Multifunctional Agriculture and the Role of Agroforestry

There are many examples from around the world of low-input, propoor approaches to rural development that enhance production, livelihoods, and ecosystem service functions. Some of these approaches are based on integrated management systems such as reduced- or no-tillage, conservation agriculture, ecoagriculture, agroforestry, permaculture, and organic agriculture. Of these, agroforestry seems to be particularly relevant to the delivery of multifunctional agriculture. Like the other systems, it addresses the issues of soil fertility management; the rehabilitation of degraded farming systems; loss of biodiversity above- and belowground; carbon sequestration; and soil and watershed protection. However, in addition, agroforestry also provides three crucial outputs that are not provided by the other systems, namely: (1) useful, underutilized, and marketable indigenous tree products for income generation, fuel, food, and nutritional security/health and the enhancement of local livelihoods; (2) complex, mature, and functioning agroecosystems akin to natural woodlands and forests; (3) linkages with culture through the food and other products of traditional importance to local people (Leakey, 2010). Thus, the aims of agroforestry are to simultaneously restore: biological resources and natural capital (soil fertility, water, forests, etc.); livelihoods (nutrition, health, culture, equity, income); and agroecological processes (nutrient and water cycles, pest and disease control, etc.).

In agroforestry, the domestication of underutilized and indigenous trees was initiated in the mid-1990s by the World Agroforestry Centre (ICRAF) and its partners aimed at improving the quality and yield of products from traditionally important species that used to be gathered from forests and woodlands. Since then other groups, such as the Agroforestry and Novel Crops Unit of James Cook University and its partners in Oceania, have joined the initiative. As well as meeting the everyday needs of local people, these products are widely traded in local and regional markets and so have the potential to become new cash crops for income generation and to counter malnutrition and disease by diversifying dietary uptake of micronutrients that boost the immune system. These indigenous tree species also play an important role in enhancing agroecological function and, through carbon sequestration, help to counter climate change.

Agroforestry practices are especially numerous in the tropics and are used by more than 1.2 billion people. They produce the products that are important for the livelihoods of millions of other people in developing countries. The area under agroforestry worldwide has not been determined, but over 1 billion hectares (46%) of farmland have more than 10% tree cover, affecting about 30% of rural people (Zomer et al., 2009). Like organic farming, conservation agriculture and ecoagriculture, agroforestry addresses soil fertility management issues for the rehabilitation of degraded farming systems; loss of biodiversity above- and belowground; carbon sequestration; and soil and watershed protection. On the down side, trees are competitive with crops (Cooper et al., 1996) and the net benefits of agroforestry can be slow to materialize due to the longevity of trees. However, techniques such as the vegetative propagation of ontogenetically mature tissues speed up the benefit flows by creating cultivars from parts of the tree that already have the capacity to flower and fruit without going through a long juvenile phase.

Domestication of Plant Species

Crop domestication is human-induced change in the genetics of a plant to conform to human desires and agroecosystems (Harlan, 1975). Crop domestication has been limited to less than 0.05% of all plant species and about 0.5% of edible species (Leakey and Tomich, 1999) and the process goes back thousands of years; for example, the domestication of oranges and apples goes back about 3000 years in China and central Asia, respectively (Simmonds, 1976). According to Diamond (1997), the domestication of useful species has been “the precursor to the development of settled, politically centralized, socially stratified, economically complex, and technologically innovative societies.”

Domestication is also said to be stimulated when demand exceeds supply. The latter would explain this recent interest in domesticating tree crops from wild forest species in the tropics, as deforestation has increased in proportion to population growth. This has made the underutilized wild species a scarce resource, which is much in demand. Interestingly, some poor smallholder farmers have reacted to deforestation by starting to select useful trees for growth within their farms (Leakey et al., 2004; Leakey, 2005). These farmers can probably be said to be practicing “commensal” domestication as they have retained natural seedlings in their fields and home gardens and cut down those that do not have desirable characteristics when they clear land for other crops. Secondly, they also sow and disperse the seeds of the tastier fruits that they eat, close to the homestead. This commensal approach to domestication provides a good foundation for the “direct” pathway to domestication that is now being taken by agroforesters working to empower local communities through participatory approaches.

