K. F. W IERSUM
4.3 Coevolution between Trees and Production Systems in the Process of Domestication
The concept of domestication as a coevolutionary process between trees and production systems is particularly apt when considering fruit tree production.
Fruit tree exploitation normally starts in the forests, and increasing exploitation involves a gradual modification of forests by changing their composition and structure (Verheij, 1991; Wiersum, 1997b). This process starts with enriching forests with useful crops, often in the form of fruit species. The first phase of domestication of trees involves a process of concentration of naturally occurring useful tree resources in natural forests. In subsequent phases, new species may also be introduced in these forests. At first this will take the form of transplanting of wildlings or seeding of wild species. But as management intensity increases, selected varieties may be introduced as well (Table 4.2). As a result of these dynamics in exploitation systems, fruit trees may be grown in a variety of production systems (Wiersum, 1997a):
● Natural forests in which wild fruit trees are protected: specific areas or specific fruit tree species in natural forests that are favoured and protected because of their value for providing useful materials.
● Resource-enriched natural forests (Anderson, 1990): natural forests, either old-growth or fallow vegetation, whose composition has been altered by selective protection and incidental or purposeful propagule dispersion of fruit trees. Schroth et al. (2004b) characterized these production systems as
‘permanent agroforests’, which are continuously renovated in a small-scale pattern of replanting and spontaneous regeneration.
● Reconstructed natural forests (Anderson, 1990): (semi-)cultivated forest stands with several planted fruit tree species, tolerated or encouraged wild species of lesser value, and non-tree plants (herbs, lianas) composed of mainly wild species. Schroth et al. (2004b) characterized these production systems as ‘cyclic agroforests’, undergoing cycles of distinct management phases, including periodic replanting with agricultural intercropping. The term forest garden is used to refer to both resource-enriched and reconstructed natural forests (Wiersum, 2004).
● Mixed arboriculture: cultivated mixed stands, almost exclusively of planted, and often biologically modified, tree species. Typical examples are
homegardens with a mixture of fruit trees, other tree crops and vegetables, or mixed smallholder plantations.
● Mixed or monocultural fruit tree plantations: cultivated mixed stands, almost exclusively of planted, and often biologically adjusted, fruit tree species. Often this concerns commercial plantations.
The different categories are not discrete: gradual transformation from one category to another may occur. Many of these systems have been developed through the creativity of local farmers (Wiersum, 1997b). The presence of the various indigenously developed fruit production systems has been extensively studied, notably in South-east Asia (Michon, 2005). Box 4.1 gives an example of an indigenous process of domestication of production systems in respect to the popular South-east Asian fruit tree, the durian (Durio zibethinus).
The locally evolved fruit tree production systems are often dynamic, as they gradually evolve in response to changing conditions. Such changes may involve a variety of ecological, socio-economic, cultural and political factors (Arnold and Dewees, 1995; Belcher et al., 2005). The four most important changes which may affect the structure and species composition of fruit tree production are:
1. Changed ecological conditions, such as resource depletion or land degradation.
2. Changed technological conditions caused by the introduction of new agricultural and forestry techniques.
3. Changed economic conditions such as development of new markets and increased commercialization, changed demands for forest products and changed opportunities for off-farm employment.
Table 4.2. Phases in the process of exploitation of tree crops (Wiersum, 1997a).
Phase 1
Procurement of wild tree products by Gradual change from uncontrolled, open- gathering/collection access gathering of forest products to controlled gathering of wild tree products Phase 2
Initial production of wild tree products Gradual change from systematic collection of wild tree products with protective tending of valued tree species to selective cultivation of valued trees by artificial in situ
regeneration of native trees Phase 3
Cultivation of wild trees Cultivation of selected native tree species in artificially established plantations
Phase 4
Cultivation of fully domesticated trees Cultivation of genetically selected or improved tree crops in intensively managed
plantations
Box 4.1. Co-domestication of trees and forests: the example of Durio zibethinus.
Durian (Durio zibethinus Murray) is a popular fruit in South-east Asia. Wild durian are found in Borneo and Sumatra, but as a cultivated species the tree has spread over a much larger area, ranging from Sri Lanka and South India to New Guinea. The tree is not only popular because of the fruit’s unique taste, well liked by South-east-Asian people, but also because of its good production capacity. A major tree can produce 200–800 fruits a year and maintain such production over several generations. Fruits may be sold with common prices ranging from US$0.25 to US$4, making it one of the most profitable fruit trees in the region for local households (Goloubinoff and Hoshi, 2004). It has even been reported that the fruit is liked so much that rice harvesting suffers when it coincides with the durian harvest (Subhadrabandhu et al., 1991). In its area of origin the fruit is still collected from the wild, and its cultivation mostly takes place in mixed cultivation systems such as forest and homegardens or on field boundaries of agricultural fields. It is only in Thailand that the tree is predominantly cultivated in orchards. Propagation is still mostly by seeds, but in Thailand clonal propagation methods are common (Subhadrabandhu et al., 1991).
Because of its local popularity, durian has undergone a long process of domestication by local people, and only relatively recently has it been possible to state that ‘(professional) standardization of husbandry techniques is being achieved in durian orchards in Thailand’ (Subhadrabandhu et al., 1991). The process of domestication of durian by local people clearly reflects the notion of domestication as a coevolutionary process between trees and forests. On the one hand, trees were selected on the basis of their taste, resulting in the development of several local varieties. On the other hand, the extraction of fruits from wild plants was gradually replaced by cultivation in forest and homegardens. Within Indonesia, the various phases in this process of domestication are still represented:
1. The first step in the domestication of durian consists of the development of social measures for control over valuable tree species in the form of local rights of use of wild durian trees. Such tree tenure rights may relate either to individual trees or fruit tree groves; often they are maintained for several generations. The tenure rights are often complex (Peluso, 1996); they do not only pertain to rights to collect durian trees, but also to compensation for damaging trees, e.g. as a result of timber exploitation.
