a Thiollay, 1995. b Deharveng, 1992. c Sibuea and Herdimansyah, 1993. d Michon and de Foresta, 1995.

a Thiollay, 1995. b Deharveng, 1992. c Sibuea and Herdimansyah, 1993. d Michon and de Foresta, 1995.

of tropical forest biodiversity and profitable use of natural resources, since in addition to their biodiversity these multistrata damar agroforests in Sumatra are financially attractive.

Damar resins are utilized by industries in Indonesia or exported worldwide. In 1984, the export market represented one third of the harvested volume, a trade rising from 250 to 400 t/year between 1972 and 1983 (Michon et al., 1998). In 1994, the damar production was expected to reach 10,000 t (Dupain, 1994), at a value of U.S. $300 to 400/t. Of this trade, 80% is met by the damar agroforests. The economic value of the damar trade and its associated activities is of major significance to the villages around Krui. In 1993, the profits from damar production were U.S. $7.2 million from sales, U.S. $2.6 million from added value, and U.S. $1.4 million from wages. To this is added U.S. $0.3 million in profits made by Krui traders (Michon et al., 1998). This analysis excludes the locally consumed products from these agroforests, e.g., fruits, vegetables, spices, fuelwood, timber, palm thatching, rattan, bamboo, fibers, as well as paddy rice.

With the exception of plantation crops, many farming systems in the tropics, including traditional subsistence swidden farming, are based on mixtures and are frequently haphazard in their configuration and spacing. In contrast, monocultures are particularly prevalent in countries with temperate climates. It is not clear whether or not the tendency to complexity and random distribution of the components of farming systems in the tropics is a deliberate attempt by farmers in the tropics to mimic the diversity of natural ecosystems in order to minimize risk.

In contrast to traditional agroforestry, the recent development of agroforestry as a science by agronomists and foresters has tended to adopt the temperate model and to plant the tree component in lines, regular patterns, or along the contour of sloping land (see review by Cooper et al., 1996). This is especially the case in countries where farm size is large (e.g., Australia), where large areas of countryside are planted in geometric patterns.

Modern agroforestry has also tended to be 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 (Nair, 1989). Recently, however, it has been suggested that agroforestry practices should be successional phases in the development of a productive and complex agroecosystem, akin to the succession of natural ecosystems (Leakey, 1996). In this way, trees producing different products can be used to fill niches in a mosaic of patches in the landscape, making the system ecologically more stable and biologically more diverse. It is anticipated that this diversity would increase with each phase of the agroecological succession.

Toward this end, current activities at ICRAF are focusing on the development of agroforestry as "a dynamic, ecologically-based, natural resource management system that, through the integration of trees on farms and in the landscape, diversifies and sustains production for increased social, economic and environmental benefits." One aspect of this is to determine, through the use of models, the best land-use options for agricultural productivity and biodiversity conservation: the choice between integration or segregation (van Noordwijk et al., 1995b).

In parallel with these developments in agroforestry there has also been a move to promote the domestication of indigenous trees, the "Cinderella" trees overlooked by science (Leakey and Newton, 1994a; Leakey and Jaenicke, 1995; Leakey and Izac, 1996).

Bringing the new ideas about agroforestry and about domestication together provides one with a new paradigm for sustainable land-use development that focuses on two aspects of biodiversity:

1. Diversifying agroecosystems

2. Capturing and enhancing intraspecific diversity

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