The definition of domestication used for agroforestry trees (Leakey and Newton, 1994a) encompasses the socioeconomic and biophysical processes involved in the identification and characterization of germplasm resources; the capture, selection, and management of genetic resources; and the regeneration and sustainable cultivation of the species in managed ecosystems. This definition therefore stresses that domesticates will be compatible with sustainable land-use systems and have beneficial socioeconomic and environmental impacts. Consequently, the domestication of agroforestry trees is an incentive to promote sustainable agriculture through diversification with species which generate income, improve diets and health, meet domestic needs, and restore functional agroecosystems, as well as empowering local communities (Leakey, 2012c).

The recent history of agroforestry tree domestication has been reviewed by Leakey et al. (2005a, 2007, 2012), and the products of these cultivated trees have been named AFTPs to distinguish them from the extractive resource of NTFPs (Simons and Leakey, 2004).

Strategies of Domestication for Agroforestry Trees

The tree domestication strategy involves the maintenance and use of three interlinked populations (Leakey and Akinnifesi, 2008):

The strategy is equally appropriate for the domestication of species producing fruits and nuts; medicinal products; leafy vegetable and animal fodder; timber and wood; and extractives like essential oils, resins, etc. (Table 31.1). For the purpose of efficiency and speed, the domestication strategy adopted by agroforestry has been a clonal one. This is based on well-known horticultural techniques of vegetative propagation (Leakey, 2004), applied in a simple, robust, and low-tech manner (Leakey et al., 1990) so as to be appropriate for implementation in remote areas of tropical countries which lack reliable supplies of running water or electricity. Vegetative propagation is a uniquely powerful means of capturing existing genetic traits and fixing them so that they can be used as the basis of a genetic variety or “cultivar.” The advantage of using clonal propagules outweighs those of seedlings when the products are valuable, or when the tree has a long generation time and when the seeds are scarce or difficult to keep in storage (Leakey and Akinnifesi, 2008). The consequent uniformity in the crop is advantageous in terms of maximizing quality, meeting market specifications and increasing productivity, but it also increases the risks of pest and disease problems. Consequently, risk aversion through the diversification of the clonal production population is a crucial component of the strategies used. Agroforestry enhances this risk aversion by diversifying agroecosystems in ways that improve agroecosystem function (Leakey, 1999b).

Secondly, to benefit the target population of poor smallholder farmers, the strategy is based on participatory approaches to both decision making and implementation (Tchoundjeu et al., 1998; Leakey et al., 2003). This foundation in participatory processes ensures that domestication is a farmer-driven process that also has an eye on the local market to ensure that farmers will be able to sell their products (Simons, 1996; Leakey and Simons, 1998; Simons and Leakey, 2004). The first participatory step involved an exercise in priority setting, in which farmers listed their preferred species for domestication (Franzel et al., 1996, 2008). This was to ensure that the outputs of the program were relevant to farmers’ needs and so to encourage their active interest and involvement. Interestingly, almost everywhere in the world where this priority setting has been done, farmers have selected familiar and locally marketed indigenous fruits and nuts as their top priority. This is because these traditionally important products are no longer readily available in the wild and are important domestically to rural people because of their cultural and nutritional value. The second step is a participatory approach to project implementation aimed at empowering local communities, promoting food self-sufficiency, generating income and employment, and enhancing nutritional benefits. By providing knowledge and training, the program assists farmers to develop the skills to set up village nurseries and apply simple and adoptable approaches to nursery management; the horticultural techniques of vegetative propagation and tree selection; agroforestry and community development. The participatory approach has been adopted in order to provide the incentive for farmers to raise themselves out of poverty, malnutrition, and hunger through enhanced livelihoods, and food and nutritional security. Together these two steps to participatory domestication probably also explain the rapid adoption by rural communities (Tchoundjeu et al., 2006, 2010a, 2010b). After about 12 years the number of engaged communities had grown from two pilot villages in Cameroon to 485 villages centered on five Rural Resource Centres and involving about 7100 farmers (Asaah et al., 2011). The concept has also spread to neighboring countries (Tchoundjeu et al., 2006): 11 villages in Nigeria (about 2000 farmers), 3 villages in Gabon (about 800 farmers), and 2 villages in Equatorial Guinea (about 500 farmers).

