Overstory #225 - Tree domestication for multi-functional farming systems
The increasing loss of forest resources in tropical countries leaves farmers without the food and other products that used to be gathered locally. This coupled with land degradation creates a poverty trap from which it is difficult for smallholder farmers to escape. To address these problems, the domestication of new perennial crops from traditionally important indigenous trees is seen as a way to diversify farming systems making them more sustainable through the provision of a range of products and environmental services. This enriches existing mixed tree/crop farming systems and creates new ones that are more productive and enhance the livelihoods of poor households. A participatory approach to tree domestication is used to ensure that farmers’ needs are met. This approach is in accord with the findings of the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD), which has recently identified the need for agriculture to be more multi-functional and to simultaneously achieve economic, social and environmentally sustainability by restoring: 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.).
The International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD) has recently reviewed the state of global agriculture vis à vis sustainable rural development (McIntyre et al., 2009). It concluded that to achieve economic, social and environmental sustainability it was necessary to redirect agriculture towards multi-functionality in recognition of the ‘inescapable interconnectedness of agriculture’s different roles and functions’. Thus in future agriculture should be as much about enhancing the livelihoods, health and nutrition of rural households and restoring natural capital, as about increasing food production and economic growth.
Land degradation is one of the most serious problems facing agriculture as it affects 2000 million hectares (38% of world’s cropland) and is intimately interconnected with increasing population densities, declining livelihoods, malnutrition, hunger and poverty (Leakey et al., 2009). To rehabilitate degraded land and restore sustainability requires soil fertility replenishment, diversification at the plot and landscape level and perennial vegetation to provide environmental services and increase the number of niches in the agroecosystem. The ‘Green Revolution’ promoted intensive production of high-yielding staple food crops on land cleared of much of its natural vegetation. In many tropical countries poor farmers are unable to have access to agricultural inputs such as fertilizers and pesticides. Consequently, other ways have to be found to maintain and restore soil fertility and maintain sustainable production, such as low-input resource-conserving technologies based on integrated management systems and an understanding of agroecology and soil science (e.g. agroforestry, conservation agriculture, ecoagriculture, organic agriculture and permaculture) which minimise the need for high inputs. These low-input systems are pro-poor, approaches to agriculture that can also build social capital at community and landscape levels and are especially relevant to smallholder agriculture in the tropics – i.e. multi-functional agriculture.
With the exception of agroforestry, there has been very little plant breeding or crop domestication aimed specifically at these forms of low-input agriculture, yet domestication has an important role to play by promoting the diversification of farming systems with new crops. The domestication of agroforestry trees was initiated in the mid 1990’s, 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. 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 micro-nutrients 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.
Multi-functional agriculture and the role of agroforestry
There are many examples from around the world of low-input, pro-poor, 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 multi-functional agriculture. Like the other systems, it addresses the issues of soil fertility management; the rehabilitation of degraded farming systems; loss of biodiversity above and below ground; 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: (i) useful and marketable indigenous tree products for income generation, fuel, food and nutritional security/health and the enhancement of local livelihoods; (ii) complex mature and functioning agroecosystems akin to natural woodlands and forests; (iii) linkages with culture through the food and other products of traditional importance to local people. 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.).
Agroforestry practices are especially numerous in the tropics and 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 probably exceeds 100 million hectares. 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 below ground; 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 speeds-up the benefit flows by creating cultivars from parts of the tree which already have the capacity to flower and fruit without going through a long juvenile phase.
The definition of domestication used for agroforestry trees (Leakey and Newton, 2004 a/b) encompasses the socio-economic and biophysical processes involved in the identification and characterisation 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 socio-economic 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.
Retention and protection of genetic diversity
Typically only the best plants are brought into domestication programmes, so domestication is generally considered to reduce the genetic diversity of the species being domesticated; creating the so-called ‘domestication bottleneck’. 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, 2005) found that the trees with the largest kernels were found in many different populations and so 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. This population variation is another advantage of implementing a participatory domestication strategy implemented 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 if 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, 1999; 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 (Ndoye et al., 1997). 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 Agroforestry Tree Products (AFTPs) do contribute significantly to household income (Gockowski et al., 1997) 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 Dacryodes 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 (Brigham et al., 1996; Shackleton et al., 2000; 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; Leakey in press a), 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. 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 (Leakey and Tentchou, 2009) that go a long way towards meeting the goals of multi-functional agriculture.
Awono A, O Ndoye, K Schreckenberg, H Tabuna, F Isseri and L Temple. 2002. Production and marketing of Safou (Dacryodes edulis) in Cameroon and internationally: Market development issues. Forest, Trees and Livelihoods 12:125–147.
Brigham T, A Chihongo and E Chidumayo. 1996. Trade in woodland products from the miombo region. p. 137–174 in B.M. Campbell (ed.) The Miombo in Transition: Woodlands and Welfare in Africa. CIFOR, Bogor, Indonesia.
Bunt C and RRB Leakey. 2008. Domestication potential and marketing of Canarium indicum nuts in the Pacific: Commercialization and market development. Forests, Trees and Livelihoods 18:271-289.
Cooper PJ, RRB Leakey, MR Rao and L Reynolds. 1996. Agroforestry and the mitigation of land degradation in the humid and sub-humid tropics of Africa. Experimental Agriculture 32:235-290.
