Overstory #258 - The benefits of agroforestry systems for food and nutritional security

As well as directly providing edible products, agroforestry trees support food production by a range of other means, including by providing shade and support for crops that need it, supporting animal production and improving soil fertility.

Introduction

Agroforestry – the integration of trees with annual crop cultivation, livestock production and other farm activities – is a series of land management approaches practised by more than 1.2 billion people worldwide. Integration increases farm productivity when the various components occupy complementary niches and their associations are managed effectively (Steffan-Dewenter et al. 2007). Agroforestry systems may range from open parkland assemblages, to dense imitations of tropical rainforests such as home gardens, to planted mixtures of only a few species, to trees planted in hedges or on boundaries of fields and farms, with differing levels of human management of the various components. Agroforestry systems provide a variety of products and services that are important locally, nationally and globally (Garrity 2004); but their role is not always fully acknowledged in development policies and practices, reflecting the difficult-to-measure, diverse pathways by which trees affect people’s lives. Women who are unable to afford high-cost technologies due to severe cash and credit constraints often favour relatively low-input agroforestry options (Kiptot and Franzel 2012).

With recent world food price spikes, anthropogenic climate change concerns, and the challenge of a growing global human population, the roles of farms and forests in supporting food availability and nutritional security have returned centre-stage in politics and development. In order to provide context for the on-going discussions concerning the importance of different potential interventions to support food and nutritional security, in this Working Paper we assess the direct and indirect roles of agroforestry. In the following section we discuss agroforestry’s importance in providing food directly, in providing incomes to support access to food, in providing fuel for cooking, and through ecosystem service provision. Many of the examples presented are from sub-Saharan Africa, a region of particular concern where nine of the 20 nations with the highest burden of child under-nutrition worldwide are found (Bryce et al. 2008). Subsequent sections provide an overview of the current challenges that agroforestry faces in better supporting food and nutritional security, and discuss opportunities for action to improve the present situation. For further information on the roles of trees and agroforestry in food provision, earlier summaries on the topic should not be neglected (e.g., Arnold 1990, Hoskins 1990).

Agroforestry for food production

Solving the problems of food and nutritional security requires among other interventions a range of interconnected agricultural approaches, including improvements in staple crop productivity, the bio- fortification of staples, and the cultivation of a wider range of edible plants that provide fruits, nuts, vegetables, etc., for more diverse diets (Frison et al. 2011). Potential for the diversification of crop production lies in the great range of lesser-used indigenous foods found in forests and wooded lands that are often richer in micronutrients, fibre and protein than staple crops (Leakey 1999, Malézieux 2013). Although such foods have traditionally been harvested from forests and woodlands, access to these resources is declining with deforestation and forest degradation (FAO 2010). In this context, cultivation provides an alternative resource. Moreover, the yield and quality of production can be improved during cultivation if attention is given to genetic improvement and the adoption of efficient farm management methods, making planting an attractive option: for many wild trees, including indigenous fruits, a two-fold yield improvement or more is possible through genetic selection (Jamnadass et al. 2011).

When bringing trees from the wild into cultivation it is essential to increase yields: if indigenous trees are perceived as relatively unproductive, agriculture in deforested areas is likely to be dominated by staple crops and agro-biodiversity will be reduced (Sunderland 2011). Some food-providing trees and palms, especially fruit-producing ones, have been managed by people in a transition from the wild to cultivation in farmland for millennia, resulting in complex agroforestry systems that contain many different foods; for other tree foods, the move to domestication is much more recent and is based on scientific inquiry (Torquebiau 1984, Clement 2004). A combination of indigenous and exotic tree foods in agroforestry systems supports nutrition, the stability of production, and farmers’ incomes. Mixtures of fruit trees that spread production provide a year- round supply of important nutrients (fig. 1).

As well as directly providing edible products, agroforestry trees support food production by a range of other means, including by providing shade and support for crops that need it, supporting animal production and improving soil fertility. Agroforestry has an important role in increasing the yields of vegetables that, with fruit, provide varied and nutritionally-balanced diets rather than calories alone (Susila et al. 2012). Trees can modify the microclimate for garden crops under harsh climates and support climbing plants such as yam (Maliki et al. 2012). In an initiative in East Africa, more than 200 000 smallholder dairy farmers are growing fodder shrubs as supplementary feed. The typical increase in milk yield achieved is enabling smallholders to raise extra revenue from milk sales of more than USD 100 per cow per year, and allows farmers to provide more milk more efficiently to urban consumers (Place et al. 2009).

Figure 1

A fruit tree ‘portfolio’ consisting of nine tree species fruiting at different times of the year. The portfolio shown is based on indigenous fruits in Malawi.

