The management of forest commons requires coordination within a community and between communities. This coordination is usually challenging given the incentives to free ride on the use of a valuable common resource, creating social dilemmas. Recent literature suggests that these dilemmas are more likely to arise in communities with heterogeneous members, particularly from diﬀerent ethnic groups. In this paper, we propose a new approach to deﬁne common forest units within the areas of exclusively shared territory between pairs of neighboring villages using second-order Voronoi polygons. We adapt dyadic regression methods using data from the majority of villages in rural Gambia. Our results suggest that areas shared by communities with similar ethnic distribution do not diﬀer in forest cover and deforestation (in a period of 15 years) in comparison to areas shared by ethnically distant communities. Therefore, we do not ﬁnd evidence that ethnic diversity implies degradation of forest commons. We suggest that previous results may be biased due to unobserved heterogeneity at the village-level, which we can control with our empirical strategy.