This strategy of village-level participatory domestication is also important because it conforms to the Convention on Biological Diversity (Tchoundjeu et al., 1998; Leakey et al., 2003; Simons and Leakey, 2004), by recognizing the rights of local people to their indigenous knowledge and traditional use of native plant species. Protection of the farmers’ intellectual property is needed to ensure that participatory domestication by local farmers can be recognized as a good model of biodiscovery; an alternative to biopiracy by expatriate or local entrepreneurs. However, until global negotiations create an effective means of protecting the intellectual property of farmers they remain at risk of being exploited, although some procedures to register farmers’ cultivars have been proposed as an interim measure (Lombard and Leakey, 2010).

Constraints to Domestication

One constraint to tree domestication is that agroforestry trees are notoriously difficult to domesticate because they are predominantly outbreeding. This means that gains in selected traits are on average small because of the wide range of intraspecific variation in the progeny arising from controlled pollinations. Additionally the long generation time of many trees (10–20 years) means that an individual geneticist does not produce many generations within his/her career. These problems can be overcome by the horticultural approach to domestication, by using vegetative propagation to mass produce individual trees with superior characteristics. Until recently, however, trees have had the reputation of being very difficult to propagate by stem cuttings. This perception has arisen from poor understanding of the principles determining success, mainly the result of poor experimental reporting leading to a confused research literature (Leakey, 2004). The techniques of grafting and budding and marcotting have provided an alternative means of capturing phenotypic variation, but they too have some technical difficulties (e.g., graft incompatibility, dominance by the rootstock, etc.), as well as requiring some special skills. Currently, the numbers of people in many developing countries with appropriate skills in all approaches to vegetative propagation may be a constraint to the widespread upscaling and adoption of participatory domestication in the future (Simons and Leakey, 2004). Nevertheless, perhaps the overriding factor that has constrained the “direct” approach to tree domestication has been the disinterest of colonists and development agencies in products that did not appeal to “western” tastes. Consequently they were neither promoted by early European settlers, nor were they funded by the Green Revolution.

Putting Tree Domestication Into Practice

A fundamental requirement of the clonal approach to domestication is a good understanding of the intraspecific variation in all traits of importance for selection and improvement. Consequently, quantitative studies have been made of the tree-to-tree variation in a range of fruit and nut traits to determine the potential for highly productive and qualitatively superior cultivars with a high Harvest Index (reviewed by Leakey et al., 2005a). This information is needed in order to identify the elite trees with the desirable combinations of different traits that would be appreciated by different markets (e.g., edible fruits, edible nuts, nuts for food oil, nuts for cosmetic oils, or fruits and nuts for medicinal products). The practical approach is to seek trees, which have particular, market-oriented, trait combinations—such as big, sweet fruits (even seedlessness) for the fresh fruit market (a fruit ideotype); big, easily extracted kernels for the kernel market (kernel ideotype), etc. Ideotypes can then be subdivided into those meeting the demands of different markets (Leakey and Page, 2006), such as food-thickening agents conferring drawability and viscosity (Leakey et al., 2005d), or other products, such as pectins or oils for the food or cosmetic industries (reviewed by Leakey, 1999a). Likewise a preliminary analysis of Sclerocarya birrea fruits has identified considerable tree-to-tree variation in protein and vitamin C (Thiong’o et al., 2002), while preliminary studies in Canarium indicum from Papua New Guinea have evaluated tree-to-tree variation in fatty acid profiles, protein and vitamin E contents (Leakey et al., 2008). Fatty acid profiles have also been the subject of studies in Allanblackia species (Atangana et al., 2011), species which are being developed as a new oil crop for Africa (Jamnadass et al., 2010).

One of the key findings of these characterization studies is that each trait shows very considerable and continuous variation from low to high values. Interestingly, this is greatest at the village level, while the variation between villages is only modest. Importantly, it is also found that high values of one trait are not necessarily associated with high values of another trait: thus large fruits are not necessarily sweet fruits, and do not necessarily contain large nuts or kernels. Consequently the more trees that are examined, the greater are the opportunities for creating exciting new cultivars.