At least one species in the portfolio is ripe every month, including over traditional periods of hunger due to lulls in the production of staple crops (around January and February in Malawi). Based on the vitamin C content of the fruit of these trees and the recommended daily dietary intake, ~50% of the vitamin C needs of an adult man can be met by the daily consumption of 100 g of fruit pulp of one of two species, azanza (Azanza garckeana) or bush orange (Strychnos cocculoides), for the period November to March, with only 25 g daily of the vitamin C-rich baobab (Adansonia digitata) fruit pulp providing the requirement for the rest of the year, excluding October. Knowing the vitamin contents and phenologies of different fruits allows them to be combined appropriately in cultivation. Fruit production can also be spread across the year by cultivating late- and early-fruiting varieties of a particular species and/or by applying to only some trees pruning or coppicing practices to delay production. Source: modified from Jamnadass et al. (2011).

An analysis of more than 90 peer-reviewed studies on soil fertility improvement found consistent evidence of higher maize yields in Africa from planting nitrogen-fixing green fertilisers, including trees and shrubs, although the level of response varied by soil type and technology (Sileshi et al. 2008). As well as increasing average yields, the planting of trees as green fertilisers in southern Africa is able to stabilise crop production in drought years and during other extreme weather events, and improve crop rain use efficiency (Sileshi et al. 2011, 2012) (fig. 2). This is important for food security in the context of climate change, which is increasing drought incidence in the region.

Supporting the regeneration of natural vegetation in agroforestry systems can also provide significant benefits for staple crops production. Farmer-managed natural regeneration (FMNR) of faidherbia (Faidherbia albida) and other leguminous trees in dryland agroforests (parklands) in semi-arid and sub-humid Africa is a good example. Since 1985, FMNR has been supported in Niger by a policy shift that awarded tree tenure to farmers (as well as by more favourable wetter weather); it has led to the ‘regreening’ of approximately 5 million hectares (Sendzimir et al. 2011). FMNR in the Sahel has led to improvements in sorghum and millet yields, and positive relationships have been observed with dietary diversity and household income (Place and Binam 2013).

Figure 2

Maize yields in five districts in Malawi with and without the intervention of the Agroforestry Food Security Programme. Figures are based on 283 beneficiaries and 200 non-beneficiaries distributed across districts.

Note: bars represent 95% confidence intervals; in three cases (Dedza, Mulanje and Salima) the difference between categories is statistically significant.

Agroforestry for incomes to support access to food

Examples from Africa of widely traded agroforestry tree foods that support farmers’ incomes include the indigenous semi-domesticated and widely cultivated fruit safou (Dacryodes edulis, Schreckenberg et al. 2006), the indigenous incipient domesticate shea nut (Vitellaria paradoxa, Masters and Addaquay 2011) and exotic mango. New commercial markets for fruit are developing in Africa as a result of recent investments by Coca Cola, Del Monte and others to source produce locally for juice manufacture. The production of timber and other agroforestry tree products for markets also provide incomes for food purchase. Many trees are cultivated to provide medicines from bark, leaves, roots, etc., which are sold to support incomes and are used for self treatment, supporting the health of communities along with the provision of healthy foods (Muriuki et al. 2012).

Market data recorded for agroforestry tree products are sparse, but information on export value is quantified for tree commodity crops such as palm oil (derived from oil palm, Elaeis guineensis), coffee (primarily from Coffea arabica), rubber (from Hevea brasiliensis), cocoa (from cacao, Theobroma cacao) and tea (primarily from Camellia sinensis). Each of these crops is grown to a significant extent by smallholders, as illustrated in Indonesia where, in 2011, small farms were estimated to contribute 42%, 96%, 85%, 94% and 46% of the country’s total production area for palm oil, coffee, rubber, cocoa and tea, respectively (Government of Indonesia 2013). Unlike Indonesia, many countries do not formally differentiate between smallholder and larger-scale plantation production, but more than 67% of coffee produced worldwide is estimated to be from smallholdings (International Coffee Organization 2013), while the figure is 90% for cocoa (International Cocoa Organization 2013).

Taken together, the annual export value of the above five tree commodity crops is tens of billions of USD (FAO 2013a). Less clear is the proportion of the export value that accrues to smallholder producers, but often production constitutes a considerable proportion of farm takings. There is a danger, however, that the planting of commodities will result in the conversion of natural forest – which contains important local foods – to agricultural land, and a risk that food crops will be displaced from farmland in a trend towards the growing of monocultures (e.g., oil palm, Danielsen et al. 2009). Buying food using the income received from a single commodity crop can also lead to food insecurity for farm households when payments are one-off, delayed or unpredictable in value. Monocultures also reduce resilience to shocks such as drought, flood and, often (although not always), the outbreak of pests and diseases. As a result, tree commodity crops are sometimes viewed sceptically within agricultural production-based strategies to improve nutrition (FAO 2012). For farmers who have too little land to cultivate enough food to meet their needs, however, incomes from tree commodity crops may be the only way to obtain sufficient food (Arnold 1990).

