One of the main causes of tropical deforestation is conversion to agriculture, which is continuously increasing as a dominant land cover in the tropics. The loss of forests greatly affects biodiversity and ecosystem services. Tree-based farming, in a range of agroforestry systems, has been proposed as a mechanism for sustaining both biodiversity and its associated ecosystem services in agricultural areas, by increasing tree cover, while maintaining agricultural production. The main aim of this thesis is to assess the rate of return resulting from incorporating trees into food-crop-based smallholder agricultural systems, in order to assess the economic potential of agroforestry systems that may also help protect local forest, the barriers to their widespread adoption, and how the landscape approaches (land sharing and land sparing) work best in the study sites in eastern Bangladesh and West Java, Indonesia. The four papers included in the thesis specifically address the following issues. 1. The types of agroforestry practiced, in order to characterize their differences in basic structure, management and associated crop plant diversity, and the problem of classifying them into a specific land-use category (i.e. agriculture or forestry). 2. The economic and social potential of agroforestry systems and the barriers to their widespread adoption, as a land use alternative to swidden cultivation, which may potentially help protect local forest. 3. The trade-offs between income and tree cover when incorporating trees into food-crop-based smallholder agricultural systems, and the associated factors that influence farmers’ choice of tree-based farming in place of seasonal cultivation. 4. The major challenges facing farmers using current local land-use systems, the conditions and policy context that could facilitate smallholder tree farming, and how landscape-scale approaches work best in a local perspective to reconcile agricultural and environmental goals. Data were collected through rapid rural appraisals, focus group discussions, field observations, semi-structured interviews of farm households and key informant interviews of state agricultural officers. Data have been analysed through narrative qualitative methods, and through quantitative methods such as descriptive statistics, analysis of variance, and cost-benefit analysis. x Five main agroforestry systems (homegarden, fruit tree, timber tree, mixed fruit-timber, and cropping in the forest understory) exist in the Java study area, and can be categorized into two main types, i) integral, rotational and ii) integral, permanent, both of which exhibit a noticeable diversity in terms of both species composition and utilization. In both Java and Bangladesh the inclusion of tree crops in seasonal agriculture improved the systems’ overall economic performance (NPV), even when it reduced understorey crop production. In the Java study area, tree ownership was associated with more permanent rights to farmland and was prestigious in the community, which also helped strengthen social cohesion when the products (fruit, vegetables, etc.) were shared with neighbours. In the Java study area, agroforestry farmers were less involved in forest clearing and forest product collection indicating that agroforestry may contribute positively to reduce pressure on local forests. However, seasonal agriculture (food-crop-based monoculture agriculture in Java, and swidden in Bangladesh) has a higher income per unit of land area used for crop cultivation compared with the tree establishment and development phase of agroforestry systems. There is thus a trade-off between short-term loss of agricultural income and longer-term economic gain from planting trees in farmland. However, constraints of local food crop cultivation traditions, insecure land tenure, insufficient investment capital, lack of knowledge, lack of technical assistance, and perceived risk of investing in land due to local conflict (in Bangladesh) limit farmers’ willingness to adopt this land use alternative. Various conditions can facilitate tree farming, including a carefully designed landscape approach, with the elements of both segregation and integration of land uses, supported by competent government policies and local communities having sufficiently high social capital. In land-use classifications agroforestry systems are not recognized as forestry, but like forests they provide tree products and services. Classification will always be problematic if a binary system is applied, thus a more sophisticated approach should be adopted that incorporates the economic and environmental characteristics of a wider range of systems.