A start has been made to look at the genetic variability in sensory and medicinal traits in a few AFTP producing crops. Kengni et al. (2001) have made a preliminary examination of the variability in flavor, astringency, taste, and aroma in samples of Dacryodes edulis, while Leakey et al. (2008) have assessed antioxidant activity and phenolic content in C. indicum. Interestingly, the latter study also identified very considerable tree-to-tree variation in the antiinflammatory property of kernel oil between just 10 trees. This finding illustrates the very real opportunity to develop cultivars for medicinal properties. Other evidence of tree-to-tree variation in medicinal value has been recorded in the major sterol component, B-sitosterol, from the bark of Prunus africana, which is of importance for the treatment of benign prostatic hyperplasia (Simons and Leakey, 2004). This variability in nutritional quality and medicinal properties is likely to affect the potential for different markets, so there is an urgent need for agroforesters to work closely with the food, nutraceutical, and pharmaceutical industries to optimize the domestication/commercialization partnerships (Leakey, 1999a). One aspect of the potential health benefits of agroforestry is the fortification of the immune systems of HIV/AIDS sufferers through the selection of especially nutritious cultivars of indigenous fruits and nuts (Barany et al., 2001), something that requires further investigation as an output from agroforestry (Villarreal et al., 2006).

Up to this point, the focus of tree domestication has been almost exclusively on food, fodder, and medicinal products, but is the approach relevant to other tree products, such as extractives? To test this, a recent study of four essential oils in two sandalwood species (Santalum austrocaledonicum and Santalum lanceolatum) has shown that these fragrant oils extracted from heartwood have very marked but similar patterns of continuous tree-to-tree variation (Page et al., 2010a). This result therefore offers opportunities to use these techniques to rebuild the sandalwood industry of the Pacific using participatory domestication and agroforestry (Page et al., 2010b).

In addition to the previous qualitative traits, there is also the opportunity for cultivars to capture variation in quantitative traits and in phenology, such as yield, seasonality, and regularity of production, reproductive biology and reduction of susceptibility to pests and diseases which can reduce productivity or quality (Kengue et al., 2002b). High yield is obviously a desirable trait, but in the early stages of domestication it may be even more important economically, nutritionally, etc., to expand the fruiting season from 2–4 to 6–8, or even 12 months. Emerging evidence suggest that in many species there are rare individuals that flower and fruit outside the main season. This seasonality of production offers important opportunities to increase the duration of the productive season and so reduce the periodicity of income generation for the farmer, as well as to make it easier to provide commercial markets with year-round supply.

Having identified which are the elite trees worthy of becoming cultivars, they are propagated vegetatively to capture the specific combination of genetic traits as a clone (Leakey et al., 1990). To ensure that optimal use of the genetic resource is achieved, the clonal approach is integrated with others to ensure that a wise genetic improvement strategy is adopted (Leakey and Akinnifesi, 2008).

Retention and Protection of Genetic Diversity

Typically only the best plants are brought into domestication programs, so domestication is generally considered to reduce the genetic diversity of the species being domesticated, creating the so-called domestication bottleneck (Cornelius et al., 2006). This is probably true in situations where the domesticated plant replaces or dominates the wild origin, but is probably not the case at the current level of domestication of agroforestry trees. So, for example, in most of the trees currently being domesticated there is still a robust wild population. Evidence from molecular studies of Barringtonia procera in the Solomon Islands (Pauku et al., 2010) found that the trees with the largest kernels were found in many different populations and were not closely related. Thus selected cultivars produced by different communities will all have large kernels but they will be genetically diverse in all the unselected traits, such as pest and disease resistance, etc. Similar results have been obtained by Assogbadjo et al. (2009) in baobab (Adansonia digitata).

The high frequency of intraspecific variation in village populations (about 80%) indicates that cultivar development at the village level also minimizes loss of genetic diversity, especially when wild populations are also present. This therefore is another advantage of implementing a participatory domestication strategy independently in different villages (Leakey et al., 2003). Modern molecular techniques are useful in the development of a wise strategy for the maintenance of genetic diversity, as within the geographic range of a particular species they can be used to identify the ‘hot-spots’ of intraspecific diversity (e.g., Lowe et al., 1998, 2000), places which should, whenever possible, be protected for in situ genetic conservation, or be the source of germplasm collections if ex situ conservation is required.

