For the decade 2013–2022, Leakey et al. (2012) identified the scaling up of successful domestication practices (such as the participatory approach described in Appendix B) to be one of the major challenges. Impact studies are required to understand which of the tree domestication methods that have been applied to date have been most effective in benefiting tropical smallholders’ incomes, food and nutritional security, and what effect different approaches have on the genetic diversity of species in the long term, and hence on the sustainability of production (see more in Section 3.3). Particular opportunities for new tree domestications were identified for Africa, where genetic diversity in a range of essentially wild fruits has been found to be large, providing the possibility for large genetic gains under cultivation (e.g., for allanblackia
[Allanblackia spp.] see Jamnadass et al., 2010; for marula [Sclerocarya birrea] see Thiongo and Jaenicke, 2000). Forests are therefore important sources of germplasm for ongoing and future domestications, for AFTPs as well as for tree commodity crops (see Section 4.3), and this requires their management for the characterisation and maintenance of these resources (Jamnadass et al., 2011). A wider focus on indigenous trees rather than the exotic that are currently widely used to fulfil different production and service functions (as illustrated by the figures on exotic and indigenous tree usage proportions given in Table 2) may bring conservation benefits and be more sustainable in the long term (see Section
3.3).