Although my dissertation topic remains unfinalised, it is likely to be in the area of agroforestry. In particular, the role of agroforestry in achieving international development objectives in the tropics. It seems fitting that my first post should be an attempt to explain the basic concepts of agroforestry, so that’s what I will do.
The traditional definition of agroforestry is land-use systems and practices/technologies in which woody perennials are spatially or temporally integrated with crops and/or livestock on the same land-management unit, in ecologically and economically interacting combinations, The modern definition has been expanded to include the contribution of agroforestry to the development of sustainable agroecosystems that can provide various ecosystem services, economically valuable products, and improve social indicators, from the landscape-scale to the individual scale. Leakey (1996) takes this modern view and defines agroforestry as “a dynamic, ecologically-based, natural resource management system that, through the integration of trees in farm- and rangeland, diversifies and sustains smallholder production for increased social, economic and environmental benefits.”. A shorter definition based on Leakey’s words may be written as follows: Agroforestry is an ecological approach to land use management that integrates trees into agricultural land, to diversify and sustain agricultural production for increased social, economic and environmental benefits. When designing agroforestry systems, the aim should be to create productive (increase outputs), sustainable (protect the natural resource base, mainly soils), and adoptable (acceptable and beneficial to the farmers who use them, often conforming to local farming practices) systems.
Agroforestry describes a diverse variety of systems along a gradient of complexity, from simple forms of shifting cultivation like improved fallows, to complex intercropping and multi-strata systems, that occur in all ecological and geographical regions of the world—most distinctively in the tropics. Agroforestry systems may be classified according to their (1) structure (spatial or temporal arrangement), their (2) function/output (e.g. food, fodder, soil improvement, shade, etc.), their (3) socioeconomic/management nature (based on input, or socioeconomic level of practitioners), or their (4) ecology/geography (i.e. ecological suitability e.g. humid tropics systems). Using a primarily structural and functional classification system, Nair (1993) identifies roughly 20 distinct agroforestry practices (a distinctive functional arrangement of agroforestry components in space and time), but notes that the variations on these practices has resulted in hundreds of different agroforestry systems (i.e., specific local examples of agroforestry practices, characterized by environment, plant species, and their arrangement). The terms “agroforestry systems” and “agroforestry practices/technologies” are often used interchangeably.
These roughly 20 distinct practices can be categorised within three basic types of agroforestry, i.e., (1) agrisilvicultural systems (trees and crops), (2) Silvopastoral systems (trees and animals/pasture), and (3) agrosilvopastoral systems (trees and crops and animals/pasture). A fourth category of “Other” is necessary as some there are some agroforestry systems that do not strictly fall into these three basic categories, e.g., apiculture and tree systems, aquaforestry, and multi-storey woodlots, which do not contain herbaceous species. Despite not containing any herbaceous species, plantation crop mixture systems are generally categorised as agrisilviculture, namely because at least one of the woody perennials is a productive food crop, such as, coffee or cacao. The structural and functional classification used by Nair (1985, 1989) can then be stratified further using socioeconomic nature and ecology, e.g., improved fallows are temporal agrisilviculture-based agroforestry systems that improve soil fertility, and that are predominantly used by smallholder subsistence farmers in semi-hunid and humid tropical lowlands. Some of the crossovers between these systems may make them distinct practices, or may simply be considered a system variation. This is largely subjective.
Agroforestry is not defined by strict cut-off points regarding the percentage of tree cover on agricultural land. It is better thought of as gradient, with any agricultural land than has tree cover above 0% and up to 100% having the potential to be considered agroforestry. However, if agroforestry is defined by tree cover of >10% on agricultural land, it accounts for 46% of global agricultural land area (1.012 billion ha), an area that accounts for 30% of the world’s rural population (558 million people). 27% of agricultural land has >20% tree cover, 17% of agricultural land has >30% tree cover, and 7% of agricultural land has >50% tree cover. Agroforestry is particularly prominent in Southeast Asia, Central America, and South America, with over 80% of area under (>10% tree cover) agroforestry.
The humid and sub-humid tropics is arguably the most important ecological region for agroforestry, largely because agroforestry supports more people there than anywhere else in the world, and because it has the most diverse agroforestry systems—a product of a climate that favours rapid plant growth and a diverse array of species. The most common agroforestry systems in the humid and sub-humid tropical lowlands are shifting cultivation, taungya systems, homegardens, plantation crop combinations, and various intercropping systems. The most common agroforestry systems in the semi-arid and arid tropics are various forms of silvopastoral systems, windbreaks and shelterbelts, and multipurpose trees on croplands (usually for fuel and fodder). The most common agroforestry systems in the tropical highlands are plantation crop combinations (e.g. coffee and tea), trees used for soil conservation and soil fertility maintenance (mostly soil conservation hedges), improved fallows, and silvopastoral systems. Although the ecology and geography of an area seems to be the key factor in determining what agroforestry systems are used, the variations and intensity levels of agroforestry systems are strongly influenced by population density, land productivity, and the socioeconomic and ecological needs of the practitioners. Using this reasoning, agroforestry interventions can be designed by aligning agroecologically suitable agroforestry practices with the main ecological and socioeconomic needs for any given area.
Key References:
Nair, P.K.R. 1985. “Classification of agroforestry systems.” Agroforestry Systems 3 (2):97-128.
Nair, P.K.R. 1989. Agroforestry Systems in the Tropics. Dordrecht, The Netherlands: Kluwer Academic Publishers.
Nair, P.K.R. 1992. “Agroforestry system design: An ecozone approach.” In Managing the World’s Forests: Looking for Balance Between Conservation and Development, edited by N.P. Sharma, 403-432. Kendall/Hunt Publishing and The World Bank: Dubuque, Iowa and Washington, DC, USA.
Nair, P.K.R. 1993. An introduction to agroforestry. Dordrecht, the Netherlands: Kluwer Academic Publishers.
Zomer, R.J., A. Trabucco, R. Coe, and F. Place. 2009. Trees on Farm: Analysis of Global Extent and Geographical Patterns of Agroforestry. ICRAF Working Paper No. 89. Nairobi, Kenya: World Agroforestry Centre (ICRAF).