2. The next step in the process of domestication consists of the development of technical measures to stimulate in situ production (e.g. by removing competing vegetation) and natural regeneration (e.g. by protecting or transplanting wildlings or through seeding). These measures result in gradual enrichment of natural forests with durian trees and development of forest gardens; in such gardens other local fruit species are also maintained. As a result of the popularity of the durian, the species is not only maintained in forest gardens in its area of origin in Kalimantan and Sumatra (e.g.
Aumeeruddy and Sansonnens, 1994; Salafsky, 1995; Marjokorpi and Ruokolainen, 2003), but has also been incorporated in forest gardens on other islands such as Sulawesi (Brodbeck et al., 2003) and Maluku (Kaya et al., 2002).
3. Further intensification in the process of domestication entails the incorporation in home gardening systems such as on the island of Java (e.g. Dury et al., 1996). In rural areas such homegardens often consist of a mixture of trees, vegetables and other useful
plants. However, in case of good commercial prospects near cities, they may be gradually transferred into mixed fruit-tree plantations (Verheij, 1991).
The various types of durian exploitation systems are not just production systems, but also have important social functions. The development of access and use rights to wild trees forms a component in the territorialization strategies of local communities and households (Peluso, 1996). In areas with more intensive durian production, the guarding and collection of ripened fruits is often a joint activity of the tree owner, relatives and friends (Goloubinoff and Hoshi, 2004). In West Java, the trees serve as a form of financial security for owners who may pawn trees from homegardens (Dury et al., 1996).
These examples demonstrate that the process of domestication does not only involve a change in tree characteristics and production systems, but also the incorporation in socio-economic networks.
Although the incorporation of the durian in forest and homegardens illustrates its popularity in mixed production systems of multi-enterprise households, horticulturists have claimed that the trees usually have a low productivity, which keeps up the price and limits consumption. This is related to the irregular fruiting cycle; it can be improved through manipulation of the growth rhythm of the tree, thus extending the harvest season (Subhadrabandhu et al., 1991). This production-oriented view on the need for further specialization in cultivation is in accordance with the view that ‘in a typical home gardening situation, where everybody grows fruit but nobody is a fruit grower, the traditional expertise is dispersed in the community and much of it is latent, i.e. not put to use … It is difficult to take stock of local knowledge as long as it has not yet been accumulated by professional growers’ (Verheij, 1991).
However, several authors have recently suggested that durian production in mixed multistoreyed cropping systems is a promising multifunctional production system for meeting several newly arising concerns. Four major arguments have been brought forward for considering such production systems as being adjusted to both social, environmental and production demands rather than only forming an ‘intermediate’
position in the process of co-domestication of forests and trees:
1. The mixed production systems, yielding a multitude of products for use in the household and generating cash income, have an important role as a ‘safety net’ in times of hardship and hence play an important role in the coping strategies of rural people, contributing to livelihood security (Brodbeck et al., 2003). Thus, these systems can play an important role in programmes for poverty alleviation.
2. Rather than considering that the management of forest and homegardens is based on a low degree of professional knowledge of fruit production, it can be considered that it represents a profound knowledge of maintaining multi-species production systems. For instance, Salafsky (1995) demonstrated that durian producers have accurate perceptions as to how ecological factors influence durian production in forest gardens.
3. The forest garden systems can play an important role in the conservation of biodiversity (Marjokorpi and Ruokolainen, 2003). Consequently, they could play an important role in the management of buffer zones around protection areas (Aumeeruddy and Sansonnens, 1994).
4. Establishment of multi-stratum fruit-based systems incorporating durian can contribute towards the sequestration of carbon dioxide, while providing a positive financial return (Ginoga et al., 2002).
4. Changed socio-political conditions, e.g. population growth and migration, increased interaction with other (ethnic) groups, changed tenure conditions including gradual privatization or nationalization of forest lands, development of state organizations for forest management and rural development.
These changes increase pressure on forest and tree resources. In several cases this has resulted in deforestation and forest degradation, but in other cases farmers have reacted by modifying their management strategies, e.g. by intensifying or reducing the cultivation of valuable tree species (Belsky, 1993;
Dove, 1994; Arnold and Dewees, 1995). Recently, it has been noted that in several forest and homegarden systems such intensification has resulted in a gradual transfer from mixed-species multistoreyed cropping systems towards more uniform systems (Belcher et al., 2005). However, the process of change in these systems is not always uniform, and detailed studies have shown that whereas some smallholder cultivators gradually change their ‘intermediate’ fruit tree production systems towards more specialized arboricultural practices, other smallholders maintain these systems, although they modify the species composition and/or specific management practices (Peyre et al., 2006).
The dynamics of the fruit exploitation systems demonstrate that many local communities have been actively engaged in domesticating tree species as well as production systems, and gradually adapting these to their household needs.
Berkes et al. (2000) have characterized such locally evolved coevolutionary processes as an excellent example of adaptive management. It may be suggested that research to stimulate domestication of fruit tree species as a context-specific process, rather than a standard biological process, will be most successful if it is built upon such locally evolved domestication processes (Wiersum, 1996). An intriguing question then becomes what the future scope is for the ‘intermediate’ production systems such as forest and homegardens.