooking and cosmetics. Young leaves and tender shoots are used as a vegetable.
Marula: The fruit pulp of Sclerocarya birrea is used to produce jam, juice, beer and, in South Africa, the liqueur Amarula Cream, while the oily kernels are consumed raw, roasted and in sauces.
Njansang: A spicy sauce made from the kernels of Ricinodendron heudelotii is widely used in stews, and the high oil content of the seeds makes them suitable for use in the soap industry.
Safou: Extensively sold in local markets in Central and West Africa, Dacryodes edulis fruit are rich in vitamins and amino acids, and are eaten boiled or roasted.
Star apple: The fleshy and juicy fruits of Chrysophyllum albidum are popularly eaten, and can be fermented and distilled for the production of wine and spirits.
Tamarind: The fruit pulp of Tamarindus indica is used to prepare juice and jam, and is an ingredient in curries, chutneys and sauces. The ripe fruits of 'sweet' types are eaten fresh as a snack.
Wild loquat: The fruit of Uapaca kirkiana is highly regarded and is eaten fresh as well as to prepare jams and beverages. Harvesting of fruit from the wild is an important coping strategy during famine.
which — although very important — does not address the many other elements required for a successful tree cultivation programme, including decisions by communities on which species to prioritise for cultivation [25], developing efficient farm management methods in a smallholder context, and addressing the many other bottlenecks small-scale farmers face in planting a new crop, including social and political constraints [23].
In the last decade, greater attention has been given to more decentralised and holistic strategies in Africa. One decentralised method, referred to in the literature as the participatory domestication approach, has been developed through close collaboration between scientists and farmers and involves combining scientific advances in germplasm selection, propagation, processing, etc., with local communities' experiences in management to
bring indigenous fruits and nuts into wider cultivation [26**]. The initial focus in participatory domestication is on satisfying immediate household needs for tree foods and then growth occurs through producing planting material for sale to other farmers and by the commercialisation of tree products [27**,28]. By supporting the domestication of a range of different trees, chosen by farmers who are guided in their choices by markets and other considerations, the approach is able to buffer production and market risks that may result from a focus on an individual species [29*]. The approach is being extended through the development of rural resource centres managed by local communities that: train farmers in how to propagate and manage trees; hold stock-plants for vegetative propagation; link with smaller nurseries to provide germplasm more widely; provide fruit processing facilities and business training; and act as venues for farmers to meet and form associations that allow them to market their products and obtain services more effectively [30*].
The benefits of tree domestication
Increasing yield and value when bringing indigenous food trees into cultivation is essential, as if indigenous trees are not productive they have little chance of becoming properly established in farming systems, which will otherwise be dominated by a few staple crops, reducing agrobiodi-versity and limiting resilience [31]. Genetic variation within wild and semi-wild populations of African food tree species is often high [17**], with >2- [32], >4- [33] and >5-fold variation common in nutrient content, yield and economic value, respectively, and lower but still important variation in other important traits [34]. Using simple cloning methods adopted by farmers, gains in multiple food traits (seed size, fruit thickness, shape, etc.) can be captured simultaneously, addressing markets' particular preferences [35], and the time between planting and maturity can be reduced compared to planting from seed, decreasing the time gap between investment and return for farmers [36].
Adoption of the participatory domestication method, particularly in the humid forest margins of Central Africa, where indigenous fruits and nuts are highly valued in the local economy [37-39], has resulted in significant improvements in incomes, diets and in rural business development, supporting diversified, more resilient and more productive farms and improving the social well-being of the communities involved [29*,30*]. A multi-faceted approach by which agroforestry supports food and nutritional security, and provides other tree products and environmental services, involves the following steps: first, support for soil fertility replenishment technologies to improve overall farm productivity and increase staple crop self-reliance; second, participatory tree domestication of more nutritious fruit and nut trees (as described above); and, third, entrepreneurship and value-addition
to increase returns from tree product sales [40]. The allanblackia tree (a range of species in the Allanblackia genus), found wild in the humid forests of Central, East and West Africa, provides a model for the involvement of private-public partnerships in sustainable business development (www.allanblackia.info) [41,42*]. The seed of allanblackia yield edible oil with significant potential in the global food market of >100 000 tonnes annually. Wild harvesting, cultivation, market-development and conservation activities are being promoted in parallel, and the integration of allanblackia into small-scale cocoa farms is being promoted to support more biodiverse and resilient agricultural landscapes that spread farm production and farmers' incomes across the year. The involvement of Unilever and other commercial partners helps drive investment [41].
