Agroforestry is a collective name for land-use systems and technologies where woody perennials, such as trees, shrubs, palms and bamboos, are deliberately used in the same land management unit as agricultural crops and/or animals (FAO, 2009c). Agroforestry practices are numerous and diverse and used by 1.2 billion people (World Bank, 2004), with many of the benefits arising from local marketing (Shackleton et al., 2007).
• Diversity. Agroforestry systems are well known as providers of enhanced biodiversity. Agroforestry types such as forest gardens have 100–200 species growing in them (Crawford 2010), and hold high potential for even increasing biodiversity. One of the most well-known forest gardens, the Schumacher Forest Garden in Totnes, Devon, England, grows some 500 species on 0.8 ha. Through the integration of trees in farming systems, agroforestry encourages the development of an agroecological succession (Leakey, 1996; Schroth et al., 2004), which creates niches for colonization by a wide range of other above- and below-ground organisms in field systems (Ewel, 1999; Leakey, 1999b; Schroth et al., 2004; Schroth and Harvey, 2007). Agroforestry systems provide a large range of diversified outputs including products (timber, fuelwood, food and medicines), inputs for crop and livestock production (fodder, soil nutrients and pollination) and services (watershed protection, climate regulation, carbon storage and biodiversity conservation).
• Coherence. Integrating trees encourages and enhances internal coherence of agroecosystems by promoting active life cycles, food chains, nutrient cycling and pollination at all trophic levels and helping to control pests, diseases and weeds (Collins and Qualset, 1999) in about two-thirds of the agroforests tested (Schroth et al., 2000).
• Connectedness. Perennial trees, shrubs and vines reduce soil erosion by providing cover from heavy rain and reducing wind speed. Their integration into farming systems also creates a cool, shady microclimate, with increased humidity and lower soil temperatures (Ong and Huxley, 1996; Ong et al., 1996; van Noordwijk et al., 2004). The deep and widespread roots provide permanent physical support to the soil and aid in deep nutrient pumping, decreasing nutrient losses from leaching and erosion (Young, 1997; Huxley, 1999). Herbicide retention by buffers also can be substantial (Arora et al., 2003). On a global scale, agroforestry systems could potentially store 12-228 (median 95) tonnes C per ha, under current climate and soil conditions (Dixon, 1995).
• Efficiency. Due to tree capacity to capture energy, nutrients and carbon, efficiency of agroforestry systems is higher than for most other farming systems. Furthermore, agroforestry can increase farmers’ income. For example, project activities in the Nhambita community, Mozambique, yield carbon offsets equal to 24 117 tonnes CO2 per annum over an area of about 20 000 ha. Farmers receive carbon payments at a rate of USD 4.5 per tonne of CO2, or in the range of USD 433–808 per ha over 7 years. The project shows that carbon sequestration through land use, land use change and forestry (LULUCF) can promote sustainable rural livelihoods and also generate verifiable carbon emission reductions for the international community (World Agroforestry Centre, 2009a; 2009b). Domesticating wild fruit trees, such as African plums and the bush mango, has allowed smallholder farmers in Cameroon to increase their earnings fivefold, and indigenous, nitrogen-fixing trees planted with unfertilized maize have increased yields in numerous countries of Africa and are being grown on over 5 million hectares of cropland in Niger (Garrity and Stapleton, 2011).
• Resilience. Moving the “tree element” back into the farming landscape improves the resilience of the farming system as a whole by improving its diversity, both environmental and socio-economic. Many agroforestry tree crops are important as sources of feed for livestock (Bonkoungou et al., 1998), and offer potential new markets such as vegetable oils (Kapseu et al., 2002), pharmaceuticals or nutriceuticals (Mander et al., 1996; Mander, 1998). They also help farmers meet specific income needs, e.g. school fees and uniforms (Schreckenberg et al., 2002), and buffer the effects of price fluctuations in cocoa and other cash crops (Gockowski and Dury, 1999).
Capacity for a green economy. Agroforests have always made important contributions to the food security of a large part of the world’s food insecure people and will likely have an even more crucial role in situations of increased food prices. They provide products (timber, fuelwood, food and medicines), inputs for crop and livestock production (fodder, soil nutrients and pollination) and services (watershed protection, climate regulation, carbon storage and biodiversity conservation). Scaling-up agroforestry practices will require knowledge sharing and management skills to ensure higher efficiency of the system. Carbon projects with agroforestry practices have proven that scaling-up is a viable possibility since farmers are rewarded for their extra efforts.