Potential multifaceted agroforestry impacts on farming household's livelihoods in Viet Nam: need to account for agroforestry type, magnitude and maturity for non-biased evaluation

Agroforestry is widely recommended in the mountainous areas of Southeast Asia to improve farmers' livelihoods and reverse current land degradation trends. However, studies of the impacts of adoption of agroforestry practices on smallholder farmer livelihoods are limited to field-scale assessments and landscape potential. In this paper, we assess the difference in terms of farming system performance between agroforestry adopters and non-adopters in northwest Viet Nam using propensity score matching (PSM) calculating the average treatment (agroforestry adoption) effect on the treated (adopters) on core economic, environmental, and social indicators. The results of the PSM indicate an increase in revenues of about 8 million VND ha−1 yr−1 (about 325$) per household when adopting agroforestry, but a counterintuitive outcome regarding erosion. This outcome is likely due to an improperly selected farmer control group, which is located on less erosion-prone land, as well as the presence of immature trees in agroforestry systems, whose canopies have not yet contributed to reducing erosion. A typology of adopters was produced and revealed a wide diversity of agroforestry adoption pathways across the population, which may have blurred the results of the PSM. Six farming household types were obtained ranging from 'Off-farm income-dependent farmers' with low proportion of agroforestry to 'Specialists mixed agroforesters' with higher proportion of agroforestry practices on their farm and different levels of input intensity in their farming systems. This typology highlights the need for greater context awareness in agricultural system research and proper control of the agroforestry type, the proportion of agroforestry in the farming systems, and the maturity of the agroforestry system. This will help to better capture the real-life, farm-scale impacts of agroforestry practices.