The dangers of domestication
Domestication processes always result in shifts and/or losses in underlying genetic diversity in manipulated populations that have implications for the sustainability of cultivation, but impacts on diversity depend on the domestication method adopted, with some approaches providing a better balance between productivity gains and conserving sufficient genetic variation to support longer term use [40,43]. Cloning may for example result in significant diversity bottlenecks, potentially mimicking commercial monoculture tree plantations which may be more vulnerable to pests and diseases [44] and other environmental catastrophes [31]. Risks are however reduced in participatory domestication when different villages each clone their local superior genotypes for planting, as a range of genotypes are maintained in the wider landscape. To be avoided, however, are production systems where a new tree crop takes over the farming landscape to the detriment of other crops, as has for example been observed in palm oil production systems elsewhere in the tropics [45,46] and in west Africa in cocoa production [47]. Mixed agroforestry regimes such as shade coffee and shade cocoa production systems (www.cocoasustainability.com/) that combine commodity crops, food trees (such as allanblackia, see above [41,42*]), staple crops and vegetables, etc., which maintain commodity yields and profitability and at the same time promote resilience [48] and maximise synergy [49], are required. Multi-functional, multi-species agroforestry systems are often favoured by small-scale farmers [30*], reducing overall production risks associated with losses of genetic diversity in any one species planted for a particular use.
Future directions
The domestication of high-value trees species in agricultural landscapes is increasingly being recognised for its important contribution to rural livelihoods, especially as natural forests that have otherwise provided tree products and services recede in the face of demand for
agricultural land [19]. As human populations continue to grow and the demand for resources increases, tree domestication to provide food, fodder, medicines and other products is an important approach to meet demand. These tree products need to be grown in the right niches (hedgerows, gardens, contour strips, etc.) to complement other agricultural production options [30*,40]. For the future, a better understanding is required of the consequences of cultivation and market development for various livelihood indicators (poverty-, malnutrition-, hunger-alleviation, etc.) and for the status of and interactions between resources in forest and farmland [40,41]. A recent review of >400 papers on the topic [50**] assessed the progress that had been made in agroforestry tree domestication over the last ten years in comparison to the decade before. Between 1992 and 2001, there was a focus on assessing tree species potential and the development of propagation techniques. Between 2002 and 2011, more emphasis was placed on new techniques for assessing variation, on product commercialisation, and on adoption and impact issues. For the decade 2012 to 2021, it has been suggested [50**] that one of the major challenges in Africa and worldwide is to scale up successful agroforestry tree domestication approaches. To do this, an understanding of what approaches to tree domestication to date have been most effective in benefiting smallholders in improving incomes, food and nutritional security, health, etc., based on a more extensive quantification of impacts of past and present initiatives, is required. Particular attention should be given to evaluating the utility of the participatory domestication approach [26**] outside Central Africa, where to date it has been practiced most widely.
A second major challenge is better engagement with markets [50**]. Value chain analysis [51,52], used to map the actors participating in the production, distribution, marketing and sale of a particular product and to bring about positive change for smallholders and small-scale enterprises, is an important approach. For example, by organising smallholder banana growers into producer business groups linked buyers, TechnoServe (www. technoserve.org) improved farmers' incomes >80% in East Africa [53]. 'Nutrient-sensitive' value chains are required that improve nutritional knowledge and awareness among value-chain actors and consumers, that focus on promoting the involvement of women, and that consider markets for a wide range of tree foods [17**]. Lessons can be learnt from existing tree commodity crops such as cocoa, rubber and coffee that have an important role in supporting rural livelihoods. Abetter understanding of the complicating factors in the conversion of land to monoculture production of these commodities, and the effects of single-source incomes on food and nutritional security, are also required [9]. Commodity varieties that are highly productive and combine more effectively with other components in mixed farming systems, such as
better shade-adapted cocoa and coffee (and also other shade-tolerant crops such as yams, cocoyam, beans and sweet potatoes), are needed [22].
There has been an under-investment in the development of new tree lines, cultivars, etc., that have high yields and provide quality products under smallholder production conditions, with insufficient scientists working on bringing indigenous food trees into cultivation [17**] and in developing methods to deliver new culti-vars to farmers [24]. Research should support existing and newly developing technologies [54] for tree domestication that are appropriate for meeting smallholders' needs, and assess complementarity and resilience in agroforestry systems under climate change, in the context of other global challenges to food and nutritional security [55].
Acknowledgements
Tree domestication research at ICRAF is conducted by a team of scientists, and we acknowledge useful contributions from many colleagues in the production of this review.
References and recommended reading
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