Section 1. Agroecology and the Role of Trees
There are many definitions of agroforestry, one of the delivery mechanisms of multifunctional agriculture. Until the mid-1990s these definitions related to the many ways of integrating trees into farming systems as stand-alone agronomic technologies. This viewpoint overlooks the ecological functions that underpin the ways that allow it to enhance the environmental sustainability, as well as the productivity, of farming systems. Here, agroforestry is seen as applied agroecology in which the planting of trees in many combinations and/or configurations creates niches in farming systems that are colonized by a wide range of wild organisms initiating successive phases of an agroecological succession with increasing ecological integrity. The niche-forming principle within this functional definition also opens the opportunity for farmers to add diversity and fill some niches with plants and animals producing useful and marketable products in ways that increase total productivity and promote the social and economic sustainability of the farm.
Diversified and functional agroecosystems thus rehabilitate degraded agroecosystems, making them more productive: an unconventional approach to agricultural intensification. The processes are becoming better understoodâboth in the early pioneer and later mature phases of succession. This knowledge emerged when biodiversity studies found that mature cash crop systems, such as cacao and coffee with shade trees, provide habitat for wildlife of importance for conservation. These findings then led to studies on the ways that insectivorous birds and other natural predators reduce the numbers of pests and pathogens, providing information about the complexity of interacting factors that regulate ecological food chains. However, much more research is needed to better understand how these processes can be managed and manipulated so that environmentally friendly farming systems can provide enhanced productivity for food and nutritional security, as well as poverty alleviation, in harmony with wildlife.
Chapter 1
Definition of Agroforestry Revisited
This chapter was previously published in Leakey, R.R.B., 1996. Agroforestry Today, 8 (1), 5â7, with permission of World Agroforestry Center
Abstract
The current definition of agroforestry views it as a set of stand-alone technologies in which trees are sequentially or simultaneously integrated with crops and/or livestock. This falls far short of its ultimate potential as a way to mitigate deforestation and land degradation and thus alleviate poverty. A different view, however, is that agroforestry practices can be seen as phases in the development of a productive agroecosystem, akin to the normal dynamics of natural ecosystems â i.e., an ecologically based, natural resource management system that diversifies and sustains smallholder production for increased social, economic, and environmental benefits.
Keywords
Agroforestry; agroecosystem succession; agronomy; biodiversity; land degradation; natural resource management; niche; rehabilitation; technology
Agroforestry has been defined in several ways (Nair, 1989). The current definition of the International Center for Research in Agroforestry (ICRAFânow called the World Agroforestry Center) is a collective name for land-use systems and practices in which woody perennials are deliberately integrated with crops and/or animals on the same land-management unit. The integration can be either in a spatial mixture or in a temporal sequence. There are normally both ecological and economic interactions between the woody and nonwoody components in agroforestry. This definition has served well and helped agroforestry to become recognized as a branch of agricultural science in its own right (Sanchez, 1995).
Agroforestry practices come in many forms but fall into two groups: those that are sequential, such as fallows, and those that are simultaneous, such as alley-cropping (Cooper et al., 1996). In all, some 18 different agroforestry practices have been recognized by Nair (1993a,b), although each has an infinite number of variations. Thus, at the moment, agroforestry is viewed as a set of stand-alone technologies that together form various land-use systems in which trees are sequentially or simultaneously integrated with crops and/or livestock. In agroforestry research, practices are often applied after diagnosis and design, participatory research or characterization studies, as appropriate, depending on the social, economic, and environmental problems in an area.
Agroforestry is generally practiced with the intention of developing a more sustainable form of land-use that can improve farm productivity and the welfare of the rural community.
My problem with the current view of agroforestry is that many people still see it as a set of distinct prescriptions for land-use. As a result, it falls far short of its ultimate potential as a way to mitigate deforestation and land degradation and thus alleviate poverty. A different view, however, is that agroforestry practices can be seen as phases in the development of a productive agroecosystem, akin to the normal dynamics of natural ecosystems. Over time, the increasing integration of trees into land-use systems through agroforestry can be seen as the passage toward a mature agroforest of increasing ecological integrity. By the same token, with increasing scale, the integration of various agroforestry practices into a landscape is like the formation of a complex mosaic of patches in an ecosystem, each of which is composed of many niches.
These niches are occupied by different organisms, making the system ecologically stable and biologically diverse. Filling some of these niches with species that provide important environmental services or economically valuable products, or both, should result in land-use that is both more sustainable and productive. Furthermore, the benefits with increasing scale from the farm to the landscape and the region are exponential, since the ecological and social benefi...