Tropical deforestation and forest degradation (DD) contribute approximately 15% of the annual global anthropogenic greenhouse gas (GHG) emissions. However, they are considered the main emissions sources in most developing countries. Despite the potentials of forest and tree plantations to mitigate the effects of climate change through carbon sequestration, DD still remains a challenge in Africa. Globally, the forests of Africa are the most depleted of all tropical regions, with only 30% of

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... rical forest area still remaining. In addition, Africa's complexity in terms of its geography, politics, socioculture, economy, institutions etc. is an indication of why Africa has defied all simple solutions in addressing DD: a phenomenon considered location-and situation-specific. The biophysical setting of Burkina Faso exposes the central and northern region to drought and desertification. Such conditions have caused human migration to the southwestern regions, which offer better opportunities for rain-fed agriculture, but also experiences the highest rates of deforestation. On the other hand, the ongoing regreening process in the Sahel through tree planting and assisted natural regeneration of indigenous tree species is a signal for regrowth and revegetation. This study contributes to understanding the drivers of DD in four adjacent village communities in the Ziro province, southern Burkina Faso in the light of the forest transition theory. Specifically, this study assesses the drivers of DD at the farm/forest level and also identifies options for regrowth/revegetation. This dissertation consists of four articles (studies I, II, III, and IV). Studies I and II refer to stage two of the forest transition curve (forest frontier) while studies III and IV refer to stage four of the curve (forest/plantations/agricultural mosaics). Various methods were used during data collection, including interviews with key informants, focus group discussions (FGDs), two hundred household interviews (studies I, II, and III), gathering a list of local botanical knowledge from 48 participants (study IV), and a field survey. Qualitative and quantitative methods were used in analyzing the data. Low agricultural production expressed in the sizes (areas) and ages of farms together with land tenure insecurity were found to lead to increased deforestation. Results suggested that a 10% increase in farm size would result in a 4% increase in annual deforestation (study I). Furthermore, results in study II indicated that non-poor and fairly poor farmers contributed more towards activities considered environmentally degrading, such as deforestation, overgrazing etc., than the poorest farmers. On the other hand, the adoption of sustainable land management practices was relatively low among the poorest farmers. Tree planters were mainly farmers who held large and old farm areas, were literate and relatively wealthy, held favorable attitudes towards tree planting, and had participated in a farmers' group for several years (study III). Local knowledge of tree species was found to be unevenly distributed in relation to gender, age, ethnic group, and location. Plant species assigned relatively high use-values for livelihood include Adansonia digitata, Parkia biglobosa, Vitellaria paradoxa, and Balanites aegyptiaca. On the other hand, Adansonia digitata, Tamarindus indica, and Ficus thonningii were considered more important for environmental protection (study IV). The dissertation concludes that tenure insecurity and low agricultural production contribute to DD at the farm/forest level on the one hand while tree plantations, land management practices, such as fallow, zai pits (a traditional soil and water conservation technique), and assisted natural regeneration of indigenous tree species are important activities promoting regrowth/revegetation. 4