Diamond J. 1997. Guns, Germs and Steel: The Fates of Human Societies. W.W. Norton & Co, London, UK.
Gockowski J, J Tonye and D Baker. 1997. Characterisation and diagnosis of agricultural systems in the Alternatives to Slash and Burn forest margins benchmark of southern Cameroon, Report to ASB Programme, IITA, Ibadan, Nigeria, 68pp.
Leakey RRB. In press. Smallholder cocoa agroforests: multiple forest products and services – a model for sustainable development? In AB Bennett, C Keen and H Shapiro (eds.) Theobroma cacao: Biology, Chemistry and Human Health.
Leakey RRB and FK Akinnifesi. 2008. Towards a domestication strategy for indigenous fruit trees in the tropics. p. 28-49 in FK Akinnifesi, RRB Leakey, OC Ajayi, G Sileshi, Z Tchoundjeu, P Matakala and F Kwesiga (eds.) Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization, CAB International, Wallingford, UK.
Leakey RRB and AC Newton (eds.). 1994a. Tropical Trees: The Potential for Domestication and the Rebuilding of Forest Resources, HMSO, London.
Leakey RRB and AC Newton. 1994b. Domestication of Tropical Trees for Timber and Non-Timber Forest Products. MAB Digest No. 17, UNESCO, Paris, 94 pp.
Leakey RRB and TP Tomich. 1999. Domestication of tropical trees: from biology to economics and policy. p. 319-338 in LE Buck, JP Lassoie and ECM Fernandes (eds) Agroforestry in Sustainable Ecosystems, CRC Press/Lewis Publishers, New York, USA.
Leakey, R.R.B. and Tentchou, J. 2009. Consultants Report, Mid-Term Evaluation, Agricultural and Tree Products Program, Food For Progress 2006, 26 Jan – 13 Feb 2009. Report to World Agroforestry Centre, Yaoundé, Cameroon, 86pp.
Leakey, R.R.B. and Tchoundjeu, Z. 2001. Diversification of tree crops: Domestication of companion crops for poverty reduction and environmental services, Experimental Agriculture, 37: 279-296.
Leakey RRB, K Schreckenberg and Z Tchoundjeu. 2003. The participatory domestication of West African indigenous fruits. International Forestry Review 5:338-347.
Lowe AJ, JR Russell, W Powell and IK Dawson. 1998. Identification and characterization of nuclear, cleaved amplified polymorphic sequences (CAPS) loci in Irvingia gabonensis and I. wombolu, indigenous fruit trees of west and central Africa. Molecular Ecology 7:1771–1788.
Lowe AJ, ACM Gillies, J Wilson and IK Dawson. 2000. Conservation genetics of bush mango from central/west Africa: implications from random amplified polymorphic DNA analysis. Molecular Ecology 9:831-841.
McIntyre BD, H Herren, J Wakhungu and R Watson. 2008. International Assessment of Agricultural Science and Technology for Development: Global Report. Island Press, New York, USA.
Ndoye O, M Ruiz-Perez and A Ayebe. 1997. The markets of non-timber forest products in the humid forest zone of Cameroon. Rural Development Forestry Network, Network Paper 22c, Overseas Development Institute, London, 20p.
Pauku RL. 2005. Domestication of indigenous nuts for agroforestry in the Solomon Islands. PhD Thesis, James Cook University, Cairns, Queensland, Australia, 381p.
Schreckenberg K, A Degrande, C Mbosso, Z Boli Baboulé, C Boyd, L Enyong, J Kanmegne and C Ngong. 2002. The social and economic importance of Dacryodes edulis (G.Don) H.J. Lam in southern Cameroon. Forests, Trees and Livelihoods 12:15-40.
Shackleton CM, CM Dzerefos, SE Shackleton and FR Mathabela. 2000. The use of and trade in indigenous edible fruits in the Bushbuckridge savanna region, South Africa. Ecology of Food and Nutrition 39:225–245.
Shackleton SE, CM Shackleton, AB Cunningham, C Lombard, CA Sullivan and TR Netshiluvhi. 2002. Knowledge on Sclerocarya birrea in South and Southern Africa: A Summary. Part 1. Taxonomy, ecology and role in rural livelihoods. Southern African Forestry Journal 194:27-41.
This article was excerpted with the kind permission of the publisher from:
Leakey, R.R.B., Nevenimo, T., Moxon, J., Pauku, R., Tate, H., Page, T. and Cornelius, J. 2010. Domestication and improvement of tropical crops for multi-functional farming systems. In: Contemporary Crop Improvement: A Tropical View, 14th APBC/11th SABRAO Congress, August 2009, Cairns Australia.
About the Authors
Roger R.B. Leakey, Tony Page and Jonathan Cornelius
Agroforestry and Novel Crops Unit, School of Marine and Tropical Biology, James Cook University, Cairns, Australia QLD 4780
Tio Nevenimo and John Moxon
Lowlands Agricultural Experiment Station, National Agricultural Research Institute, PO Box 204, Kokopo, Keravat, East New Britain, Papua New Guinea
Maraghoto Consultancy Services, PO Box 1322, Honiara, Solomon Islands
Vanuatu Department of Forests, PMB 9064, Port Vila, Vanuatu.
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