Social, Economic, and Environmental Benefits of Domestication

Crop domestication has been credited with being one of the major stimulants of agricultural development and hence the diversification of civil society and economic development, and even the evolution of civilization (Diamond, 1997). This illustrates the close linkage between domestication and the commercialization of the products. Recognizing this linkage and deliberately promoting the parallel development of domestication and commercialization is a very important part of the domestication strategy for agroforestry trees (Leakey, 1999a; Leakey and Akinnifesi, 2008; Bunt and Leakey, 2008). In West and Central Africa, a number of indigenous fruits and nuts, mostly gathered from farm trees, contribute to regional trade. In Cameroon, the annual trade of the products of five key species has been valued at US$7.5 million, of which exports generate US$2.5 million (Awono et al., 2002). Perhaps because of this trade, evidence is accumulating that AFTPs do contribute significantly to household income and to household welfare (Schreckenberg et al., 2002; Degrande et al., 2006).

In terms of social benefits, women, who are the main retailers of NTFPs (Awono et al., 2002), are often the beneficiaries of this trade and they have especially indicated their interest in marketing D. edulis fruits because the fruiting season coincides with the time to pay school fees and to buy school uniforms (Schreckenberg et al., 2002). The role of women in trade and marketing of AFTPs is being enhanced by domestication, and hopefully children will also benefit, not only from improved nutrition, but by greater access to education. Similar trends are emerging in southern Africa, where indigenous fruits have relatively new local and international markets (Shackleton et al., 2002). Because the production and trading of AFTPs are based on traditional lifestyles, it is relatively easy for new producers to enter into production and trade with minimal skills, low capital requirement, and with little need for external inputs. Together these things make this approach to intensifying production and enhancing household livelihoods very easy and adoptable by poor people.

Integrating Domesticates Into the Cropping System

Domesticated trees for the production of AFTPs can be integrated into farming systems in many ways, either in home gardens, or as shade in cash-cropping systems such as cocoa or coffee (Leakey and Tchoundjeu, 2001), as scattered trees in food crop fields, or as boundary trees, to generate income, provide products for domestic use as well as to provide environmental services. Trees also used to maintain tenure of customary land which would otherwise have to be forfeited if not seen to be in use.

Agroforestry often creates opportunities for shade-adapted species to fill shady niches and increase the benefits derived from mixed-cropping systems. In this connection, most existing food crops have been selected and bred for cultivation in full sun, so there are opportunities for plant breeders and domesticators to develop new crops or crop varieties that are better adapted to partial shade—e.g., Eru (Gnetum africanum) in Cameroon. When new agroforestry crops are integrated with other agroforestry practices, such as improved fallows for soil fertility management, the combined impacts can reduce the crop Yield Gap (the difference between potential yield of a food crop and the actual yield achieved by farmers) and result in many economic, social and environmental benefits (Asaah et al., 2011) that go a long way toward meeting the goals of multifunctional agriculture.

To date, one tree domestication project—Agricultural and Tree Products Program in west and northwest regions of Cameroon—has been outstanding as an example of how the participatory domestication of underutilized species can be a catalyst for the adoption and delivery of multifunctional agriculture within an integrated rural development program (Asaah et al., 2011). This success has been the outcome of the dissemination of knowledge and skills to neighboring communities, via Rural Resource Centres to break the cycles of land degradation and social deprivation that have kept nearly half the world’s population in poverty. These activities are now steering the participating villages down a path toward social, economic, and environmental sustainability. Part of the package on new techniques and knowledge is access to and use of microfinance. This has helped over 1000 farmers to obtain short and small-scale loans (about $200 over a period of a few months) for the purchase of inputs such as seeds, fertilizers and hired labor. This has enhanced crop production and had additional benefits such as releasing children from farm work so that they can attend school.

To rebuild the forest resource of useful indigenous trees the Agricultural and Tree Products Programme has taken an innovative three-step approach (Asaah et al., 2011):

The village nurseries have produced 1,508,000 fertilizer trees over 3 years for use in improved fallows which have more than doubled crop yields. These leguminous trees and shrubs are also popular with beekeepers, who have significantly increased their honey production. They have also produced over 159,060 trees of indigenous fruit and nut trees for home use, for sale and for integration into the tree improvement program (Table 31.2).