Mixed agroforestry regimes can help to avoid many of the negative effects described above by combining tree commodities in diverse production systems with locally important food trees, staple crops, vegetables and edible fungi. Such regimes include shade coffee and shade cocoa systems (Jagoret et al. 2011, 2012, Sustainable Cocoa Initiative 2013), which increase or at least do not decrease commodity yields and profitability (Clough et al. 2011). Such systems have often been traditionally practised but are now being actively encouraged through certification and other schemes by some international purchasers of tree commodity crops (Millard 2011). There are also opportunities to develop valuable new tree commodities that are compatible with other crops. Not all tree commodities are, however, amenable to production in diversified systems, for example, oil palm is not well suited (Donald 2004).

Agroforestry, fuel and food

Traditional energy sources have received little attention in current energy debates, but firewood and charcoal from trees are crucial for the survival and well-being of perhaps two billion people, enabling them to cook food to make it safe for consumption and palatable and to release the energy within it (FAO 2008). In sub-Saharan Africa, the use of charcoal is still increasing rapidly, with the value of the charcoal industry there approximately USD 8 billion in 2007 (World Bank 2011). The charcoal industry is therefore important for food and nutritional security, because it produces both energy and income; with the increasing prices of ‘modern’ energy sources, this situation is unlikely to change for some time.

In poor households, firewood and charcoal are often burnt in open fires or poorly-functioning stoves with substantial emissions of pollutants (especially from firewood) that damage human health and may lead to the deaths of more than one million people annually worldwide, the majority women (Bailis et al. 2005). Fuel quality depends on the tree species being burnt, with poor families often using species that were traditionally avoided because of their harmful smoke or that were maintained for other products such as fruit (Brouwer et al. 1997).

Reduced access and increased prices of wood-based biomass have led to initiatives to promote agroforestry cultivation. Where smallholders practise agroforestry, less fuelwood needs to be purchased, there is less reliance on collecting from natural stands, and less time is involved in collection. This leaves more time for income-generating activities, especially for women who are usually the major fuelwood collectors (Thorlakson and Neufeldt 2012). Access to cooking fuel provides people with more flexibility in what they can eat, including foods with better nutritional profiles that require more energy to cook. The cultivation of woodlots allows the production of wood that is less harmful when burnt and has higher energy content. The use of better stoves – with greater efficiency – reduces greenhouse gas emissions relative to the energy generated for cooking purposes.

Agroforestry, ecosystem services, climate change and food

Agroforestry trees provide important ecosystem services including: soil, spring, stream and watershed protection; animal and plant biodiversity conservation; and carbon sequestration and storage, all of which ultimately affect food and nutritional security (Garrity 2004). Individual farmers can be encouraged to preserve and reinforce functions that extend beyond their farms by payments for ecosystem services, but more important in determining their behaviour is the direct products and services they receive from trees (Roshetko et al. 2007a). An advantage of smallholder agroforestry systems is that they can perform wider services while directly supporting local production (Leakey 2010).

Appropriate combinations of crops, animals and trees in agroforestry systems can not only increase farm yields, but promote ecological and social resilience to change because the various components of a system and the interactions between them will respond in differing ways to disturbances. A diversity of species and functions within integrated production systems is therefore a risk reduction strategy, and agroforestry is recognised as an important component in climate-smart agriculture for both its adaptation and mitigation roles (Neufeldt et al. 2012). For example, soil fertility improvement technologies can stabilise crop yields in drought conditions. In Niger, farmers explain that increasing the number of tree species per function insures them against ‘function failure’ in their farming systems because at least some species will provide each required function even in the driest years (Faye et al. 2011). In western Kenya, subsistence farmers practising agroforestry (e.g., for soil erosion control, improving soil fertility and fuelwood provision) identify more coping strategies when exposed to climate-related hazards than those who do not practise agroforestry (Thorlakson and Neufeldt 2012).

Kristjanson et al. (2012) explored the relationship between food security and farmer innovation in the context of changing circumstances, including climate variability, with farmers in Ethiopia, Kenya, Uganda and the United Republic of Tanzania. A strong positive relationship was demonstrated between food security and the adoption of new farming practices, although it was not possible to determine whether this was because innovative households are more food-secure as a result of innovation, or if more food-secure households are better placed to subsequently innovate. Many of the 700 surveyed households were practising agroforestry, but generally they were only planting small numbers of trees, suggesting that there is a need to understand why there has not been wider uptake of agroforestry. Possibly, the initial investment required before benefits are received from trees (perhaps some years after planting) is an important factor.

A diversity of trees in farmland and neighbouring natural forest fragments, where present, supports populations of pollinator species such as insects and birds that are essential for the production of many crops (Garibaldi et al. 2013). Many fruit tree species that are important as human foods rely on insect pollinators for their production (Klein et al. 2007), while diverse farms that provide an alternative habitat for pollinator communities can support the regeneration of food plants in neighbouring forests (Hagen and Kraemer 2010).