In recent years, commercialization of non-timber forest products (NTFPs) has been widely promoted as an appropriate  means  of  developing  tropical  forest resources (Lawrence 2003, Arnold and Ruiz Pérez  1998,  Ruiz Pérez  and Arnold  1996). This reflects a growing recognition of the contribution made by many NTFPs to rural livelihoods, both in terms of supporting subsistence and as a means of generating financial income (Arnold and Ruiz Pérez1998, Belcher 2003).  At  the same time,  because harvesting of NTFPs is generally considered to be less  damaging  to  forest  resources  than  timber extraction, NTFP exploitation is widely believed to be relatively  compatible with forest  conservation(Arnold and Ruiz Pérez 1998, Belcher 2003, Peters1996).  Thus,  commercialization  of  NTFP spot entially  offers  a  means  of  achieving  both conservation and development goals concurrently(Plotkin  and Famol are  1992, Counsell  and  Rice1992), by increasing the value of forest resources to local communities (the “conservation-through-use” or “use it or lose it” principle; Dickinson et al. 1996).Recent reviews suggest that approaches to NTFP commercialization  have  not,  however,  been universally  successful,  and  that  the  scope  for improving rural livelihoods through NTFPs is in doubt  (Ros-Tonen  and  Wiersum  2005).  For example,  Sheil and  Wunder (2002)  suggest  that donor investments  for the development  of NTFP resources  have  often  been  misdirected,  and expectations of local income generation potential have frequently been unrealistic. Many NTFPs have been  harvested  destructively  or  unsustainably, resulting in resource degradation (Peters 1996)

Commercialization of non-timber forest products (NTFPs) has been widely promoted as a means of sustainably developing tropical forest resources, in a way that promotes forest conservation while supporting rural livelihoods. However, in practice, NTFP commercialization has often failed to deliver the expected benefits. Progress in analyzing the causes of such failure has been hindered by the lack of a suitable framework for the analysis of NTFP case studies, and by the lack of predictive theory .We address these needs by developing a probabilistic model based on a livelihood framework, enabling the impact of NTFP commercialization on livelihoods to be predicted.