Together these village nursery activities have enriched local farms and generated significant income. Typically, this income stream gathers momentum after about 3 years (Fig. 28.9). For example, after 10 years, plant sales from MIFACIG Rural Resource Centre at Belo, and its 35 satellite nurseries in the Northwest region of Cameroon, were valued at US$28,350. Impressively, income was especially high after only 5 years (US$40,000) at the GIC PROAGRO Rural Resource Centre in Bayangam, which has eight satellite nurseries in the West region of Cameroon. This was due to its strong focus on fruit trees. Soon, these communities will also be able to further increase their income by selling fruits from their named cultivars.

To encourage the processing of both food crops and AFTPs, the project, through the activities of WINROCK International, has encouraged the development and fabrication of simple equipment in local towns. Nine local metal workers have been trained and are making equipment for drying, and grinding products. At least 150 discharge mills and 50 dryers have been sold, generating income in excess of US$120,000. This has created employment opportunities for about 200 machine operators. Profits from this enterprise are about 10–20%. Local entrepreneurs and producers are benefiting from the use of this equipment to improve the quality and shelf life of their produce. For example, one trader in Bamenda market, North West Region, Cameroon is selling sealed packages of Nyangsang (Ricinodendron heudelottii), Bitter leaf (Vernonia spp.), and Eru (G. africanum). His trade increased threefold in four months as he gained a reputation for quality products. These small businesses have also created employment for local people. In addition, many women’s groups are setting up businesses for grinding crops like cassava and producing “gari” which is substantially increasing their income.

Putting all this together, the farmers have reported over 30 life-changing positive impacts, which are now being verified and quantified. These impacts range from increased income from the sale of plants and AFTPs, improved diet, improved health, ability to send children to school, improved buildings and other infrastructure, such as wells (Asaah et al., 2011). In addition these farmers are also reporting a feeling of empowerment from increased knowledge and success and they are recognizing that they have a pathway out of poverty. However, perhaps the most important impact has been the decision of young men to stay in the community rather than migrating to town, because they now could see a future in the village. Overall, therefore, this program is delivering a suite of impacts as part of a much bigger package, which is improving the social, economic and environmental sustainability of rural life in Cameroon. It therefore seems that this is the pathway to more widely applied rural development for the alleviation of hunger, malnutrition and poverty. As such it is an example of agroforestry delivering multifunctional agriculture (Leakey, 2010).

Taken together, all these impacts achieved in just 12 years strongly suggest that the domestication of indigenous fruit and nut trees is promoting self-sufficiency through the empowerment of individuals and community groups by disseminating new skills in agroforestry, food production and processing. This project therefore addresses the key socioeconomic and biophysical problems facing smallholder farmers in Cameroon. This success can be attributed to the relevance of the work to the farmers’ needs and interests and the fact that the program builds on traditional knowledge, local culture, local species and local markets. This initiative has hit the right set of buttons to appeal to farmers and rural communities. Impressively, this process also snowballs, as each community draws in new neighboring communities in a continuous progression of adoption and knowledge dissemination. As a consequence, these communities are on a path toward a better standard of living that is based on the recognition of traditional knowledge of locally important underutilized species. This approach therefore builds on their traditional “life-support systems” derived from indigenous species formerly ignored by agricultural science (Asaah et al., 2011).

What is needed now is to disseminate these skills and experience to millions of other poor people in Africa and other tropical countries. There are many ways of doing this, but one very interesting and outstanding lesson from this project has been the importance of building rural development from the grassroots, using technologies that are simple, practical and easy to implement without spending large amounts of money. The nurseries are a good example; the facilities needed are well within the reach of most farmers once they have had training in the simple technologies developed by the World Agroforestry Centre for soil fertility management and tree domestication. Once established, these activities are self-supporting. Additionally, the philosophy of self-help integrated rural development promulgated by the Rural Resource Centres has been proven to encourage very strong local participation, and ensured the sustainability of the diverse set of activities.

The challenge now is to scale this project up from 7100 farmers in 485 villages to hundreds of millions of rural people across the tropics, and to help some of them to find employment and business opportunities in the rural economy, but outside farming.